Aluminum Frame RD

[Shadow Catcher]

Stress panel construction, CR has 1 X 1.5 X .060 aluminum framing between Filon outer skin and typical RV wall board which is Vinyl wall paperon Luan both not more than an 1/8" glued to EPS. It is strong enough to stand on. It is the panels that keep it strong!

[KCStudly]

Stress panel construction... It is the panels that keep it strong!

...and light weight, and insulated. All good things.

It does take more planning, $$$, and time to build than just straight plywood, so there is that to consider, as well.

Rather than dado the wall to fit over the side edge of the frame (I think that is what you were describing), how about gluing and screwing a small 3/4 inch cleat to the inside of the wall and resting that on top of the floor? Once the mattress goes in you'll never even know that the cleat is there, and you can keep the 1/2 ply full thickness.

[RandyG]

Rather than dado the wall to fit over the side edge of the frame (I think that is what you were describing), how about gluing and screwing a small 3/4 inch cleat to the inside of the wall and resting that on top of the floor? Once the mattress goes in you'll never even know that the cleat is there, and you can keep the 1/2 ply full thickness.

Why not both? I think the dado on the wall will add more strength than anything I glue onto it.

[KCStudly]

Why not both? I think the dado on the wall will add more strength than anything I glue onto it.

Because I share your original concern about making the 1/2 ply too thin. That, and it also creates another path to the end grains of the ply fibers down where road spray is a big concern.

Both of these concerns could easily be debunked by the voice of hundreds of more experienced TDers who have "been there and done that" before. Nothing a little (insert your preferred glue here) and (insert your preferred sealing method here) won't take care of.

The dado by itself will be lighter, so that probably is your answer. The ledger strip would probably be easier to do for most people that have a table saw, but not a router.

I'm just spewing some thoughts out there for the sake of healthy discussion, and I'm excited to see your build progress.

[Junkboy999]

Randy
I have not started my teardrop build so I’m not a TD expert, But as a seasoned woodworker can I suggest a little input.
plywood gets its strength because of multiple layers of wood with grain running in perpendicular to each other. I’m sure
you know this. Cutting a Dado in to a sheet of plywood will remove one of these layer. It is like scoring a plate of glass,
If the plywood is bent, that is where it will brake. Glueing in the edge of the cabinets or Backwall ( bulkhead ), will
replace the wood removed by the dado and make a strong joint but the wood will still tend to break on one side or the
other side of that joint if it is bent.

How to stop this.
Do not use a dado that goes from top to bottom of your wall height in a streight line. This will weaken your walls. If you
can, plan your back wall, cabinets walls, and bulkhead to interlock ( most TD are made this way ) A horizontal dado and
vertical dado system interlocking will stop all racking and make it super strong. You can, and I suggest add Cleats where
needed like under the countertop and the inside cabinets where weight might bow the the self and try to pull the dado apart.
In the late 70’s when I started woodworking with my Dad, making interlocking art deco selfing with dado's where the rage. Here
is an Example pic just to show an interlocking system and a offset back wall ( bulkhead. ) Cleats are in red.

In the picture I also added an idea for a floor that is called a torsion box. This can be ½ ply sheets and 2x2 with insulation
in there. This is just an idea if you're still worried about your frame twisting. The torsion box is how I plan to beef up my
TD build to strengthen the body because mine will have a removable top. Detaching the top of a box make the walls weaker.

[RandyG]

So, what you said is... If I cut a dado and have another piece of plywood glued in there it will replace the strength of the dado? Also I was going with the torsion box method but I was also doing it to tie in my walls to the floor.

[Junkboy999]

The plywood is strong but still flexible. A dado cuts in to that strengths. Once you place in the edge of a
shelf in to that dado it will replace some of that lost strength but now that join because rigid to any
flex in the plywood. It now becomes a stress point, if the plywood flexes. ( so don't let it flex, so support it is
what I'm trying to get across )

Your front end of your TD will be fine. The exposed side of your galley will be really flexible. Your floor will
hold the bottom sides together. The top near the hinge will hold the top. The countertop will hold the middle.
My little TD has sides are around ⅝ and they flex in and out if pushed on. Half Inch plywood now days is less
than ½ and might flex in and out while driving down the road. You might have to stiffen up the back lip of the
galley walls before you start your galley lid. (Test the out first before starting your hatch.)

Ps I spent 20 year in the AF my self. Can’t tell you know many nutplates I knocked out trying to remove HF coupler
panels. ( sorry ) Ha hahahah


Pss I fly RC planes as well so, what is that in your Avatar pic?

[RandyG]

Ok, I understand what you were saying (the 2nd time I read each post). I'm going with 1/2". It'll be fine, and the galley edge will be reinforced per another idea I have for that.

Were you a crew chief? What airframe? My avatar is a piece of tubing that we made to look like a B-52, my airframe, while deployed (many days of boredom).

[91kuhndog]

The frame is looking good Randy. Don't stress the flex in the frame too much. The HF and Northern trailers all flex alot if you step on one corner. I had gone to Northern here by the Air Base with intentions to buy one for my build but was pretty bummed at the quality. I'm not knocking those who've used a Northen Tool 5x8 but I was hoping for a more rigid frame. I've opted for a 2x3x1/8th box with 2"x3/16 cross beams. Looking at your design, I think you have a great starting point that will be plenty strong enough for what your building!

[RandyG]

Thanks Kuhndog! Right now I got the skin for the bottom but a lack of motivation, time and my garage is a wreck from the old washer and dryer in there. But I have clean close from the new washer dryer! I'm also looking into getting the axle and a hitch for my TV. I'm all over the place trying to get stuff together.

[91kuhndog]

I understand completely. I'm holding tight on starting my build until late March, when we're have a UCI and LCAP inspection.... I have about 80% of the materials needed to put it together, I'm just waiting for time. Once I get through these inspections, it'll be free sailing through the rest of the year.

[Shadow Catcher]

One of the things to remember is that aluminum has a finite modulus of elasticity that is much less than steel. MM #1 failed at the tongue with its second owner. One example of what can happen http://www.youtube.com/watch?v=TBcC8zqNjKk However there are a bunch of DC 3's still flying.

[rowerwet]

the DC-3 was wildly over-built, the joke is they took all the same frames and spaced them out double to make the DC-4, having seen both inside and out I think there is some truth to the joke. The rivet spacing is super tight on the DC-3 also, compared to any current aircraft coming off the line.
An aluminum tongue could work, but I think it may end up much like many car wheels, where the aluminum wheel is heavier than the steel one of the same dia.

[angib]

And don't forget that the DC-3 was made with aluminium alloys that didn't age-harden (like Duralumin, for example) so they are much less prone to cracking from fatigue (and not as strong) - which is how come so many DC-3s are not being withdrawn from service for having used up all their airframe hours as more modern planes would.

[Ron Dickey]

And don't forget that the DC-3 was made with aluminum alloys that didn't age-harden (like Duralumin, for example) so they are much less prone to cracking from fatigue (and not as strong) - which is how come so many DC-3s are not being withdrawn from service for having used up all their airframe hours as more modern planes would.

So how long do you think his will last assuming he stays on the road and does not go in the outback?

Randy, where did you get the aluminum? I wondered it would not be a good idea to run a bolt every once in a while to make sure the rivet's stay? I hear welding aluminum is a bear!

Ron Dickey
working on similar build the Cross Bow but am still working on frame ideas!