At the moment carbon is legal. There was a proposal to ban it in the class with the reason being to try and keep costs in control.

I think the way the rules are currently written it does not matter. A min tip weight on the mast, min weight of the platform and non-glued beams pretty much makes the use of carbon a non-issue. The potential performance difference is limited with these rules and the cost to go with carbon is significant. If some one want to have bling they can, but IMO with these limits it still will not win you any races.

Agree 100% with Matt on carbon use and the class rules.

Our carbon use is a special case due to some very special logistical issues. Like having to import suitable sections while the carbon weavers is in our backyard. Carbon beams is a really poor way to use carbon.

I think part of the reason for non-glued beams is that the width of the platform wouldn't allow the boats to fit into a container. Goodall was the one who pushed this from memory. A-Cats can get away with it as they are narrower and just can fit into a container.

Well Rolf, my only real concern here is about drilling holes into carbon tubes, through bolting them, and any potential crushing if over-tightened, or cracking if there is any slop, at the drilled hole area.

Are they (the tube builders) going to beef them up in the area of the holes to be drilled?

You are speaking with the tube builder to be
There will be compression chocks inside the tubes to handle compression loads and to stop any deformation. Just like what you find on a Marstrøm Tornado.

Drilling holes is not that bad, as long as there is no movement of the beams while they are under load. Overtightening bolts on beams is a big no-no in any circumstances. Stripped nuts inside the hull or crushed alu beams is no fun either.

Carbon beams are legal. Glued in beams are not. That is where my illegal coment was coming from.

Finally some activity on the forum again. It has been way too quiet for some time now!

Since there is some interest on the topic, here is the post about the first test tube we made, in glass. Learnt a lot, but there is still more to learn before we wet out any carbon: http://woodastic.blogspot.com/2009/05/first-tube-test.html

Rolf - No 45 degree fibres in your beam? Might be trickier to build by hand but definitely better torsion properties with some.

There will be 45deg fibers in the beams, yes. Will have to lay up uni to do that. I'll dig out the lamination plan and post it before we go. Still building hull panels so the test tubes are a side project for now.

I got some Divinycell PVC foam to test out - 6mm H60. A bit underwhelmed... not the magic material I thought it would be - flexible, and feels soft wonder why it costs so much more than blue foam or foam core from the Art shop..

The best way I've seen for a home builder to do beams is by Dr Mark Drela of MIT. You need to get low temp prepreg carbon unidirectional and roll over an aluminium tube thats covered with mylar release film. You have to build a makeshift oven but it only needs 275 deg Fahrenheit. You need to bind it with shrink tape before you stick it in. First the outside heatshrink tape tightens, then the epoxy liquifies and the excess soaks into the paper as the carbon fibers get compacted, then the
epoxy gels and finally solidifies.
http://www.cstsales.com/carbon_prepreg.html

$40 per pound - maybe 7lbs per beam? $280 for hitech carbon beams...

Unfortunately, I dont think they can ship prepreg to Singapore since it needs to be kept refridgerated.

Shane

Pilgrim, the advantage of divinycell over your blue foam will be in the shear strength. This is the crucial property when designing a foam sandwich structure. The flexibility is actually an advantagous feature not only in building but also in the strength of the final structure is it means the skins will take the majority of the load instead of the foam. Most people would use primarily 80kg foam for your application. The 60kg will bruise easily unless you put a lot of glass/carbon over it.

Thanks Scarecrow, will keep that in mind. If I do use divinycell I will probably go all the way and use carbon fibre. The extra USD 1500 or so will repay itself if I ever want to sell the boat.. I love wood but people are unfairly prejudiced against wood in boats except for teak.

Drew up the forms incorporating some of the suggestions that Ncik gave - more volume by using a constant radius circular chine and a narrower transom.. Here are the hand drawn forms... I now realise it looks weird because I dont have the waterline horizontal..the transom bottom should be aligned with the bottom of the bow
drats.. I
I'll redraw it tomorrow but now its late..

Looks like a "modern" hullshape. I am not qualified to voice any opinion other than that.

Have you decided on a building method yet?


Keep it up, and do create a blog to document the process if you get to the implementation stage.

Looks pretty good.... the real trick now is to draw up the corresponding water line and kiel line and make sure you're happy with them.

Just another quick note, and this may happen later.... see if you can let the lines flow a little more.... not just straight line to a radius. This will make it easier to get a nice surface when you get to that stage. This is pretty important in CAD modelling but the same can be said in the real world.

http://en.wikipedia.org/wiki/Geometric_continuity

Try the other way around:
Fee!ship
or the free version of delftship. Don't ask me which one is better.

The basic idea is that you control the shape of the hull indirectly with a few parameters. Main characteristics as displacement, prismatic and block coefficient, water plane area etc. are immediatly calculated. As a result you get the section shape and a hull surface which fulfils geometric continuity. You can even check which parts of the hull are developable.
A few hours spend in lofting can save days in the workshop...

Cheers,

Klaus

Thanks all, still a bit green so I will probably try to Keep it Simple.. Freeship is fun to play with and one day I will understand how to use it fully...

Hey Rolf, now that the word is out, we are all coming over! You got a couch? ;^)

http://www.msnbc.msn.com/id/33178495/ns/world_news/?GT1=43001

This probably belongs in that "drill" trainwreck of a thread
There is lots of room here and we could need some new people.. You are going to hate both the summers and winters though, especially if you settle north of the artic circle which is where there is a lot of room.

Tim,
Rolf has a couch and plenty of whisky too!