Building Aft and Bow Decks

[Tightlines72]

Hello iBoats,

I have been on the forums here for a while now; mostly reading but occasionally asking questions with great results. I have an old flats boat that had a completely rotted deck though luckily after removal, i found that the stringers were solid. Everything is now out of the boat and everything has been ground, and per the wise advice on here I have my order from US Composites on my way to my house. I thought I had a good plan, but after a few eager nights of no sleep, I am starting to second guess myself.

My question comes in how best I should attach the raised aft and bow casting decks. The original design had two bulkheads rising from the bottom deck that ran perpendicular to the hull and ended about 1/2" below the top of the gunnels to allow the deck to sit flush with the gunnel. Each of these bulkheads was 1/2" marine ply that appeared to be simply tabbed to the hull. My original plan was to attach my new ply wood bulkheads to the deck with SS deck screws from under the deck before installing, then PBing, glassing, and tabbing the deck in, then finally tabbing the bulkheads to the hull and to the deck.

My concern is that the bulkheads won't sit completely vertical and will provide an uneven support structure for the deck to sit on. Beyond that, I'm worried that the weight of the top deck and people standing on it will cause the bulkheads to buckle to one side or another.

I know this probably is hard to follow, so if someone could post a suggestion as to how to install bulkheads onto a bottom deck to allow for the construction of a raised aft and bow deck, I would be hugely grateful. I'm not great with paint, so please forgive these pictures.


Old bulkhead layout:



New bulkhead plan:

 

[Mechanicalmike08]

I would avoid screws anywhere, the pb and tabing should be plenty of attachment strength. I don't think I'd worry about them buckling if eveything is tabbed and PB'd down but I don't see why you could not add cross bracing between the parallel runs. It would only take 2 to give it some real strength. If this is ur first fiberglass experience you will be pleasantly surprised in its strength when done correctly.

 

[gm280]

Two things to consider. First, what are you using for the vertical support braces? Second what is the span between the two vertical support brackets?

1/2" plywood, properly fiberglassed on all sides, will work for the decks, but not if the span is too far apart. In other words, if your decks are more then 3 feet wide, I would install a center brace. And I would position the plywood with the grain going crosswise and not lengthwise. But there is no rule specifying that. It is more my feelings for support then anything else. I don't know how much weight you are talking about on top. A center brace would add a bit more support in my opinion.

I also would glass all sides of any wood being used and the plywood HAS TO BE EXTERIOR GRADE! Once you glass all the exposed wood, you will be amazed at how strong it gets.And that can be glassed with either polyester resin or epoxy. resin. I'd go poly to reduce cost. It is what most boaters use on their projects. Epoxy can work as well, but that is your decision.

I suggest you read some of the project threads on here and get a feel for what you want to do...JMHO

 

[Tightlines72]

The weight on both decks would be at most about 400 lbs (2 fishermen trying to land a fish). I'm not necessarily worried about the deck itself flexing, but rather whether my vertical supports are going to start to flex and eventually buckle to one side or another. My worry with just tabbing them in to the bottom deck is that if they don't go in perfectly straight they will start to bend over time. I guess additional supports that run bow to stern would solve that problem, my only hesitation was that these weren't present in the original layout. I also suppose the tabbing that runs up the gunnels will prevent any movement in the aft/bow direction.

I've done a good bit of fiberglass work in the past and am confident in the procedure for covering my marine ply, so this was more of a planning question for the design of everything before I start getting my hands dirty.

 

[gm280]

The weight on both decks would be at most about 400 lbs (2 fishermen trying to land a fish). I'm not necessarily worried about the deck itself flexing, but rather whether my vertical supports are going to start to flex and eventually buckle to one side or another. My worry with just tabbing them in to the bottom deck is that if they don't go in perfectly straight they will start to bend over time. I guess additional supports that run bow to stern would solve that problem, my only hesitation was that these weren't present in the original layout. I also suppose the tabbing that runs up the gunnels will prevent any movement in the aft/bow direction.

I've done a good bit of fiberglass work in the past and am confident in the procedure for covering my marine ply, so this was more of a planning question for the design of everything before I start getting my hands dirty.

If you are installing the vertical braces from one side of the hull to the other, and PBing (tabbing) them in from top to bottom along the boat sides, I don't see any problems. The PBing the ribs in-place along the bottom and side makes them extremely strong and stops the flex you're worried about. JMHO