Fiberglass over XPS

[RJ Howell]

I started a conversation with the resident FG dude through PM and figured I should bring it on a thread for all to learn along with me.

I'm not completely satisfied with my PMF finish, as unique as it is. It did work and is holding up nicely, yet I don't think 'I' saved much vs fiberglassing it. I"m going to glass my next build.

I watch a video where a guy used Polyester resin, by his system, and it worked. The claim being it's less expensive this way. I did a pricing chart for myself and came up with just >$100 going polyester and >$160 going resin. To use the Polyester he had to put 5 coats of latex interior paint on the XPS and let that dry tp prep the board. So let's add 2 gallons to the cost and we have now I'm at $140 to $160, Polyester vs. Resin. Not much of a savings...

Another showed using Polycrylic vs. resin. https://www.youtube.com/watch?v=WuEHe6cmnp4 and compared. Interesting! Costs... I'm at $160 for the resin. The polycrylic(water based for low order) $50 a gallon. I figure 2 gallons to cover 28yds of cloth. I'm now at $100 compared to the $160. There's a savings worth talking about!

Let's talk some Pro's & Con's about going fiberglass over XPS. Especially would like to know if anyone has done any work using Polycrylic and cloth.

[saywhatthat]

that sample I sent you is just ploy resin over the right foam Why do all the extra work and cost?

[Pmullen503]

If that paint barrier fails, polyester resin will dissolve the XPS foam and all your work is trashed. Polyisocyanurate foam can be glassed with polyester resin.

Back in the day, we built cedar strip boats with polyester resin. Then we started using epoxy. A couple $100 more per boat than poly and worth every penny. The boats done with poly have been partially or fully redone after 20 or 30 years. The epoxy boats are still going strong.

Try a small project with both and make up your own mind. Polyester is really unpleasant to work with.

Fiberglass cloth over foam with waterbased polyurethane. I done a lot of that for RC planes. But we do it there mostly for light weight especially under a flat paint job. I've never tried with the heavier cloth I would use on a trailer. Might take a lot fill the weave of the cloth. Under a smooth glossy finish I'll use epoxy over wood.

If finish is your priority, use the material that lends itself to that. It's difficult to get a really flat smooth surface over foam. Something that looks good under glossy paint. The foam is too soft, even with glass over it to sand it truly flat and straight. I would use either a surface material that has the look I want or fiberglass and epoxy over plywood for paint.

A foamie is what it is. You get lightweight, easy and cheap construction. You also get a certain kind of finish.

[greygoos]

that sample I sent you is just ploy resin over the right foam Why do all the extra work and cost?

What specific type of foam are you using and where are you located ? They type of foam that you are using may not be available in all areas. Thank you

[RJ Howell]

I was hoping for 2.5oz cloth. Could 4oz..

I'm going to pickup a small package of cloth to test out. I have fresh polycrylic here and will pickup some resin. Not sure what choices in fiberglass I will have though.

[Pmullen503]

Either of those would work. The heavier, the more dent resistant. However, you can steam out small dents.

I suspect it will take many coats of polyacrylic to fill the weave.

[RJ Howell]

Either of those would work. The heavier, the more dent resistant. However, you can steam out small dents.

I suspect it will take many coats of polyacrylic to fill the weave.

And that would spend the savings and costs would then even out.. In the video he used 3/4oz cloth and only two coats. He speaks of it being so much lighter, but probably due to thickness differences in coats. So I tend to think the same thing, more coats.

I tend to lean towards resin, but mainly due to experience with it. I say, little of mine and mostly from you folks! I'm trying to source some 4oz (or lighter) locally and so far I'm finding 6 & 8oz everywhere. Won't make a good test for my purpose.. I'll keep looking.

[RJ Howell]

If that paint barrier fails, polyester resin will dissolve the XPS foam and all your work is trashed. Polyisocyanurate foam can be glassed with polyester resin.

I think I've ruled out the Polyester Resin now. Cost cost savings is little for the risk and added time/labor. Weight savings is seems to be 25%, again not really enough to be concerning.

Try a small project with both and make up your own mind. Polyester is really unpleasant to work with.

And here I though it would be better to work with.. Seems like strike 3 to me.

If finish is your priority, use the material that lends itself to that. It's difficult to get a really flat smooth surface over foam. Something that looks good under glossy paint. The foam is too soft, even with glass over it to sand it truly flat and straight. I would use either a surface material that has the look I want or fiberglass and epoxy over plywood for paint.

This will be on a boondocking camper so blending in is more the thought. No high gloss for me!

A foamie is what it is. You get lightweight, easy and cheap construction. You also get a certain kind of finish.

[saywhatthat]

Wgreygoos What specific type of foam are you using and where are you located ? They type of foam that you are using may not be available in all areas. Thank you

We use Polyisocyanurate foam Can get at any box store home depot ..There so much BS on the web
from dum ass about poly .Why are most boats made from poly planes cars ..... This 2020 ply is not like it was in the 50 &60s. IF YOU HAVE SOMETHING that will soak water covering with poly is not the Best .Anything thing more goes to a fool and there money are soon parted.
Risk and added time/labor poly is way faster Epoxy will kill you faster . With the new poly .It is the MEK that has the smell use 75% then push it into the sun for a day a lot less smell

[tony.latham]

Why are most boats made from poly planes cars ...

Mike:

What glass car or aircraft are made using polyester resin? I know of lot aircraft and they are made using epoxy/glass or carbon fiber. The trend now is the use of prepeg carbon fiber. Which of course is epoxy. (I used to be in the experimental aircraft world.)

Here's Boeing whipping out a carbon fiber/epoxy fuselage:



There are boat manufacturers that still build glass hulls using a method of spraying on chopped fiber and polyester resin from a pneumatic gun. It's a cheap way to make a heavy boat.

Here is the sparyer in action. You can almost feel it getting heavy.



I don't know about glass cars. Perhaps you're onto something and you know what aircraft or quality boat manufacturer is using polyester resin and can set the record straight.

Either way, there's a cold one in my cooler if we (hopefully) run into each other.



Tony

[saywhatthat]

Corvettes tell the last 10 years then when to vinyl ester that is a poly. Just for under 40%
SR 71 A10, F111 airplanes the new plane by airbus , Boeing Business Jets,Embraer-Empresa Brasileira DR AeronÁutica,•Gulfstream Aerospace,Textron Aviation most Kit cars
YES choppergun is crap spraying on chopped fiber I am talking Hand laid. At the shop I receive my Glass from Builds parts for kit planes kits helicopters. Yes they use prepegs They have a 13 meter autoclave .
Ask yourself why most trailers in Europe are build with foam and poly.
With many prepegs The cost is lower .Labor air quality and much easier for any thing that has pedigree (doc. from start to finish )
We are talking home built trailers..
Tony With your last build you have open the gates of HELL. First a bit of epoxy Then soon in New York asking for a bit of poly .On a darken corner .Which no 12 steep can help.
You are right Epoxy should go over wood
Added The Mosquito XE Ultralight Helicopter airframe is a unibody construction made entirely of high quality fiberglass in a vinyl-ester matrix .Type of Ploy.CH-7 Kompress Charlie,The pod-and-boom fuselage has a fiberglass cabin .

[tony.latham]

SR 71 A10, F111 airplanes the new plane by airbus , Boeing Business Jets,Embraer-Empresa Brasileira DR AeronÁutica,•Gulfstream Aerospace,Textron Aviation

Mike:

The SR71 was made from titanium. The A10 is an aluminum monocoque aircraft. The F-111 was made from titanium and aluminum (and retired twenty years ago).

You and I are going to disagree concerning modern airliners being made using polyester or vinyl ester resins.

From: http://www.dexcraft.com/ (They specialize in carbon fiber.)

Resins are classified into two types:

Epoxy resins– top class resins used for manufacture of elements of F1 racing cars, Boeing airplanes, frames of professional bicycles, professional surfboards and other elements that offer top quality, strength and low weight.

Polyester resins– resins of lower grade used for manufacture of huge and massive elements that are not required to meet some special requirements regarding construction e.g.: bath tubs, large water tanks, slides etc..[/color]

From: https://www.compositesworld.com/articles/boeing-787-update

Prepregs for primary structure
Without a doubt, the largest supplier of 787 composite materials is Toray Industries (Tokyo, Japan). The company is providing its trademarked Torayca 3900-series highly toughened carbon fiber-reinforced epoxy prepreg for the 787’s primary structure in unidirectional tape (various widths), narrow slit tape (for fiber placement), and woven fabric forms. The majority of the 3900-series materials will be made with intermediate modulus T800S fiber.

Carbon fiber –and that's what the aircraft industry is using for a layup- doesn't play well with polyester resin. You'll not be able to find a prepeg carbon fiber cloth that isn't epoxy.

I don't have a clue on how the Corvette body is manufactured today. Maybe they are using polyester.

Now, you make some fine teardrops using polyester resin and I tip my hat to your builds. You certainly don't need to bump up to carbon fiber prepeg, so here's another toast to you:

Tony

[saywhatthat]

Should have posted they use parts that are made from poly. aircraft industry is using for a layup- doesn't play well with polyester resin .But in cars ,utv, boats. Many have Carbon fiber layup with vinyl ester and backed up with poly. And some use home depot crap for the Whole thing
My first job I lost was over a repair job on a f111 from the UK I Missed up on the paper work on where the poly came from' for a repair.
You forgot to add AX-4210 Flame Retardant, Modified Vinyl Ester Aramid Prepreg ,AX-4230 Flame Retardant, Modified Polyester Aramid Prepreg ' Product: F149. High Strength, Structural, Flame-Resistant,Laminate Grade Polyester Matrix. Polyester prepregs cure temperatures from 220ºF to 325ºF with cures times from 30 minutes to 2 hours. That what they use at where I get my fiberglass.
And the many phenolic, polyester, cyanate ester, vinyl ester and polyimide. Prepregs Which few know about that have not done some work in compose. Just a paper pusher
Just think if we got together What cool trailer we could build with AX-5112T Off-white on black with AX-5110 honeycomb foam panels black walnut inter. With rattlesnake hides
My hat off to all wood builders. For me to hard to many tools way to much up keep. The biggest thing is if I mess up so much cheaper and easer to fix than wood.

[tony.latham]

With rattlesnake hides...

Tony

[GPW]

RJHowell said : "I'm not completely satisfied with my PMF finish, as unique as it is. It did work and is holding up nicely, yet I don't think 'I' saved much vs fiberglassing it. I"m going to glass my next build.”


We’ve heard this a few times before ...