Bracing the Factory Alum Decking

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FuzzyGrub

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On my current project, the mod v jon has a factory alum deck in the bow, common on most jons I've seen. I have been mocking up trolling motor, anchor, nav light, ff, etc positions and feel that it will need reinforcement. The metal is 0.100" but does not have any ribs. Numerous ideas/methods have crossed my mind. The biggest hurdle is working through the available hatch space.

I am thinking a small section of plywood backer for the trolling motor, and a pair of L channel (T) or square tubing followed by a couple of verticle supports. The supports placement will be slightly tricky with the mod v bow, and may need some floor support. When finished, will stuff some additional foam in the bow, before closing off the hatch. The new deck will prevent access. I do have a round deck access hatch that will be installed, but will only be good to reach wiring, etc.

I am interested in how others have solved a similiar issue. Pictures would be great, if you have them. thx.
 
You should post a pic of what you have to work with.

I would suggest a 1/8" or thicker aluminum backer plate instead of plywood if there isn't going to be easy access in the future. Make the plate as big as you can fit through the access hole.

I take it you're working on a welded instead of riveted boat? That's one of the nice things about riveted boats, easy dismantling, refit, and reassembly.
 
Speaking of pictures, can you post a few of your boat so we can see exactly what you mean :wink:

You'd be surprised at how sturdy those decks really are, but I understand wanting to be better safe than sorry.
 
Here are some of the pics I already have posted. I will upload some better ones, which will include some mock-up of what will be mounted there, this evening.

JonBoat2.jpg


JonProject001.jpg


JonProject010.jpg



The boat has welded seams, but rivited structure. I believe the existing front dect is one piece of aluminum that is rivited to the hull. I am not planning on removing it.

It is not strong enough as is. I can cause it to "tin can" by moving the trolling motor around and certainly by stepping on it. I do have to add 2" above deck to mount the trolling motor bracket.
 
FuzzyGrub said:
It is not strong enough as is. I can cause it to "tin can" by moving the trolling motor around and certainly by stepping on it. I do have to add 2" above deck to mount the trolling motor bracket.

I would cut a piece of 3/4" plywood to cover that deck (the whole front deck) to strengthen it and fasten it with blind rivets for ease of installation or fasten with SS bolts and screws which would be harder to do. Then all you would have to do is mount a piece of 2x6 to the plywood for the trolling motor base.

Of course you'd have to seal the plywood and cover it with carpet, vinyl, or paint and then install it... but it would look good and really strengthen that deck.
 
In my experience, it is very hard to prevent water wicking between the plywood and sheet aluminum. And once it happens, it never drys out. Multiple holes in the alum might prevent that. Still think I'd prefer something on the inside.

My first thought was one horizontal brace (same direction as cross ribs), but it would be too long to get through the access hole. Then two parrellel ones running perpendicular to the the cross ribs.

Hopefully, the 3M 5200 will be dry enough so I can get in the boat and feel around inside to figure out exactly what the challenges are for the support poles.
 
FuzzyGrub said:
In my experience, it is very hard to prevent water wicking between the plywood and sheet aluminum. And once it happens, it never drys out. Multiple holes in the alum might prevent that. Still think I'd prefer something on the inside.

My first thought was one horizontal brace (same direction as cross ribs), but it would be too long to get through the access hole. Then two parrellel ones running perpendicular to the the cross ribs.

Hopefully, the 3M 5200 will be dry enough so I can get in the boat and feel around inside to figure out exactly what the challenges are for the support poles.

Some 1/8" spacers between the deck and the plywood, plus a water shedding finish on top of the plywood like vinyl or paint and sealing the underside of the plywood would solve that problem pretty easy and you wouldn't have a noisy "tin canning" deck.
 
Surprise, surprise! I took a closer look at it, and there are already two beams. I rechecked the oil canning, and it is only in the very nose, in front of the most forward beam. The rest seems stong. See pics below:

JonProject012.jpg


JonProject013.jpg


JonProject014.jpg



I think I am just going to add backer board there. I might have enough king starboard, but if not, primed, sealed, and painted plywood.
 

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