Fabricating a Fiberglass hull

[Ryan Archer]

Hello,
My name is Ryan, and i'm interested in building a composite hull for a 13 foot dolphin looking ship, see pics. i plan on carving the plug out of foam and then fiberglassing over it, i'd then hollow out most of the foam.
I've been looking for a layup schedule for a boat of a similar size and cannot find one, is there a layup schedule that anyone knows of for a similar vessel?
thanks,
ryan

 

[tashasdaddy]

Re: Fabricating a composite hull

Re: Fabricating a composite hull

Ryan, welcome, you did not post your pics.

 

[erikgreen]

Re: Fabricating a composite hull

Re: Fabricating a composite hull

Sure, for a 13 footer I think most builders would go about 2-3 ply, where one ply is one layer of mat and 18 oz. roving. Actually a lot of builders would use a chopper gun instead of all that fabric, but it'd be the same thickness.

So I'd recommend the following, applied from the foam out, assuming you're using poly resin. Mat is 3/4 oz. or similar, roving is 18-24 oz.

Mat-roving-mat-roving-mat-surfacing veil (or cloth).

You could add another layer of mat-roving if you want extra strength, but a 13 footer would be find with two plys unless it's doing something unusual.

If ondarvr stops by this thread, all his advice is better than mine

Erik

 

[Ryan Archer]

Re: Fabricating a composite hull

Re: Fabricating a composite hull

Hi guys,
thanks for the help.
also here are a few pics.
ryan


edit...
i'm planning on using a rotax 440 with a jet drive.

 

[erikgreen]

Re: Fabricating a composite hull

Re: Fabricating a composite hull

That looks a lot like those "dolphin boats" in the news recently... semi-submersible, with a fast drive.

If you're planning on being acrobatic, use three plys on the outside, leave about an inch of foam, and then use two plys on the inside. The space between the two skins will act like the web in an I-beam, and you'll have a very strong hull.

And do post pics of the work, I've been interested in free-form construction using polyurethane foam and fiberglass for a while.

Erik

 

[drewmitch44]

Re: Fabricating a composite hull

Re: Fabricating a composite hull

Yea i looked that up. That looks like so much fun. Here is a link of what im talking about. That looks like a blast!!

http://www.youtube.com/watch?v=yTRbRrqRs7Y&feature=related

 

[Ryan Archer]

Re: Fabricating a composite hull

Re: Fabricating a composite hull

Thanks Erik, that is a HUGE help, yes i know, it's a shameless copy. i just had to have one but i wanted to do a few things differently, like use a jet instead of a vdrive and prop, for the lakes around here have a lot of rocks and then i could dock it on shore instead of the dock, also i have an old jetski that i will take apart for the motor and drive. so i wanted to build it to these specs, it's exactely 13 feet long, with a little more control surface area than the sea breacher, scale wise anyways,,
here is my price list

200$ for the foam to carve into the shape
300$ for the fiberglass and resin, i already have some of the required glass, i'll have to buy new resin though.
100$ for the materials to make the seat, i plan to drive all of the controls though pushrods, i'll have pushrods coming from the back for the rudder/elevons, and then the roll control, ailerons, will be controlled by sticks coming staight from the ailerons/fins.
50$ for interior stuff aka fake leather and stuff like that.

how does that sound? thanks,
ryan

That looks a lot like those "dolphin boats" in the news recently... semi-submersible, with a fast drive.

If you're planning on being acrobatic, use three plys on the outside, leave about an inch of foam, and then use two plys on the inside. The space between the two skins will act like the web in an I-beam, and you'll have a very strong hull.

And do post pics of the work, I've been interested in free-form construction using polyurethane foam and fiberglass for a while.

Erik

 

[Renny_D]

Re: Fabricating a composite hull

Re: Fabricating a composite hull

That looks like fun. Balance on the controls would be tricky - too much balance and those would be unstable at speed and too little and you'd end up with Samson arms. I wonder if you could also attach a compressor and a tank so that more submerged time was possible. It would also be cool as an automatic buoyancy control - as the tank filled it would become less buoyant. When all the air is gone the boat would be more buoyant. Either way it looks like fun. I wonder if the original builder has patents out on it. Let us know and post pics.

Thanks
Renny

 

[seven up]

Re: Fabricating a composite hull

Re: Fabricating a composite hull

Ryan, for "composite" you need another material added in to give the "fiberglass composite" designation.

Not trying to be a know-it-all but may be an issue with registration and insurance. Composite versus Hand Laid.

That design is a great idea. Keep us posted.




Enjoy

 

[Ryan Archer]

Re: Fabricating a composite hull

Re: Fabricating a composite hull

Thanks for the correction Seven up,
i always thought the resin was the part that made it a composite? probably a stupid question. but anyways i've been doing the interior and controls, and here it is so far.
ryan

edit....
i added a pic of the taileron control

Ryan, for "composite" you need another material added in to give the "fiberglass composite" designation.

Not trying to be a know-it-all but may be an issue with registration and insurance. Composite versus Hand Laid.

That design is a great idea. Keep us posted.




Enjoy

 

[erikgreen]

Re: Fabricating a composite hull

Re: Fabricating a composite hull

Ryan, for "composite" you need another material added in to give the "fiberglass composite" designation.

Not trying to be a know-it-all but may be an issue with registration and insurance. Composite versus Hand Laid.

That design is a great idea. Keep us posted.




Enjoy

Actually, any two materials count as a "composite". I'm building a plywood-fiberglass composite hull this winter.

I wouldn't put a tank of air in it... most scuba divers know that if you're breathing compressed air, you have to ascend slowly through the water, because you need to give your lungs time to vent the air that's expanding inside them (less depth = less pressure)... so coming up too fast pops your lungs, which is usually fatal....

But, this is a fun idea. I'd recommend a seatbelt

You could weight the whole thing to have positive buoyancy, but not a lot, so that when you drove your bow underwater you'd take a short trip under the waves. Dangerous in any kind of rough water, but you knew that I think.

Again, post pics as you do this so we can watch and comment

 

[marquette]

Re: Fabricating a Fiberglass hull

fiberglass over foam is what surfboard builders use. check some of the sights on building surf boards for some good advice. weight vs strength is a major concern for them so you may get some good ideas. but of course the smartest people will be on this site.

 

[Mark42]

Re: Fabricating a Fiberglass hull

If you use a glass product like 1708 Biax, it will save you a bit of time and trouble. 1708 biax is a 17 oz biaxial fabric with 8oz of mat stitched to one side. Cloth and mat all in one. Used for building hulls. The supplier I bought from said they use 3 layers w/ epoxy to make a 17' boat hull. I bet two layers would do for your project. I used one layer over foam for my Bayliner hard top and it is increadably strong . Check out the Bayliner hard top project in my signature below. Its still a work in progress, but I'm getting there.

The problem with alternating layers of matt and glass is the mat does not lay flat (strands poking up, varying thickness, etc), and needs a lot of sanding between layers to get a flat smooth surface. The 1708 is applied with the mat side down, so the fabric side is on top and smooth, needing minimal prep between layers.

Also, most mat is coated with a glue that disolves in polyester resin, but not epoxy, preventing the glass from making a good bond with the epoxy. So plain mat should not be used with epoxy. The 1708 does not have that problem.

Another issue is that polystyrene foam will melt with polyester resin, so epoxy must be used, increasing the cost of the project. If you use polyisocyanurate foam (what surf boards are made from) it will cost hundreds of dollars more than polystyrene foam. Here is a test of polyester resin on both polystyrene foam (the pink stuff) and polyisocyanurate foam (the white stuff). You can see how the polyester ate right into the polystyrene, but not the polyisocyanurate.

I did read somewhere on this forum a year or two ago that one member used polystyrene foam with polyester resin. To prevent the polystyrene from melting, they painted the foam with Elmers glue first. Guess that provided the barrier needed to protect the foam. Don't know how well it held up or how well the poly stuck to the Elmers glue. But it is something to experiment with, especially if it will save a few hundred dollars in foam and epoxy.

 

[oops!]

Re: Fabricating a Fiberglass hull

really cool project.....love to see it happen.....i think your budget might be a little shy....but they allways are.....

the foam plug will need a lot of finessing......but dont get too anal on making it smooth....as the glass will be rough after its layed.....just try to get the shape right......you will de doing a lot of fairing after its glassed

you will also have to get the centerline straight......a little bulk on one side more than the other might cause handeling problems......try to remember that when glassing

actually ..... i would check on a computer c&c machine in your area to carve the mold.....it may be possible to have that crutial step done by machine.....

i would also consider the use of epoxy with this proj.....but the poly should do fine.......

ill give this one some thought for you.......i wish you luck on this one....its a lot of work....if you have the guts to see this one thru......it will be a really cool toy.....and a fantastic project.

cheers
oops

 

[fdmsiv]

Re: Fabricating a Fiberglass hull

I would suggest getting a ton of those pink Styrofoam insulation sheets, glue em up and carve the shape you want. Use this as a plug to make a mold.

My other suggestion would be to look into vacuum bagging, it is done extensively with the wooden car Splinter.

How does the engine breath?

 

[oops!]

Re: Fabricating a Fiberglass hull

I would suggest getting a ton of those pink Styrofoam insulation sheets, glue em up and carve the shape you want. Use this as a plug to make a mold.

My other suggestion would be to look into vacuum bagging, it is done extensively with the wooden car Splinter.

How does the engine breath?

those pink insulation sheets are good....but in a sculpting situation....the pros prefer to use dence expanding foam.....as it can easily be sanded.....

and vac bagging somthing like this would be fantastic......use search...as two of our gurus here figgured it out a while back......

vac bagging would allow you to keep the weight down and totally saturate the glass while keeping the resin to glass ratio at the perfect 60-40 mix.....(some pros go as low as 70% glass 30 % resin

 

[jonesg]

Re: Fabricating a Fiberglass hull

I would suggest getting a ton of those pink Styrofoam insulation sheets, glue em up and carve the shape you want. Use this as a plug to make a mold.

My other suggestion would be to look into vacuum bagging, it is done extensively with the wooden car Splinter.

How does the engine breath?

I've done that, it works good.
Lay down a keel with formers notched into it.
Have the formers at several stages , then sandwich the pink foam with sandable carpenter glue and carve the foam to match the formers with an elec bread knife, finish w/ a sanding block and spackle.

The formers will keep both sides perfectly even ( if the formers are even).

It works easier if you can do the hull in 2 lateral halves, then you can make each half mold using any flat surface to lay up onto.

I would finish the foam with epoxy and light glass for good finish, sand then spray paint for perfect finish.

Take the drawing and project it to the size you want and trace the formers onto door panel or stiff cardboard.