Fasteners and Fiberglass for a Plywood Squaredrop Build

[MojaveD]

Thanks for the add, glad to find a community of tiny trailer builders. Two questions so far, and please let me know if there’s a better place to post them: 1) can I use fiberglass just on the corners where the plywood walls meet (plus seems) and 2) are drywall screws okay for attaching plywood to spars? I saw 1/4” crown staples recommended but I don’t currently have a staple gun/compressor. TIA

 

[Tony Latham]

1) can I use fiberglass just on the corners where the plywood walls meet (plus seems) and 2) are drywall screws okay for attaching plywood to spars?

What are you finishing the plywood with? Aluminum? Paint or something else? Here's a link to what can happen to plywood with a paint product –including bed liner– directly over plywood.

Wood sided trailer is having issues. Suggestions wanted

Fiberglassing the entire cabin isn't difficult, as long as you mix small batches of epoxy to avoid it from popping off in the cup.

I think you need an exterior screw for exterior purposes. Sheet rock screws can rust (and I hate Phillips head screws). Something like this:

Amazon.com

Of course, you'll need to select the right length of screw and the correct adhesive.

Tony

 

[KCStudly]

Drywall screws are high strength steel which allows them to be thin so they go into drywall easily, but have adequate strength. However the high strength alloy also makes them more brittle, so in our dynamic load environment they can snap when jolted. Standard wood or deck screws are better. Gluing and screwing is always better... the glue typically does most of the work.

 

[MojaveD]

What are you finishing the plywood with? Aluminum? Paint or something else? Here's a link to what can happen to plywood with a paint product –including bed liner– directly over plywood.

Wood sided trailer is having issues. Suggestions wanted

I think you need an exterior screw for exterior purposes. Sheet rock screws can rust (and I hate Phillips head screws). Something like this:

Amazon.com

Of course, you'll need to select the right length of screw and the correct adhesive.

Tony

Plan is to sand with orbital sander, apply an exterior primer/sealer followed by exterior acrylic enamel. The camper will be garage kept and will see scant rain (I’m in the desert southwest). For sealing seams, is fiberglass a good option? I would round over the sharp edges with a router. Aluminum is beyond my budget.

Thanks for the tip about screws. Is DAP Dynaflex Ultra acceptable over screw heads? Claims to remain flexible.

 

[MojaveD]

Drywall screws are high strength steel which allows them to be thin so they go into drywall easily, but have adequate strength. However the high strength alloy also makes them more brittle, so in our dynamic load environment they can snap when jolted. Standard wood or deck screws are better. Gluing and screwing is always better... the glue typically does most of the work.

Thank you for this, will pursue a deck screw. Speaking of glue, do you recommend construction adhesive, or will titebond 3 suffice?

 

[KCStudly]

I mostly only used construction adhesive for my wall to floor joints (wood-to-wood) where I wanted to be sure I had good gap filling and working time (long before I made the switch to working with epoxy and fillers). For wood-to-wood cabinetry and framing joints where I could control the fit well, I mostly used TB2. For the foam I used a variety of products in "the grand experiment"... TMI to go into here.

 

[Tony Latham]

Plan is to sand with orbital sander, apply an exterior primer/sealer followed by exterior acrylic enamel. The camper will be garage kept and will see scant rain (I’m in the desert southwest). For sealing seams, is fiberglass a good option?

I believe it's best to cover all the surfaces with a 6 oz layer of glass/epoxy. You don't want the plywood to check down the road, and in your heat, it may. Call it insurance.

I didn't cover the seams of my cabin, nor did I suggest it in my book. After seven years, it's fine. Covering a 90% corner with fiberglass is difficult. A roundover is easier, but the radius needs to be about 1/2". A bias-ply tape–if you can find it–makes it doable.

Tony

 

[MojaveD]

What are you finishing the plywood with? Aluminum? Paint or something else? Here's a link to what can happen to plywood with a paint product –including bed liner– directly over plywood.

Wood sided trailer is having issues. Suggestions wanted

Fiberglassing the entire cabin isn't difficult, as long as you mix small batches of epoxy to avoid it from popping off in the cup.

I think you need an exterior screw for exterior purposes. Sheet rock screws can rust (and I hate Phillips head screws). Something like this:

Amazon.com

Of course, you'll need to select the right length of screw and the correct adhesive.

Tony

Hi Tony, just now watched your video applying fiberglass to the roof. How do you then seal the seam where roof and side walls meet — do you fiberglass that as well? I know some guys use aluminum 90 degree trim but I like the look of radiused corners — I’m trying to mimic the Freedom foam camper that way. I’m doing a squaredrop if that makes a difference, framing with 2x2 and 3/16 sheathing.

 

[Pmullen503]

There is a way to get fiberglass to conform to a 90 degree outside corner.

Apply fiberglass and epoxy. Then tape a larger piece of polyethylene plastic over it. Use tape strips every few inches to apply tension to the poly to pull the fiberglass tightly to the corner. Keep moving the tape and pulling the poly tight, eliminating wrinkles, until the fiberglass conforms to the corner. Don't use too much resin as the poly will squeeze any excess out of the fiberglass cloth.

Once the epoxy cures, remove the poly and block sand the corner flat. A couple layers of lighter cloth works better than a single layer of heavier cloth. Cutting your cloth on the bias allows all the fibers to cross the corner, not just 1/2 of them making a stronger corner.

 

[KCStudly]

A flocked or flox corner works, too. Bevel the corner; build a dam with packing tape release flush to one face; pack the corner with thickened epoxy; remove the dam, fill and fair any small stuff in the filler; then glass up to the corner from each side. The flocked corner allows you to knock the very sharp corner off (or suffer contusions) without lifting an edge. This works good where you want crisp lines, like door or galley hatch lines, but I prefer a nice big radius on my profile corners between roof and walls.

 

[Pmullen503]

A flocked or flox corner works, too. Bevel the corner; build a dam with packing tape release flush to one face; pack the corner with thickened epoxy; remove the dam, fill and fair any small stuff in the filler; then glass up to the corner from each side. The flocked corner allows you to knock the very sharp corner off (or suffer contusions) without lifting an edge. This works good where you want crisp lines, like door or galley hatch lines, but I prefer a nice big radius on my profile corners between roof and walls.

It helps to radius that corner under under the flocked material to solidify the edge, especially if it's in any area subject to dings and chips.

In my case, I had a high stress area with inadequate wooden structure underneath to handle the loads and racking alone. Having continuous fibers around the joint to hold it together was essential. The sharp corner was an aesthetic choice, a radiused corner could have been stronger.

 

[Tony Latham]

How do you then seal the seam where roof and side walls meet

I butted the side and roof glass. No issues in six years.

Tony