aluminum boat hull restore/repair

[jtscudder]

Hello ::iboat members ,I recently bought a used 14ft Grumman aluminum boat used and discovered that the hull had greater damage than I had suspected.On the first outing I tried to get up on plane and the bottom rose up to meet me.The floor rose up a full 6 inches in front of the rear bench seat...funny now but it was very disturbing in the moment.I decided to attempt a repair and strenghtening of the hull and my pictures are here for all to see.I will test drive and leak test this following week and report back about how everything worked out.Thank you for looking....This was my first boat restore/repair.,John

 

[CN Spots]

Re: aluminum boat hull restore/repair

Welcome to iboats John! I'm trying to grasp exactly what happened... is the hull bending under power? What size motor is on your boat?

 

[bananaboater]

Re: aluminum boat hull restore/repair

If CN Spots is correct in that the hull bent inwards it sounds like it is a rib problem, not stringer. And it sounds scary. Your lines of aluminum angle are like stringers, they run fore and aft and may help but not solve the problem.

Have you asked the PBO about this?

 

[jtscudder]

Re: aluminum boat hull restore/repair

Welcome to iboats John! I'm trying to grasp exactly what happened... is the hull bending under power? What size motor is on your boat?

8 of the 9 ribs were cracked in the center,the keel was hit by a log cutting a 0.5 inch slice out of the bottom of the keel.When I tried to plane off with a person sitting in the bow seat, the keel kinked and the ribs were already cracked so the boat tried to bend in half at the point were the keel had been
pinched.The bottom was pushing upward from just in front of the rear seat to
just behind the bow seat during plane .I decided to push the bottom of the hull back out slowly using a scissor jack from my truck, a chain running under the trailer and a 4x4 on the bottom(longways) and a 4x4 on top of the jack like a yoke/beam.The jack pushed up on the beam and don on the 4x4 at the same time.This worked surprisingly well.After that each rib was Mig welded and the
flanges hammered back into place.All rivets that were compromised were replaced and sealed with silicone upon bucking.I decided to add doublers to the ribs to help stiffen the ribs for I understand that welding aluminum can weaken the material.After that I installed stringers over top of the doublers and installed vertical tubing under the seats to keep the stringer down against the doublers.The stringers are 1.5 x 3/16 6061 aluminum 10 ft long.Then to keep the doublers in place I installed an outer set of angle on each side .The angle stringer also adds lateral strenght by helping to spread the load,and under the seat are the vetical tubes that intersect with another piece of 3/16 6061 riveted in place under the seat.I also had a doubler piece
welded over the damaged part of the keel which I will have to feather in using crc minute mend,sand and then paint.WHEW,WAS A lot of work but I am having a great time experimenting in the lab and sharing on i boat forum..Thanks for ques....John

 

[J Hartman]

Re: aluminum boat hull restore/repair

sounds like a visit to the welding man would be in order to me... Fixing those ribs would definately help to start solving the problem

 

[jtscudder]

Re: aluminum boat hull restore/repair

If CN Spots is correct in that the hull bent inwards it sounds like it is a rib problem, not stringer. And it sounds scary. Your lines of aluminum angle are like stringers, they run fore and aft and may help but not solve the problem.

Have you asked the PBO about this?

Thanks for the observation.I have rewelded a doubler over the damaged keel piece,re seated all 8 ribs and had them mig welded.I have also installed doubler pieces over top of the center most part of each rib.Then on top of each doubler is a piece of angle stringer keeping downward pressure on each doubler.Lastly another piece of angle/stringer is added on the outside edges of the rib doublers to keep them from escaping their position over the center of each rib.The last idea I had was to add vertical tubing under the seats to keep down force on the top stringers.I am hoping I have covered all the angles with angle as it were.I am going to take the boat next week and will report my findings,..Nice to talk with people who have so much experience
and who can see things through another pair of eyes...This was intimidating at first now I think I am enjoying the obsession and limitless possibilities.Thanks everyone for the input....John

 

[jtscudder]

Re: aluminum boat hull restore/repair

Welcome to iboats John! I'm trying to grasp exactly what happened... is the hull bending under power? What size motor is on your boat?

Whoops forgot ,the motor is a 25 hp mercury tiller .I am thinking about later adding a 2x4 aluminum box beam connected through the oar locks ,adding pulleys and installing a steering wheel,I so much enjoy the side to side range and feel of a pulley steering system..Costs less than a cable helm also...Thanks for the message...John

 

[Woodonglass]

Re: aluminum boat hull restore/repair

Using silicone on your rivets is a NO NO. It will NOT do the job. You should investigate a product called GLUVIT. Works great for sealing Aluminum boats.

 

[CN Spots]

Re: aluminum boat hull restore/repair

Sounds like you've done as much as you can to stiffen her up. Still, take it easy on the next few outings and check on those welds throughout the day.

 

[jtscudder]

Re: aluminum boat hull restore/repair

Using silicone on your rivets is a NO NO. It will NOT do the job. You should investigate a product called GLUVIT. Works great for sealing Aluminum boats.

Thank you woodonglass,I have already noticed that the silicone can peel off around the rivets...Hopefully I can get through the weekend with the silicone and then when I can afford a can I would love to use the Gluvit..Thanks for looking out for me there...John.Oh by the way does Gluvit make a large difference in surface ,i.e if I paint over will it be an uneven and un attractive surface?,,,Thanks...John

 

[Woodonglass]

Re: aluminum boat hull restore/repair

Gluvit is used on the INTERIOR of the Boat. Not recommended for the exterior. It has NO UV protection and is kinda rough in texture. Make sure and use it BEFORE the deck goes in.

 

[jtscudder]

Re: aluminum boat hull restore/repair

Gluvit is used on the INTERIOR of the Boat. Not recommended for the exterior. It has NO UV protection and is kinda rough in texture. Make sure and use it BEFORE the deck goes in.

Thank you sir...much obliged..John

 

[jtscudder]

Re: aluminum boat hull restore/repair

The hull rebuild on 14ft grumman aluminum was a great success.The boat has very minimal flex,if none at all,during plane and no leaks whatsoever after 5 outings and lots of hull/bottom punishment.Instead of silicone around my rivets i chose to use crc minute mend epoxy.It cures under water and is very strong,I mixed the two part clay like pieces and rolled out a thin string between my fingers then wrapped it around the rivetshaft.I then pushed the rivet into its hole and ,using an air riveter and 3/16 rivets ,pulled the trigger,the excess epoxy oozed out and was wiped off.The resutl wasa strong water tight seal that would also help stabilize the rivet.Next season and more usage will determine if i have done a good job ,but for now its a nice dependable boat once again.Thanks for reading and Happy Thanksgiving to all people on iboats.John