07-08-2017 - Been working on analysing a 360 Tonne capacity trailer for a copper mine. The drilling and digging equipment can’t go faster then a walk. So they trailer the equipment on and off the blasting face with huge trailers to speed up production. The bearings for the mast arrived and the machinist was thrilled when he could turn the mast with one finger. Looks like that job is complete. They now can complete the home journey from Port Lincoln to Perth. Seems I’m becoming a sign maker, two more signs to do and here’s a couple of shots of current work.
I made a small vacuum clamp for the signs. Makes set up so much faster.
04-07-2017 – Well we’ve hit the halfway point in the calendar year. I’ve been asked to do a few signs and boards lately. Here’s an open mike sandwich board sign I’m working on for the Gold Coast Acoustics Club.
It will have black legs and a varnished neck. More images soon. Will get into more technical objects with Scoot soon. Maybe a scale model V foil to figure out how these will work. This weeks job is to upgrade the bench to a heavier more stab;e one. The current light steel frame moves around if I run Scoot fast Plus the new bench has drawers and slots for sheet product storage. Will be nice.
06-06-2017 – Been asked to revisit a free standing mast bearing I designed some 12 years ago. On its delivery voyage from the Gold Coast to Perth the bearings became cranky so they pulled in at Port Lincoln SA. We will retire some of the parts and rebuild the bearings. They had rough weather across the Bight and also had rudder problems so they have put the boat on the hard for some shore work.
10-04-17 – I’ve spoken to the Men’s Shed at Murwillumbah and they are happy to “nurse” Scoot until I get my shed or it sells. I intended to join this group anyway to make a new network at M’bah. I visit them this week to check them out. Last night I ran Scoot for the first time under program control!
I need to recalibrate the axis as it cut an ellipse not a circle but that’s fair for the first CNC cut.
03-04-2017 – Scoot Alpha is now functional. But due to the move coming up Scoot will have to go into storage so I’ve decided to try to sell it. It will be a few months before we get our new house/shed built and someone may as well benefit from scoot. Then I’ll build a bigger 5 axis router at Dum Dum where are are moving to.
Two small things have hindered the final push to get Scoot working. 1) was a hardware issue that conflicted with the UC-CNC software. This was resolved by using a different computer. The HP laptop is much easier to use then the desktop as well. 2) The Gecko motor controller had an issue with an internal gain circuit. This becomes a problem with a G540 when 4 high amp motors are used like I’m doing. After the model I bought they have changed the circuit so the unit does not hurry into fault mode as fast as mine. They sent me a description of how to modify the circuit or they would send me a new motherboard FOC. I said I’d give the mod a go and within 15 mins Scoot was moving around and holding things without faulting. Excellent. I then cut some plywood and now I’m busy studying G code and Visualcam to write my first CAM program in 35 years. So now its time to commercialise Scoot and get two more models ready for market. A very big one and smaller 3D printer.
13-3-2017 – Been sorting the electrons on Scoot. I had picked Mach3 as the CNC Controller but my machine was checked by a tech and he upgraded it to 64 bit so M3 won’t work on it. So I decided M3 was technically at its end so M4 would be the go. But M4 needs a motion controller so had to research these. Decided on a UC100 and the same company has a CNC Controller called UCCNC and it looks good so I’m getting these. This should be the last hurdle to getting Scoot to move!!
5-2-2017 – Some time ago I published the scan of my jaw. Well know I’ve had the implant and it has integrated with my jaw very well the dentist says. Now I’d had the abutment (post) installed and tomorrow I get the crown fitted. My jaw and mouth have been scanned and the dentist has designed a ceramic crown from this data. I watched as he sculpted the crown and used smoothing tools and push and pull tools on the model tooth. I took a snapshot of the screen. This surgery is in Coolangatta.
He will then machine the crown on a 6 axis mini mill, put it in his pocket and come down to my local dental surgery and install it in my jaw.
6-12-2016 – Heading for the end of the year and tiding up all the projects. Over the past year I have been corresponding with an Engineer I worked with on a composite work platform project. The main thrust of the conversation is predicting failure of composites using FEA. There are some common failure theories but these are difficult to calibrate & the World Wide Failure Exercise casts some doubt on how good these are . Plus their are considerations of what level do we homogenise at? Homogenisation is the mathematical process to turn a real ply, real laminate or sometimes even the constituents into a mathematical entity. Once homogenised the material loses many of its mechanical characteristics. Also we have the problem of testing the material to determine its mechanical properties. Lately we have been looking at the inter-laminar shear strength values. The test for this uses a short beam, three point bend test. But the load anvil creates a compression field right at the place that the coupon tends to fail. This field means that the ILSS probably is stronger then calculated or predicted buy the test. So its predicted value is a bit low to use as a design value. Some FEA modelling and testing is required to weed out these issues a bit better and gain an understanding of whats happening.
20-11-2016 – Well I have picked up the cnc router project again now various things have cleared. I have ordered the mechanical parts and today I laminated the router bed. In two weeks I should be able to start assembling the critter!!
2x15mm bits of ply laminated together for the router bed. I have an old massage table steel frame for the its frame. Once running I’ll update this to a storage table and bed arrangement. Tomorrow I undo all the screws and mount this on the table frame.
15-10-2016 – Over the last 2 months I have been learning the didgeridoo. Its been on my bucket list for a few years. Took me a few weeks to train the circular breathing but it came together and now I’m working on some rythmes and animal noises. Then I decided to make a fibreglass didge so I started laminating the mould today. Been researching shapes and seems a taper gives good volume. So I’m making a long tapered big didge! Can always cut it down to a smaller one to get it to work. Lots of debate about straight then a bell, internal termite shapes giving better tone etc etc. Only way to find out is to do it. I’ll do a sheet a day so the stack will be done in a few days. Then I’ll start planing!! Will give my Stanley a work out.
27-09-2016 – Time flies when your having fun. For the last eight weeks I have been supervising a group of Griffith University students for a company called SORT for two days a week. They are a not for profit company involved in computer & plastic recycling that decided to make a 3D printer from some of the waste(resource) stream they handle. The students are a blend of design, engineering and business skills. I gave them various jobs to research about printers like thermodynamics of the hot end & drying of the filament. Others worked on whether it should be an XYZ machine or a scara type. The business students worked on delivery logistics and bill of materials costing and sourcing. Unfortunately we did not get to execute any of the stuff uncovered by the students but maybe sort.org.au will be able to progress the project in another form soon.
Other projects have been a foiling sit ski and I have progressed the birthing bath to its next level. I’m also waiting for feedback about the birthing stool I designed for an obstetric clinic.
24-08-2016 – Just been for a CAT scan of my jaw prior to a titanium implant I’m getting. I asked the dentist if I could have the scan and he gave me a CD with the data and a viewer on it. Unfortunately can’t get it in a format that my CAD systems could use. But the viewer is cool. The system is called Galileos by Sirona.
31-07-2016 – Here we are end of the month. Been busy with a 3D printer project, the patient lifter, some survey calculations for a large catamaran, setting up the torsion test for an ICV and three microphone stands for the Victorian Premiers Dept. A Dept representative got in touch wanting a carbon fibre stand to reduce the weight of the one they had. On explanation of the moulds and cost involved and that an aluminium one would reach the requested weight they choose to go with anodised aluminium. A design was issued for approval and then they ordered three units. These travel with the media party for various site interviews.
10-07-2016 – Recently I’ve had two inquiries about individually constructed vehicles (ICV’s). Some 12 years ago I used to be an Approved Person (Engineer) with Qld transport for light vehicle modifications. So I contacted the Qld DOT and reactivated my approval. So now I’m supervising a rebuild of a 1952 GMC ratrod and a kit Cobra. Have a look at the Services page for more details about the classifications Carbon-Works can approve.
In a year or two this will be on the road being enjoyed by the owner. Quite a bit of work to do but it will come together quite well.
The big topic over the last week has been hot cracking of aluminium welds. A client has been discussing their welding practice for 6000 series aluminium. They have been welding it to 5053 plate material with 5356 rods. They have had early failures of the weld and did not know about hot cracking issues. This occurs when certain combinations of rod and parent are used. As the weld freezes it cracks either down the weld centreline or at the toe of the weld. For instance using the 5356 rod with 6000 series is a known contributor to hot cracks. For 6000 series alloys 4043 is recommended. Plus in the clients case they need to use 6061 plate not 5000 series plate in the structures so as to keep the entire structure in 6000/4043 combination.
Some neat welding work…
A hot crack in a 6351 tubing bicycle frame while using a 5356 welding rod. The freezing weld is stronger then the tube and as it cools the tube cracks. If 4043 is used it freezes over a greater temperature range and is plastic longer reducing the mechanical reason for hot cracking. Very good fits also help. Plus the ER4043 rod is metallurgically more suitable for use on 6000 series material. This image also shows some contamination from the drawn tube surface in the welds. I manufactured over 2000 aluminium bike frames in the early 1990’s and had to figure out things like hot cracks, stress relief, aging and alloy spec so the frames did not fail early. The fatigue performance of the Technicomps and Pedal-Tech frames at the time exceeded all expectations.
28-06-2016 – I had an article about soft wing sails published at http://news4yachts.com/index.php/2016-06-08-13-35-41/equipment/the-state-of-the-art-of-soft-wing-sails. On the weekend a friend launched his Yawl. He’s spent the last two years building it and its a very pretty Iain Oughtred design – Caledonian Yawl. He named it Pearl. He finished it to a professional level so its a very impressive timber boat. Now he wants to sail heaps and get out of the shed.
22-04-2016 – Been busy with the current projects and many people have started talking to me about foiling their big boats. Designing the foils is relatively easy, integrating the control systems and foundations are the hurdle!! I was out on a cycle today and the sunset was spectacular.
Paradise Point, back harbour
https://youtu.be/x4pShcrpUbw is the link to the video of my Materials talk at the Multi-hull Club of Queensland, enjoy. One client is testing adhesive bulkhead connections vs bonding and tapping. The adhesive is Crestomer 1152 and it is proving to be very strong! It tears the laminate apart. This will save considerable time in taping the connections on a boat.
13-03-2016 – Two main projects have consumed a lot of time and headspace over the last couple of months. One – the patient lifter has passed its speed and load tests so now we are getting ready for hospital trials. Had an issue with the bearings which was unexpected! But that’s what prototypes are for. Now it runs very smoothly on linear bearing tracks vs the original bushes. Unfortunately I can’t show photos as its going through a patent process at the moment. The other is a composite ground anchor and again I’m in the middle of making prototypes for these. On another front I was asked to speak at the MYCQ again so I put together a talk on Yachting Materials – Gilligans Materials. I ran it as a Q&A so instead of hours of Q’s after the talk they were done at the end of each 5min segment. This worked really well.Through this I was asked to talk on the upcoming Americas Cup the week later! to a group of Rotarians at Southport Yacht Club SYC which was short notice but I rejigged a talk from the last AC. AC35-How Why When No2. They were a happy group and the evening went well, the SYC put on excellent food and they gave me a huge slice of cheesecake for talking, YUMMY Been too much business to progress the router so have decided to schedule a day a week back on it to get it moving again. My experience with the lifer has made me rethink the router bearings and also the bed layout so onwards to a better router.
26-01-2016 – Been a slow start to 2016 but the burner has suddenly been turned up. Composite Ground anchors and a slurry pump are high on the list. The ground anchor needs to move to prototyping asap so the client is making a sheet metal mould for a trial. I’m selling our Farr 6000 if anyone is interested? We want to downsize to the 5000. Or if a Kendrick 16 footer trimaran is out there I’d be interested. I’ve been asked to talk at the Multihull Yacht Club of Qld in March so I’ve decided to talk about Yachting Materials. Should be fun. Going to run it in a Q&A format vs a talk if possible. 2016 is looking challenging!!
25-12-2015 – Well its suddenly Christmas and time to contemplate 2016. We are having a short break and will be back at our desks early next year. Highlights of this year are commissioning a medical device I have been working on for 1.5 years, speaking at the Australian Composite Conference, Helping ideate a 60ft catamaran and developing a twin rig concept for the client. That project should develop more in 2016. We are generally having fun on the water and on our push scooters. I’ve taken up time lapse photography and look forward to more of that next year as well. Be safe and see you all next year.
27-11-2015 – Been very busy commissioning a machine over the last few weeks. But last week I went to a 3D Printer & Scanning workshop in Brisbane. It was put on by Griffith University and the Queensland Manufacturing Institute (QMI). It had guest speakers from Sweden and England. Very interesting stuff.
This was done by a hand held Artec scanner. Took about 30secs. If they had taken their time the scan would have been much better. There were at least 80 people at the workshop. Lionel Dean and Olaf Diegel were there. Olaf builds 3D printed guitars and Lionel does art pieces and furniture.
Here is the bump map for the scan.
Looks very weird!!
13-10-2015 - Scoot has gone down a blind alley, see the Scoot page for details. But sometimes you have to chase cheese and fail to know not to go there again. On another matter, Always interested in aircraft structural tests. Here’s a shot of a Fokker elevator (I think ) test. Love how aircraft are riveted together.
27-09-2015 – The busyness has slowed which has allowed me time to detail Scoot the Gantry Router/3DPrinter I’ve been designing as a Carbon-Works product. See the Projects page for more information on this. I’ve added more shelving in my shed and cleared some space for a clients machine build in the next month so I wanted to get Scoot off the prototype board into its control box this week. I’ve completed the manufacturing dwgs and have sent all of Scoots dgws out to quote. By end of this week I’m hoping to have all the parts ordered so I can start building. I’ll be using Mach4 for the control and VisualCam for the G code stuff.
I’m building the control box today, hope to get a couple of coats of paint on as well.
13-7-2015 Been very busy with a couple of projects. One is a SCARA robot arm that moves a scanner over a conveyor belt. The design needs to be scalable from 900mm wide belts to 2400mm wide belts. We looked at several mechanical configurations to try and find the simplest one. But its not simple! Its controlled using stepper motors.
We also looked at a Sarrus config but decided that we may not have the headroom in some installations
Sarrus Arm concept – unfortunately needs too much head room.
I’ve done some kinematic analysis Beam No2-1 this is a Strand7 analysis that figures out velocities and torques required to move the arm.
Gudgeon Update 12-7-2015
Andrew sent me the installed photo above. Can’t tell much really but these are a step up from aluminium. The originals were 5083-H32 which has a tensile strength of about 300MPa but the welding would reduce this strength. The laminate is triaxial in construction and last time I had it tested it had a flexural strength of 950MPa. The metal ones were 16mm thick the laminate came out at 19mm, but they are lighter then the aluminium ones. Aluminium has a density of 2700kg/m3 and an infused glass laminate has a density of 1800kg/m3 so size for size an infused fibreglass object is 1800/2700=67% the weight of aluminium. If we did it in carbon fibre it would be 1500/2700=56% the weight of aluminium. If its a strength design requirement then these ratios get even better as the laminates are much stronger then metal. If its a stiffness requirement it can be a juggle. If we can make the composite part bigger, we can get good weight reductions due to the rigidity gain. If we can’t increase the size then sometimes we only get smaller weight gains due to the laminates lesser stiffness to metals particularly steel.
1-06-2015 Early last month I was asked out for a sail on a 50ft light cruiser catamaran that always does well in racing so I went along and had a great day out on Fantasia. A few days after the sail one of the aluminium gudgeons broke and they asked me about welding a new one. I suggested we make infused fibreglass ones that will be significantly lighter and stronger then aluminium ones. Andrew the owner is always interested when you say “lighter” or “stronger” so he came along with some materials and a timber form and I showed him how to infuse them. We made a new set for the boat (4 in all, 2 at a time). Its his first experience with infusion and not getting resin on his hands when you make something. He was quite impressed and is going to write an article on the build for a local magazine.
Here’s No2 set with the vacuum pot in the background. They had less then 30% by weight resin in them and rang like a bell when you tapped them so I’m happy with that.
Andrew helping the cure along. Was a tad cold that day.
The thick laminate got up to about 70degs so was a nice start to the post cure. Once the temp started to drop I placed it in a polystyrene box with a heater for 8 hrs to fully cook.
Poly box has a heater in it to keep it at 60degs for 8 hours. Was a good cook. I had forgotten I made this for preheating polyurethane resin so Andrew had to stand there for a while with the heat gun for the first pair. But I got this out of the racks for the second set!
23-05-2015 – I’m stressing!! I’ve been analysing an aluminium boats hull for a naval architect. The welding has cracked about one year into service. They have been repaired once but have cracked again. We checked the original calculations and they conformed to Lloyds Survey Calcs. So the designer has done it correctly. The stresses are quite low by manual calculations so we need to figure out what is happening.
We then built FE models of flat plates to mimic the manual calculation and they agreed with the theory. With this knowledge in place I built the hull geometry and applied the same loads to the hull panels and they showed that the edge stresses are very low and they meet the code as well. I applied overloaded pressures, side by side and asymmetric loads but I haven’t been able to get the stresses to be very high where the cracks are. I have also run the panels in non-linear and as the panels are narrow they do not behave non linearly so over deflections or membrane stresses are out. Welding and fatigue have always been a bit of a mystery bag problem. When I was at Hayman Reese we did lots of FE and fatigue testing of towbars and we rarely predicted failures. With the steel towbars we did see trends that cracks occurred at weld starts and weld ends. These had craters which are pretty much a crack from day dot. The weld toe can be a huge stress concentration if its steep, undercut or dry. Then there’s hot cracking (craters) and poor work practice issues. I think this one will remain in the too hard bag to predict why. We will see next week after more discussions.
Here is an image of the stress vectors. This is the principle stress direction plot. The cracks are orthogonal to the principle stress direction which means the general loading is correct.
This is a von mises stress plot of the same area. With welding analysis the stress at T’s and edges needs to be ignored as these are discontinuities. Some standards have specified distances from weldlines to look at the stress value eg 1.3x the weld size or 1.6x the weld size. So I have made plate “strips” at about 8mm from the edges and T’s so I can look at the guass points in the elements at the right distance from the weld. We don’t look at node stress as this is extrapolated from the guass points and there are averaging issues to contend with at edges and intersections.
21-05-15 – Well Dean Barker has joined the Japanese! That will be interesting to see what they come up with! Would like to get some early glimpses of what the teams AC62’s look like!
NEPs Daggerboard is nearly done. I used the old boards top to provide some provenance to the original builder. I also used black as contrast for final smoothing but Gus likes it so I’ll topcoat in black. I’ll put an orange safety stripe along the bottom and were on the water again.
10-01-2015 a New Year!!
Welcome to 2015, may it be the great year for you all out there!
Before our Christmas break I took out Neptune and we hit a sandbar and broke the daggerboard (again!). So rebuilding a new one is high on the list. The original board is made from very light timbers. Looks like paulonia so not very strong. I’ve been wanting to play with a new polyaspartic resin but the supplier won’t sell me small amounts to play with, so I’m using the usual epoxies. I think I’ll buy a cnc router!!
Lots of sawdust. Up to the filling stage. The marine plywood has a poor internal ply and it has lots of splintering to fix on one side. On the project front I get back into the hospital patient crane next week and reboot last years stuff. I’m setting up a presentation for the Australian Composite Conference in April on “Composite Failure Criteria” and I think I’ll do one for the Multihull Club on boating materials.
Well its nearly Christmas. I wish everyone out there a safe and happy Christmas and New Year. Particularly after what has happened in Sydney this week. I’ve repaired a cat mast in the last two weeks. Its gooseneck fitting damaged the mast so I reinforced the area with two composite plates.
Making the plates to match the mast shape.
Finished reinforcement port side, stbd side is the same. I’m having a short break and will reboot my computer early Jan 2015. 2015 will be a great year, see you all then.
Took Neptune out yesterday. Asked a work friend and his family along and the smile says it all. Was a great day out, good wind and company. Three adults, 2 sub-adults and two eskies but Neptune did well. Lots of jellyfish at the moment we could feel them hit the board and rudder, donk. One popped the rudder up. I got home and received a SMS from an A cat owner who had hit a jellie, brok his rudder, skewed across and hit a permanent marker and dinged his boat. All of which needs to be fixed… Ouch!
Concept diagrid membrane roof for double bowling green. 80m long by 40m wide
Been involved with lightweight roof structures on and off for many years. I’m very interested in domes and grid structures. Large scale grid structures are becoming more common. Eg the St Marys Axe in London, airports and stations have huge sweeping free flowing shapes. These are usually difficult to design but with modern computers and automated grid functions they come out quite well. Manufacture is still a problem as every connection is different and every length is different but sure beats a boring box!! Composites offer the opportunity to provide very light and strong members for such work. Being able to flex but not fail means that the inaccuracies that build up in this sort of construction can be accommodated, even taken advantage of. Using flex plate connectors would result in a pre-stressed shell not wanting to turn inside out. This article started out trying to create a hexgrid panel that filled double curvature space. But this concept failed and the diagrid won out.
10-10-2014 Been very busy and away in Europe for the last six weeks. We went to France and Northern Italy. Hired a canal boat for two weeks in France, was great. Lake Como in Italy was spectacular. Didn’t do any sailing but we must go back and do lots. So now pick up the pieces of the projects I had to park and get rolling again… The weather has warmed up here in our absence so will be able to get Neptune out more often. I’ve planned a wing sail for her…
18-7-2014 The MYCQ talk went very well. They asked questions well into the night and the hot topic is foil design. Here are the slides and comments from the night. AC62-How Why When No2.
17-6-2014 I’ve been asked to give a talk at the Multihull Yacht Club of Queensland about the AC62 boats. The Class Rules have just been released so I have read over them and shall compare them to the AC72 Rules. Foiling is the big interest so I have designed AC type foils for three of the club boats as an exercise. I’ll publish the presentation here once I give it on the 3rd July at MYCQ Manly Qld 8:30pm.
25-4-2014 Sorting Neptune before launch
Launch of NEP. Some weeks ago I was looking through the boat ads and saw this timber trimaran. Its a one off, built up here but the owner moved to southern Melbourne and then decided to sell her. I decided it was too far away to bother about. It would be a 3000km round trip to get her! I sent the details off to a friend who is into timber boats and he got quite excited about it but at the moment would have nowhere to store it. NEP has two rigs a big rig and a small rig. Shes 16ft long and 4m wide western red cedar and fibreglass construction. Sails flat and is very stiff as we found out on her shakedown yesterday. Gus rang another friend who has a shed and they decided to try and buy it together. They then spoke to me and said lets split it three ways and so it came to be. I can sail/store it, they can sail it and its cheap at a three way split. Could buy the Honda engine, new sails and trailer for the price we got the lot!! Peter took a couple of days off over easter and did the long haul to get her up here. Yesterday I sifted through the bits and set her up at home. Then we all took her to the local ramp and get her wet. Only trouble is it needs a good wide space to set her up before we get to the ramp. Perfect 10kn breeze tor the shakedown. We’ve been talking about doing the Tawe Nunnegah Raid near Hobart next year and this will be a great boat for the job. All round a great outcome. I’m already thinking about making a wing sail for her!
NEP ready to launch, with small rig. Need to tune the battens, this sail has been used twice I’d say! 25-4-2014
8-3-14 Leonie bought a hardcase over the internet so the CF guitar case won’t happen. I’ve been going through some old projects archiving stuff and came across a couple of notes I sent to the AC34 Team Australia in 2011 about AC45 sailing. They maybe useful to someone else. The “Team Australia” for AC35 is now on Sydney Harbour training with Oracle. I’m looking forward to 2017! A presentation on secondary bonding is coming together in my head, RINA is looking for a talk this year so maybe thats a good spot for it.
124-10 AC45 Technical Notes Rev1 A note following up my Auckland visit and watching a couple of AC45’s being built and sailed
124-11 AC45 Technical Note 2- Rev2 A discussion on AC45’s and sailing wings
1-3-2014 My wife has started playing guitar again. She played as teengaer in a folk band. She went out and bought a guitar on ebay last week. She wants a hard case for it and so I’ve designed a carbon fibre one. It will combine carbon and timber ply panels. The next trick is to decide its closure. Shoebox? Square and how does it seal? Where do I get nice hinges and hardware. The devil is always in the detail!! I’ll have to change the profile slightly for the hinge alignment. Leonie likes this shape so lets get cracking.
Case Assembly No3-2 3D pdf of guitar case
20-01-2014 First entry for 2014!!
Been mucking about modelling resin flow in infusion and VARTM processes. Infusion or VARTM parts fill according to Darcy’s Law. It happens that Darchys law is an analogue of the Thermal Conduction Equation. So we can use an FE transient thermal solver if we mimic the values correctly. Over the years I’ve done lots of strip tests with infusion. So from a strip test I calculate the porosity and permiability. The other variables are thickness, density and the thermal constants. This will allow me to do “what if” analysis.
Thing No1-1A – video of an arbitrary shape filling using infusion
Temperature is used for pressure and I have used 100degC to equal 100kPa. When the element gets to 100degC (100ka) the element is filled. The trick is to ratio thermal conductivity with specific heat so the temperature gradient is very tight. But it now seems that I should model the media as a surface tessellated on a brick element,. This will allow me to better control the “fill” vs the “flow” situation. So the “temp or resin” will flow across the plate element, down into the brick element exactly like in the real situation. By modelling as a plate I have to lump everything together as averages and its not quite accurate enough. As I usually do a 600x600mm test panel when I use new materials I modelled a 600×600 initially as I know how that should look. Then I modelled the arbitrary shape. The interesting thing about this shape is that if you consider the fill comes in from the edges at constant velocity the ligament across the middle should close out and we would need two vacuum ports to fill the part. But as people doing this sort of thing will know, one side slows down and allows the other to catch up so the flow front converges at one point. This is illustrated in this fill pattern which is really neat. So now I can predict where the vacuum port needs to be in a perimeter fill.
5-12-2013 Been a few interests in Zippy so heres another image. I’m about to add the rowing rig and set up the mould station model.
Well 2013 is nearly finished. My small sailboat or rowboat has progressed slowly as many things in general existence are getting in the way… but I have settled on a 4m hull and have done some hydrostatics and stablity investigations and its looking pretty good.
Zippy, a 4m sailboat design
The design is called Zippy and she is 4m long and 1.4m wide. She’ll be made from cold moulded veneer using hoop pine/epoxy.
test 1-1 rear (15Mb AVI) is a video of Zippy being “floated” using FEA. Its a non linear transient dynamic solution of dropping Zippy into the water. It has a 50kg person sitting on one gunnel, me 78kg sitting on the other and 300kg in the bottom. It wobbles about until stable at about 30degs list. Takes about an hour to solve and It becomes stable in about 1.2secs and the maximum acceleration is 8g which is on the unsupported edge of the front deck as it wobbles. Generally the hull sees about 0.5g. At “start” the bow is depressed into the water 600mm with the hull at 10degs. The stern is out of the water. Unfortunately I can’t reproduce the splash!! I solve the floating for every 0.01secs for 2 seconds. The process simulates reality in which gravity is used to pull the boat down into the water and hydrostatic force is used to push it up. A pressure/position table is created to get the correct pressure gradient on the hull and the dynamic solver is set to solve fast by not calculating stress in the structure only the displacements, velocities & accelerations. My aim has been to design a hull that as it heels keeps the Cf and Cb very close together which makes it a stable boat. In this case they stay within 2% (80mm) of each other relative to the waterline so as the boat heels it does not try and rebalance itself dramatically. It should heel and trim smoothly. The main investigation task over the last 2 years has been how to build a properly blended bow on a parametric modeller with no bulge or blending capability. The answer has been to build a very fine bow and trick the CAD into filleting across the two outside surfaces eg use a 1mm wide bow so a 30mm fillet jumps across the 1mm face. But there is also another part to this which I’ll keep to myself!! Have fun and be safe over Christmas 2013
4-10-2013 AC34 is now over!!
Well its been a remarkable event. I first was involved early 2011 with the Australian Challenge from the MYCQ and have followed it closly since. Been a fast tracked AC only two years from Rules to finish and what a finish!! I’m sure there will be long and strong debate on how Oracle did it, but they did and we are now onward to AC35. Hope the Oatleys put on a good event, seems we will get another AC World series and since it has to be out at 2017+ we will need a small foiling multi that keeps some momentum going. Perhaps a foiling AC45?? I think the AC72 platform was really good they just had an overpowered rig. If they had picked the small wing we would have seen similiar speeds, perhaps more in the higher wind ranges and it would have been “safer”. The future is already being moulded so we shall know more soon I’m sure.
Who will win AC34 and why 13-9-2013 Who will win AC34 & why?
Last week I decided to have a Q&A session about the AC34 with the MYCQ just before AC34 started. I only thought about it a week before so didn’t have much time to get it organised. I asked a couple of the connected people in the club to get the word out and get questions to me early so I could mould the talk around them. Got 4 good questions not enough but good enough!! Talked from 8:30pm till after 11pm which was great. Very good questions and I hope good answers!! I tried to convince people that OTUSA was the best but to no avail. Seems ETNZ is the favorite and I have to agree. Now we have seen 6 races to NZ it seems the sentiment is in the right place. Next races will be the crux for USA, been great racing so far. Peter 13-9-2013
A couple of weeks ago I was asked to write an article about the Americas Cup “Rudder Gate”. As usual the AC is as much about the off the water stouches, as the on the water performance. The foils have taken center stage over the wing. If the boat can’t foil it can’t win. When the rules were made foiling a 72 footer was at the edge of plausible. But the boundaries of impossible & possible change daily now we have winged hydro-flyers that cruise at 40kts and have at least 50kn in them if the skipper is game! Heres the article published in August 2013 in Multihull World magazine. AC72 Hydroflyers Multihul Mag Aug2013 Enjoy… Peter S
A couple of weeks ago I did a talk at the Multihull Yacht Club of Queensland on Sailing Rig Design and Interesting stuff. Went really well as usual. They asked hours of questions and were a great group.
Rig Design MYCQ June 2013 I showed a couple of videos on the Americas Cup and as this was the 5th talk I’d done at the club decided to also do a short Bio on what I have done on sailing rigs professionally over the years. Sailing rigs and masts is how I got into the Boating Industry as I was employed by Goldspar many years ago doing Engineering, Product Design and Production work.
19-5-2013 – The Brisbane Timber & Wood Exhibition
Gus decided to exhibit his timber frames at the Brisbane T&W Show this year. He also decided to take his timber rowboat as part of the stand. So I tagged along for moral support and to do some research on our kitboat idea. I handed out flyers and talked to as many boaties as possible about stuff. Not many boaties at the show, mainly furniture and general public types. But I did have a great conversation with a retired timber boat builder who answered a few questions about stringers, ribands and shutters that changed my thoughts on how to build the mould. Experience counts!!…
Gus did not stop talking all day and I kept track of how the brochers were going. I had a very good chat to a guy who I thought was a strong lead for a frame sale.
Gus talking to an interested person…
The most common questions were; How much are they? Answer $5000-$6000AUD depends on what you want and what timber is this? Pointing to one of the laminates… Ebony, Jarra etc.
Gus’ Whitehall rowboat called Vineger Stroke
Most people were very impressed with the workmanship and the notion of a wooden bike! We could have sold rides all day long but we were not allowed to ride in the building…. This was Friday, he was there yesterday and today. Hopefully it all goes well and he gets a direction for his bikes. My findings are that there is an interest in small boats, Dorys were mentioned a bit and that if the hull exists then it probably will sell, so onward to the Prism mould.
I’ve been nesting out Prism stations but after talking to a boat builder at the show I’ll not do the bottom flange and leave a “shutter” at the mould line bottom. Need to draw this up and re-nest it today.
20-04-2013 A good Shellacing!
The 0ld hutch tarted up – The shellac matched the Taiwinese vinyl quite well.
Story – I’ve had an old student desk as my computer desk for many years. It now sits in the loungeroom and has looked quite daggy for some years. So I decided to get a new computer desk and visited many office furniture places to find out whats there. Once I had a coupe of candidate desks the next thing was to let Leonie have a look since its in our lounge room. She liked the one at the top of the list so it was into the truck and “come on home”. Its a two box flat pack with about 150 parts to put together. The instructions where not bad but I had to think about a few things as the words where quite sparce. Once the new desk was in place the Hutch looked wrong as I never finished it when I built it some 12 years ago when I was working at ATL Composites. So since I did a timber polishing course some 4 weeks ago out came the shellac and 6 coats later the honey shellac was really good. A quick Carnaubia wax and its ready for another 12 years of holding up monitors and printers! Sorry I can’t talk about the work I’m doing at present its under a confidence agreement. But I was thinking about using shellac to seal and polish the MDF moulds I’m about to start for the Prism rowboat project. Anybody out there used shellac for moulds? It seals ands builds fast I’ll have to do a trial bit to see if its vacuum proof…
1-04-2013 A brand new month!!
Zsa Zsa No7-1 29-3-2013 drawing of zsa zsa
Well the dust has settled on the Torii and I can get back to my boats. I’ve been playing around with a training catamaran. 12-13ft long with a large wing mast. Lots of people I talk to say that theres nothing for the younger sailor to sail in terms of solo multihulls. So I thought I’d work one up.
To cope wih the problem of “aging out” Zsa Zsa would have three rig levels. “Entry level” would be a simple mast, mainsail and spinnaker, then advanced level would have the large wing mast, then the flyer level would have a foiling package. The wing mast is modular so extra length can be added. The CAD work is coming along. The trick is what sailor weight range to design to. The spine will support the centreboard and be the spinnaker chute. Lots of little details to sort but it will take time and interest. Making a light little cat is quite hard. Don’t have enough length to get really slender hulls may have to be 14ft long. So Zsa Zsa will be the mind exercise for now and its time to crank up Prism in the shed. Time to design & build its mould. Decided to minimise tooling cost so no strongback, will build it on frames straight to the floor.
Got up this morning and it was dry!! Been about 4 weeks since we had a sunny day! So off to hire the hole auger and dug two holes and dropped it in. Squared it up and leonie decided it was in the wrong spot! So had to pull it down and dig more holes about 1.5m “in-front” of where we had decided to put it. The curved brace is the original experimental arch. So a quick touch up of the lintel and arch and its complete!!
Its been raining off and on for over 3 weeks now and every day I’ve decided to dig the holes the skys have opened. So I havn’t been able to plant the Torii. I’ll have to clean up the shed and work around it I suppose. I’d like to start the rowboat strongback. Theres lots of talk about the need for a trainer catamaran at present so I may have to accelerate that project. A 10ft cat for youths with 3 levels of rigs… beginner, intermediate and advanced (a wing and foils). I’m off to a Composite Conference in Melbourne over the next couple of days so stay tuned.
Yesterday we went out on the support team for the local Catamaran Championships. Was a great day, wind slowly picked up through the day from about 10kts to 15 in the afternoon. Only a couple of capsizes, one of note was a Cobra that stuck its mast into the sea bed at the bottom mark. The other support boat pulled it out and although the rig seemed to load up and bend a long way as it popped up no damage was done and they continued to race. The photo shows an F16 that capsized at the top mark. They came in too shallow and tried to steer then gybe, then tack around the mark. But there was traffic and the mark to dodge… and over they went. The F16 was clearly the fastest boat in the fleet. It sailed faster and higher than the NACRA 5.8’s (as it should!) The organiser asked if I could do another talk so I’ll do the Multihull hull design talk in March for the club.
Been painting the Torii before I do the final assembly. I like painting. My father was a builder in the days when everyting was done by hand. Not many power tools around. The painters would arrive on site with their big brushes and big tins of white paint, in their spotted white bib and braces.They would have lots of colour charts and do the tinting before they started. The job would smell of turps for days. I haven’t done any fine finishing for quite a while so the Torii has jogged my memory about several things. So much so I”ve enrolled in a furnature finishing course next month. I spoke to several paint company techs about solvent vs acrylic finishes and all agreed that Acrylic lasts longer than solvent and its easier to use and clean up. There was lots of debate about sealers and primers, but I picked a paint that technically didn’t need these. I “sealed” the timber with the topcoat thinned with water about 50% for a couple of coats. Then I did the “prime” with it thinned 25% then the topcoats neat. Similiar to how you would do a varnishing job. As its garden furniture I didn’t want a fine finish, more of a rustic look. So I didn’t finish the timber “too” well. But the checking in one of the posts I should have filled. Paint can’t be expected to be a filler! it only reflects whats under it. Hopefully I get some good top coats on today and maybe will be able to bond it all together this week. Its a bit dreary and rainy today so the paint is drying slow.
Well here we are in February. Times slipping away. Today I chamfered, rounded and sanded the arch and lintel of the Torii. Yesterday I spent time talking to paint companies about primers and top coats. I want to get this arch stood up and then I can get serious with the rowboat build. The Torii has been a prelude to the rowboat in which I have played with adhesives, bending wood, laminating wood and organising all my tools… which I have not used in a long time.
Have made the Lintel and Arch for the Torri. Usually I would use epoxy for this sort of thing but it has been raining for several days as a cyclone is in the neigbourhood and all the timber is damp. I’ve been wanting to try foaming urethane for a while and as its moisture curing seems its the time to do it. So off to Boatcraft Pacific and get some Purbond. Made the lintel and tried different notched applicators but didin’t find they applied easily. For the Arch I used an aluminium roller and this worked a treat. The vac bagging was straight forward and the purbond once cured planed easily. Epoxy is tough and hard and blunts the tools. But the purbond was a joy to plane. Now I have to dress and finish the lintel and arch and start on the posts and Gargoyles (finials). Speaking of planes yesterday I got my planes out and sharpened them. Some time spent with wet and dry and a stone makes the work so much easier. At last years Timber & Wood show I bought a little thumb plane and this was ideal for edge work and removing glue. I think I’ll get a spokeshave soon. My friend Gus dropped in so the arch was done quick sticks. He applied one end while I did the other. Heaps of time left to get it in the bag. I was a bit worried yesterday as I was close to gel time for the PU. A tip is to get a squeeze bottle like a sauce bottle, makes application so much eaiser than tipping from the bottle! I think this would be great for the laminated hulls planned but I think we need much more gel time than this PU allows for.
Entering the next stage of the rowboat project. Modelled and fitted the rigger last week. Seems the gunnel is too high for it so I’ve had to reshape the sheer. Cleaned up the shed getting ready for the strongback build.
19-01-2013 Had some ply cut by CNC router for the Torri Arch and Lintel. The Torii has been a bit of a prelude to the rowboat. Been playing with bending wood, laminateing veneer and setting up cutting files both 3D and 2D.
Been working on the best way to build a strongback for the rowboat and trimaran project. I had some ply cut for the Torii project by a local CNC router and its clearly the way to go in terms of accuracy and time. So this unit has been designed so we can store tools and things under it while the build is on. It screws and glues together in 2.4m sections. I only need 4.8m at present but the trimaran maybe longer so I’ll add to it when required. Next step is to section the hull shape into 16mm slices and set up the cutting files for quotes.
First entry for the New Year. Been designing a Torii for our garden. Today I take the materials to the cnc router for cutting. Then I’ll epoxy and vacbag it all togther ready for my wife to finish. Been playing with it as a prelude to the lamwood boat project.
I’ve talked to a couple of CNC router people about cutting a 700mm model of Prism. This is to check the surface quality of the hull. I was involved in a kayak project some time ago and we were very disappointed with the plug when it was machined. Even though we looked at zebra plots, curvatature analysis and various things on CAD we still didn’t pick up subtle things about the surface until we saw it in the flesh. Then we had to manually fair it and correct it to the intent. Which was not the plan! Looks like this will be next year. To everyone out there have a safe and Happy Christmas and New Year. See you in 2013 if I don’t get back to the blog next week.
2-12-2012 – More on the rowboat project:
Tugboat 5 nearly got the nod! But its displacement range was a bit heavy for day rowing. So Prism was developed. Prism is a block form bezier network, with a tapered fillet chine for the techical people out there. I usually use 5 stations but this time I have used 4 to make the hull easier to fair. To control the fwd shape I have tilted the 25% station. This has proved to be a good tactic vs the extra station. Next time I shall tilt the 75% station as well. The bow and transom stations also tilt. All the tilted stations can be adjusted in angle and longitudinal placement. The whole curve network is parametric. We are now talking to CNC router people to have a model made to check the surfaces. Prior experience with having boat hulls CNC’ed has shown its very difficult to see if the surface is fair on the computer screen!
Tugboat turned out to be a bit more displacement than needed for the first project. Looks like Tugboat is more of a two person boat, so she will be moored until we need her. Prism has shaped up to be 100-150kg which is on the money for the rig and the expected mode of rowing. Which is solo fast day rowing with some good food and perhaps a light friend.
23-11-2012 – Tugboat
Been further developing the Tugboat Concept. See the projects page for more information. Mainly trying to model various features on the rowboat so that they remain parametric. Should be finalising the general arrangment soon and then we move onto making the hull mould. Tugboat’s intent other then having fun rowing is to prove the manufacturing concepts of moulding timber veneer into boat parts.
Tugboat No2-3 with slates & benches 23-11-2012 A 3D pdf of tugboat with benches. The real tugboat will be using a sliding seat rig which I am about to model so it can be used in the hydrostatic and manufacturing data.
An early version of Tugboat.
12-10-2012 – Dolphin Heads, Mental Movie
Went to see the movie “Mental” the other day. Not a very good movie but I mainly went to see the Dolphin Heads sign. Early this year I had to certify it. The movie company designed it and I built an FE model of the sign and had to provide an Engineers Report. I then advised about changing a few things as it was designed to withstand a cyclone. It was only up for 8 days and it was in the movie for about 30secs. They hung a huge shark off it in one scene. My report was reviewed by the Evans Head Council and by a third party Engineer. Went well!! The sign straddled two bridges on the Pacific Highway. It had to be built to guarantee no residual damage to the bridges and if the cyclone hit it wouldn’t fall on any vehicles.
Last night I talked at the Multihull Yacht Club of Queensland (MYCQ). We started about 9am and questions finished after 11pm! Had to pack up and leave otherwise I’d be there today. Foiling is big news.AC72 Design Study No3 4-10-2012 slides from the talk
Leonie (my wife) and I where out on the Race Support Crew off Southport a few weeks ago. Was a tad rough but was a great day out. We rescued a sailor overboard, moved some markers and enjoyed the scenary. “Australia” the ex Orma60 tri was there and then gone. Very fast boat.
My resume is a very popular download plus all the presentations about the AC72 and upcoming Americas Cup. I’m happy to answer any questions out there! Peter
Been mainly designing high access equipment for a company. The elevated work platforms need to be insulated so they can be used on high voltage electrical distibution lines. The boom and jib elements are made from fibre glass.
07-05-2012 A person has asked me about Technicomps bicycle frames. A factory I set up in joint venture with Europa Cycles. We made about 2300 aluminium frames from 1989 till 1992. See the About Us / Interest page for more details. We had a very good work shop and did our own heat treating of the aluminium frames. We repaired alot of carbon fibre frames and made a few Titanium frames as well.
The links to pdf’s are working now. They take a little more time to load then usual but they do open. Looks like it was something to do with a new virus checker. Peter S
Hi All, I’ve updated wordpress and it seems to have stopped me being able to link to pdf’s. I’m working on fixing this. In the meantime if you want a file just ask and I’ll send it to you. Regards Peter S
Two weeks ago I presentated a talk to the Royal Motor Yacht Club in Newport NSW. They have monohull and multihull divisions. Over 30 people turned up to hear about aero-hydrodynamics for sailors. I started at 8pm and finished before 9pm, but the questions went to 10:30pm. Great bunch of sailors asking great questions. Thanks RYMC for having me.
RMYC April 2012 – The Presentation Slides for people who are interested.
Photos have just come in on the Cairns Waterpark work I did last year. I especially like the bucket. It was a bit of a mission to get the balance right!
Been working on a concept Podcat for a client. Easily trailerable and will have a free standing semi wing sail. Fast comfy weekend sailing. The floats swing rearward and are deployed on the water. This concept model is to establish some human factors for weekending and to start on the weight study.
Been building an FE model of a 384 tonne tip truck for a company that refurbishes mining vehicles. Plus designing a Hilux ROPS. For both have been investigating ways and means for converting solid geometry to mid plane contiguous surfaces. No automation out there yet for this problem. Just a lot of work surface extracting and retrimming. But nearly done… will move onto the stress analysis tomorrow. Unfortunately both companies don’t want images of these published.
Well the year has become very busy. Been analysing Roll Over Structures for utilities, Dump truck trays for mines and Bollards for pontoons. I’ve started designing an 8m sports catamaran for a client. Havn’t been able to convince them on a Wing Sail yet! Started writting the next instalment for the Multihull Yacht Club of Qld. The presentation will be called Aero-Hydrodynamics for Sailors and delivered in early march.
Back on deck for a great 2012. Tidy a few things and lets see what 2012 will bring. Peter
Winding up the year, completed the waterpark and marina stuff. A couple of odd jobs to do and the year will be done. A client has accepted the budget for building moulds and protoype VAWT blades so looking forward to building these next year. Also a new enquiry is keen to build a composite chassis & body for a custom V8 sports car he is building. This is shaping up to be a really good project so stay tuned in 2012!
This is my last week at work for 2011 and I’m busy wrapping up a Waterpark Project and a Marina Project. Next year I hope to get serious with the C-Class and Zinger projects. All out there watching have a Safe and Happy Christmas (if you celebrate this) and I’ll be back blogging in 3 weeks. Merry Christmas!
We’ll the MYCQ has been consistent, I started the presentation at 8:25pm and questions finished at 11:05pm. As we live just over an hour away from the yacht club I got home the next day! Questions were really good. So here are the presentation slides.
Multihull Hulls 3 – A presentation of a potpurri of Multihull “hull” design factors
Well we’re nearly at the end of the year. Looking at the site logs it seems many people are interested in “Rigid Wings” or “solid wings”. In the various sailing forums I track there are massive amounts of discussion about the aerodynamics of these. Being a mechanical engineer I’m interested in how to control them, mainly how to twist them. So looking at the Patient Lady (PL) type control has been interesting. The AC45 and other designs have simplified the PL type control to using one control arm vs the ganged system on PL. I have modelled the PL system and here is an AVI of how the trailing edge can be twisted. The FEA model uses “string” elements which simulate the sheets. As the lever at the boom box is moved it moves the trailing edge of the wing via the control arms. In reality this system limits the wing from twisting vs twisting the wing directly. The aero loads “fold” and push the sail to one side. The sheets limit the amount of movement each element can make by resisting the aero loads. By letting out the “twist sheet” the “flap or panel 2″ can twist more. By sheeting “in” the flap twists less. The system allows the wing to tack and maintain the same twist on each side. The same goes for camber. Pull the camber sheet in and the wing cambers more. If the boat tacks the camber remains the same on each side.
Twist Test 3 – Wing Twist Control AVI of FEA model
Tomorrow night I present my “Design of Multihull Hulls” to the Queeensland Multihull Yacht Club. Should be fun. Last time I presented to them they asked questions till 11pm from a 8:30pm start. I was still answering Q’s going to the carpark to leave! They are an enthusiastic lot!
The most popular download from this site this month is the RPAYC presentation on Wing Sails.
1) Next week (1st Dec 8:00am at the club) I’m doing a presentation on Multihull Hull Design for the Multihull Yacht Club of Queensland. I’ll publish it here after I present it.
2) Added the C-Class Catamaran section to projects. Will be adding more to this as the project develops.
I’ve added copies of three presentations I’ve done on the Americas Cup earlier this year. See the Americas Cup page.
Hi all out there. I’ve been looking at the logs and a lot of people have looked at my site from all over the world. Please leave a comment and say hi! Ask a question or two! I’m happy to discuss anything technically interesting!
The moth wing video is the most popular download so I’ve added another moth wing in the Structures-Yachts area. I’ve been doodling a few Moth wings but until the new rules are settled its not much use designing one. Its clear two panel wings are out (unless there is no slot) so it will be a large wing mast with soft sail when the time comes.
I updated the blade design document.
I wrote an article on blade design for a client and added a link in the Structures – Wind Turbine section
31-10-2011 ~ Wing Sails or Rigid Wings
For various reasons Wings have not been developed for sailing to a high degree. These reasons relate to the Recreational Sailing Rules, Organisational Sailing Politics and general conservativism within the sailing community. In the past when sail power was commercial it developed as fast as technologoly allowed, similiar to the Automotive Industry. If it was easier, faster or cheaper then the technology would be adopted. Once sailing became a sport and recreation, various rules and traditions developed to keep the supposed playing field flat. However you can’t keep a good idea down and the C-Class catamarans have taken Wings to a high degree of development within their arena. Wings offer several advantages over soft sails. 1) They produce more lift with less drag 2) The secondary loads are very much reduced. Secondary loads in soft sails are the membrane loads that the sails develop. These can be extremely large in large sails. eg the mainsheet load on USA17 with soft sail was over 35 tonne, yet it reduced to 3 tonne even with the bigger Wing. 3) They are easier to control in terms of depowering and powering up 4) They offer a more useful range of power in all conditions. They do have negatives however but these just need time, understanding and development to overcome. The aircraft industry ditched wires and soft sails very early on in its development timeline, realising that drag was too big a penalty to pay for these systems. I’m sure that Wings will be seen more often now that the America’s Cup have taken them on seriously. Wings could even provide the path for powering commercial vessels again. In short Wings provide twice the lift (or power) from the same sail area, they have the opportunity to get rid of rigging (free standing wings just like on aircraft) this reduces the lift/drag ratio allowing them to sail closer to the wind and much faster than the wind, say 3x the wind speed. The first thing sailors say is how do I reef the Wing? To depower the wing you reduce its camber. This is easy to do just haul in the camber control and flatten the sail to reduce its lift. As the wing does not flap or flutter (luffing, a huge drag) it remains stable and well behaved. So we can tune the amount of lift required to the wind or the conditions. There are other points such as what happens at a mooring? What about the extra weight etc etc. These issues all have solutions, they just need implementing and refining. Time will tell but what works on the race course usually filters down to working at a daily level, if it has some usefullness. Peter
24-10-2010 ~ Carbon Fibre or Fiber
Carbon fibre is a relatively expensive material. But its difficult to get such a high stiffness and low weight in any other material outside of aerospace or military budgets. Its possible to produce laminates the same stiffnes as aluminium yet 7x stronger and half the weight. The main property we are interested in with carbon fibres is its stiffness. Standard modulus carbon has a stiffness which is 235GPa which is slighty stiffer than steel. By the time we make it into a laminate however this property reduces. Short fibres of over 1000MPa are available and 650GPa is the stiffest long fibre available. High perfomance laminates have about 60% by volume fibres in them. Using special techniques this volume can be increased, but very high performance resins need to be used as the fibres then become very close together and become difficult to bond together. Infusion and VARTM techniques can produce very high quality out of autoclave laminates. When carbon fibres were first made available there were two ypes PAN and Pitch based. PAN fibes were made from acrylic fibres and were called high strength. Pitch (a type of coal tar product) based fibres had high stiffness but low stretch. The High Strength (HS) tag has stayed on to apply to the std modulus fibres. Nowadays fibres are mainly described by their modulus. std, intermediate, high and ultra high modulus.
The next property we are interested in is the fibres elongation. These vary from <1.0% to over 2%. Pick the fibre with the highest elongation if you have a choice. Generally speaking the higher the modulus the lower the elongation.
What would you like to know about carbon fibre or other fibres? I’ll answer any questions posted here. Regards Peter
17th Oct 2011 ~ Stainless Steel Fasteners
The marine environment is very hard on fasteners. There are many types out there with various finishes. Often my clients’ drawings just have SS on them or 316 to describe the bolt’s material. This can get you into trouble! There are “no-names” S316 or S304 type fasteners out there. S31600 is the UNS (unified numbering system) designation for the material, but does not require any minimum material strength. If you just specifiy 316 or 304 then you may get these alloys but in a very weak bolt. Plain 316 & 304 for instance has a yeild strength of about <250MPa which is not very strong.
If stainless steel is required then here is what you need to do. Specify Class 70-A2 or A4. The strength is called a “class” and the “grade” is the material specification. Class 70 means the bolt has a 700MPa UTS which is very strong. It has a yeild strength (YS) of about 450MPa which is more than twice as strong as an unspecified 316 bolt for instance. The grade determines the material, A4 is S316 and A2 means S304. These are readily available and nearly as strong as a Class 8.8 alloy steel bolt. Alloy steel class 8.8 has a UTS=800MPa and as the last bit is .8 it means its YS is 800x.8=640MPa.
Unfortunately the American System calls the strength spec “Grade” whereas the metric system calls the strength spec “Class”. To correctly specify a bolt you need to write or say the following: M12x1.75xlength 70-A4. There are other things as well, like fit, assembly tensions and manufacturing standards but these get complicated. The M12 bolt I have just mentioned has a pitch of 1.75mm, a strength of class 70 and its material is S316.
Any questions you may have please ask. Peter