Ouachita boat repair

Project: To repair a 4" crack on bottom of aluminum boat

Boat: Late 70's model 12' Ouachita

Problem: I acquired this boat from my grandfather and it came with a 4" long crack directly in the middle of the bottom of the boat. The crack lies directly under one of the two seats that has styrofoam packed in it for boat boyancy. The repair materials I have are a propane torch and an aluminum brazing rod.

Fix Idea #1: Turn the boat upside down and lay a welding blanket between the seat and the bottom of the boat to keep the styrofoam from igniting or melting while using the torch to heat the aluminum.

Problems I foresee: I am afraid the welding blanket will not be able to shield or reflect the heat away from the styrofoam enough to keep it from igniting.

Fix Idea #2: Drill out the rivets holding the seat in, then repair the crack.

Problems: I do not own a rivet gun large enough to handle the large rivets that would be needed to put seat back in boat. Also, I do not know if the seat is part of the structural integrity of the hull. If I take out the seat, will it let the sides of the boat extend outward, making it harder to fasten the seat back in later.

Any ideas or suggestions, I am on a tight budget here and cannot afford to send it to a repair shop. Plus the boat is not worth much anyways.

 

The easiest would be to rivet a patch bedded in 5200

 

Update:

Now that the weather has warmed back up I have moved the boat outside and have begun restoration again. Yesterday and today I began removing the 4 old layers of paint which consisted of (Primer, Paint, Aluminum roof paint, and yet another coat of exterior paint). The exterior is just about done, I still have to wire brush the exterior of the hull to finish cleaning the paint off of it.

Due to my lack of attention, my idea of brazing the crack in the hull is not going to work until the seat is removed. The middle seat is riveted to the bottom of the inside hull, so I guess I will be drilling out the rivets which should be a whole ton of fun… While I am at it though I am thinking of removing the front seat and the rear seat, the rear brace which is attached to the aft and refinishing the inside as well.

Instead of painting the boat myself, I am seriously considering having it powdercoated.

I have found the culprit that caused the crack in the hull. When the boat is sitting on the trailer the crack is sitting directly on the middle roller which is a flat roller instead of a V shaped roller. Over the years the boat has flexed and stressed enough in the area that it cracked, so I will be replacing that roller.

I am also going to buy a new tongue for the trailer due to the old one being twisted. Don’t ask me how that happened, but it is. I am also going to remove the old rusted U bolts from the trailer springs/axle and replace those, and wire brush the rust off the springs so they can be painted.

I have attached some pictures of the work so far.

 

I guess the old saying is true: out of sight, out of mind. You just reminded me that I have a similar old aluminum boat, that someone sold me dirt cheap about ten years ago. The previous owner had grounded it hard enough to stretch some rivets in the bottom, so I stuck it away for a rainy-day project. And it's been sitting on the back end of my property gathering rainwater ever since -- or at least it would be gathering rainwater, if it didn't leak.

I should either do something with it, or hand it off to someone who will. I'm sure there's someone in my neighborhood who would treasure it and give it the TLC it deserves.

 

Drilled the heads off the rivets this afternoon and removed the seat to get to the damaged area. I'm going to have to replace the styrofoam due to rodents eating away at it.

I tried to braze the crack shut but it didn't work. My propane torch couldn't get the alum hot enough to work. I ended up making more of a bubblegum mess than anything. So now I will have to grind it out and take it to a welding shop to have it Tig welded.

I also began removing the bolts holding the old transom board in place. Someone decided to use regular metal bolts and most were severely rusted and it took awhile to get them freed up enough to remove. On my next paycheck I'll need to get the crack taken care of, purchase new styrofoam, and get a new piece of W/P Exterior plyboard to replace the transom.

 

This past week I have been stopping at different places to get prices on materials I will need.

I found that Lowe's carries 4' x 8' x 23/32" Exterior plyboard @ $29.97 a sheet as well as styrofoam panels 4' x 8' x 2" @ $24.12 a sheet.

I still need to come up with a 5 1/4" v roller for the trailer.

I also stopped at a local paint supplier and found Mar-Hyde single stage self etching pretreatment primer for aluminum. 1 Gallon was $62.99, so I think I'll shop around a bit and try to find a better price.

I inspected the trailer tongue much closer and found that there is some severe damage to it. It is crushed in on the bottom, it is twisted and has a split in one of the bottom corners. I can find these really easy as most of the local retailers around here have a wide assortment of them.

 

So in this previous week I have taken the boat to a welding shop to have the crack fixed. The guy who fixed the boat laid a piece of aluminum angle in the V part of the hull and welded it into the boat above the crack as well as filled the hole. I am 99.9% done stripping paint off the boat, and I have also taken out the completely rotten transom board. To my dismay the aluminum part of transom/aft has corroded away severely in places and I can almost push right through the aluminum with 1 finger. My thought for a fix for this is to take it back to the welding shop and have a sheet of aluminum welded to the exterior transom to regain the integrity of the transom. Any better suggestions than this. The corrosion is not isolated, it is spread over the entire transom.

 

Since you got the boat from your grandfather it may have enough sentimental value to you to justify any expense, but you need to be aware that a lot of small aluminum boats are not built out of marine grade aluminum.
Aluminum of different grades will have drastically different welding capabilities.

Trying to braze thin aluminum plates (from one of your previous posts) will almost never work because the amount of heat you need to put into the plate to get the brazing rod to melt will almost certainly melt the plate before the rod, causing a larger hole which requires more rod which causes a larger hole etc....
The approach the local shop did on the doubler plate was probably the easiest way to repair the crack. Allowed the crack to be sealed on the outside and filled on from the inside using the applied angle as a backing plate for the filler.

If you elect to use plywood to repair your transom (after the aluminum repairs), please be aware that some of the new wood preservative chemicals used in "pressure treated woods" when combined with water (especially salt water) will cause the aluminum to corrode at an alarming rate. There have been recent cases where commercialy produced aluminum boats, after being launched and re-trailered in salt water, had pitting through the hull within weeks.

Hopefully your repairs have gone sucessfully.

 

Hello, I have a 14' Ouachita flat bottom boat. It has aluminium ribs that run starboard to port every 2 feet. Only two of these ribs are good and the rest have cracks in them. Does any one know where I can get new ones. And does any have any info they could share about the rivets. Any information would be greatly appreciated. thanks.

 

Welcome to the forum Andrew.

This thread is 5 years old and I'm sure you did a search for "Ouachita" and this brought you to us.

To answer your question, the ribs are standard straight extrusions and bent as required by the manufacture. I don't know of replacement parts as you might think of them, but it's probable the extrusions are still available. These can be bent to fit, but riveting them in is a bit difficult for the backyard repair person. Sealed head pop rivets might do, though finding the right size might prove troublesome and the size is key.