C-channel break. What to do?

[TxDave]

So, I'm replacing the subfloor in the rear of my '71 Sovereign. The last 18" or so was rotted away. I decided to go ahead and replace the entire 4' section. Fortunately, the frame looks pretty good except for surface rust which I will take care of.

You will notice the break in the C-channel at both rear corners. How should I go about repairing this? Thanks, in advance.

[MarkR]

I'd say you could solve that a few different ways.

Best way would be to have a sheet metal shop (heating and ac shop) "brake" a new C-Channel, maybe 24" long. Cut out the old / corroded piece, replace w/new. You can splice, simply by placing an 1-1/2" x 6" long piece of aluminum in the base of the C-Channel, spanning 3" on the new and 3" onto the Existing and then screwing it down to the new plywood . . .

You could also just brake a simple "L" shape w/ an 1-1/2" bottom leg and an inch or 2 side leg and "nest" it in over the top of the bad/corroded piece and overlapping some of the good C-Channel and screw to plywood and rivet to the outer skin . . . that's probably what I would do.

Insert Disclaimer Here: I'm just an aluminum hack, not a professional.

[thesignlady]

First I would check it is indeed a break and not that it is simply a flaw in quality control in that the back and the curves of your C-Channel are sitting not a a parallel. My C-channels had a space but it was on the other edge of the curve. (road and curb side, not at the rear) And its not a flaw, it was made like that. (That is why a lot of leaks appear in the corners of these trailers as the water follows along the channel till it hits these spaces and makes its appearance inside.

First look at that space in the channel and see if it does look stretched and torn or it looks like it could have been cut at the factory with tin snips, then go outside and see what the condition of your rivets are in that area. If your rivet holes are stretched out the corresponding amount and your quarter panel aluminum is buckled inwards than you may have an issue but lets hope its just a simpler issue of bad quality control many moons ago

[Alumineer]

Originally Posted by TxDave

You will notice the break in the C-channel at both rear corners. How should I go about repairing this? Thanks, in advance.

Looks like a stress fracture... and because it's partway around the corners, it will require a compound bend to create the right shape from a flat piece of replacement stock.

It would be possible to create that shape by making a plywood former that fit the inside of the C channel (at least 3/4" ply); then cut out a piece of aluminum that fits the shape, plus an inch on each side to form the vertical sides. Clamp the aluminum to the plywood section by section and hammer-form the sides. With diligence and patience you should be able to recreate the shape of the channel. I would overlap the replacement piece with the existing side pieces by at least three or four inches, and use several rivets per side on each vertical to bridge them together.

[TxDave]

Thanks for the great ideas. You guys have me pointed in the right direction.

Thesignlady...I followed your advice and did notice that some of the rivets in that area had pulled through the exterior skin.

MarkR...I have a 10' bending brake. I'm sort of "semi-famous" for a bending brake I designed to build an aluminum airplane completely from scratch. (Google "Dave's bending brake").

Alumineer...that's the same method I used to form wing ribs for my Sonex aircraft. Don't know why I didn't think of this.

Here's a photo of my first aluminum project. I fabricated every piece of this airplane in my garage. 6061 T-6 aluminum with 9,000 rivets.

[OilnH2o]

TXDave
Nice to know someone else likes "all-aluminum" toys! Nice Sonex, too!

[SpitFireRX]

You can also buy one, worked for me

Floor Channel Bow - Narrow Body104463 [104463] - $69.95 : Out-of-Doors Mart!, More Airstream Parts on-line than anyone!

[twolanehwy]

I'm surprised you had to ask anyone anything if you built a plane...LOL!

[TxDave]

OilnH2o...that's a sweet Bonanza.

SpitFireRX...do you remember how much you paid for shipping. Their website says it ships freight.

twolanehwy...one important lesson I learned while building my Sonex was to take advantage of other folks knowledge and experience. Its that old "2 heads are better than one" thing. I am a total Airstream newbie. But, if you ever need any advice on building an airplane from scratch...I'm your man.

[Aerowood]

I don't own it though. I have built a Pitts S2B and a Harmon Rocket.

[SpitFireRX]

TxDave

total freight $134.17 but i also purchased a Channel Floor Molding 16ft Piece 100986 that i had cut in half for me.

[rumrunner]

I have to second Alumineer on the stress fracture diagnosis. It seems too coincidental that both sides broke at the frame ends. Was the floor badly rotted in this area? if so the unsupported shell probably flexed excessively relative to the frame. Adding a front hold down plate to keep the shell more rigidly attached at the A frame might be a good idea to help avoid a repeat.
tim

[TxDave]

Yes, rumrunner, the last 18" or so of the plywood subfloor was pretty much toast. I think your explanation makes sense. Thanks.

[twolanehwy]

Originally Posted by TxDave

OilnH2o...that's a sweet Bonanza.

SpitFireRX...do you remember how much you paid for shipping. Their website says it ships freight.

twolanehwy...one important lesson I learned while building my Sonex was to take advantage of other folks knowledge and experience. Its that old "2 heads are better than one" thing. I am a total Airstream newbie. But, if you ever need any advice on building an airplane from scratch...I'm your man.

I'm just about to have some channel formed up. What alloy do you think would be best?
I've seen just about every alloy used on this forum.
I was gonna use 5052. What do you think would have best characteristics for bending and not cracking after being bent?

[FC7039]

I do not think the allow matters (My opinion). Use scrap or the cheapest you can find. There is no need to fix the break in the channel. The channel is not continuos and has gaps in many places.


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[Aerowood]

Originally Posted by FC7039

I do not think the allow matters (My opinion). Use scrap or the cheapest you can find. There is no need to fix the break in the channel. The channel is not continuos and has gaps in many places.


Sent from my iPad using Airstream Forums

I agree, if you feel the need just put a plate in the bottom of the channel.

[Aerowood]

Originally Posted by FC7039

I do not think the allow matters (My opinion). Use scrap or the cheapest you can find. There is no need to fix the break in the channel. The channel is not continuos and has gaps in many places.


Sent from my iPad using Airstream Forums

I agree, if you feel the need just put a plate in the bottom of the channel.

[MarkR]

ditto to your double dittos

[TxDave]

I'm thinking I'll clean up the edges where the break occurred and bend a couple of short sections of channel to use as a splice. I have lots of scrap 6061 T-6 left over from building my airplane. Thanks for the advice.

[toastie]

Originally Posted by TxDave

So, I'm replacing the subfloor in the rear of my '71 Sovereign. The last 18" or so was rotted away. I decided to go ahead and replace the entire 4' section. Fortunately, the frame looks pretty good except for surface rust which I will take care of.

You will notice the break in the C-channel at both rear corners. How should I go about repairing this? Thanks, in advance.

See my post #174 and #276 at http://www.airforums.com/forums/f36/...-38289-13.html

toastie