Dare I? A fiberglass question..

[RJ Howell]

I'm heading into the the step of skinning. Well, for me it's all part of construction/structure..

I have a steel frame that will be filled with XPS foam. Plan is to fiberglass directly over that and skip any other skin (like plywood). Not seeing any issues (yet) with the side walls, and actually not much for the roof (no steel there but going to strut it).

The floor is where I'm debating... I'm looking at just doing a 1/4 plywood floor adhered to the XPS foam and steel frame then fiberglassed over. My joist spans are about 30" right now and originally thought of going 5/8" T&G plywood, but....

Is fiberglassed 1/4" close to or equal to 5/8" plywood? Hoping to use 4oz glass cloth.

[tony.latham]

Is fiberglassed 1/4" close to or equal to 5/8" plywood? Hoping to use 4oz glass cloth.

I don't think so. With a 90% confidence with that answer.

For my last floor, I used this internal framework:



It's sheathed with 1/4" on both sides and filled with foam board. The skinny cross-members are doubled 3/4" ply set on edge. (I removed the gussets after I had one skin on.)

Anywho, it's stiff and strong because the two layers form a torsion box. It's walkable.



Tony

[Pmullen503]

One layer of 1/4" over 30" oc frame is not enough even with glass. Cover both sides, yes. My trailer is a torsion box of 1/4" skins on a 1" thick wood core, 24" oc. Even that will flex if you kneel in the center of a 2' x2' unsupported square even with the foam core.

4 oz glass is great for waterproofing but it won't add much stiffness, not like using 5/8" plywood.

[John61CT]

I would support the floor foam properly so no wood is at all needed for load bearing.

Has good compressive strength on its own.

Then the floor covering is just puncture-resistant skin, lighter is better go thin.

[RJ Howell]

Bought my cloth, 2.5oz @ 56" width. The width was fairly critical for my waste management. Sourcing my epoxy now. Seems most places I looked at so far it's either a good deal on the cloth or resin.. Only saw one place so far that stated they would try to combined shipping, yet at checkout.. not so much.

I'm seeing a lot of this 'Tabletop' epoxy out there. Pricing is near half the costs... Why? Curious is all..

Also seems to be by supplier what their Fast, Medium, Slow cure times at.. strange, but caught on to it, whew

@Tony: I am looking at Raka as you suggested.

[John61CT]

https://fiberglasssource.com/collections/epoxy-resin

[tony.latham]

@Tony: I am looking at Raka as you suggested.

I use their medium no-blush... Just make sure you buy pumps too.

Tony

[Pmullen503]

@Tony: I am looking at Raka as you suggested.

I use their medium no-blush... Just make sure you buy pumps too.

Tony

+1. Pumps for epoxy are worth every penny.

[RJ Howell]

Purchased from Raka. The other was US Composites. USC had a smaller kit so less money, but I have a little extra cloth coming, so might as well have a little extra epoxy resin.

[RJ Howell]

The cage is built and before I do the floor, I need to get the underside and wall at the truck cab done. Figure it's coming off the truck for this.



Over the cab I've added the cross rails (not shown here) and the wall will get plywood studded. both will have the xps foam infilled. This is the next debate...
I always had in mind to just fiberglass over the xps foam. I see now the steel tube has rounded edges that would show (reflect through) unless I fill that..

Not really seeing the need for epoxy filler (and hoping not to have to add that amount of work). Alternative filler folks? Or is working with epoxy/wood flour easy??

[Pmullen503]

You will have a problem using filler.

It's always difficult to blend when you have materials of dissimilar hardness. In this case it's extreme: steel and foam. The key here is to make your foam fit so well that you need minimal if any filler once you sand it down to the steel. If it was mine I'd fit foam pieces around the frame and put the seam for the foam somewhere in the middle. Again fitting the foam well so minimal filler is needed and then use a filler that sands easier than the foam, something like spackling compound to fill any cracks.

Another strategy would be to rout a channel over your foam seams and fill it with a tight fitting foam piece. Be careful to glue only the bottom of the channel to avoid glue squeeze out. Then you should be able to sand it flush and have a virtually invisible seam. It all depends on the quality of the finish you are trying to achieve.

Seeing your set up, I would go take the weight penalty and go with a thicker floor. The foam underneath just providing insulation. Unless you want to weld in more supports.

[RJ Howell]

I do agree with as tight a fit as possible, I just know something will be needed. Happily the first two areas I can play with a bit, well at last the underside. I'll play with routing an edge and see where that goes.

Good input and do appreciate it!

The floor (and the upper platform) I will go T&G plywood over. Seams in the plywood will be covered by bed or cabinets (depending on side). Ya, I'll take a weight penalty as you put it!

[RJ Howell]

I caught a couple of fiberglass canoe builds where it was cloth over frame. This has me again wondering if indeed I will need any filler.

Basically, I'll have a 1/8" to 3/16" space (the steel tube round) and hoping to make that smaller with a cut/rout of kind. I would think the cloth would span this... no?

It's been a while since I F/G'ed last and working through the process before supplies arrive. Thought one is to wet the XPS surface and lay the cloth (dry) on that. This system is said to have less bubbles and let's gravity do it's thing. Interesting and may allow for a bit extra resin in any gaps I may (will..) still have. Of course the other is traditional of wetting over the cloth and I guess coating again if the cloth does not span the gaps.

I'm leaning towards going the wetting the XPS and placing the cloth (thought one above).

Experiences my friends?

[saywhatthat]

Why a steel frame? Seam a waste of time and money & weight ? just use the foam with a thicker band of glass to make the frame.
Alternative filler folks can foam sanded down will glue
foam to steel

[tony.latham]

I'm leaning towards going the wetting the XPS and placing the cloth (thought one above).

I can't help you with that answer. No experience on this end of the stick.

I'm guessing you may want to do some fairing after you've glassed it ––assuming I understand your plan. An epoxy/micro-balloon slurry is easy to sand and if applied with a long trail it won't take too much sanding.

But we shall see!

Tony