How much is too little?

[PonyExpress]

Everytime I get my design worked out, gas prices go up and I go back to the drawing board wondering if I can cut any more weight... but, I don't want to cut too far.

On the HF 1175 folding trailer, how many cross members do I really need? Can I get by with just my wood framed 1/2" ply floor bolted to the outside frame with no crossmembers at all? What if I changed to a torsion box design for the floor?

Could I use one cross member cut in half to join the two halves of the trailer together? If I get the two halves welded, can I do without any cross members run inside the frame? Anybody know how much a crossmember actually weighs (maybe I'm not saving that much weight)?

Thanks for your help,

PonyExpress

[mandy]

I think there is a td the fits that catagory in the design library.
Here you go http://www.angib.pwp.blueyonder.co.uk/teardrop/tear32.htm

Have Fun
Mandy

[angib]

If you want to save weight, it's more important to look at the body, rather than tinker with the frame.

A 1/2" ply floor with light framing (ie, none of that 2x4 nonsense) will weigh around 2.5lb/ft2 - around 80lb for a 4'x8'. If you're going to have a mattress inside all the time, so you won't kneel with all your weight on one knee on a small area, then 3/8" or even 1/4" ply would be enough. It needs regular support so either light wood framing (1x2 at 16" centres?) or the original trailer cross members.

The lightest simple floor is probably ply laid straight on the HF frame, but then you get a joining problem to the wall at the edges, which is where some wood framing is useful. If you have wood framing, then having frame cross members becomes pointless and you can go for an all-wood/ply floor.

Lots of people build teardrop floors as though they were house floors, which they aren't - the load from a person kneeling part of their weight on one knee (the highest point load in a teardrop, I'd say) is way, way less than the load from a person jumping on one foot, which is what house floors need to withstand.

It's worth looking Rik Kellers' Road Toad for an all-wood floor - two skins of 4mm (5/32") ply with 1x poplar framing (and too much framing around the edges, in my view)

Not sure that helped you, but I vented my prejudice!

Andrew

[Arne]

I built my floor like an interior house hollow-core door. 3/8 ply on top, 1/8 on the bottom, foam in between.

if you go to www.freewebs.com/aero-1 the first pic is my frame in it's final form..

The floor has wood in it only where I need support for walls and mounting points (like spare tire underneath). Where I needed little strength, I cut strips of 1/2" ply and stood them on end every 12" as x-members in the floor for the I-beam effect between top and bottom ply.

[del]

If you want to save weight, it's more important to look at the body, rather than tinker with the frame.

A 1/2" ply floor with light framing (ie, none of that 2x4 nonsense) will weigh around 2.5lb/ft2 - around 80lb for a 4'x8'. If you're going to have a mattress inside all the time, so you won't kneel with all your weight on one knee on a small area, then 3/8" or even 1/4" ply would be enough. It needs regular support so either light wood framing (1x2 at 16" centres?) or the original trailer cross members.


Andrew

I used 3/8" ply for my floor on the jelly belly, it has proved more than sufficient for tear drop floor before I put In the mattress. With the mattress 1/4" would have been fine. One guy from Idaho built a floor with two 1/8" plys for the top of the floor, one bys for structure and an 1/8" skin on the bottom, all this with no frame (using no frame is alot of work and not forgiving, (read a small flaw will destroy your work) Andrews Superleggera frame would be an easier answer). Too work on the thinner floor, lay thicker scraps of ply on the floor to put your knees on. Walls to can be lightened to, Steve used on the pufin I believe 3/8" ply for the "solid" wall type construction, if making sandwich walls consider 1/8" ply for the inside and outside skin. I used 1/8" ply covered in fiberglass on mine and have towed it 6,000 plus miles this winter with no problems.

my 2c's del

[PonyExpress]

Thanks for the ideas.

Apparently, the strength of the trailer is mostly in its shape, not the thickness of the materials. It looks like 1/2 ply is more floor than I need and framing can be 1x2s. My wife is pushing for a 54x80 mattress so I'll need a frame out over the wheels.

[starleen2]

if it is gas mileage vs weight that you are concerned over - the addition (or subtraction)of a hundred to two hundred pounds might result in a small decrease (increase)in mileage - do you worry about mileage when you carry an extra passenger in your vehicle? I haven’t noticed any appreciable mileage savings when I’m fully loaded vs empty. And I tow with a Jeep wrangler! Gas prices shouldn't dictate your build. However there is a lot to be said about being too heavy!

[Alphacarina]

I haven’t noticed any appreciable mileage savings when I’m fully loaded vs empty. And I tow with a Jeep wrangler! Gas prices shouldn't dictate your build. However there is a lot to be said about being too heavy!

Some vehicles are like that - I have an F-350 flatbed which gets 13 MPG empty and gets about 12 MPG towing 10,000 pounds

If he's towing with a small car though, a couple hundred pounds and/or a slight increase in frontal area can add up to a marked decrease in fuel economy - 10 or 15% probably and that wouldn't be acceptible to me

Everything I tow with my little 4 cylinder station wagon was designed and built with gas mileage in mind . . . . and that was back when gas was $2 a gallon. I get 30 to 33 MPG when not towing (assuming I don't have a couple of 200 pounders in the back seat) and I would really like to find a way to still get 30 when I'm towing too - If at all possible

I buy my cars with the 30 MPG number in mind - Not even slightly interested in anything which can't get at least 30, so if you have a small car, why would you not have gas mileage in mind when building a camping trailer??

Don

[Mini Renegade]

I`m building my trailer as light as I possibly can with the exception of a 1/2" floor, and It is light, the whole thing can be lifted by 3 people, the only problem is its TOO light, not enough weight in the back end, which has given me an unladen nose/tongue weight of 70-80 kg, about 150 pounds. Just need to load it up in the back to tow it.Strength wise its rock solid, I can stand on the roof!