Isolating a Foamie Trailer Body From Frame Vibration

[Chefsonora]

So I'm building a hybrid foamie/plywood frame body with a foam/plywood sandwich floor. My thought is to isolate the through mounting holes with polyurethane bushings sealed in epoxy (to keep from crushing the foam/seal).

Curious to see if anyone has tried any dampening between the frame and body with epdm/ neoprene tape and how effective it has been?

I'm building the body as a pod, so since it can be separated from the frame I want to consider mounting wear and vibration mitigation

 

[dt400]

I'm in a similar situation. I built a foam/fiberglass pod that sits on a custom trailer frame for off-road use.
My concern with any sort of tape is if/when the adhesive gets hot in the sun it may become soft and squish out. My plan, at least until I do a bit of testing, is to use a polyurethane or polymer modified adhesive. OSI QUAD MAX is the one I'm leaning toward now. It has great adhesive properties and stays very flexible.
I have bedlined the entire exterior of the pod to there is a bit of protection from that. Plan is to lay the OSI on the top of the frame rails, then put strips of either a poly visqueen or wax paper (whatever I can find that the OSI won't stick to) set the pod down and line up the bolts and let it cure. Once cured then remove the plastic from between the pod and frame. I may use so 1/16" shims temporarily to keep the OSI from being completely squished and leave a bit of cushion. I will use the OSI to create some bushings for the bolts with rubber washers under the heads to prevent cracking......At least that is the plan for now until I come up with a better idea.
Good luck with yours.

Darrell

 

[Falco-4]

Plan is to lay the OSI on the top of the frame rails, then put strips of either a poly visqueen or wax paper (whatever I can find that the OSI won't stick to) set the pod down and line up the bolts and let it cure. Once cured then remove the plastic from between the pod and frame.

If you do some testing of this, I'd be very interested in what you find. I had thought about using OSI to keep water out from between the frame and floor and reduce any rubbing between the two, but my hesitation was if I ever need to pull the camper off the frame.

 

[Chefsonora]

If you do some testing of this, I'd be very interested in what you find. I had thought about using OSI to keep water out from between the frame and floor and reduce any rubbing between the two, but my hesitation was if I ever need to pull the camper off the frame.

Im reluctant to go full adhesion to the frame (as I'm basically building a pod for the camper to test my design)so I'm thinking more of a floating mount with abrasion/ wear strips between the frame and body.

 

[dt400]

If you do some testing of this, I'd be very interested in what you find. I had thought about using OSI to keep water out from between the frame and floor and reduce any rubbing between the two, but my hesitation was if I ever need to pull the camper off the frame.

If you re-read my post you'll see where I mentioned using some kind of parting film, either wax paper or visqeen plastic, then removing it once cured. The adhesion to the frame is important but no bond to the pod.

Darrell

 

[dt400]

Im reluctant to go full adhesion to the frame (as I'm basically building a pod for the camper to test my design)so I'm thinking more of a floating mount with abrasion/ wear strips between the frame and body.

I built a foam and FG pod as well.

If you re-read my post you'll see where I mentioned using some kind of parting film, either wax paper or visqeen plastic, then removing it once cured. The adhesion to the frame is important but no bond to the pod.

Darrell

 

[Chefsonora]

I see what you are saying now, so you get the benefit of the rub resistance without having to stick it all down.

 

[dt400]

I see what you are saying now, so you get the benefit of the rub resistance without having to stick it all down.

Yes and hopefully a bit of high frequency vibration isolation.

Darrell

 

[philpom]

Boat trailers have somehow figured this out, check out what they do.

 

[dt400]

Boat trailers have somehow figured this out, check out what they do.

I'm not a boat guy so I'm not sure. But it always looed like they just used carpeting wrapped around the bunk boards.

Darrell

 

[philpom]

Boat trailers have somehow figured this out, check out what they do

I'm not a boat guy so I'm not sure. But it always looed like they just used carpeting wrapped around the bunk boards.

Darrell

I think that's basically it but it's waterproof, high heat doesn't impact it and it protects the fiberglass hull from damage by the trailer.

 

[Chefsonora]

The boat analogy is good to me though because I don't want to really hard mount the body to the trailer so that all of the stress and flex of the trailer is more dissipated.

 

[iamroot]

BTW I was thinking about this too over at Removable 5x10 Camper Body on HF 4x8 Frame but I don't have an answer yet. Was considering TPU 3D-printed gaskets, but I'm leaning toward some really thin foam tape mostly just to keep from rubbing away the paint.

I don't want to really hard mount the body to the trailer so that all of the stress and flex of the trailer is more dissipated.

You can't really "hard mount" and allow "the stress and flex of the trailer is more dissipated" without having a strong and compliant bushings like the bodies of frame-on-body trucks have, which then means your pod must have its own internal frame capable of holding all forces, then you might as well just mount a torsion axle directly to it and skip the "trailer" part entirely.

 

[kipa]

Is this really a big problem? I understand the stresses and wear will be real, but how much of an issue is that really?

My tub is technically removable from my 5x10 HF frame. I only have 4 attachment points through the 1/2" plywood subfloor on top of fiberglassed 2" XPS, but I also added an additional inch of glassed XPS to sit inside of the outer frame rails to lock in the tub position. It will still shift with flex, but the attachment bolts themselves are just there to hold it down, not eliminate shifting.

It's unclear to me if this mount method will be an issue long term. (I also intend to install an internal front plywood bulkhead layer and use vertical unistrut to tie that in with the front rail of the frame.)

 

[Falco-4]

Is this really a big problem?

I've had a hard time determining this too. @ghcoe first suggested it as a possible problem in my thread, he had seen wear and water holding on the metal frame and added wood pieces on top of the cross members.

Most of the build journals I see don't spend a lot of time discussing how they do the floor to frame attachment. Add to that the HF 5x10 frame is unconventional and I've been a bit stuck. I think I'm going to use truck camper foam just to give a bit padding.

 

[Chefsonora]

I'm trying to decide my best mounting options too. I am doing a foam sandwich floor with 1-1/2" foam and 2 sheets of 3/8" AC Plywood. My vertical ribs are basically hoops with flat bottoms that will be encapsulated into the foam/ plywood sandwich. I'm thinking to harden and isolate the mounts to either block it out with solid wood or to cast some polyurethane bushings to go between the layers and get sealed and isolated with some thickened epoxy. Probably 4 or 6 spots to bolt through to tabs on the frame. Debating how to level the frame/ cover the bolt heads (HF 1720# folding trailer). Kinda want something other than wood. I wish I could get strips of the rubber horse stall liner!

 

[iamroot]

If you're not intending it to be easily removable, I'm sure a thin layer of Dynaflex 230 between the frame and bottom piece of plywood would be just fine. Caulk it, squeegee it to uniform thickness (I suggest about 1/16", but more is fine too), install the floor. The moisture will be excluded and it'll provide just a little bit of vibration absorption.

Alternatively, plywood (not OSB ) is very good at moving moisture horizontally, so you can take advantage of that by not sealing your plywood before installation, caulk every edge between the plywood and frame (so, both sides of each frame rail) with Dynaflex 230 or OSI Quad, then paint it with a slightly-breathable paint (i.e. your normal waterborne latex) or even a highly breathable one. If any moisture ever did get between the plywood and frame, it'll be quickly redistributed across the sheet.

 

[iamroot]

or to cast some polyurethane bushings to go between the layers and get sealed and isolated with some thickened epoxy.

You also said "foam sandwich floor", if you mean the foam is between the two sheets of plywood, you should use a foam-safe adhesive, including, but not limited to, spray subfloor adhesive.

 

[Chefsonora]

You also said "foam sandwich floor", if you mean the foam is between the two sheets of plywood, you should use a foam-safe adhesive, including, but not limited to, spray underfloor adhesive.

Intending to use original gorilla glue to bond it all together and fill gaps with good stuff foam (got the Pro applicator for better control and less waste), then treating the plywood with penetrating epoxy.

 

[iamroot]

Intending to use original gorilla glue to bond it all together

I would not because it expands with great force, which makes keeping the surfaces flat difficult. That's why I recommended spray subfloor adhesive (oops, I see I wrote "underfloor" before)