Weight difference of foam vs plywood

[katozzi]

Well, we are pretty close to making a decision and a game plan.
Id like to use a foam wall and carve it to our shape, we'd have wood paneling on the inside of the cabin for a nice homey feel, and I want to fiberglass right over the foam and have that be the exterior skin. I have worked with fiberglass before and can attest to its strength. But the only problem is, were not sure of the aesthetic of the fiberglass. Does anyone have pictures of a home built fiberglass skin TTT? Any thoughts on that type construction?

[linuxmanxxx]

Traditional fiberglass resin will eat the foam so you need to either use epoxy or coat the foam with something the fiberglass won't eat before you put the glass and resin down. I tested some fiberglass on my prototype I built and warn you it's toxic nasty stinks and very difficult to work with if you are a novice to wetting in fiberglass layers. I'm looking at a water based epoxy and will try some tests of it with some fiberglass or rough woven cloth and see how it fairs. It should get a lot more flexible with the cloth embedded as standard fiberglass resin without cloth is rather brittle but with the cloth it gets very flexible.

[Wobbly Wheels]

Check my build thread katozzie. I've only got the door done so far as a tester, but I'm building about 13' long and about 6 1/2' tall and glassing it with Epiglass and two units of 6oz E-glass on the outside and a single over 1/8" luan on the inside.

I've made molds this way in the past and the finish is pretty good - like everything else in glassing: it's all in the prep...

[GPW]

Epoxy resin works fine with F/glass cloth ... remains flexible ... Have to paint it though for the UV .. Less stinky/Toxic than the polyester , still Nasty ...

Anybody remember Glassice and his Fiberglass Foamie trailer ? ... As I recall, it took a GOOD bit of effort , and then we never heard from him again ..

[Larry C]

Traditional fiberglass resin will eat the foam so you need to either use epoxy or coat the foam with something the fiberglass won't eat before you put the glass and resin down. I tested some fiberglass on my prototype I built and warn you it's toxic nasty stinks and very difficult to work with if you are a novice to wetting in fiberglass layers. I'm looking at a water based epoxy and will try some tests of it with some fiberglass or rough woven cloth and see how it fairs. It should get a lot more flexible with the cloth embedded as standard fiberglass resin without cloth is rather brittle but with the cloth it gets very flexible.

I think we should clarify what you refer to as "fiberglass resin" is actually Polyester resin, and yes it's nasty stinky stuff. Also it will eat most foams. Fiberglass is actually woven glass filaments (fibers) and is the reinforcement used with both Polyester and the much less toxic, and much more expensive Epoxy resin. Both Polyester and Epoxy are 2 part systems, consisting of "resin" and a hardener that are mixed together.
IMO, epoxy is what you should be using, leave the Polyester on the shelf.

Larry C

[starleen2]

OK since most of the conversation has been dominated by foam discusssion - lets get back to the topic which is weight differences. I'd like to throw in another example of plywood weight difference. Here is the lady bug WW that I built. It weighed 950 lbs it's measurements 10L X 6' 4 W X 4'11 (collapsed) 6'0 expanded. It was constructed out of 5mm luan with with traditional framing and 3/4 foam insulation sandwich method. As you can clearly see that 950 lbs is very lightweight for the size of this TTT.





ladybug build Thread

I think that the persuit of "lightness" may not be the answer for some.
A parachute is very light indeed - but the drag will slow you down in a hurry. Drag is an important consideration when thinking about building a TTT. Smaller cars could theorically pull a 1000lbs TTT, but the drag would certaily have an impact since most of a TTT will be outside of the "shadow" of the Tow vehicle.

[Larry C]

Epoxy resin works fine with F/glass cloth ... remains flexible ... Have to paint it though for the UV .. Less stinky/Toxic than the polyester , still Nasty ...

Anybody remember Glassice and his Fiberglass Foamie trailer ? ... As I recall, it took a GOOD bit of effort , and then we never heard from him again ..

Actually Epoxy is pretty benign. It can cause skin contact problems for some people, but if handled properly, like many things we encounter every day, it is pretty safe. Case in point is filling your car with gasoline is dangerous. The gas contains benzine which is absorbed through the skin, plus you shouldn't breath the vapors. However, we all are exposed to these dangers everyday.
I am just saying that Epoxy is not something that should be considered extremely dangerous, just something that needs reasonable precautions.
Referring to it as "nasty" I think puts it in the fear category that it really doesn't belong.

Larry C

[Oldragbaggers]

Once you have the mixing and handling down and understand the very reasonable safety precautions required to deal with fiberglass cloth and epoxy resin, I do not think it is any more difficult to work with than glue or paint and canvas.

Essentially it is the same technique, which is laying a layer of "cloth" and then saturating it with the coating. Getting your cloth cut well, laid on straight and saturated thoroughly are needed in both methods, but the strength of the end product, IMHO, will be much superior with the fiberglass.

I've seen threads where people talk about the edges of their canvas starting to fray and come up. That's not ever going to happen with a good fiberglass layup. I also think the canvas and paint would be much easier to damage. Fiberglass will be completely waterproof. And can be quite beautiful with a good paint job. (Ever seen a fiberglass yacht??)

The main drawback for most people will be the cost. Obviously fiberglass cloth and epoxy resin will be much costlier than canvas and paint or glue. Any additional work/difficulty will come in the sanding, especially if it's a bad layup. But I would encourage anyone to try it. Make a test panel, get comfortable with the process. Your TD will last and last.

[starleen2]

Does anyone have pictures of a home built fiberglass skin TTT? Any thoughts on that type construction?

Dave and Cindy built the Bluebonnet 2 similar to what you are describing.

I think the Bluebonnet II should qualify as a Foamie. It's a build in progress but has been camping for 2 years now.

http://www.tnttt.com/viewtopic.php?t=44632

http://www.tearsoftexas.com/gallery/main.php?g2_itemId=673

[Larry C]

Once you have the mixing and handling down and understand the very reasonable safety precautions required to deal with fiberglass cloth and epoxy resin, I do not think it is any more difficult to work with than glue or paint and canvas.

Essentially it is the same technique, which is laying a layer of "cloth" and then saturating it with the coating. Getting your cloth cut well, laid on straight and saturated thoroughly are needed in both methods, but the strength of the end product, IMHO, will be much superior with the fiberglass.

I've seen threads where people talk about the edges of their canvas starting to fray and come up. That's not ever going to happen with a good fiberglass layup. I also think the canvas and paint would be much easier to damage. Fiberglass will be completely waterproof. And can be quite beautiful with a good paint job. (Ever seen a fiberglass yacht??)

The main drawback for most people will be the cost. Obviously fiberglass cloth and epoxy resin will be much costlier than canvas and paint or glue. Any additional work/difficulty will come in the sanding, especially if it's a bad layup. But I would encourage anyone to try it. Make a test panel, get comfortable with the process. Your TD will last and last.

Well put Becky! However, I don't think epoxy/glass is much more expensive than Titebond glue & canvas cloth and might actually be lighter.
I think the key to success with epoxy/glass is using a glass type that requires the least amount of resin which saves weight and $ without sacrificing strength.
I think I am going to build a tongue box with foam covered with glass. The foam will allow me to carve a nice radius on the edges.

Larry C

[linuxmanxxx]

Yes epoxy is way more nose and user friendly than polyester resin no doubt but in other threads this group has been theorizing and investigating alternative nontoxic solutions to the traditional coatings and have come up with several very interesting variants.

We just need to remember that fiberglass and resin or canvas and glue are just hybrid methods for taking 2 substances and embedding them together and having a stronger result.....same as age old adding of rebar into concrete.

We have some alternative things we are looking at made for foam one is a mix and brush on instant plastic coating and another is a concrete type coating that can have flex agents added and any of this combined with an embedded strengthening agent can possibly be alternatives.

I did lay up some fiberglass and have done all kinds of things in my long tenure of life and found it to be a very unpleasant experience and nothing I'd care to do on a large area at all.

I think we are moving in the right direction to find that holy mantra coating that will balance ease of application/cost/toxiciity/end look/strength and will just take some experimenting. My goal is strength adhesion and hardness balanced and not to break the bank or back to do it. I'm amazed at how a simple forum has been very effective at hammering out alternative solutions in very non traditional thoughts and ideas.

We are actually like an open source consortium for construction ideas and techniques like my beloved linux. How cool is that!!!

[katozzi]

Sorry for the delay, been real busy with work.. but Wow, that blue bonnet II is awesome. I think that we are going to use that build as a guide in our process. Thanks for sharing that! I think I have found some good prices on fiberglass, so I don't think this will be pushing our budget. Were looking forward getting started! I will update with lots of pics!
Thanks for the help everyone!

[linuxmanxxx]

http://www.foamez.com/resin-research-epoxy-3-gallon-kit-p-477.html This kit will do both sides several layers on 5 long board surf boards so should do good at covering a complete camper and with their guide seems much easier than standard polyester fiberglass wetting.

[katozzi]

Thanks for that link! That looks like a real good system, and I like that this one has UV inhibitors.