Mould less fiberglass construction

Hey guys, this is my first post here as I am new to this forum & to boat building in general.
I have been reading the posts in here for a couple of weeks now and it seems that most of you who build fiberglass hulls tend to use a mould which in my opinion takes up a lot of time & adds to the total cost of the boat.
Now I have been doing custom installations in the car audio industry for a few years & in particular, custom interiors where by I completely strip the interior and create new panels out of fiberglass using an MDF frame.
My question is, if you were to build a skeleton of the hull u want to build (like you would if u were going to make a mould) then used some sort of stretchy material ie cotton etc and then staple it to the frame where ever possible (as much as possible) then apply a coat of catalyzed polyester/ epoxy resin, it would harden and form a shell on which u could then lay up your fiberglass. You could then insert the core material of your choice & continue as normal to finish the hull.
I would think that this would work, however if I knew all of the pitfalls of boatbuilding then I wouldn’t be an amateur
So any opinions are welcome.
Cheers.

 

I am unsure if I understood your post. However, I will offer this point.Generally the use of molds allows the builder the ability to create the exact form of the boat, or parts of the boat, in female form that he desires. Building hulls over a male mold is common when the medium is wood (Cold molding for example...) There would be way too much time spent addressing the fairing issues if one tried to build with polester or epoxy in consort with fiberglass substrate.

 

dr.j I am sorry if my original post was unclear, but what i was asking was whether it would be possible to build a hull without a mould.
As for your comment about the time spent in fairing, I may be wrong but wouldnt that be somewhat less than the time taken to produce the mould in the first place? As i said i have never built one so i cant say for sure but as i see it, all u would have to do in relation to fairing would be to apply some 2 part body filler and sand smooth, as after fiberglassing u would have a rough surface due to the glass fibers, the shape in general should be perfect if u built the skeleton acurately.
Please, if i am way off track, feel free to put me on the right one.

 

It is always possible. Is it labor AND dollar cost competitive? Many would say no. Professionals, almost without exception, use some form of a mould.------------------------------------- To do what I think you are asking. Would require 4' x 8' sheets of pre made fibreglass sheets or boards that could be cut on power saws. That market does not exist now.

 

Yes it is possible to build one hull without a "mould". By using cross sectional forms and strip planking. You can also do cylinder molding. Google Kurth Hughes.

 

Usually the expense of making female molds is offset somewhere around 3-5 units, depending on complexity.

Yoke.

 

RAVenous-
I am in the middle of making my first boat mold. (20 foot Shark catamaran sailboat). I am using 3/8 ply for the formers, 2x4s for the backbone. The stringers will be 3/4x3/4 cut from 2x4's. So far, I am out $34 for the wood and $8.24 for the fasteners.
I expect to spend $40 more for the 2x4's to cut up, and maybe $10 for the spackling compound.
I did splurge $2.42 for three new jigsaw blades, of which I have used one. I already had the drill bits.(Yipster, if you are reading this-sorry- my old dull bits still work!)

I realize I may be a cheapskate, but even with my standards this is not too expensive of an adventure.

I would advise using a thicker plywood- I was just trying to keep the mold light because I have to move it around.

Rob

 

Building in fiberglass without a mold has been done for years. You build a framework of molds and cover them with fore/aft battens about 6-8 inches apart. Then you fasten the foam of your choice over the battens, fastening from underneath with small screws. You then fair the foam and layup the outer skin. After you have sanded and faired it, you pull the screws from underneath and pull the hull from the mold/form. You flip it over into a cradle to maintain its shape, fair the inside and layup the inner skin and structure.

Core-Cell also sells a product called bead and cove strips which allow you to plank right over your section molds with the foam, fair and glass - skipping the batten step. A book has been written explaining how to do it by Andre Bilodeau.

If the boat is a very simple shape, you can also build a female mold from Masonite and lay the part up inside it. After your done, take it to the dump.

 

Cflex

Glen L has a how-to tutorial on using C-flex which was developed just for the technique you are interested in using. I don't think would give you as light a hull as the foam methods already mentioned but it is another method to consider.

 

RAVenous,
The term is "one-off" fiberglass or composite boat-building and is certainly common, in both amateur AND professional boatbuilding. Timm has well described how it's done above...
frank

 

Alan Vaitsis published a book some years ago titled "One Off In Fiberglass" in which he explores all of the methods that he used in his yard. If you can find his book it is worth having on the shelf.
Also Corecell is produced as CorePlank, 2 inch wide cove and bead planking strips used for laying the shape on the forms. This is then glassed, faired, and supporting cradle is built and the hull is turned and the interior work is started.