Aluminum hull with frp running surface

[aktmboyd]

Hi everyone, I recently picked up a Princecraft 196 riveted aluminum hull with a 150 Yamaha on the back. The hull has some issues and I am hoping someone here can tell me if the idea I have for repairing it is good or bad.

The hulls keel is bent up pretty bad and has a number of the rivets either missing or damaged, rocks have bent and twisted the keel out of shape creating a number of obvious problems. The previous owner has tried the normal repairs to the keel several times but, always with limited success. The boat leaks like a sieve and has for many years. .

The plan I have is; Flip the boat over, run a tape line on either side of the boats centre line, maybe about 8” or so on either side of centre from just under the cap at the bow all the way to the stern. Then run plastic from the tape line to the cap down the sides. Spray with PVA or maybe use a paste wax for some added insurance around the remaining rivets. Then run some fibreglass from bow to stern to around 10mm or so thickness, giving the hull a completely new running surface. I have a bunch of 1700 8” wide tape a large roll of 1708 and a large roll of uni, left from another project. Once the epoxy has cured, peel the new running surface off, clean the PVA or wax off the hull and then bed the whole new fibreglass running surface in either 3M’s 4000 or 4200 and then. through bolt the piece on with stainless hardware, most likely a carriage bolt and obviously insulating them from the aluminum hull.

Is this a bad idea or ? I figure the 4000 or 4200 will give enough flex to compensate for any different expansion rates between the glass and aluminum with out shearing, and give me a longer working time window then a standard silicone.

Thanks in advance for any and all of your responses.

 

[bajansailor]

It should be possible - can you post a few photos to illustrate what the hull looks like please?

I was half tempted to suggest that if you are going that far, why not use the hull as a mould to make a complete new fibreglass boat instead, but I won't.

 

[Mr Efficiency]

So it is only 8" either side of the centreline, that will get the treatment ?

 

[Mr Efficiency]

If rocks caused this problem, then I don't see any GRP repair tolerating similar treatment.

 

[aktmboyd]

It should be possible - can you post a few photos to illustrate what the hull looks like please?

I was half tempted to suggest that if you are going that far, why not use the hull as a mould to make a complete new fibreglass boat instead, but I won't.

build a whole boat! jeez! my attention span will be pushed almost to its limits building this 1/16 of a boat as it is Sorry no pics at the moment. I’ll try to get some though.

 

[aktmboyd]

If rocks caused this problem, then I don't see any GRP repair tolerating similar treatment.

Yes that’s right about 8” each side of centre line total about 14-16” or so. I think will be able to straighten the running surface and build a nice delta at the same time to maybe give a little speed boost, that’s is if my other motor thats planned to go on this hull will push it that fast. And the rock damage is from the previous owner mooring the boat to the side of our rocky boat launch for basically the whole boating season, leaving the boat to the elements and beat the rocks in our tidal flow and wind. Was a bit of a shame but he had no vehicle or trailer to pull the boat from the water. I was thinking an frp running surface from bow to stern then place some of that stick on keel protector at the bow just for added bump absorption when using the boat and dropping people off at waters edge and also pull the boat out of the water when not in use.

 

[Mr Efficiency]

Well, if what caused the damage is not going to be continued, it gives you some hope.

 

[aktmboyd]

Well, if what caused the damage is not going to be continued, it gives you some hope.

Glad to hear so far that it’s not a complete lame brain idea, rejected by all. I had some concerns when first considering this idea about possibly having to much rigidity in the FRP and maybe creating hard spot along the hull cracking the aluminum plate. We‘ll see I guess. And yes I will be able to minimize any further damages, other than an opps! situation that is anyways. My trailer will take up to a 22’ boat so no more sitting on the ground.

 

[Mr Efficiency]

GRP is more flexible, so I doubt that will be a problem.

 

[aktmboyd]

GRP is more flexible, so I doubt that will be a problem.

Thank you for that, gives a little more piece of mind. Wasn't sure if I was going to be creating a problem or not. Seeing how it’s going to be used solely in the Hudson Strait along the south shore of Baffin Island, it at some time’s is going to be a long way from home and honestly a long way from anywhere. So I didn’t want to be a bigger problem causer then I already am .

 

[Mr Efficiency]

The safety aspect here is paramount, you cant have a situation where this little experiment separates from the old hull and water gushes in, that has to insured against convincingly. I think it is the sort of thing where both inside and outside pictures of the boat bottom, are needed for anyone to offer an opinion of the best way to proceed.

 

[aktmboyd]

The safety aspect here is paramount, you cant have a situation where this little experiment separates from the old hull and water gushes in, that has to insured against convincingly. I think it is the sort of thing where both inside and outside pictures of the boat bottom, are needed for anyone to offer an opinion of the best way to proceed.

Thank you, we are in a bit of a snow storm at the moment so no pics for a while. I understand the safety aspect and also your reservations about commenting. At the rate that this boat was sinking anything has to be better. I think if it was just a pad that was attached to the bottom of the hull then it could have potentially be an issue, but I was thinking with this being a complete new running surface glued and bolted from under the cap at the bow all the way to the stern it'll be different and the rushing water won't be able to get under and lift it off.

a break down of my thoughts
- new fiberglass running surface 10"-20" wide not set on the width yet. The propeller I am currently using is 14.63" so any thing with a total width wider than that I think would be best.
- continue with the V form from the bow to near 6' or so near the stern where I think I will start building the outside of the pad thicker to create more of a padded running surface. Princesscrafts already ride hard so I am not worried of a little more pounding.
- 3M 4000 or 4200 or possibly even 3000 used as an adhesive, I think the adhesive with the longest skin time is most beneficial to me. longer time for me to butter the piece in place and then squeeze out with through bolts.
- through bolt using stainless carriage bolts, not sure at the moment if going through the ribs would be best, the rib flange where it is riveted to the hull or possibly on the plate portion of the aluminum.
- if through bolted on the plate portion, GRP washers will be made for the inside probably in the 4" or so Dia to sandwich the plate and sealed with whatever the exterior adhesive is.
- Gator Guard keel shield for added bow fiberglass protection when bumping rocks while dropping people off at our rocky shorelines.
- and don't hate me on this one, but I think I am going to scrub the rest of the hull from keel to gunwales with a wire brush and spray the whole boat with U-pol Raptor liner. Maybe not going to be the best looking, probably a good from far but far from good kinda thing, but honest I think it will be the best to seal and also help protect a rough old flexi alloy boat.

Those were my thoughts anyways! but I wasn't sure of the whole mixing of the 2 types of materials, flexing and expansion and contraction rates. I am hoping the right adhesive should take care of that though.