Untralight foam topper idea.

[sushidog]

Ok, being an ultra noob, I've got an idea.

I'm trying to build a pop-up TD with an ultra light top. The base of the camper will be a rectangular box and the upper walls and top will pop-up 3ft.

The problem is to make it super light so I can tow it behing a small car.

The proposed solution for the top is to make it entirely out of 1.5" thick Foamular 250 (pink styrofoam insulation) covered with 2 thin layers of 6-8oz fiberglass. This will be a fairly large top (about 500sq ft of total surface area inside and out) To prevent the fiberglass/epoxy from delaminating from the eps, I propose to use drywall screws spaced about every foot between the layers of cloth.

I calculate that the weight of this 15'x5'3"x3' monstrosity will only come to about 160lbs with foam, glass and screws. Of course the fiberglass shell will only be .026" thick.

The question is, will it work without cracking or delaminating?

Here's an illustration of my proposed topper cross-section.



I'd love for you guys to tell me why it won't work. Any ideas to make it work?

Here is a drawing of the proposed pop-up in the up position (repost.)

I've decided to do away with the side door to improve it's structural integrity. Instead I will use a rear entry (no porn jokes please), with a 26" wide hatch: the bottom of the rear apex droping down, forming steps, and the top hinging upwards on struts in classic TD fashion. Sort of like entering a flying saucer. The a/c will also be relocated to the bow of this land yaght, attached to the 5'x12' inner bottom and above a tongue mounted, horizontal l/p tank. The bottom will be a more conventional, foamular-core, wood-framed build. The only twist will be that it'll be mounted on an aluminum trailer with the 3' high sides framed in aluminum angle and strapping for rigidity.

Has anyone tried anything like this before?

[Keith B]

That oughta be super slick

[Chuck Craven]

The only thing I see is that with the AC / LP and the kitchen all up front your tong weight is going to be very high. It maybe as high a 50% of the trailer, could be even more than that with the ultra light body.

Chuck

[Guy]

Dear Sushidog,

Many folk have pondered this notion and tackled the problem. You should search this forum.

One thing you must do is check your assumptions, which seem to be that styrofoam with glass and epoxy will be lighter and stronger than plywood and styrofoam or urethane foam. Such is not the case. A year and a half ago I spoke with Larry Steeves who owns http://www.raka.com, a glass and epoxy house that many of the folk on this board use. Larry said that pound for pound plywood is the strongest material available for the intended purpose. You can check this forum for comparative weights since they have been posted before.

Also check http://www.insulation4less.com for much more effective and lighter insulation which many of us have used.

[sushidog]

Dear Sushidog,

Many folk have pondered this notion and tackled the problem. You should search this forum.

One thing you must do is check your assumptions, which seem to be that styrofoam with glass and epoxy will be lighter and stronger than plywood and styrofoam or urethane foam. Such is not the case. A year and a half ago I spoke with Larry Steeves who owns http://www.raka.com, a glass and epoxy house that many of the folk on this board use. Larry said that pound for pound plywood is the strongest material available for the intended purpose. You can check this forum for comparative weights since they have been posted before.

Also check http://www.insulation4less.com for much more effective and lighter insulation which many of us have used.

Thanks for your reply and the insulation link. I've searched the forum, but haven't found anyone using an ultra-lightweight frameless, foam only body. I'm a noobie, so I might have missed the posts, but if you've got some links, I'd love to check them out.

I must have got some bad information. Let me run the numbers by you so you can check my math.

First, lets look at the weight of the lightest plywood available.
A 4x8 sheet of 1/8" okoume weighs 19lbs (19lbs/32sqft = .59lbs/sq ft.)

I have roughly 500sqft to cover (both inside and out) with plywood .59 x 500 = 295lbs. Add framing, glue, fasteners and insulation for another 50lbs = 345lb topper.

According to this link: http://boatdesign.net/forums/attachment ... 1126213824
Each layer of 7oz cloth cured at a 50/50 ratio with epoxy is .104lbs/sqft x 500sqft = 52lbs. x 2 layers = 104lbs +53lbs of 1.5" foamular 250 and 3lbs of screws = 160lbs., for a net savings of 185 lbs.

Now I have no doubt that the framed plywood laminate will be much stronger than the glass covered foam, especially at the thickness I'll be using. I won't need this extra strength, as my lower box will provide sufficient strength/stiffness. I'm just using the glass for encapuslation, relying on the structural integrity of the foam simply to support it's own weight and to provide rigidity. Remember this is not the actual body, just a topper. It will be supported by a strong, metal framed inner structure while traveling down the road. Others have made similar structures from simply tentage, or stretched cloth over a spruce frame (like a lightwieght aircraft canopy.)

My primary goal is light weight. I would consider the sealed and painted glued-up EPS alone if I thought it would survive, but I'm afraid that without some type of encapsulation it would come apart under the vibration and stresses of the road. I have considered a simple epoxied canvas covering as well, but I thought the fiberglass cloth would make it a little stronger.

My ultimate goal is to have a mobile retirement with a rig that gets about 30mpg. The only way I can accomplish this is with a reasonably spacious, yet lightweight, low profile pop-up tear, weighing no more than 2000lbs fully loaded. If I can limit my cargo to about 900lbs this only gives me about 1,100lbs for my empty trailer/body with cabinets, lifting struts, wiring, etc. Generator and battery will be carried in my car.

To help you better understand my dilema, here's a recent drawing of my proposed floorplan. Any advise on how to further lighten my TD will be greatly appreciated.



Thanks again for your advise.

[angib]

Each layer of 7oz cloth cured at a 50/50 ratio with epoxy is .104lbs/sqft x 500sqft = 52lbs. x 2 layers = 104lbs +53lbs of 1.5" foamular 250 and 3lbs of screws = 160lbs., for a net savings of 185 lbs.

A 50/50 ratio of glass to epoxy is appropriate for a vacuum-bagged laminate in a expert shop conditions. For a first-timer working with contact moulding, a 33/67 ratio would be more realistic. So that would add 50% to the laminate weight in your calculation.

It's still much lighter than the ply option, but then two layers of 7oz cloth is pretty thin - it will be strong enough not to fall apart but you ought to make yourself a test panel to see if you think it's 'tough' enough, particularly for stone impacts while towing.

Andrew

[GPW]

Sushi, While I think your idea is cool , it may be better to stick with "known quantities" ... These Gentlemen have put in many many thousands of hours designing and building their own versions of the vintage Teardrop trailer...and seem to have tried most everything...I think your trailer would depend upon the actual fiberglass for strength , the foam being only a support for glassing...and then heavy enough to be safe , would be too weighty to lift /PopUP... Perhaps very thin ply (1/8" laminated to foam parts would make strong , light panels... Perhaps making the pop up part start mid height on the TD, instead of lifting the whole body...???? I dunno' ...just another displaced crawfish tryin' to help...

[glassice]

Look under how i built a fiber glass trailer ! you don't need all the screw use the brown ins board .For ins. it a lot less lb than wood and ins. parts of the space shuttle are made this way. cloth will delam faster than mat. On are rentals we are using 3 layer of mat and had one renter drive his 4 Wheeler on to the top and put a few starches in to it

[madjack]

Sushi, While I think your idea is cool , it may be better to stick with "known quantities" ... These Gentlemen have put in many many thousands of hours designing and building their own versions of the vintage Teardrop trailer...and seem to have tried most everything...I think your trailer would depend upon the actual fiberglass for strength , the foam being only a support for glassing...and then heavy enough to be safe , would be too weighty to lift /PopUP... Perhaps very thin ply (1/8" laminated to foam parts would make strong , light panels... Perhaps making the pop up part start mid height on the TD, instead of lifting the whole body...???? I dunno' ...just another displaced crawfish tryin' to help...

SushiD...I haven't chimed in on your plan as of yet but believe that your goals and how you intend to accomplish them need to be rethought...unless you have a bucket of cash to throw at it...I personally think that you should wait around while plans are worked up for the Generic Standy, that Mike has started a thread on...build it and take the money saved and consider one of the new diesels that will be coming out next year for a tow vehicle...you would probably be much better served...another option would be to convert a cargo trailer into what you are looking for...JMNSHO
madjack

p.s. take a look at some of the popups and A-liners out there, for an idea as to how, what you want, is done commercially...and what their weights are...MJ

[sushidog]

Thanks for everyones input. You guys are a great bunch!

I really appreciate the thought you've given to my proposed project td.

There's great wisdom waiting and letting others break new ground - and make the mistakes. I've been considering this project for about a year, and have looked at just about all the commercially built alternatives.

Probably the most practical thing to do would be to just buy a good used A-liner lxe. It has everything I'm looking for in a hard sided pop-up and is well within my weight limits. Plus it's turn key. Just hitch up and drive away. There's a lot to be said for that. Not to mention it's a lot easier/cheaper than a custom rig would be to get repaired if something breaks on the road.

On the downside, it's 6' 6" wide and well... about as aerodynamic as a box. Nicely equipped ones go for over 15k new, but I could probably pick up a decent used one for roughly 1/2 of that. That is probably less than the TD I'm proposing, without all the work and risk.

Here's another thought to achieve my economy goals. If I mainly stay off the interstates and keep my speed down to 45-50mph range, my mileage probably won't take that big of a hit from the poor aerodynamics of the rig. I get to see more of the "real America" that way too. In a full time/retirement scenario, I will have no need to keep up the pace that I currently do with only a week's vacation. Traveling mainly at night and early morning when the roads are relatively empty is also a good way to increase my fuel mileage from more gradual stops and starts, and more constant and lower speeds.

Yes, I think using strategic trip planning coupled with better driving techniques I could easily make back the losses due to poor aerodynamics.

It's definately something to seriously consider.

[Roly Nelson]

Sushidog, it's good to see another potential builder thinking out of the box. Way out of the box. I see on your floor plan that the AC is located up front, along with the sink, stove, micro and propane tank. That's a lot of tongue weight up there. Then on your profile, it looks like the AC is located at the rear, and isn't that where the hatch opening is planned? I sure hope you plan to travel alone, because entry and exit looks like it would be an on-your-knees effort, which my sweet wife couldn't handle.

Can you provide a rear view, showing the hatch and rear window? What kind of "small car" do you have in mind? I have a 4 banger Camry which hauls my 450 lb 4x8 ft woody just fine, but it might have a real problem pulling the rig you have in mind, that looks like it would top out at 15 ft long and 5 ft wide.

Personally I would like to encourage you to give it a go. For sure, you would have a one-of-a-kind and probably have a lot of coin involved in it's manufacture. I just finished a 6 ft tear that weighs less than 250 lbs, and if you can build equally as lightweight, you will have a winner. Don't let others talk you out of your dreams, but continue to do the research as you have done so far.

Ok, it's settled, buy that insulation, fiberglass cloth, mat and epoxy and get started. Be sure to take lots of pics, we just love pics, especially of a new dream trailer that you will be enjoying as you explore our USA during your retirement.

Roly, anxious for a progress report in the near future.

[RAYVILLIAN]

Sushidog
Mike and I tend to sound like a broken record some times but have you checked out the Winter Warrior/Escape Hatch designs. We've used ours for 2 year and love the extra room and the swing up top is not that hard to build. Here's the link
http://tnttt.com/viewto ... 27e5936e67

GAry

[Tear Les]

Sushidog
Mike and I tend to sound like a broken record some times but have you checked out the Winter Warrior/Escape Hatch designs. We've used ours for 2 year and love the extra room and the swing up top is not that hard to build. Here's the link
http://tnttt.com/viewto ... 27e5936e67

GAry

Gary,

I love the WW/EH design but I've always been concerned about the weight. Any idea of what that is?

Thanks!

Sorry for the highjack...back to you Sushidog.

[sushidog]

Sushidog, it's good to see another potential builder thinking out of the box. Way out of the box. I see on your floor plan that the AC is located up front, along with the sink, stove, micro and propane tank. That's a lot of tongue weight up there. Then on your profile, it looks like the AC is located at the rear, and isn't that where the hatch opening is planned? I sure hope you plan to travel alone, because entry and exit looks like it would be an on-your-knees effort, which my sweet wife couldn't handle.

Can you provide a rear view, showing the hatch and rear window? What kind of "small car" do you have in mind? I have a 4 banger Camry which hauls my 450 lb 4x8 ft woody just fine, but it might have a real problem pulling the rig you have in mind, that looks like it would top out at 15 ft long and 5 ft wide.

Personally I would like to encourage you to give it a go. For sure, you would have a one-of-a-kind and probably have a lot of coin involved in it's manufacture. I just finished a 6 ft tear that weighs less than 250 lbs, and if you can build equally as lightweight, you will have a winner. Don't let others talk you out of your dreams, but continue to do the research as you have done so far.

Ok, it's settled, buy that insulation, fiberglass cloth, mat and epoxy and get started. Be sure to take lots of pics, we just love pics, especially of a new dream trailer that you will be enjoying as you explore our USA during your retirement.

Roly, anxious for a progress report in the near future.

Dear Roly,

The profile is and older version when I was considering a side door. I think you're right about the excess tongue weight. The a/c must be moved to the front or positioned in the starboard side (over the axle) like A-liner does. I could also position the water heater and/or propane tank over the axle directly opposite the a/c under the sofa/seat (port side.) I have since decided to go with a rear entry for structural rigidity of the long axis to resist flexing of the lower walls, which could bind the topper.

Here is a drawing from the rear perspective. My wife couldn't crawl in through a small hatch either (I'm not sure if I could), so I'm using a full door (2 seperate pieces - one on top and one on bottom, that swing together like the A-liner's door)


My tow vehicle is a Cobalt ss 2.4l auto. It has a strong engine (about 200hp with my current mods and a nice flat torque curve that puts the most of the imports to shame), and an even stronger tranny. I have removed the rear seat and lightened it somewhat to make more storage room for the generator and battery/inverter, etc..

I get great mileage now considering it's power. I'm averaging around 30mpg commuting to and from work - roughly 50/50 city/highway driving. On my last trip to the Smokies and up to Washington D/C, I averaged 34mpg of highway driving at the legal speed limit. The best it will do is 41mpg at 45mpg.

Your ultra-lightweight tear sounds intriguing. I'd love to "borrow" some of your construction ideas if I could adapt them to my design. I've got an idea about a fold-flat, pop-up shower stall with a recessed drain pan covered with a removable false floor panel. This would allow me to use the full 5' width of my galley. The cassette toilet will be on rails so it can slide under the galley and be secured behind a cabinet door when the bathroom stall is folded.

I haven't given up on my design just yet, despite the technical challenges. It's just that I'm wisely considering all my alternatives at this point.