Profile-Radius corners

[Capebuild]

I've noticed some trailer profiles, on the bottom, carry the sides straight down to the chassis frame, making the frame meet up with the corners of the trailer's profile. Others have a generous radius or curve on the profile's bottom
and where the chassis frame meets where the curve transitions to the bottom flat. See attached. One advantage I can see of having the curves is it allows the chassis frame to be less in overall length. I suppose it's also an aesthetic preference. I'm also wondering if it provides less support to the overhang of the trailer cabin in the galley area if the chassis frame does not extend out to support the galley in that area.

I'm also wondering if the chassis frame could be even less length in the rear so the trailer would overhang more than what is shown. How much overhang can there be? I'd imagine there could be a significant weight saving on the frame.

I'm asking for any thoughts others might have on this.
Thanks very much for any thoughts and insights.

John

[MickinOz]

You lose flat floor space when the profile rolls in at the bottom.
Pretty much a non-issue on a 10 footer, but not so good on an 8 footer.
Its one reason I went with a stretched Generic Benroy - 80 inches of flat floor in the cabin and 24 inches in the galley in a 9 foot length.

Structurally, a properly constructed frame and skin wall, or a 3/4 inch solid ply wall, isn't going to sag if it overhangs the trailer frame a little.
However, if the overhang gets ridiculous, outboard weight might exert a fair bit of stress on your system for securing the body of the camper to the trailer frame.
That would be quite a bit of overhang, though.

Aesthetically, the shape is pleasing to the eye, especially if you follow Tonty Latham's profile.

[Tom&Shelly]

I've noticed some trailer profiles, on the bottom, carry the sides straight down to the chassis frame, making the frame meet up with the corners of the trailer's profile. Others have a generous radius or curve on the profile's bottom
and where the chassis frame meets where the curve transitions to the bottom flat. See attached. One advantage I can see of having the curves is it allows the chassis frame to be less in overall length. I suppose it's also an aesthetic preference. I'm also wondering if it provides less support to the overhang of the trailer cabin in the galley area if the chassis frame does not extend out to support the galley in that area.

I'm also wondering if the chassis frame could be even less length in the rear so the trailer would overhang more than what is shown. How much overhang can there be? I'd imagine there could be a significant weight saving on the frame.

I'm asking for any thoughts others might have on this.
Thanks very much for any thoughts and insights.

John

Hi John,

This isn't quite an answer to your question, but just what Shelly and I thought about when we considered designs:

We used glass and epoxy, then a bed liner, to finish ours (that was the first time we tried either process). We glassed and epoxied the sides before erecting them on the frame, and, of course, did our hatch on a workbench, all to avoid working on vertical surfaces when possible. If we could have avoided having to glass and epoxy the vertical surface on the front, we would have. No way we would have considered the added complication of a surface past vertical.

That said, I don't remember any particular problems with vertical surfaces, and I suspect we would consider more interesting shapes if we ever build another one.

On the other hand, floor space in the teardrop is at a premium. I agree the curves at the bottom in your profiles look prettier, and it looks like you'll get more volume by extending past the trailer frame, but it seems you will have to be clever to be able to use that extra volume to advantage. (I have no doubt you can do that, but it bears thinking about, in my opinion.)

My 2 cents.

Tom

[bobhenry]

A flash back to Feb. 07........ viewtopic.php?f=27&t=13925&p=180832#p180832

[halfdome, Danny]

Their called roll pans and are supposed to look kind of like an old hot rod.
I have them front and rear and their 6”.
They have no impact on my floor plan just look nice.
I make them as sub-assembly’s and attach them before skinning the exterior.

Here's the sub-assemblies that attach to the underside of the floor.
After they are attached I skin them in 2 layers of 1/8" Baltic Birch plywood before skinning them in aluminum.
Danny

[noseoil]

With our 5x9 (the Benroy design) there wasn't enough floor space for the mattress, galley & headboard, unless the ends were squared off at the floor. If the bottoms were rolled-in at the frame (tumblehome), we would have lost enough room to have to get rid of something we wanted. This is just part of the compromises in thinking you need to make, for decisions on a small footprint build.

A 4x8 is pretty small for 2 people sleeping comfortably (especially if there's only one entry door), a 5x9 is the "medium" size with good enough room for a full size bed & a 5x10 is really MUCH bigger than a 4x8, it feels like twice as big in terms of storage, sleeping & a good working galley.

[tony.latham]

I'd imagine there could be a significant weight saving on the frame.

Wouldn't you be cutting maybe 12" of steel off a shorter chassis? How much weight is that?.

I built this little 4 x 8' for my sis and bro-in-law.



He drew up the profile and insisted on rolling in the front and the back. He's a graphic artist and won out. After all, it was for them, not me. My sis is ... I dunno 5' 6"? He's 6'. They lost 9" of floor space with that profile.

She can stretch out just fine. He can't. So I'm okay with it.

I still think it was a mistake. I've always said a foot is a mile in a teardrop and 9" has to be close to that.

Maybe you've done this, but I would draw out both profiles with the interior stuff such as bulkheads, etc before you make the decision.



Tony

[halfdome, Danny]

Here I've used Gorilla Glue to attach them to the underside of the floor plywood.

As you can see in these photos my roll pans have absolutely no impact on how long the floor/cabin is as the are decorative items that are attached to the underside of the floor.
The chassis is 6" shorter only at the rear and has no impact on anything.

When I bought a full sized tracing of my profile from Grant Whipp they were drawn out.
I had to come up with my own idea how to make the subassemblies.
I get positive comments on them now and then and we enjoy the look.

They show in my signature photos.
Danny

[Pmullen503]

A thought about the "roll under" detail and water. You don't want to create a place where water could pool between the frame and the body. Details like a drip edge to direct any water away should be considered.

I do like the way it looks.

[halfdome, Danny]

A thought about the "roll under" detail and water. You don't want to create a place where water could pool between the frame and the body. Details like a drip edge to direct any water away should be considered.

I do like the way it looks.

I understand you're concern this is why I make subassemblies and attach the 3/4 " plywood base upside-down to the sealed floor.
Nothing touches the frame and they become part of the body sealed with undercoating, Gorilla Glue and contact cemented on aluminum.
There's no place for water to pool, most freeway driven water never affects the underside of the floor.
The two larger ones go between the rear hitch receiver and the two small ones go up front.
Never had a water issue.
It's your choice, Danny

[Pmullen503]

I was referring to the OP. Yours is a good solution.

[MickinOz]

Danny, you have small radius roll pans that fit under the floor.
It appears your front and rear are straight up and down so, as you say, no loss of floor area.
If you look at the suggested profiles John posted, and the 8 x 4 Tony did for his sister, which has actual "tumblehome" - though I usually reserve that term for when the topsides of a boat roll in - then there can't help but be loss of floor.

Planning to do it similar to your way on the next build, by the way

[Capebuild]

Thanks all for the feedback.

Danny, what you've shown is a really great idea. Thanks for posting those photos. Before the photos in your album disappeared a while back I had grabbed a bunch of screen shots of your builds and was just looking at them and especially the bottom radius corner areas (really nice trailer BTW, as I've said before, very clean design). Just so I'm understanding how you did this (radius the corners with those add on pans you show).... I now see your cabin sides actually extend down past the bottom surface of the chassis frame, the tongue box sides extending even a bit more. I suppose you loose some road clearance. How much distance between road and bottom of trailer do you think there is? If I were to do a cross section through middle of your trailer, would it kind of look like half an I-Beam, where the sides extend down past the chassis, the chassis frame being the horizontal of the half I-Beam and the two side walls being the verticals of the half I-Beam? I guess what I'm asking is do you have a photo showing the bottom of your trailer?


Thanks, very much, again.

John

Edit: Danny, I've attached a rough layout to kind of show what I think your setup looks like to accommodate those curved pans.... having the right and left sides overhang below the chassis frame. Does this look correct? Thanks

2nd Edit: Danny, I'm assuming you have a 5 foot wide trailer...how wide and how long would you say your chassis frame is, the section where the cabin is fix to, the outer dimension of that rectangle (and I realize your cabin extends out
over the "Y" of the tongue area.... but just the rectangular area? Thanks so much if you have that info.

[MickinOz]

Its easy enough done. I will add one more proviso.

Every bit you allow down past the floor so you can have a nice radius without losing floor length, loses you some head room.

If you build with inner frame and skins on the wall, its easy enough to make the walls whatever size you like.
If you use 5 x 5 sheets of ply, you can have a 10 x 5 wall with only one join.

If you want to stick with standard 8 x 4's, head room might become an issue.

[halfdome, Danny]

Thanks all for the feedback.

Danny, what you've shown is a really great idea. Thanks for posting those photos. Before the photos in your album disappeared a while back I had grabbed a bunch of screen shots of your builds and was just looking at them and especially the bottom radius corner areas (really nice trailer BTW, as I've said before, very clean design). Just so I'm understanding how you did this (radius the corners with those add on pans you show).... I now see your cabin sides actually extend down past the bottom surface of the chassis frame, the tongue box sides extending even a bit more. I suppose you loose some road clearance. How much distance between road and bottom of trailer do you think there is? If I were to do a cross section through middle of your trailer, would it kind of look like half an I-Beam, where the sides extend down past the chassis, the chassis frame being the horizontal of the half I-Beam and the two side walls being the verticals of the half I-Beam? I guess what I'm asking is do you have a photo showing the bottom of your trailer?


Thanks, very much, again.

John

Edit: Danny, I've attached a rough layout to kind of show what I think your setup looks like to accommodate those curved pans.... having the right and left sides overhang below the chassis frame. Does this look correct? Thanks

2nd Edit: Danny, I'm assuming you have a 5 foot wide trailer...how wide and how long would you say your chassis frame is, the section where the cabin is fix to, the outer dimension of that rectangle (and I realize your cabin extends out
over the "Y" of the tongue area.... but just the rectangular area? Thanks so much if you have that info.

John, My walls are about 13 3/8" from the garage floor at the axle which is a 22 1/2 deg. down Dexter torsion axle.
My walls do hide the chassis and hang over it 3 1/2" and about 5/8" away from each side of the chassis ( 5/8" gap between outer chassis and inner wall).
I guess you could call it a half an "I" beam and my tongue box hangs down the exact same measurements.

Doing the math my overall cabin is 60" wide x 120" long, the walls are 3/4" thick and a 5/8" gap to the chassis brings me to about 57 1/4" wide for the 98" long chassis before the tongue "Y".
The cabin overhangs the rear of the chassis 6" to accommodate the roll pans, the roll pans actually strengthen the rear of the teardrop.
The piece that "Y" angles to my 4' hitch receiver is 55 1/4" cut at 30 deg at the frame and 60 deg at the front area of the 4' hitch receiver.
You'll need to lay it out to get your measurements and angles.

This picture is the closest I can come up with for chassis overhang as the rest have roll pans installed.

If you go with a removable tongue you can dial in the proper length to avoid a jack knife situation.
It's a shame Picturetrail.com has shut down it was a great picture hosting site, I'll miss it.

I hope I've answered all your questions.

Thanks for the kudos, I put my everything into whatever I'm building.
Danny