fiberglass panel boat building

[rongo]

I have a plan for an open 20ft fishing boat build with plywood.
i would like to build this boat using fiberglass panels these panels would be made laying up fiberglass on high gloss formica sheets, [ that part is simple to make] how do i convert the shape of the boat to these panels? [ so when i bend these panels i get the correct shape, is there a formula for this, what is the best way of doing this?
any help would be appreciated
thanks paul

[midnightkayaker]

Probably not much help,just a few concerns...If you laminate the formica panels and then stress them into the shape desired it seems you would have a lot of de-lamination problems. You could construct the hull out of the panels and then glass them up but this would certainly be a lot tougher than working on a horizontal surface. Do you have a stich-n-glue design in mind. Have you done any test panels? BTW cool idea.

[Stephen Ditmore]

Actually the method works well as long as you are not using an overly thick sandwich. See info on DuFlex at www.atlcomposites.com

Yacht designer Paul Bieker of Seattle is well qualified to advise you, as are Mr. Gardiner and his wife Ginger of Consolidated Boat Builders and Harry Schoell (www.pulsedrive.net). Ginger has written about this for Professional BoatBuilder magazine.

If you have patterns for cutting the plywood panels I would think the only change would be that made necessary by your method of joining the panels at the edges.

[Doug Carlson]

My work experience is not in boat building but in developing tooling for the production of commercial, electronic, and aerospace products. Your technique for creating a composite panel with a "finished" surface seems like a good one. My concern is that you wind up using the inherent strength of a cored laminate against yourself. If you could warp your formica to near net shape before layup you would shift the inherent strength to your advantage.

I guess the critical questions here are: "Is the tension created in the formed plywood of the original design a positive, neutral, or negative attribute?" and "Do the characteristics of a preformed panel override these considerations?"

[rongo]

Thanks for the help what i am thinking of doing is to just use the flat panel [ no foam sandwich] and reinforcing the inside of the panels with wooden strips to add strength to the panels and to keep the shapes. do you think this idear will work? set it up as a stitch and glue system to get the boat shape

[Stephen Ditmore]

Yes, I think it'll work, but just for the heck of it I still encourage you to get and read material on DuFlex from ATL Composites.

[flame]

As far as construction is concerned, plank thickness seems to be the important parameter taken into account when re-drawing formers, transoms etc (I suppose plywood gives thinner planks than foam sandwich)

Using planar moulds for foam panels and bending them over simple formers is done by Derek Kelsall/AU (http://www.kelsall.com - look up KSS construction). He uses longitudinal grooves in the area of small bedning radius to reduce stress, and sometimes even omits sections in the lamination process.

In general plywood has the same bending behaviour anywhere, in both dimensions, so a foam/glass structure is quite similar (unless you use monodirectional glass matts etc)

You can influence the bending behaviour of a foam/glass structure by large when you start cutting carefully into the foam after one side is laminated with glass/epoxy. By this you can successively approximate to the desired shape.

Good luck
Mike

[ted655]

You stress the panels over bulkheads mounted on a strongback. after fastening the hull is lifted clear of the bulkheads/form. Do a search for KSS boatbuilding. There is also a Yahoo group on this.

[mmd]

I have designed and built boats of this size using this method. It works like a charm. Only difference in the ones I did was that we used no wood - we used structural foam (in our case, CoreCel) for stiffeners. If the plans do not have the developed panel layouts, you have three options: Either learn the lofting techniques to develop panels (time consuming and possibly brain destroying), buy a computer program such as PlyBoats and learn to input your desired boat shape and have it develop the panel shapes (time consuming and possibly brain destroying), or set up the moulds for the boat and wrap cheap door-skin veneers or stiff cardboard panels around the moulds and mark the panel perimeters on it to use it as a pattern for the panel. The books mentioned above are all good references, too.

[Guest]

use a mold, its the only way. Use gel-coat, mat, byaxle e-glass, and vinlyester resine, no more the 2% mekp, air roll (air is your enemy) good luck

[Tom Lathrop]

Sam Devlin, who has probably built more S&G boats than anyone else, uses panel shapes lifted off a model to develop his shapes. He explains the method in his book. Some adjustment may be required to fair the lines but it does work.

A number of designers use software that when combined with a bit of knowlege of the medium, will output correct panel layouts. There are several on the forum that can do that (not me).

Unless you are familiar with the mechanical properties of fiberglass panels as opposed to plywood, you need some study in order to make the transition from one to the other. Uncored fiberglass panels will need to be much heavier than plywood to get the same required stiffness. That is why all weight sensitive boats are built with cored panels. I doubt that the boat you have in mind can be built in the way you want and still have equivalent, or even nearly equal, performance to the plywood model.

The current issue of Professional Boatbuilder has an article on pseudo cores that should be of interest to you.

I am beginning to look into the issue of converting a plywood boat to fiberglass myself but do not feel that I am nearly knowlegeable enough to do the project yet. My advice is to search for information and study. Questions to forum members, as knowleageable and complete as the answers may be, will not give you adequate information for the job you want to do.

[JR-Shine]

I am building a 16 foot flats boat stitch and glue style using Divinycell. I basically have the outside of the hull done and will flip it pretty soon. It was very easy to bend and shape. One drawback is I had to use more biax material then I would have if I'd used plywood, which results in buildups on the chine, transom, and keel that require a lot of fairing.

I am currious about this idea of using a fiberglass panel, but why not use a foam sandwich.

Joel
Boatbuildercentral.com

[War Whoop]

The Foam sandwich is the best method instead of mica I would use Mirror or Glass...The shape is not hard to develop and the Chine, Keel and Transom Junctions you just let the core in for the glass... A Core-Cell A 600 should provide the stiffness needed and only Glass on the outside the advantage is the finish is about there. The Bead And Cove is another very nice System.