Deep scratch or gouge in aluminum hull below waterline

freeisforme

Petty Officer 2nd Class
Joined
Mar 23, 2009
Messages
184
I was given a 15' Starcraft today, the boat is pretty much gutted, the transom and floor are all out and it's been stripped for repaint.
My concern is patching a fairly deep scratch or gouge along the right lower side about a foot below the water line. The last owner said he brushed past a submerged piling which had a bolt head sticking out of it. The gouge is about 5" long and it starts about 3" ahead of an internal rib, the metal is deeply scratched and slightly indented, and where the scratch met the area where the rib reinforced the outer skin it punctured through at that point and at the end of the scratch, in the middle of the rib. None of the punctures are visible from inside the boat, even with light behind it at night. Water rushes in pretty fast. There is one rivet that's about 1/8" from the puncture, but it's not hit, but it's close enough that welding will no doubt compromise the rivet. I've taken the boat to several welders in the area and none will touch it.

What would be the proper fix for this? Each puncture is less than 3/16" long. I'm thinking about roughing up the area on the outside and filling in the damaged area with Marine Tex or JB weld? Will that hold and be safe?
Will JB weld adhere permanently to un-primed aluminum?

I already bought a quart of Gluvit for the inside of the hull but Gluvit alone won't reach or fix a 'cut' in the hull like this. I'm sure this is why the boat was free, it no doubt leaked water pretty bad. The last owner had half a tube of silicone caulk spread over the repair, so he knew it was there. It's also in an area that contacts the bunks when loading.

I'm thinking of filling in the exterior with JB weld and coating the inside liberally with Gluvit as best I can?
 

Woodonglass

Supreme Mariner
Joined
Dec 29, 2009
Messages
25,924
Re: Deep scratch or gouge in aluminum hull below waterline

I think pictures are in order here. It is very difficult to SEE what you are describing without them
 

roymarine

Cadet
Joined
May 3, 2009
Messages
11
Re: Deep scratch or gouge in aluminum hull below waterline

Im on my second starcraft aluminum and i found that these hull are very easy to weld. so if you have hole or crack to fix weld it. personnally i weld them myself with a mig. if you have acces to a tig it even better.

good luck.
 

Bob_VT

Moderator & Unofficial iBoats Historian
Staff member
Joined
May 19, 2001
Messages
26,018
Re: Deep scratch or gouge in aluminum hull below waterline

Yes, the method you described will work. There is a product called PC11 (or if you use marine tex - use the gray stuff) which you can use externally and then a few coats of gluvit internally should seal it up fine. Welding is the top option but the adhesive route will work.

Now if you are real concerned about the strength you can also rivet a support patch in the inside. That would be sealed and out of site too.
 

Huron Angler

Admiral
Joined
Apr 7, 2009
Messages
6,025
Re: Deep scratch or gouge in aluminum hull below waterline

I'd probably do the internal patch method, riveted in tight and sealed with 3m 5200. If someone welds it that is not familiar with welding aluminum the welds would fail and let in even more water.

Congrats on the free Starcraft! Should be a nice boat for ya once the repairs are made. Good luck to ya, and get some photos up when you can.
 

jasoutside

Supreme Mariner
Joined
Dec 20, 2009
Messages
13,269
Re: Deep scratch or gouge in aluminum hull below waterline

Oh man, free Starcrafts are the best!!!:D:D
 

Woodonglass

Supreme Mariner
Joined
Dec 29, 2009
Messages
25,924
Re: Deep scratch or gouge in aluminum hull below waterline

I have used PC-11 and it is FANTASTIC stuff. Very much like MarineTex. Smooth and Sands very well. You can even drill and tap it.
 

freeisforme

Petty Officer 2nd Class
Joined
Mar 23, 2009
Messages
184
Re: Deep scratch or gouge in aluminum hull below waterline

I don't have any pics yet, I have to get the boat up off the bunks to get a pic of the damaged area.
It looks like a deep scratch but it's through at the one end, and that end happens to fall below an aluminum rib. The area is just about where the ribs end, the scratch is almost not visible at all unless your really looking for it. I wouldn't have seen it if the guy didn't have a load of silicone on it. The last guy to attempt a repair smeared about a half pound of silicone over the area making it look much larger than it really is. He claimed that the boat leaked about a gallon an hour, I'd say about triple that is more like it just guessing by the hole. I found the hole only since I found water dripping from the patch, it was raining really hard on the ride home and it got wet. The deck is removed, as is the transom, but the damage can't be seen from the inside at all, the scratch does make a bit of a dent but not enough to show through on the inside. I showed it to a few welders around here and all said that the leak was too close to a rivet and that the rivet would have to be sacraficed and the rib in turn welded down. It's not that bad of a scratch. The actual punture is no more than the size of a small nail hole in two places, the scratch was front to back, where the object passed over the hull around the rib, it punctured the aluminum slightly, and again where it stopped. I could probably do the same damage with an ice pick if I pushed hard and dragged it about 4" against the hull by hand.

I don't have any doubt that epoxy will fix the leak, but will it stick forever? Even if it fell out, the boat would be in no real danger of sinking in any hurry. It would take hours, if not days to take on that much water. I haven't float tested it but I did fill it to cover the ribs and water barely comes out that hole, you have to rock the boat around to make it leak there. Water needs to seep behind that particular rib to get out. Since there's a rib behind the damaged area, an inside patch won't work, and its by far not serious enough to remove the rib to repair.
I thought about those Alumiweld sticks but I've seen mixed results with that stuff. If I knew it would adhere better than epoxy, then that would be the way to go but I'm not that confident taking a torch to the hull with that stuff.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,458
Re: Deep scratch or gouge in aluminum hull below waterline

I don't have any doubt that epoxy will fix the leak, but will it stick forever?

Nope,... Probably Not... Epoxy don't like sunlight....

The alumiweld, "Might" work...
 

starcraftkid

Petty Officer 1st Class
Joined
Jul 5, 2010
Messages
224
Re: Deep scratch or gouge in aluminum hull below waterline

Epoxy doesn't like sunlight but you could paint it or cover it with filler and paint the repair.

Alumiweld works but its not really good for anything structural and if it's close to a rivet, you will most likely loosen that rivet with heat and aluminum does warp when welded. The ideal fix would be to be able to get to the rear of the hole, tap the hole closed again, and seal the rear with either epoxy or even 5200 and then fill and paint the exterior. Chances are it will out last you barring any direct impact with that area. I've found that adding any double metal patches just creates a place for corrosion to begin if the boat is used in saltwater. I've removed a few riveted patches from older boats where the aluminum corroded badly where salt got trapped behind the patch.
Most of the punctures I've dealt with on aluminum hulls were at or behind ribs. The panel area between the ribs simply gives more and resists puncture. The aluminum is held tight by the rivets behind the hollow rib and that seems to be where a sharp object makes its way through.

As far as how well epoxy sticks, I just spent two hours scraping and sanding off an epoxied on patch on a 14' boat. Someone had smeared JB weld or similar epoxy over several unused holes in the transom but the repair looked like it was done with a trough and the holes behind it were rough, one had a rusted screw snapped off, and it wrapped around under the boat. The stuff sticks and stays stuck. But this wasn't really in direct sunlight and they did brush paint over top of it. It was also below the water line and didn't leak.
 

Woodonglass

Supreme Mariner
Joined
Dec 29, 2009
Messages
25,924
Re: Deep scratch or gouge in aluminum hull below waterline

Since this is below the waterline UV is not going to be much of an issue. Will it stick for ever? If you prep the area well, i.e. wire bursh, wash down with 50/50 of white vinegar and water, dry REALLY GOOD, mix the PC-11 50/50 then YES it will last as long as you have the boat. If you are going to paint the bottom of the boat, so much the better. Just remember to prep it correctly, and use a self etching primer before you paint. Do all of this and your repair will be there as long as you have the boat.

http://www.right-tool.com/pcwhiteppas.html

Or Most Ace Hardwares Carry PC-11

Remember PREP is the KEY to good Adhesion!!!!
 

freeisforme

Petty Officer 2nd Class
Joined
Mar 23, 2009
Messages
184
Re: Deep scratch or gouge in aluminum hull below waterline

I took the bare hull down to a pond today to leak test, I wanted to see what and where the leaks were before doing anything. The area of concern really don't leak that bad, it produced only a small steady trickle of water. I got more water coming in around a set of poorly sealed screw holes on the transom. There are 17 holes drilled at bottom of the transom where things were bolted on at one time. I brought the boat home, dried it out, and figured that I'd try to see if I could make the damage any better before patching it. I drilled a 1/4 inch hole in the stringer right where the hole was, I then had a buddy hold a chunk of heavy metal where the scrape is, while I tapped the scratch out and closed up the tiny hole with a long punch. The scratch is now almost flush, the hole doesn't let any light through. I then opened up the end of the rib a bit with a bit and dripped in some Gluvit. I then sanded the scratch area and wiped it with alcohol, then I mixed and spread some white Marine Tex over the area as if I was spreading body filler. Right now, while not yet fully cured, the scratch is nearly invisible since the epoxy blends in so well with the white painted hull. The actual hole or puncture was less than the diameter of pencil lead. I also tightened up the surrounding rivets. Once it cures completely I'll give it another dunk to check for leaks. I also sanded, dimpled, and filled the screw holes the same way. Most of the screw holes were just covered over with white tub sealer.

Which is better, Marine Tex or PC-11? (PC-11 sure is cheaper).
 

Woodonglass

Supreme Mariner
Joined
Dec 29, 2009
Messages
25,924
Re: Deep scratch or gouge in aluminum hull below waterline

They are BAsically the same product. For the Price, I have always use PC-11 and gotten the same results
 

freeisforme

Petty Officer 2nd Class
Joined
Mar 23, 2009
Messages
184
Re: Deep scratch or gouge in aluminum hull below waterline

Well, the fix looks good, but I guess I'll never know first hand if it leaks.
I had the boat sitting on a trailer that I had listed for sale, it was a bunk trailer so it left the damaged area exposed to work on.
I had a guy stop by today in the rain to see the trailer and after he looked the boat over, he decided he wanted the boat and not the trailer. I sold the boat and another bunk trailer I had here for $1200 cash. The trailer was an old painted bunk trailer from the early 60's, one of those mono beam type trailers with rollers down the middle and a set of rollers in the middle on the sides. It was rusty and needed a lot of work, I was going to just scrap it. This guy had to have it.
I basically gave him the trailer with the boat. The boat was a bare hull, no wood, no steering, no nothing. I really wasn't planning on selling it but after he made me an offer of $1000, I had to stop and think, when he said $1200, he bought a boat. I'll find another.
I had no idea that these things had such a following. So much for that project, I guess it's on to another.
 
Top