# Aluminium canoe rib repair?



## Artfuldodger (Mar 2, 2016)

It's the pieces in the bottom of the canoe that are perpendicular to the keel inside the canoe.
I have a 17' Grumman and one of them has broke into.
It's actually from my own stupidity. Years ago a cut two slots in the rib to run a strap through to attach a trolling motor battery. My thoughts were if I flipped over the batter would be saved. 
Well it proved to mess with the integrity of the rib and it cracked. Now the bottom flexes more than it should in that area of the canoe. It's towards the back and right over the keel or middle of the bottom. 
I thought about trying to weld it but thought maybe a patch piece scabbed over it might be stronger. It would be like placing a piece of rib over the existing rib. I'd have to bolt it in using stainless steel bolts and nylon washers with a piece of duct seal tape. The tape that has rubber in it, not regular duct tape.
I don't know anything about aluminum welding or how strong it would be vs the patch method. Here is a picture of a similar rib. This picture is of an overlapped piece but looks the same as my broken piece.


----------



## Artfuldodger (Mar 2, 2016)

Mine was not two pieces overlapped but one solid piece. It looks just like the one in the picture riveted like the one in the picture but without the overlap. 
It was weakened when I cut slots in the "V" part of the rib parallel to the bottom for my battery strap. The "V" part of the rib cracked between my strap slots.

What about cut a hole in the "V" closer to the side and insert an aluminum rod into the cavity to give the rib support? The hole by the side wouldn't be as critical and could be welded  over once the rod was inserted.
Maybe with one of these welding rods. I would trust it to scab over the hole over on the side after inserting the rod but I wouldn't trust it to repair the broken rib in the center of the canoe. 
I might could use it to weld in the scab plate instead of bolts. Maybe insert a rod and use a scab plate;

http://www.harborfreight.com/8-piece-low-temperature-aluminum-welding-rods-44810.html


----------



## Artfuldodger (Mar 3, 2016)

I don't think my idea of making a hole closer to the side in the rib would work. I'd have trouble getting the aluminum rod inserted and slid over to the correct spot. Plus I'd have another hole in the rib to repair. I think I'll open up the original crack and insert the rod there, sliding it all the way in and then back to the middle. 
Then I'll braze it in place. I can then scab over that with an aluminum plate and braze the plate in place.


----------



## T-N-T (Mar 3, 2016)

I would take to someone who welds aluminum.   
Weld and see how strong it is.

That way you don't put more holes from bolts or anything like that.
My 2 cents.  That is actually worth 1.5c


----------



## Artfuldodger (Mar 3, 2016)

I might talk to a welder and see. I wonder if brazing vs welding would be better because the rib needs to flex.  I'd rather not have to put holes and bolts through the hull.
Maybe a TIG weld.


----------



## bronco611 (Mar 3, 2016)

take it to a metal fab shop which has the capabilities to weld aluminum and have them weld the rib then fab a doubler rib which would nest on top of the existing rib and extend 4 inches each side of the crack and weld it to the repaired rib to help keep it from flexing at the repaired point where the crack was located. on the flat sections which would be on top of the existing rib drill holes in the doubler rib along these flanges so they can weld a stitch type seam along the flange to fasten both ribs together for added strength. Only drill these holes in the fabbed doubler rib not through the existing rib or the floor of the canoe. If no one will touch it the next step would be to fab a rib section and remove the rivets which would be under it when installed. match drill to the new rib and drill new holes to run a line of rivets on each flange match drilled through the new rib section, old rib and floor and install rivets using a good sealer to seal them while installing. leave a minimum of 3.5 times the diameter of the rivet shank as an edge distance and end distance for the rivets, and space rivets approximatly .75 center to center along the flange. good luck.


----------



## Artfuldodger (Mar 3, 2016)

bronco611 said:


> take it to a metal fab shop which has the capabilities to weld aluminum and have them weld the rib then fab a doubler rib which would nest on top of the existing rib and extend 4 inches each side of the crack and weld it to the repaired rib to help keep it from flexing at the repaired point where the crack was located. on the flat sections which would be on top of the existing rib drill holes in the doubler rib along these flanges so they can weld a stitch type seam along the flange to fasten both ribs together for added strength. Only drill these holes in the fabbed doubler rib not through the existing rib or the floor of the canoe. If no one will touch it the next step would be to fab a rib section and remove the rivets which would be under it when installed. match drill to the new rib and drill new holes to run a line of rivets on each flange match drilled through the new rib section, old rib and floor and install rivets using a good sealer to seal them while installing. leave a minimum of 3.5 times the diameter of the rivet shank as an edge distance and end distance for the rivets, and space rivets approximatly .75 center to center along the flange. good luck.



Thanks, If I go the rivet route can I use standard 1/4" aluminum pop rivets?


----------



## bronco611 (Mar 3, 2016)

No you must use solid rivets and buck them with an air hammer and rivet tip and hand held anvil. This will take 2 people to accomplish this and cleco pliers and the correct size cleco devices to match the rivets size used probably a number 5 button head rivet with the correct grip length. The cleco fasteners hold every thing together while drilling and installing rivets. It is not that difficult to do, but you should practice on some scrap aluminum and install a line of rivets to get use to how much pressure to apply with the rivet gun (air hammer) and the anvil so you do not over buck the rivet and the rivet tail. The rivet head will be on the outside of the canoe just as a Jon boat is riveted together. Do not forget to install the rivets wet with sealer on them to seal under the head and on the shank to prevent any leaks. Since this canoe will not be powered by an engine you could use number 4 button head rivets but you should space them .675 apart.  To determine the correct size, remove the existing ones on the broken rib that must be replaced so that they are through the doubler rib and use that same size rivets just get the proper grip length which will be determined by totalling the thickness of the skin the broken rib and the doubler rib. With that grip length you buy the rivet by size and grip length . I hope this makes sense and has been a help. You are near Augusta there should be someone around there who is an aircraft airframe mechanic who could help you and possibly have the necessary tools to accomplish this repair. The solid rivets are also an aluminum alloy rivet but the pop rivets will not work below the water line, you will end up with a leak or a lot of leaks. The anvil is held against the rivet tail and the gun with correct tip on the rivet head when bucking the rivets.


----------



## Artfuldodger (Mar 4, 2016)

That makes sense as I can see where pop rivets would leak. The originals are as you say a more traditional rivet.


----------



## bronco611 (Mar 13, 2016)

post pictures of the repair when you finish it and a description of what it took to accomplish it.


----------

