Proof of Concept

[markhusbands]

Greetings,
I'm trying to come up with a concept for my first trailer attempt, and wanted to see if anyone cared to provide some feedback about my initial design ideas. I'm hoping that I'm at least sort of close to the mark and just need to do some refinement.

My basic design criteria are:

Built on the HF 4x8 trailer chassis, which I already have. I'm willing to move the axle to the 38" mark (which I guess is just some measuring and drilling) but I'm a little nervous about doing a lot of other mods. For example, I'm inclined to put the axle under the springs because I assume that will give better over all clearance.

5' wide of close to it for more sleep space.

Tall and strong enough to put a roof-top tent on top. There's going to be four of us - two adults and two small kids - so we'll sleep two up, two down. So the roof height needs to hit a range in the mid to upper six foot range.

I'd like to be able to sit around a puny dinette just to play cards with the kids or sit out some rain. Doesn't have to be super plush.

I need to be able to pull it with my Honda Element, which is not too strong, in Colorado, which is pretty hilly. So it needs to be fairly light.

My current concept is below. The result is something like a tall pudgy teardrop or a tiny travel trailer.

I'm assuming a few things that may be inaccurate. For example, I'm assuming a four inch thick sandwich floor on top of a two inch thick frame. That adds up. I'm totally guessing that the stock clearance with the HF wheel is 1'4" (1'6" below floor sandwich) and that the wheel is about 20" diameter. That may be too much stock clearance. I really want a better handle on this because I need to figure out the wheel well radius and I need to figure out the right total height to make the roof tent work (and right now it seems a little high).

teardrop study3.jpg (214.05 KiB) Viewed 1544 times

teardrop study 1.jpg (252.39 KiB) Viewed 1544 times

teardrop study2.jpg (212.38 KiB) Viewed 1544 times

Thanks for any recommendations you might have, Mark.

[Woodbutcher]

Hi Mark, welcome. I built a trailer on a 4x8 HF trailer. I built over the wheels and I did a drop floor to allow for sitting. Rather then try to explain what I did here is my build thread. viewtopic.php?f=50&t=39036 It is sort of long but it may help you. My floor was 3/4" and built right on the frame. I can not see any reason to make a 4" floor. I can't offer any ideas on the tent top, I have never considered that. Good luck and enjoy your build. It is really a fun way to travel.

Steve

[jeff0520]

Hello,
I built on the HF 4x8 as well. I went with an overall width of 73" to allow for a full queen sized bed. If you are going to go 5' wide, might as well go 6' and enjoy a little luxury.

As far as the roof top tent idea, a few things spring to mind. First, better carefully plan your attachment for the tent. Tents imply stakes driven in. Of course you'll have to substitute something. Maybe D rings on the sides of the camper and some sort of bungee to hold the fabric down. Be sure that however you attach the tent to the roof, it's fully waterproof. Next you'll have to figure out how to make sure tent poles don't scratch up your roof. That could cause problems with leaking depending on how you skin your roof. Maybe a dome type tent where the poles sit in a fabric pocket would work. Finally, there's the issue of access. How do you plan to get people and gear up there? If it's a wall mounted ladder, you'll have to plan hard attachment points into your wall framing to give it enough strength. I have no idea on that. I always overbuild everything. There's a few engineer types around here who might be willing to help out with that.
It's an interesting concept. I'm looking forward to seeing the build thread.

Jeff

[markhusbands]

The roof tent is a safari style folding model (tfrontunner), so all that is required is that I install a rack on the trailer roof with typical crossbars. I have the tent on a yakima rack on my Element right now. All that I have to worry about is that the rack and roof can handle the weight, and that the tent ends up in the 6'6" above ground zone. I'll post another pic of the roof tent when I can.

So maybe I can do a floor sandwich with 1/4" ply around 1"x2" cross spars equaling 2 1/2" total thickness. Or even thinner ply?

[markhusbands]

Here's the roof tent. Gives an idea of why I need to get the final trailer roof height right....try to picture a teardrop in the place of the Honda.

roof tent.jpg (205.75 KiB) Viewed 1505 times

[angib]

Assorted thoughts:
- That dinette looks awfully short, so that adults will have their knees nearly pressed into the opposite seat edge. You should try mocking up something similar at home from cardboard boxes to see if it's not too tight for you.

- Adding a table makes getting in and out the doors a problem, so I would use a small table that sits on a central tube support (as used in boats).

- You seem to be adding a deep floor in the belief that this will support the overhanging sides, but this isn't really true. The front face of the body (where the roof/front wall meets the floor) sits on the chassis and directly supports the front end of the sidewalls, so any floor strengthening at the front end is a waste of time. Normally teardrops have a galley bulkhead that crosses the chassis and connects to the sidewalls - in practice this will carry all the weight of the back half of the body from the sidewalls back into the chassis. However you appear to not have any bulkhead below the bunk level which, if true, gives a serious strength problem for the back end of the body. It might be great for storage but it's bad for strength.

If you want light weight, I suggest you continue the galley bulkhead down to the floor so that it directly connects the frame and sidewalls. You can then leave out all the floor strengthening. If you are determined to have that big hole in the body, then you do need to add lots of floor strengthening (which will be heavy). How much, I don't know.

[markhusbands]

Actually I think the dinette height at about 18" with cushion is pretty standard. If anything, it's the shallow seat at 16" and low back on one side that may be tight. And the table of course at 24" across is pretty narrow. But any wider than that and I'll have to change the design a bit (I do have an idea for how to do so). My assumption on the table is that I'd have doors on both sides (forgot to show on concept drawing) and each table end would have a piano hinge to let you slide onto the bench. We're not huge people so I'm willing to do somewhat cramped - seems like an inherent TD trade-off. Oh, and just for clarification, the tallish pad in the fore dinette bench would be fitted to the table top when the table is dropped into sleep mode.

Regarding the galley, because it is pretty shallow I thought I might put the "lower bulkhead a little forward of the "upper" bulkhead so that I could fit a cooler in longways on slides. So the bulk head would do a zig zag, BUT I'd also have the other benching going across the walls at several points to stiffen things up. My four inch floor guesstimate was originally based on the 2x4s I've seen some posters use, but it does seem like overhanging the sides a mere six inches or so shouldn't require such massive framing. Some thinner honeycombed sandwich should do it.....right?

[markhusbands]

Okay, here is what I think is the best I can do without enalrging the shell (and I really don't want to because the scale is pretty good for my tow car).

The table and dinette seats are slightly wider. Table is still a narrow 26" but I can't figure out how to make it wider without getting rid of all the galley cabinets to create headroom. I think these dimensions would work for a smallish dinette. To compensate for the narrow foot room I'd leave the under bench storage "open" with fabric storage boxes perhaps, so that there'd be a little extra heel space.

I still am very uncertain about how high the HF frame sits off the ground in standard axle configuration. If anyone knows that'd be a big help. If I have to I'd consider an "over the springs" mount to lower the roof to my target height. I guess you lose some frame clearance but no axle clearance, so maybe it doesn't matter.

teardrop study 2-1.jpg (218.53 KiB) Viewed 1469 times

[markhusbands]

Here's how it would look in sleep mode. I realized each bench panel would be 19" - so two pairs of piano hinged panels totally 6'4".

teardrop study 2 sleeper -1.jpg (185.64 KiB) Viewed 1455 times

[angib]

Actually I think the dinette height at about 18" with cushion is pretty standard.

My comment was about the length (front to back) of the dinette, not its height. Indeed if you are short on length, extra seat height is a good thing as the more upright you sit, the less length you need.

[Roly Nelson]

Looks like you have some neat ideas for your build. I have seating for four adults within my 4 x 8 woody TD, and it is accomplished by folding down the interior cabinet, flipping the table up out of the floor and having a foot well that will handle 8 adult feet. Works just great for eating the prime rib when it is raining or a secluded game of strip poker.
Roly, the li'l ol' So Cal TD guy.......and by the way, welcome to the forum, you'll love it, as we all do.

[markhusbands]

Actually I think the dinette height at about 18" with cushion is pretty standard.

My comment was about the length (front to back) of the dinette, not its height. Indeed if you are short on length, extra seat height is a good thing as the more upright you sit, the less length you need.

Got it. Yes, I think the slightly deeper version would work better. These would be a 19" seat and 19" back, each covered with 2" foam (so 17" exposed, uncompressed surface) with pretty upright seating. That really seems pretty standard. The upright measure is 16" plus 2" foam. Maybe another inch would be best...

Then that just leaves the somewhat narrow table surface to deal with.

Still a bit lost about the HF "above ground" dimensions to plan on. For example, how high should I plan the galley surface from frame up?

[markhusbands]

And thanks for the welcomes, by the way.

[Rlowell]

Welcome to the madness...

To answer one of your questions...my galley counter height is 35" from the ground. You want a comfortable working height to design around.
You can see how I did mine in my photo gallery. Over all design is looking good although I would be concerned about the overall height with the tent
on a short chassis because of cross winds and trucks. My 2 cents...

Rod

[markhusbands]

...my galley counter height is 35" from the ground. You want a comfortable working height to design around.

Did you use the HF? If so, how high from frame to counter did you go to get the 35" ground to counter height (which sounds just right)?