End of the sandpaper ... for now

Hi there,

I have decided that I'm fed up with sandpapering, so bullocks if the mold's not perfect. That just means there'll be a better tack on that boat (when not flying of coarse). I'll do the other side differently (build male mold -> polyester female).

Just to log my experiences of this first battle against DIY:

- Difficult to carve nice concave surfaces, so avoid if possible. Nevertheless adapted tools are mandatory:

- Steps: build the near-plane surfaces with plywood, roughly carve the radius's out of plaster (don't use a GF board as I did for the front roof, as it isn't stiff enough and keeps cracking the junctions). Finish the carving with polyester putty (don't use too thick layers as it shrinks allot and deforms the wood ! Once nearly finished shaping, try a layer of can paint, as it lets you see the last bumps and holes better. I used a "filler" can paint in the end and alternated the paint colors to see how much and where to sandpaper.

- I used sandpaper up to 180 to make the shapes, used mainly 240 to remove the excess paint layers and finished by hand (no wedge) with 400 and finaly, just before the wax, 600.

Forming the foam is next, then I'll clean up the workshop as there's a cm thick layer of dust which wouldn't be appreciated in the carbon.

Thanks to daddy for the help and advice (his hands have seen kms of sandpaper). Cheers from snowy Lausanne.

Back on track

Hi fellow sailers, sorry I was a bit long, but the water looks so nice in the wind... Now that it's a bit cold for some time, I'm back in the workshop !
The first half hull mold (female) is nearly finished after too many hours of sand papering. I'll do the next one as a male and mold it with polyester. Like that I'll have done it both ways. So hope to show some carbon soon.
On the other hand, I've done some simulations of the hull with the french open source FEM program "Code Aster". I'll show you some interesting results soon too.

Thanks for your posts, have fun !

Material test

Hi,
I did a test with the chosen carbonfiber and foamcore and it's no bad at all ! The unidirectional fiber (see previous post) is composed of three layer, two unidir at 45° sewn together covered with a last layer at 45° lightly glued (or just pressed). As this last layer comes free easily it's got to be on top for wetting with epoxy. This weave seems to take more time to suck up enough epoxy to glue well to the foam afterwords, so one must take care it's wet enough on both sides. The good news is it definitly leaves no pinholes and assures a watertight surface.

Mouldwise : the mould is nearly finished since to long ... I needs quite some more craftmanship as I expected. Initialy the female mould is out of wood, glassfiber plates and polyester putty. The putty shrinkes when hardening and is very hard to carve or sand. I now use plaster which expands (slightly) with drying and is softer. I'm looking for a hard wax for the ultimate smoothening, but it must stand the curing at 60°C...

That's it for now, best winds.

Pinholes and thermofoam

Hi,

I'm back at work, slow but steady. Latest news, I changed carbon form twill to unidirectionl ; it's two layers of unidir at +/- 45° sewn together. It avoids the pinhole problem. Remember the youtube vid where there put an extra layer of kevlar to assure water tightness. The reseller said it'll be a bit more difficult to use though.

I also ordered Airex R63 thermoforamable foam, it seems to be the best solution, but I'll tell you as soon as I get it and do a test.

I'll do the curing at 60° myself, so I bought polystyrene boards to build the oven, that'll need testing too !

On  more point : if you choose to do this, don't copy me and skip the male mould to build a female mould from scrap. It's so much harder to carve concave shapes and to make it slick...

Spring's already near, but I'll be sailing on my 470 in stead of a moth for a while more.

thank's for reading.

who want's a sandwich ?

Spent some time at work this week-end, the first half hull mold is well on it's way and I did my first sandwich test with the rohacell and glassfiber just to pick-up the trick. I definitly need some more practice... and different foam. I did a little review to compare as you can see.

I didn't find an other way to answer the posts, so I'll do it here. I intend to build foils too as that's he most interesting part, but I've got a lot to learn till then...

Next steps : sandwich sample test 2 ; order new foam (maybe 2 different) and some carbone fiber ; finish first hull mold.

See ya.

Thanks !

Hey ! Thanks for your posts, all very useful advice that I'm studying now. Really honoured to be part of the moth community, might win my wings soon ! My working pace is maybe a bit slower as some of you as I haven't planned any vacation for this (thicking about it though). It might just take some time before I start thinking of the foils for example... aber wäre eine gute Idee.

I would like to thank all my former colleages of Firbourg for contributing to my boat project. It is definitly very usefull ! I just bought my first load of stuff from the local composite retailer and hell it's expensive.
On this week's skedule there's finishing the frame of the hull mold and doing a first test of a flat sandwich plate (with a leftover of glass fiber). I chose to copy the half hull method of the amercans on youtube (see previous link).
The test foam I bought is 5mm Rohacell 51, but it much too stiff, not at all what I expected. I'll try Soteco next, it only comes in 6mm thickness, but that'll do. It's supposed to be more flexible and it's also available partly sliced (pic) for really sharp curves.

I can heat the workshop up to 15-20°C as long as it doesn't freeze outside, hope that'll do for the fast epoxy I bought (15min working time). I also took a slower one with 90 minutes working time, thtat will definitly need curing ; I might need to do a test at the car body shop next door which has a 60°C oven.
Well I'll try and get some pics for next week to make this look a bit better. Thank's for reading !