Removing inner bow section aluminum boat.

[73 Dolphin]

Getting ready to restore an aluminum boat. The hull ( outer ) on the bow has pitting and to repair it I have to remove the inner bow section.
Before I get into this and start drilling out rivets is there anything I should be aware of ?
Its a 1985 Grumman 5.0 meter but Admins please don't move this to Grumman section as I'm looking for general advice.
( and most of the folks there do not have this boat or even know what it is ) Thanks!

 

[GA_Boater]

Why would me move this out of the Resto section when it's where you will get the needed advice?

Nothing to be aware of, drill the rivets. It is possible flotation foam lives behind that covering.

Also removing the hatch and bin if there is a bin behind the hatch, might give you more insight.

Like you said, the Grumman section isn't very active and we don't have that many Grumman owners in the forum, so most advice will be generic.

 

[73 Dolphin]

I asked a similar question about the boat asking people with specific knowledge of the boat. It got moved the Grumman forum. Lesson learned! Though you never know, it may be fruitful too at some point. Here is a picture of the hatch and inside.
There's a serious amount of rivets to be removed!

 

[GA_Boater]

It was probably moved as you asked for specific Grumann info.

I don't see foam straight ahead of the hatch. Do you feel any to the sides.

It's a lot of rivets, but they are closed head pop rivets - That makes it easier to remove. I would remove the side pieces first. It appears the hull should be accessible then.

You have a battleship!

 

[73 Dolphin]

The frame for the front seating/storage is riveted to the inner hull side and front pieces. Under those side and front pieces you can see there is another layer that forms the enclosure for the front storage. That needs to come out too. When that's out I will be able to access the hull to repair and see what caused the corrosion in the first place. Also I will be able to see down the gunnels to see if the foam is all intact. The gunnels are closed. You can kind of see this in the second picture. Looks like I'll get a chance to start on this later this week. Ill post some pictures in case it helps someone else at some point. Thanks for the help GA_Boater!

 

[GA_Boater]

It's hard to figure out a structure with 2D pictures.

Just go easy and don't get rambunctious. :smile:

 

[73 Dolphin]

Progress! Yes she is built like a tank.

 

[73 Dolphin]

The bigger picture.

 

[73 Dolphin]

Ok so now the foam is gone I can see the holes. What is the best way to fill these? I intend to prime and paint after filling the holes. Clearly it was bare aluminum up against the foam which partly lead to the situation I am in. There is still a lower bow section that is riveted in that needs to come out. It looks like the only way to get the foam back in when I am done is to pour through the bow rail base. Any thoughts on this? Thanks!

 

[GA_Boater]

Man, you have an ice breaker!

Is that another set of panels on either side of the locker?

 

[73 Dolphin]

GA_Boater yes. The panel with the locker runs from side to side and is riveted to the hull. The kind of rivets that look like fat pan heads. There is no foam forward of this panel which is a great relief! I can access well enough to cleanup and apply gluvit. It took me about 5 hours to disassemble the front and dig the old foam out. I have about another 30mins of labor removing whats left of the foam you can see, then the lower panel needs to come out. Then of course the foam under that also needs to come out. My biggest concern is how to re-pour the foam when I am done.

 

[73 Dolphin]

Ok. I see I misunderstood. There is another set on the floor of that section either side of the locker. They are riveted to the cross-members with standard rivets. Just one hole below this area. Its odd that the above water line suffered more corrosion than below. I would have thought that water would find the lowest point. Of the foam that I pulled the vast majority was bone dry. There were a few spots where it was wet right up against the hull but only a few and to the depth of say an orange skin.
I'll reseal the gunnels really well when she goes back together to try to stop the intrusion.

 

[GA_Boater]

Any rivets with pan heads are driven rivets and access is needed to both sides to buck from the back. I don't see how Grumman did it unless that section was partially pre-assembled.

Foam replacement is going to be tricky. It looks like the foam was sprayed and the side panels were quickly stuck in place before expansion completed. Trying that at home will be messy.

The good thing about the forum is we have guys who have wandered down this road patching holes in aluminum. Watermann classiccat Ring, ring. Got any ideas for 73?

 

[classiccat]

I like that boat!

The good news is that it's all above the waterline.

1st thing i'd do is remove all of the aluminum oxide... I like nylox wheels for bulk removal and then a dremel to dig out anything in the deep recesses. the nylox is fairly selective to the aluminum and I use a dremel bit that doesn't dig into the aluminum...just cuts laterally/sideways.

wear a respirator b/c it will cloud-up pretty good.

Once the alumina is gone, i normally acid wash and do a chromate conversion on the aluminum.

What worries me here however is that the acids can get washed somewhere and hide...causing craters down the road. I was very surgical with this when I did it on my tin tub.

Since it's above the waterline & hidden, I think i'd just clean off the organics with acetone followed by alochol then hit it with self-etching primer + a topcoat (acrylic enamel spraybomb).

Now assess whether you're dealing with a few singular pinholes or large masses of pinholes. When it's dark, you can put a light inside then assess from the exterior.

For single isolated pinholes, I'd drill out the hole to 3/16 and buck a 3/16 solid rivet to seal the hole. You can add a little 5200 to the rivet for good measure.

If it's a mass of pinholes, I'd probably go the route of putting painters tape over all of the holes on the exterior... then butter-up a piece of 0.060" aluminum with JBWELD or Marine Tex, and solid-rivet the internal patch in place. You may have to preform the patch a bit so that it fits the curves; I anneal by soaping-up the aluminum then heat it up with propane until the soap burns...then form with a deadblow hammer. The painters tape will allow the epoxy-stuff to fill the holes and hold it there.

As far as foam, stick with closed-cell foam board.

I made a hot wire foam cutter using 26 awg SS wire (i think they use it for vape pens?) and a 12VDC battery charger.

You'll probably cook through a few wires until you get the length right (Power = Current x Voltage & Voltage = Current x Resistance). For the 26awg SS, I target about 20" long which is right around 3.5Ohms giving me great control of the cuts and not burn-up the wire. It slacks so I have it tied to a turn-buckle which I tighten once it gets warm and loosen before I cut the power.

 

[73 Dolphin]

Classiccat Thanks for the response.I appreciate the suggestions. One thing I love about the boat is the rivet pattern.
I don't want to change it if I can avoid it.While plugging the holes with a rivet makes great practice sense I'm not sure that I would like the look. Can I not use some aluminum backing inside the hull and JB Weld it, feathering down the ooze through on the outside to seal without a rivet? Any experience doing this? ( Badly explained probably - sorry )
The other thing is the foam. It will be a while until I get to it as the entire boat needs doing not just the bow. I really do not want to use loose foam. The poured foam must add structural strength and impact sound deadening to a degree. I do not want to lose that as it will be used in moderate chop conditions in the intracoastal and gulf of Mexico in St.Pete Florida.

 

[73 Dolphin]

Love these rivets!

 

[73 Dolphin]

Oh. I see. Are you saying use the rivet to fill the void then grind it down on the outside of the hull and smooth with WB weld?

 

[classiccat]

Classiccat Thanks for the response.I appreciate the suggestions. One thing I love about the boat is the rivet pattern.
I don't want to change it if I can avoid it.While plugging the holes with a rivet makes great practice sense I'm not sure that I would like the look. Can I not use some aluminum backing inside the hull and JB Weld it, feathering down the ooze through on the outside to seal without a rivet? Any experience doing this? ( Badly explained probably - sorry )
The other thing is the foam. It will be a while until I get to it as the entire boat needs doing not just the bow. I really do not want to use loose foam. The poured foam must add structural strength and impact sound deadening to a degree. I do not want to lose that as it will be used in moderate chop conditions in the intracoastal and gulf of Mexico in St.Pete Florida.

Yeah 73...you have alot of options since it's above the W/L.

We in the tin boat circles wear our riveted repairs with pride! :lol:

another way I've filled holes in aluminum is with a rivet where I've chamfered the beauty-side and the buckail side fills-up chamfered recess. (thread link)

^^^ I removed the anodization and polished...but you can make smooth with JBWELD or marine tex then paint.

Pour-in foam in an aluminum boat is generally a bad idea for reasons you're experiencing. Foam board is nice b/c it doesn't readily sponge-up any water and it allows it to shed.

You can cut then glue it to rough size, then trim it down.

 

[73 Dolphin]

Well that just about covers everything! Beautiful work!

 

[Watermann]

If you haven't found it yet there's my rivet tutorial in the Starcraft section.

https://forums.iboats.com/forum/own...-boats/10435722-rivets-rivets-and-more-rivets