ultra lightweight floating popup camper

Design & Construction of anything that's not a teardrop e.g. Grasshoppers or Sunspots

ultra lightweight floating popup camper

Postby coal_burner » Mon Oct 01, 2007 11:51 am

After lurking on various teardrop and tiny travel trailer sites, I decided to build something that has never been done before.(if thats even possible)
I'm building my camper out of pink foam insulation from home depot covered in 2 plys of aircraft fiberglass cloth soaked in epoxy resin.

The project started with me making a 5 foot by 9 foot torsion box platform 3 1/2 inches tall. I wasn't sure how strong the fiberglass would be in this use so I built a wooden perimeter out of 1 by 4 poplar to lend rigidity. I glued 1/4 inch plywood for the floor on top of the foam and poplar box, then covered the whole thing (both sides) with 3 plys of fiberglass.
Testing the rigidity of the torsion box was done by clamping it to the edge of my girlfriend's back deck and bouncing up and down on various spots. There was less than 1/2 inch of deflection across 6 feet of the unit, so I figure It's probably way over built.
The torsion box weighs about 125 pounds but can float over 800 pounds.
The torsion axle and 12" tires that I have bolted to the bottom of it weighs about 150 pounds, which makes this camper pretty much impossible to capsize.
The walls are about 3 ft high and the entrance is in the rear of the camper. The walls are made out of 1" thick styrofoam with 2 plys of fiberglass on each side.

So far I am about halfway done. I've already weighed it (320 lbs) and towed it to A lake to float around in it for awhile.
I still need to fabricate A hard sided pop up top with windows and the top half of the back door. I'm guessing that the top will weigh around 50 pounds.
We may have philosophy and opposable thumbs, but most humans show all the wisdom of starved raccoons. It's amazing that more of us aren't found flattened on the side of our own roads.
the original bub build thread http://www.tnttt.com/viewtopic.php?f=5&t=19227
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Postby Laredo » Mon Oct 01, 2007 12:36 pm

where're your pix?
'cause this sounds like we need to see it!
Mopar's what my busted knuckles bleed, working on my 318s...
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Postby coal_burner » Mon Oct 01, 2007 1:12 pm

pix are coming as soon as I find my electronic doohickey to transfer the pix off of my cellphone
:)
We may have philosophy and opposable thumbs, but most humans show all the wisdom of starved raccoons. It's amazing that more of us aren't found flattened on the side of our own roads.
the original bub build thread http://www.tnttt.com/viewtopic.php?f=5&t=19227
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Postby coal_burner » Mon Oct 01, 2007 5:00 pm

This is what the trailer looks like being backed into the lake for the first time. the pic shows it in about 6" of water, so it's still supported by it's wheels.
[img] http://tnttt.com/album_ ... c_id=27728
[/img]
We may have philosophy and opposable thumbs, but most humans show all the wisdom of starved raccoons. It's amazing that more of us aren't found flattened on the side of our own roads.
the original bub build thread http://www.tnttt.com/viewtopic.php?f=5&t=19227
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'nuther pic

Postby coal_burner » Mon Oct 01, 2007 5:57 pm

Image
this picture was taken standing on the tongue looking over the futon/bed.
You can see the cabinet boxes to the left and right of the doorway. Between the cabinets is about 2' by 2 1/2' of open floor space for changing clothes.

eventually there will be a one burner stove, sink, and microwave on the left.
The refrigerator and air conditioner are going to be fit in the right cabinet.
We may have philosophy and opposable thumbs, but most humans show all the wisdom of starved raccoons. It's amazing that more of us aren't found flattened on the side of our own roads.
the original bub build thread http://www.tnttt.com/viewtopic.php?f=5&t=19227
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Postby Endo » Mon Oct 01, 2007 8:08 pm

coal_burner wrote:This is what the trailer looks like being backed into the lake for the first time. the pic shows it in about 6" of water, so it's still supported by it's wheels.
Image


fixed the pic for ya

Interesting project! Keep us updated as it progresses.
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no pics anymore

Postby coal_burner » Tue Oct 02, 2007 6:40 am

thats too funny. Now all I can see is A small box with A red X in it instead of A pic.What exactly does that mean? :thinking:
Is there any way of posting videos? I have A great video of me swinging like an angry monkey from the
side of the camper trying to capsize it.
:DOH2:
We may have philosophy and opposable thumbs, but most humans show all the wisdom of starved raccoons. It's amazing that more of us aren't found flattened on the side of our own roads.
the original bub build thread http://www.tnttt.com/viewtopic.php?f=5&t=19227
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Re: no pics anymore

Postby Endo » Tue Oct 02, 2007 6:54 am

coal_burner wrote:thats too funny. Now all I can see is A small box with A red X in it instead of A pic.What exactly does that mean? :thinking:
Is there any way of posting videos? I have A great video of me swinging like an angry monkey from the
side of the camper trying to capsize it.
:DOH2:


Really?? The pic shows up fine in my post??

Not really sure how to post a video. You may need to save it on You Tube or some other similar site and link it to here.

http://www.youtube.com/
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Postby coal_burner » Tue Oct 02, 2007 8:22 am

Bing! There they are. I wonder why they weren't showing up?

Well.. Last night I took a sawzall to my camper. It now has 6 less inches in the height department.
Towing it behind my VW Golf at 80 miles an hour felt like I was trying to drag A barn door down the freeway. This I could live with because it tows so easily in all other regimes, but, when I sat on the futon inside I noticed that the walls came up almost to my nose level. I'm not willing to sacrifice my outdoor view, so off came the height. The counter tops are now at a more comfortable level also. My stove/sink is set up so that they can be used inside the camper during inclement weather(including mosquitos), or slide out trough the side wall to be used at all other times. When in outdoor mode, the stove was at almost neck level. I'm pretty sure that that would have been a horrible accident just waiting to happen.

I also am going to order a new tongue. My current tongue is 2" square 1/8" wall aluminum tube. It flexes in a scary way when I have a friend jump up and down inside the camper. Anyone have an educated opinion on whether I should move up to 3/16" wall, or go to 1/4" wall?
The tongue length is 3 FT. and has two 1/2" holes drilled top to bottom to mount it to my campers deck.
The fully outfitted weight will be about 700 pounds. (the weight includes a microvave, refrigerator 100lb futon, 2 group 31 batteries, inverter, and air conditioner.
We may have philosophy and opposable thumbs, but most humans show all the wisdom of starved raccoons. It's amazing that more of us aren't found flattened on the side of our own roads.
the original bub build thread http://www.tnttt.com/viewtopic.php?f=5&t=19227
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old pics

Postby coal_burner » Wed Oct 03, 2007 7:32 am

I was just able to locate some of my oldest building pics(from last spring).
here is A picture of the underside of my torsion box, before the foam and fiberglass were added.
Image

And here is the same box after the foam and the first layer of fiberglass was added.
Image

Since the last pic I had also added stacks of three 1x4s on each side to give me a good place to bolt the axle to.
There are 4 3/8" captured nuts buried in each stack of 1x4s to mount the axle to.
If you look closely you can see a shadow running diagonally up from the bottom left of the picture. That is where the 4ft wide sheets of fiberglass that I layed diagonally overlapped.
The second layer goes on horizontally, which gives me alot more rigidity. No matter where the deck tries to flex, it will be putting some of the fiberglass strands in tension.

If I had this to do over again, I would completely omit all of the wood framing and decking. I could have saved at least 75 LBS.
Now I know something for my next build.
:beer:
I just found this guy, and he is going to have to appear on every one of my posts from now on. This has probably already been a 500 beer build project, with lots more to come.
We may have philosophy and opposable thumbs, but most humans show all the wisdom of starved raccoons. It's amazing that more of us aren't found flattened on the side of our own roads.
the original bub build thread http://www.tnttt.com/viewtopic.php?f=5&t=19227
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Postby angib » Wed Oct 03, 2007 12:23 pm

coal_burner wrote:I also am going to order a new tongue. My current tongue is 2" square 1/8" wall aluminum tube. It flexes in a scary way when I have a friend jump up and down inside the camper.

Here's my 'worked example' to the Australian standards on my tongue strength web page:

Bending moment = 0.5 x 700lb x 36" = 12,600 lb-in

My personal rule of thumb is to assume aluminium is one third the strength of mild steel - this is a bit pessimistic on strength, but reflects aluminium's poor fatigue properties.

Required section property = 3 x 12,600 = 37,800 lb-in

A section that meets this requirement on vertical strength is 2" x 3" x 3/16" (38,800 lb-in) - it doesn't meet the horizontal strength requirement, but I wouldn't be too worried about that. Neither the 2" x 2" x 3/16" (20,900 lb-in) or the 2" x 2" x 1/4" (25,300 lb-in) comes close, though you might think they are close enough.

The 1/2" holes through the top and bottom of the tongue are scary. As well as taking away about 1/4 of the tongue's strength, it introduces a stress raiser that will encourage cracking in aluminium. Because of these holes, I suggest you don't skimp on the tongue.

Andrew
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Re: old pics

Postby bobhenry » Wed Oct 03, 2007 12:41 pm

coal_burner wrote:I just found this guy, and he is going to have to appear on every one of my posts from now on. This has probably already been a 500 beer build project, with lots more to come.



OH MY GOD !

Is beer $ inculded as a building expense ?

I'm way over budget then !
Growing older but not up !
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Postby brian_bp » Wed Oct 03, 2007 3:21 pm

Great project! :thumbsup:

Even before seeing Andrew's response I had the same thought: go taller in section, rather than thicker, for better structural efficiency.

angib wrote:The 1/2" holes through the top and bottom of the tongue are scary. As well as taking away about 1/4 of the tongue's strength, it introduces a stress raiser that will encourage cracking in aluminium. Because of these holes, I suggest you don't skimp on the tongue.

Andrew

I second the "scary" thought!
Another possibility: redesign the fastening to a U-bolt at the forward mount (where there is more stress), instead of drilling hole in the new tongue. Or, use L-brackets and bolt horizontally through the tongue (a common method for removable tongues).
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Postby angib » Thu Oct 04, 2007 5:14 pm

brian_bp wrote:Or, use L-brackets and bolt horizontally through the tongue (a common method for removable tongues).

Yes. A horizontal hole, even as big as 1/2" in a 2" tube has almost no effect on vertical bending strength - maybe 2 or 3% at most.

Of course, with a single tongue (ie, not an A-frame), you have just reduced its horizontal (transverse) strength significantly: this doesn't seem to be a big problem, though the Aussie trailer rules do demand the same horizontal strength as vertical. The only practical problem with horizontal tongue strength was Chip's (was it?) transverse sway problem - but I think that was a problem of stiffness, not strength.

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tongue strength

Postby coal_burner » Fri Oct 05, 2007 8:07 am

unfortunately, none of the local suppliers, or even any online ones that I can find, carry 2"x3" aluminum in anything other than 1/8" wall thickness.
I really wanted to stay away from A steel tongue, because the tongue gets submerged often, and it would be difficult to do an inspection of the interior of the tube for rust. I'm thinking that I may have to though. I could use A 2" square 3/16" inch thick tube, and just fill it with spay in expanding foam to help prevent water infiltration.
Another reason that I want to use aluminum for the tongue if possible is to keep the nose of the craft from dipping down too low when it's in the water. A foot of 3/8" steel tube weighs 4.6 LBS. Filled with foam, it will only displace 1.7 LBS of water. Whereas the 1/4" thick aluminum tube would only weigh 2 LBS per foot. But if it's not strong enough, then it's just not strong enough. I guess I'll just have to fabricate a small float to attach to the tip of the tongue.
I want to try to stay with 2" tall tube if at all possible because the tube is mounted to the top of my trailer deck, and any increase in height will raise the hitch itself. Right now, the trailer is perfectly level when attached to the car, and i'd really like to keep it that way because if it stays attached to my car while camping it would eliminate the need for leveling jacks.
We may have philosophy and opposable thumbs, but most humans show all the wisdom of starved raccoons. It's amazing that more of us aren't found flattened on the side of our own roads.
the original bub build thread http://www.tnttt.com/viewtopic.php?f=5&t=19227
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