Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby kimphan » Sat May 08, 2021 3:28 pm

TimC wrote:I think foam works for a bulkhead. Though I would go with 1/2" or 5/8" plywood myself. Either way there's some fiddling to do to anchor it to the floor, walls and roof.
How many bodies to you intend to sleep in there? Kids and adults? If little kids bunks might be possible.


Options:
1) what about 2X2X8 frame I think they are 7lbs, I will probably need 5, so 35 lbs. If this works, just embedded the lumber in the 3" foam of the side wall and glue, it will just be a load bearing wall to the roof and screwed to the floor. I should be able to do this. cost about $25 plus screws.
2) 1/2X4X8 plywood is 50 lbs. This will be hard to anchor to the floor walls and roof, maybe too advance for my skills. cost about $50 plus braces.
3) 3" foam board is 12 lbs, this will just be cut to shape, glue to foam, wood floor and have pmf covered. cost about $50 plus PMF cost so another $50?

There should be 2-3 adults and 2 kids (7 yr and 2 yr but they will grow up fast).

Picture to illustrate framing...
Image

Thanks,
Kim.
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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby QueticoBill » Sat May 08, 2021 4:13 pm

No lateral strength. Bulkhead = diaphragm. Push (like door slam, wind, or someone leans ir falls against side) it all folds, or parallelograms. You could use the 2x2 but diagonally. A bulkhead braces the corners - floor to walls and roof to walls. Without bracing, they "hinge".
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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby TimC » Sat May 08, 2021 4:33 pm

What Qbill says. Not enough strength with 2x2 frame unless you provide some diagonal support. It will rack back and forth as there is no diagonal bracing. That is what plywood or an entire sheet of foam would do (plywood much better). Support the wall from sidewall to sidewall. In all directions.

Now a 2x2 framed wall with 1/4" ply on each side glued and screwed to the 2x2s would be strong (a 2x2 sandwich with 1/4" ply as the bread). And the 2x2s would give you an easy way to attach to the floor. Attaching to the walls and roof would take some fiddling. Glue and PMF or fiberglass and epoxy would help with that. Similar to how a drywall corner is taped in your house but with canvas & glue or fiberglass tape and epoxy. Similar to this method I used on the foam wall to plywood floor...

Image

I have lots of 3" fiberglass tape from a boat building project and I used TBII to glue it to the wall. This is just interior reinforcement in the cabin at the floor on my son's foamie. It will also have a small wood trim piece glued in the corner to add more strength. It is not the primary attachment method.

There's a certain amount of biting the bullet on cost to make sure your structure is sound... you know that! Your trailer is a beast and will probably not flex as much as a bolt together Northern Tool or Harbor Frt trailer would. But you still need to consider head on wind and side forces that will be constant at 60 miles per hour. If you don't provide enough diagonal bracing in the center of the 12' span you will likely shake the structure beyond its limits. Think about this scenario, you are cruising down a two lane highway at speed with a stiff cross wind from your right. A semi passes going in the other direction. Suddenly the force of the wind from your right side is fighting the force of the semi's wake. Your beast of a trailer stays steady and doesn't give much to either force, because it is a beast. But your walls and roof are forced left, then hard right, than back left again. If this happens too many times all your hard work is toast.
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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby ghcoe » Sat May 08, 2021 5:38 pm

kimphan wrote:I've been thinking about getting rid of the old 1/2 inches wood floor all night and just go with method similar to what you describe.

Looking at the picture and what you describe, I do have a couple of questions...
1. How to do keep the outter PMF skin at the bottom from slipping and peeling off the OSB board? Do you staple them (after glueing and before painting)? or drill them (after they're dried and hard) and clamp them with more wood? Or are we thinking that the hard "L" PMF skin wrapped around is enough for it to not slip off.
2. How many inches should the canvas be overlapping under the floor? The standard 4 inches?
3. I don't see an inner PMF skin, would that compromise the load and it could collapse the foam body inward?

Thanks,
Kim.


1. I use full strength TBII along all edges. It is plenty strong to hold the canvas in place.
2. I overlap the bottom and all edges 2"
3. I cut back the inner PMF 1 1/2" up from the floor so there is no PMF behind the inner frame rail. That way you are gluing directly to the foam rather than to PMF.

Here is a explanation of how the system works together.

Inner Frame Rail and PMF explanined.png
Explanation
Inner Frame Rail and PMF explanined.png (36.23 KiB) Viewed 986 times
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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby kimphan » Sat May 08, 2021 11:16 pm

ghcoe wrote:Here is a explanation of how the system works together.


Thank you, George, this is eye opening, pmf and wood clamping the wall and how the glue help with sliding.

I was wondering if a 3" foam is not as strong as 2" foam since the pmf clamping skins are too far apart?
I was planning on 3" walls and roof since my build is wide and long and is worried about that now.
But was adviced that I could make side walls 1 1/2 inches, leaning towards that more heavily now.


Thanks,
Kim
Last edited by kimphan on Sun May 09, 2021 12:05 am, edited 1 time in total.
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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby kimphan » Sat May 08, 2021 11:42 pm

TimC wrote:Now a 2x2 framed wall with 1/4" ply on each side glued and screwed to the 2x2s would be strong (a 2x2 sandwich with 1/4" ply as the bread). And the 2x2s would give you an easy way to attach to the floor. Attaching to the walls and roof would take some fiddling. Glue and PMF or fiberglass and epoxy would help with that. Similar to how a drywall corner is taped in your house but with canvas & glue or fiberglass tape and epoxy. Similar to this method I used on the foam wall to plywood floor...

I have lots of 3" fiberglass tape from a boat building project and I used TBII to glue it to the wall. This is just interior reinforcement in the cabin at the floor on my son's foamie. It will also have a small wood trim piece glued in the corner to add more strength. It is not the primary attachment method.

There's a certain amount of biting the bullet on cost to make sure your structure is sound... you know that! Your trailer is a beast and will probably not flex as much as a bolt together Northern Tool or Harbor Frt trailer would. But you still need to consider head on wind and side forces that will be constant at 60 miles per hour. If you don't provide enough diagonal bracing in the center of the 12' span you will likely shake the structure beyond its limits. Think about this scenario, you are cruising down a two lane highway at speed with a stiff cross wind from your right. A semi passes going in the other direction. Suddenly the force of the wind from your right side is fighting the force of the semi's wake. Your beast of a trailer stays steady and doesn't give much to either force, because it is a beast. But your walls and roof are forced left, then hard right, than back left again. If this happens too many times all your hard work is toast.


Thank you QBill and TimC for explanation on diagonal bracing.
The 1/4 and 1/4 and frame is great, its the best of both world.
I will contemplate how to adhere them to the walls, George helps me realized that solutions need to be something that move together so they don't slide, rub and rattle. It is tricky since we need to canvas the foam side walls

Still considering foam walls, not as strong, but will make pmf canvasing easier and don't have to deal with sliding, rattling since they will be glued and move together. The all foam aspect is really appealing. If it is strong enough I am leaning towards it.

Thanks,
Kim.
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Re: Kim's "Puff" the magic dragon 4Hx8WX12L foamie camper

Postby kimphan » Sat May 08, 2021 11:55 pm

QueticoBill wrote:Most tear drops are a little shorter and have a "bulkhead" behind hatch compartment. It could be considered a wall across the cabin. This adds a lot of bracing of the walls and roof, resisting the tendency for walls to parallelogram.

The 3" walls and 2" roof seem a little backward. More depth or in this case thickness is what resists bending as a span gets longer. Your roof not only is a longer span between walls than the wall from floor to ceiling, but also has more load. Think of a typical house with 2x4 walls and 2 x 8 or 10 or 12 ceiling or roof framing. The 2 x 2s will compensate some but more suitable for a typical 5' wide tear, and iirc yours is 7'.

In the sketch of the bottom of the wall, i think it would be much better if that trim on outside was beveled at top and the pmf was over the wood. I would not trust the silicone to keep water from penetrating between wall and trim.

Still intrigued by wood trailer frame.

And your progress and enthusiasm is wonderful! Very much enjoying your posts.


Thank you for the encouraging words, it is making a big difference... I feel a bit challenged right now but hopeful thanks to everyone's kind suggestions and education.

So I probably want to use 2x4 for load bearing walls and they are 16" apart? Maybe 2x3 could work is 1x4? Worried a bunches of 2x4 too heavy for the side walls to take?

About the bottom of the wall issue, I think I will remove that extra 2x6 strip all together and rely on the pmf (illustration later)

Thanks,
Kim.
Last edited by kimphan on Sun May 09, 2021 12:13 am, edited 1 time in total.
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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby kimphan » Sun May 09, 2021 12:02 am

QueticoBill wrote:As far as light weight, the trailer looks like a behemoth. It looks like it alone could weigh more than the average teardrop. Do you know? Can it be registered? And pretty sure you need at least marker lights if its 8' wide. I'm nit an expert on DMV trailer rules.

I think your walls could be thinner. Only 4' tall, probably 1 1/2" foam will do if braced by front and back and roof AND mid ship bulkhead, even if that he as a 6' x 3' opening in it. And all foam joints are covered with pmf in side and out. All the fiam dies structurally is keep the skins apart and not letting them move differently, just like the paper honeycomb keeps the thin skins of a hollow core door apart.

The roof span and it deflecting - sagging under its own weight let alone ponding water - is not solved by thicker foam. Curving front to back or side to side like a vardo would be options, or a ridge the long way, or a slope. Even a shallow slope maybe with ridge crosswise. I do not know what appeals you or what the "smartest" or mist elegant solution is. Just pretty certain you won't be pleased with current roof after a while.

Go to Home Depot/Lowes/Menards/other with someone, and hold a 4 x 8 piece of thickest foam at ends, and I think you'll see the sag. Put any weight on it and I'm sure you will. 20 pounds in the middle would be about same as just 1/4" of water over entire 4 x 8. Hold both ends of a 2x2 and see how little pushing at center it takes to sag.

Not trying to be difficult but look at other trailers here - few near 8' wide except maybe the conversions.

And don't rush so much that it seems like work. Should be fun!



Got it, I will add more slope/curve to avoid flat roof.
Great to know that side wall could be thinner.

Reading and re reading your post digesting, thanks for the info!!!!!
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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby kimphan » Sun May 09, 2021 12:34 am

Wow, I just realized that if I have a separation foam wall with pmf skin, technically I am building 2 smaller side by side side way camper 5.5 X 7.5 and 6.5 X 7.5, it's a camper duplex lol.

This is the case maybe I can make all foam walls and roof 2" plus load bearing spars (2 X3 or 1 X 4) every 16 inches should be ok?
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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby ghcoe » Sun May 09, 2021 8:39 am

QueticoBill wrote:Go to Home Depot/Lowes/Menards/other with someone, and hold a 4 x 8 piece of thickest foam at ends, and I think you'll see the sag. Put any weight on it and I'm sure you will. 20 pounds in the middle would be about same as just 1/4" of water over entire 4 x 8. Hold both ends of a 2x2 and see how little pushing at center it takes to sag.


Foam is just part of the structure, the PMF is the other. If PMF is on both sides of the foam it is much more rigid than foam alone. Similar to a I beam, foam acts as the vertical strength of the
I beam and PMF acts as the horizontal strength of the I beam. This will make a foam alot stronger for spans than just foam alone.

PMF strength explained.png
I beam
PMF strength explained.png (14.79 KiB) Viewed 905 times
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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby ghcoe » Sun May 09, 2021 8:54 am

kimphan wrote:Wow, I just realized that if I have a separation foam wall with pmf skin, technically I am building 2 smaller side by side side way camper 5.5 X 7.5 and 6.5 X 7.5, it's a camper duplex lol.

This is the case maybe I can make all foam walls and roof 2" plus load bearing spars (2 X3 or 1 X 4) every 16 inches should be ok?


With the I beam explained above you are building strength into the foam panel if you PMF both sides of the foam panel. If you feel you need more strength for the span you can add wood for extra strength.

This is how I did it on my current build.

First I made a simple template to mark out the rafter positions on the PMF.

20200925_162318 s.jpg
template
20200925_162318 s.jpg (35.53 KiB) Viewed 903 times


The template lets me know where to cut the PMF to remove it.

20200925_162336 s.jpg
rafter mark
20200925_162336 s.jpg (37.92 KiB) Viewed 903 times


20200925_162538 s.jpg
PMF removed
20200925_162538 s.jpg (44.42 KiB) Viewed 903 times
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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby ghcoe » Sun May 09, 2021 9:11 am

Once the PMF is removed I use a hot wire (converted soldering iron) to cut out a notch for the rafter. I cut in a little over a inch into the wall.

20200925_164611 s.jpg
hot wire
20200925_164611 s.jpg (46.65 KiB) Viewed 895 times


Test fit the rafters to make sure they fit.

20200925_165516 s.jpg
rafters test fitted
20200925_165516 s.jpg (283.34 KiB) Viewed 895 times


Then I bed the rafters in with Dap Caulking.

20200927_153227 s.jpg
"bedding"
20200927_153227 s.jpg (48.8 KiB) Viewed 895 times


Formula 250 (pink foam) has a compression strength of 25lbs per square inch. A 2"x2" is actually 1 1/2"x1 1/2" so with 25lbs per square inch we can see than the foam will support about 37lbs just by itself. Not to mention the extra strength once we "bed" the rafter into the wall with Dap Caulking. Once bedded the rafter will also have support of the calk working in shear on 3 sides. I would say easy 50lbs per side. That is 100lbs total per rafter when considering you are supporting the roof weight on two walls.
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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby ghcoe » Sun May 09, 2021 9:26 am

This is what is looks like once the rafter is fitted.

20200927_154244 s.jpg
finished appearance
20200927_154244 s.jpg (46.78 KiB) Viewed 893 times


You could possibly add a small spacer in the middle of the rafter to push the center of the roof up slightly. This would allow water to flow off the roof a bit easier. I however don't think it would be needed since I usually store my trailers with the tongue down (or up) to shed water when not in use. I have had 1' of wet snow on the roof of #2 and have not noticed any roof defection due to it.

Rafter Idea.png
rafter idea
Rafter Idea.png (8.03 KiB) Viewed 893 times
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Gorrilla Glue, Great Stuff and Gripper. The three G's of foamie construction.

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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby TimC » Sun May 09, 2021 11:30 am

Kim, pay close attention to George's methods. There are a handful of folks on tnttt with foam experience and George is among the best and most helpful...
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#3 My son's Benroy Foamie team build - Started July '20 - http://www.tnttt.com/viewtopic.php?f=50&t=72877

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Re: Kim's "Puff" the magic dragon 4Hx7.5WX12L foamie camper

Postby QueticoBill » Sun May 09, 2021 11:32 am

ghcoe wrote:
QueticoBill wrote:Go to Home Depot/Lowes/Menards/other with someone, and hold a 4 x 8 piece of thickest foam at ends, and I think you'll see the sag. Put any weight on it and I'm sure you will. 20 pounds in the middle would be about same as just 1/4" of water over entire 4 x 8. Hold both ends of a 2x2 and see how little pushing at center it takes to sag.


Foam is just part of the structure, the PMF is the other. If PMF is on both sides of the foam it is much more rigid than foam alone. Similar to a I beam, foam acts as the vertical strength of the
I beam and PMF acts as the horizontal strength of the I beam. This will make a foam alot stronger for spans than just foam alone.

PMF strength explained.png


Yes of course. Do you have 8' x 8' flat roof areas with no sag, and that won't pond? I have not seen any examples posted, though I have searched a lot. Most foam with pmf spans seem to max out around 5', and not many flat. Also, beam flanges or even plywood skins resist compression in the top, and tension in the bottom. I do not believe pmf resists much compression on top.
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