Fleece/cotton fiberglass boat

Finding that video and stills collection took a good hour or so, as I couldn't for the life of me recall where I'd seen it before.

The reason I found it originally was because of a plan I had (which I may still do) to re-skin my very light skin-on-frame boat Aero with an even lighter aircraft fabric, shrink it tight and then lay up a Kevlar/glass/epoxy skin over the top, to hopefully retain some of the weight advantage of the light structure, but give it a bit more abrasion resistance. Shrunk Dacron SOF is great, plenty strong enough against impacts, but not very tolerant of abrasion, I've found.

 

Sure to be plenty of interesting old footage on that British Pathe site, BBC Motion Gallery is another one worth investigating.

 

thank you! someone finally got what I was talking about, when you haven't done it yourself its easy to bash. Pull some tshirt over a frame and staple it in place, its pretty easy to make it not sag when you wet it out

 

Well, if you haven't done it yourself, it's also easy to say it's easy. The process has been around for a long time, if it was a good way to build a boat you'd think it would be more widespread. The film was a little misleading, going from step 1, stretching the fabric, to step maybe 300, cruising around the lake. I can think of a lot of possible problems, first would be how to keep t-shirt material that is woven to allow it to stretch from stretching and sagging when it's wet out, the next would be all the probable filling and fairing required, another would be attaching your frame to the hull, as the staples through the cloth won't work. But, maybe it is a better way to do it, you should try it.

 

As I stated before, never done on such a large scale, however the staples are just to keep the fabric stretched while your applying resin to the shell, the resin doubles as adhesive, when your shell is done you could try to pull the staples out but id would be near impossible to remove your frame from the shell regardless of staples without destroying it, it sticks (for lack of better words) very well, I will probably give this a shot something small scale before I waste a bunch of materials, flat back canoe or something

 

Dress form

You could do as BMW did and make a strong frame to strech tough fabric onto for some interesting shape shifting. http://www.wired.com/autopia/2008/06/bmw-builds-a-ca/

Rapid mold making is a long sought ideal in boat development, your on the right track. C-flex is the best right now, an old system proven for its dual curvature capability and strength.

David

 

Yep, why not? The solution is simple: experiment on a small scale.

M

 

The shape which can be obtained by stretching a fabric over a frame has a limitation. The surface will have saddle type curvature unless there is a pressure differential across the fabric surface or the fabric has bending stiffenss. There is a limiting case possible of a developable surface but this requires particular combination of boundary frame shape and fabric tension. Of course a flat, planar frame will result in a flat surface. Simple concave or convex curvature is not possible without a pressure differential or bending stiffness.

The concise mathematical expression is the surface will have non-positive Guassian curvature everywhere in the absence of a pressure differential or bending stiffness.

The "Sock Boat" uses cardboard under the fabric for most of the bottom, presumably to change the shape of the bottom.

 

Shapes

No, the speaker forms have a simple minimized round frame stood on webs and the fabric tension forms the flare and majority of the shape with no underlying cardboard or "stuffing to make the shape. True you are limited to negative or convex shapes with tension structure, but that presents an inventive opportunity. (I have put some thought into this) to inject a slight (not inflate) positive air pressure withing the framed "fabric structure" for a fuller cambered surface styling. The attractive aspect of a tension fabric/cast base for incremental lamination is two fold. The first is that for very little effort and cost you can generate a large complex sculptural shapes. The second thing is the overall inherent fairness due to the even tension of the larger panels which is a very costly, labor intensive and a highly skilled endeavor otherwise. The minor surface roughness is more easily corrected while the longitudinal fairness is not.

 

You could use nylon as the sock, then rip it out as well, but I can't see avoiding oil canning and the resulting huge fairing requirements to fix it.

 

I'm curious what you were responding to with the statement quoted above.

 

The choice of shapes is limited and control of the shape and local dimensions is challenging unless a large number of frames/stringers/etc are used.

The surface will generally have a discontinuity of slope as well as curvature where any internal frames/stringers/etc contact the fabric which limits the extent of the fairness.

 

Dacron skins over a wood frame are a whole class of Kayak building.
Bill Hamm teaches a course on building a dacron covered kayak, then fiberglassing to get a rigid shell. I believe he also builds boats on commission.
Check out the Guillemot Kayak Forum and search on skin on frame, and Bil Hamm.

There some of the forumites have built skin on frame sailboats, but not with rigid skins to my knowledge (which is probably limited). Search for Dave Gentry

http://www.kayakforum.com/cgi-bin/Building/index.cgi/page/1/md/index/#m_215803

Typical skin on frame results in boats which look like plywood stitch and glue, since the skin only touches the longitudinal members.

Take a look at http://www.Yostwerks.com for examples of SOF kayaks and their construction. This is not the only method. But the outside shape is still the same - flat "planks".
Check out http://www.capefalconkayaks.com for the more traditional frame construction

 

you can also use aluminium wire to make your frame and use a hot glue gun to hold it together and then pull a fine glass cloth over the frame and resin that !! when its hard just gently add a layer of csm and after that you can add what ever you want . depending on what its is you making the wire can stay


so why bother with things that are not compatible like fleece you need to stay with the materials you intend to use throughout the making of what ever it is !!

 

I greatly appreciate what everyone has to say, I wont pretend to know anything about boat design, I want to say that upfront, and I dont mean to insult anyone, you all seem to know boat design... has anyone actually built a fiberglass enclosure using the method im talking about?