Spars (roof supports)

[GPW]

Rob , curved like everyone elses... greater than a 2.5' radius on the smallest curve , was going to work in layers with Fiberglas mesh in between (lightopen mesh like sheetrock stuff) ... and now Mike has concerned me with rocks ...??? and now tree limbs ???
Joined panels will be the sides , the most important structure ... so will err on the side of STRONG ...

#1 Pine (clear) is pretty common here, did all the millwork in the house /studio with it ...but our common cypress , works better , holds nails/screws better and is insect /rot resistant ...besides being available in trees....Cheap that way ...

[48Rob]

GPW,

Do you mean "tub" as in bathtub, ot "tub" as in big unfinished shell?
...Yes, it is a bathtub...

The sides are oversized for most teardrops, 3/4".
The frame (chassis) is heavier than needed, mostly 'cause I wanted to recycle an old frame.
Roof ribs are 1 x 2, actual size is 3/4" x 2 and are Oak.
At the seams on the roof (skin) there is an extra rib turned horizontally, that is well fastened to the vertical rib.
Because when you form two layers of ply over a curved surface, the joints do not line up (nor do you want them to) the 3/4" with of one rib is not sufficient as a nailing surface.
Roof skin is two sheets of 1/8" Birch plywood glued together, and well fastened to the ribs and sides.
Did this for three reasons; strength, ease in conforming to the radius, and the need for a "face" side both inside and out.

Worked out well, I can walk on the roof, carefully.


Other than that, the dimensions of the construction material are pretty standard.

Rob

[EZ]

The width of my roof will be 5 1/2 feet. I am concerned that the 6mm Luan will sag in the middle where the roofline is flat (about 4 feet between the front and rear curve). Maybe I will need to install a "beam" across the middle that protrudes into the cabin? I was only planning on using 3/4" insulation for the top with 3/4" (1 X's) for the roof supports because the 3/4" insulation costs half of what the 1 1/2" does and my roof will take 4-5 sheets. Maybe the roof gets stronger than I think as the inside and outside skin is installed. Or maybe I will have to go with 1 1/2".

Ed

[48Rob]

Ed,

Sag?

The luan won't sag unless the supports sag (assuming the support centers are reasonable ie; not 24") ...from snowload, windload, or just the weight of the building material.

A 1" x 3/4 roof support seems to be stretching the margin pretty thin...I wouldn't.

Now if it were a steel support, maybe, but only if the centers were 12" or less, and I'd still be concerned (because of the span) if I ever needed to climb up on top.

No offense, but if you feel a need for a support beam under your roof framing, then perhaps the roof frame design needs to be reconsidered.

If you're just concerned about rainwater collecting on the flat area, you can cut arch shaped roof supports, or chose bowed lumber to cut them from.

The roof structure will become stronger because of the two sheets of ply attached to the ribs, but not that much stronger in an unsupported area (out in the middle).
Adding supports that go from rib to rib to spread/share the weight put on one rib, to the next will also help, but a given dimension can only handle a given amount of weight.
If cost is a big concern, you could go with a larger support, and still use the 3/4" insulation.
A dead air space is a good thing too!

Rob

[48Rob]

GPW,

IF you were using a single sheet of 1/8" ply for the roof, and nothing else, then yes, you would need to be very worried about something breaking through it.

If you plan to get your 3/8" thick roof by laminating three sheets of 1/8" ply, then you'll have a very strong roof, and no problems following the curves.

As for the tree limbs, well, that's a personal thing.
Chances are pretty slim, but stuff happens

Most generally folks in camgrounds park under trees...
Rob included (except for large old trees waiting to drop large old limbs...)

The don't publicize such incidents too often, but again, stuff happens.

Tree limbs tend to fall across things, as opposed to straight through, like a spear, so the floor to ceiling divider walls should slow it down enough to be survivable, I hope

Rob

[Kens]

Happened to me. I was tent camping under a pine tree heard a crack in the middle of the night a limb took out my dinning canopy. Scared the s#@t out of me. Didn't sleep well after that. Kens

[IndyTom]

Just a thought on "clear" pine. If I am needing 1X2's or 2X2's and wanting them clear, I shop for pieces of lumber sized from 2X6 and up and then cut what I need. It seems, that at least here in Indiana, the clearest trees are saved for larger pieces of framing lumber. I have cut many 1X2's and 2X2's from larger lumber and gotten all perfectly clear pieces at a fraction of the cost of buying them already cut. I have found that I can do it with a Skil saw and a cutting guide.

[mikeschn]

There ya go IndyTom... that's what I did too...

Mike...

[GPW]

Guys , since I'm going with a slightly larger TD like Rob , I'll be using the 3/4" sides , battened/lapped at the joins... I'm thinking now that a T-shaped bow (spar) would be the ticket , say 1"x3" for the vertical glued/screwed perpendicular to a 1"x4" for a flat surface to attach the roof too ... wouldn't be heavy , should be strong ... I'm really trying to get by not cutting "filler blocks between the ribs on the sides... Pia job of custom fitting, probably take more time than the combined rest of the chassis ... I have full size cardboard patterns that I made , but that aspect seems daunting ....I dunno ... By reading everything else , have laid out all cross walls /shelves/cabinets to add to the torsional stiffness of the TD cab ... have even included a pipe/flange clothes rod across the top cabin to
1. Hold her worships haute' coture... and my camo jacket
2. further strengthen the cab ..bolted between the sides at the batten joint ...
Using all all the angles I've picked up here (Thanks !!!) and trying to think ahead.... But things change as I learn more...gonna' have to make the leap sometime ...



is it really a bathtub ??? For who .... Herve Villachasse hahahaha

[EZ]

Rob,

I wrote that description kind of badly. I was planning on using 1 X 2's horizontally instead of on end so the roof would use 3/4" foam. I don't think there is much strength in them that way. I might as well do it right with 1 1/2" and then I can use 2 X 2's for the long, flat span. I like the idea of using some slightly bowed pieces. That might woork really well. Maybe I can use fiberglass insulation instead of poly foam for a large cost saving. Not as many R's but affordable. Or maybe I wasn't supposed to because of condensation. I will have to search the forum again.....

Thanks for the feedback.

Ed

[48Rob]

Morning Ed,

Could be that I read it wrong too

The idea of a thinner profile roof is not a bad one, but as you suspect, there is very little strength in a 1 x laid flat.
In fact, it will likely bow under its own weight.

Condensation is a valid concern.
Fiberglass can be used, and should not be discounted because of that potential.
However, if someone implies that using fiberglass will cause problems because of condensation, but foam won't, please study those thoughts carefully!
While it is true that fiberglass will "soak up" and hold moisture, and rigid foam will not...it makes a whole lot more sense to correct the condensation problem, and not worry about which kind of insulation to use.

A condensation problem will destroy a trailer in short order.
If you are paneling the inside (ceiling) a vapor barrier should be placed between the paneling and the roof ribs, with the insulation above that, topped off with a dead air space if desired, or resulting.

A strong majority of condensation in a tear is the result of human presence.
Some can occur while in storage, but most at night while sleeping.
Much of the potential for damage can be prevented by leaving a roof vent and side window cracked open, to allow the warm moist air to escape.
In fact, if your tear is anywhere near airtight (most are) if you don't leave a window or vent cracked open, you may not wake up...

A small sidewall vent, that stays open all the time is a good idea, both for breathing and venting the tear.

Anyway, point is, condensation happens.
Proper venting helps a lot, a plastic vapor barrier only costs a couple dollars...

Rob

PS. Here is a link to an article on condensation if you're interested.
http://groups.msn.com/RepairingYesterdaysTrailers/faq21.msnw

[GPW]

Not wake up ???Full time vent is certainly a mandatory thing to consider ... noticed all the old timers had em ' ...must have known something ...Thanks Rob , would have overlooked that ....
Hoping the small AC will keep out alot of the condensation ...will probably be used as much as possible with "her worship" on board ...

Rob , I'm building a bigger one like yours , by about how much did you upsize your materials for the larger size....Yours came out GREAT !!!!

Now the ole' lady wants a tub also .... Hmmmmmmm?

[48Rob]

GPW,

Now the ole' lady wants a tub also .... Hmmmmmmm?

She looks like Herve...right?

Okay, enough poking...the tub is small, and not ideal, but at 6'-2 I fit, and getting clean in my own space is important.
Usually the camp showers are nice, but I, like many others have been to those where you worry about catching something from the floor!

And then there are the multi day swap meet stays, with no showers, or anything available...some fellas are okay with no showers for days on end, but not me.

I didn't really upsize many things.
The frame is a bit beefier than a tear, but mostly cause it was already bigger from carying a travel trailer.
The walls, at 3/4" didn't have to be, I just wanted them thicker.
My roof ribs are 1 x 2 Oak, but are on or near 12" centers.
Nothing else I can think of is/was supersized because of the larger dimensions.
It is 12'-4" long.
7' wide.
And 5'-2" tall.

Rob

[GPW]

She has a much better moustache !!!!!
Rob , Thanks for the specs .... building roughly the SAME size... The tub is really cool , plus a potty , mrs. Herve will be in Fantasy Teardrop Island.. Nice for a place to wash !!! Important !!
Is your outer trim "structural"??? It looks great !!! I had thought of making my side frames out of 3/4" Birch ply ... cutting out the "middles" , leaving framework to be covered on both sides and insulated .... enormous amount of waste ply ... but easier than "piecing" (unless you know a better way )... all those straight lengths together ...

Looks like I'm going to have to build my own trailer to fit ... going to use mostly 3"x3"x1/4" angle iron , and a 3x3 tube for the trailer spine ... think that's enough ??? or too much???

[48Rob]

GPW,

The outer trim is not structural.
It is not a "true" woody.
The uprights do serve a purpose though, as they hold the side panels together.

If you're stick framing it anyway (in effect) it would be easier to use dimension lumber...

On a 2000-3000# trailer, 2 x 3 x 1/4" tube is the smallest I'd go.
For using angle, I think I'd consult a pro...

The 3 x 3 tongue seems large and ungainly, I used 2 x 2 x 1/4", but also added a section underneath to keep it from flexing so much, because it is rather long.

Rob