Beginner needs help with fiberglass panel making

[UniCamper]

Hello from the cold Finland everyone,

This is my first post here, but I have lurked in the corners for some time now. Lots of good information here, thank you everyone!

My problem does not have anything to do with boats, but since people have a lot of experience with fiberglass I thought that I'd come here for advice.

I'm in progress of building my own camper truck and I since I have always been a DIY person I'd love to make pretty much everything by myself. The cabin will be based on a steel structure with the outer skin made from fiberglass.

Here is the problem: What would be a good method for making the fiberglass panels which will be attached to the steel structure?

At the moment I'm planning on making a flat "mould" from coated plywood and then laminate a couple of layers of woven fiberglass with polyester and make it waterproof by painting with good epoxy paint when cured. How does this sound?

Basically only one side (outer side) of the panels would have to be smooth and nice looking and the inner side needs to be smooth enough so that it can be glued to the steel. This is why I thought that just a simple coated veneer mould would suffice as the side of the panel which is facing the mould would be smooth.

The panels do not have to be the correct size in the mould as I can cut them into shape and if needed seal the cuts with polyester again.

The panels would have to be about 2-3 mm thick I think and as light as possible.

Here are a few pics of a similar project except that ready-made panels were used: http://www.ki7xh.com/boxskin.htm

So now you know what I'm going to attempt and how. I'd love to hear how other would do this. Please share your opinions and comments, thanks!

[Itchy&Scratchy]

Hey Uni
Just buy yourself some 8 x 4 ft sheets of melamine, give them five coats of release wax , apply gelcoat, wait for it to go off and laminate directly onto that, leave overnight or longer and pop them off - perfectly flat panel with a nice stippled finish. cut with an angle grinder, with a diamond blade or metal cutting disc. Dont forget to wear a mask
For extra stifness , add a layer of number 1 or 2 coremat in between your layers ..

Have fun

J

[jim lee]

^^ What he said!

[UniCamper]

Thank for the replies guys.

I have done some tests with gelcoat as I have never really used it before, but so far the results haven't been great... For some reason the gelcoat has flaked off the fiberglass in some parts of the test panels.

How thick should the gelcoat layer be and should it be 100% cured before I put the fiberglass on?

Could the gelcoat be replaced with epoxy paint? Would be cheaper than gelcoat I think and propably lighter, too. Any downsides?

[Itchy&Scratchy]

You are leaving the gelcoat too long before applying the laminate.

As soon as the gelcoat starts to gel, usually about twenty minutes at normal room temperature,you can laminate onto it.
If you leave it too long the gel dries out and reduces the chemical bond to the laminate.

Also make sure you use enough resin, dont skimp on resin and use a roller to laminate.
J

[Itchy&Scratchy]

The gelcoat technically should be no thicker than 1.5 mm so it can flex with the laminate, but up to about 3.0 mm is fine. Use a large brush and move quickly to disperse your gel, the faster you move the flatter your gelcoat will be, therefore easier to laminate.
No you cant replace gel with Epoxy- there willl be no bond between the epoxy and the polyester laminate( see other posts on this subject), gel is not too costly when used properly.

Your can always spray the panels with epoxy afterwards, but if you gelcoat carefully , you shouldnt have too.
J

[UniCamper]

Excellent! Thank you! This will greatly reduce the trial-and-error costs.

I'm looking at one suppliers web page at the moment and I have some questions about the weights or thicknesses of the materials. I'm sorry I don't know all the terms in english.

First the gelcoat. They suggest 2 layers of 300 g / m2. How does this sound?

Then a layer of "non-woven" cheap glassfiber mat like this: http://www.jatek.fi/auto-osat/site_m...katkokuitu.jpg, 300 g / m2.

Next one layer of 2 mm Coremat. How much resin does this need?

Last A layer of 280 g / m2 woven glassfiber. This is the surface that's going to be glued so I thought that the woven mat would give smooth enough surface for the glue.

So the panel would be constructed like this:

Gelcoat
Non-woven mat
2mm coremat
Woven mat

Does it make sense?

[Steve W]

Uni,the gelcoat does not want to be fully cured before laminating but it needs to be cured enough.Test it by sticking your finger in it,as soon as it wont transfer color to your finger its good to go.Another test is as soon as you can write it with a ballpoint pen.Do your testing on an area which will be outside of what you will be using.You can get a mil gauge from the gelcoat supplier to help you get the thickness right.
Steve.

Originally Posted by UniCamper

Excellent! Thank you! This will greatly reduce the trial-and-error costs.
Gelcoat
Non-woven mat
2mm coremat
Woven mat

Does it make sense?

No sorry,

thats insufficient and too heavy.

Gel
80 to 100 gsm mat (does´nt add strength just smoothens the surface)
240gsm woven fabric
coremat
240gsm woven fabric
120gsm woven fabric

is a layup that could be sufficient. That depends on the largest unsupported area of course, but you must take into account, that it has to bear its own weight too!
You can calculate, as a rule of thumb: weight of glass is equal to the weight of resin to saturate it.

Regards
Richard

[UniCamper]

Originally Posted by apex1

No sorry,

thats insufficient and too heavy.

Gel
80 to 100 gsm mat (does´nt add strength just smoothens the surface)
240gsm woven fabric
coremat
240gsm woven fabric
120gsm woven fabric

is a layup that could be sufficient. That depends on the largest unsupported area of course, but you must take into account, that it has to bear its own weight too!
You can calculate, as a rule of thumb: weight of glass is equal to the weight of resin to saturate it.

Regards
Richard

Largest unsupported area is approximately 600 mm wide and 2000 mm high.

Insulating foam will be glued onto the inside of the panels. This I think will add rigidity and maybe add some stress to the fiberglass panels.

You suggested several thin layers instead of thicker layers. I'm sure it is better this way, but why? What's the magic behind several thin layers?

Originally Posted by UniCamper

Largest unsupported area is approximately 600 mm wide and 2000 mm high.

You suggested several thin layers instead of thicker layers. I'm sure it is better this way, but why? What's the magic behind several thin layers?

Well, that is exactly what I feared. 600 x 2000 is a laaarge area for a unsupported panel on a (twisting and vibrating) vessel.

Leave the coremat crap. (eats resin and money) And do:

gel
mat 80 to 100
fabric-45°
fabric 0°
fabric+45°
all three layers about 160gsm

than your insulation foam glued on it (take the dense quality and make sure you buy the stuff that does´nt escape the room when Styrol is around.)

then put a layup

mat 80
fabric-45°
fabric 0°
fabric+45°
all three layers about 120gsm.

on your foam.

This way you have rigid sandwich panel that can bear some punishment.

Here you can find a little program to calculate laminates:

http://www.r-g.de/laminatberechnung.html

Though the website is available in English too, the prog is in German only. But easy to understand.

Regards
Richard

and sorry please I do´nt go deeper into it, I am with fever in bed.

[UniCamper]

Originally Posted by apex1

Well, that is exactly what I feared. 600 x 2000 is a laaarge area for a unsupported panel on a (twisting and vibrating) vessel.

Leave the coremat crap. (eats resin and money) And do:

gel
mat 80 to 100
fabric-45°
fabric 0°
fabric+45°
all three layers about 160gsm

than your insulation foam glued on it (take the dense quality and make sure you buy the stuff that does´nt escape the room when Styrol is around.)

then put a layup

mat 80
fabric-45°
fabric 0°
fabric+45°
all three layers about 120gsm.

on your foam.

This way you have rigid sandwich panel that can bear some punishment.

Here you can find a little program to calculate laminates:

http://www.r-g.de/laminatberechnung.html

Though the website is available in English too, the prog is in German only. But easy to understand.

Regards
Richard

and sorry please I do´nt go deeper into it, I am with fever in bed.

I can't really make sandwich panels because the foam needs to go inside the steel structure. Please see the attached picture.

But if I make the panels like you described, glue them to the steel parts, then glue the insulating foam inbetween and finally glue the inside panels (which are not shown in the pic). The inside panels may be something simple like plywood as they don't need to stand up against the elements.

Maybe this would lead to a good result?

Originally Posted by UniCamper

Maybe this would lead to a good result?

Yea!!!

And of course you can make a sandwich! Using ply on the inside is a very good idea, but cover it at least with some exterior house paint on the inner side. Mold and mildew behind a panel is not nice!pland some wooden reinforcements where you will install cabinetry or "bulkheads" (room dividers, walls).
When your steel tube framing is done and primered!!, drill three to four holes in the tubes (on a 200cm length) -and inject the cheapest window mounting PU foam you can find! It not only makes the structure stiffer, it reduces much of the noise and prevents "cold bridges" between in and outside.

Regards
Richard

[Itchy&Scratchy]

Nothing wrong with coremat, if you are laminating properly it doesnt use any extra resin, if you are using no 1 or 2 matt.

If you are using the thicker matt, numbers 4, 5 & 6 then yes- it does use extra resin
J

[UniCamper]

I guess I'll make some more test panels during the xmas time. Thank you for your help again everyone.