Bulkhead replacement Aft of Engine

[jackryan]

I am nearing the completion of my cockpit deck and cockpit support/stringer project. One of the last things I need to do is replace the bulkhead that is aft of the engines. The bulkhead currently in the boat is made of plywood and in bad shape.

I was wondering if I could get some advice from any of the faithful that have attacked this project. Wondering what type of material others have used for this? Coosa? We are thinking of lamenting several pieces of coosa together and and encapsulating with fiberglas.

I am also wondering how much hull support this bulkhead provides? Is it safe to remove this bulkhead while the boat is in the water, or will removing it cause potential hull issues by eliminating the support it provides?

Also, it is in a tight spot, so I'm wondering how to get get the shape of the new bulkhead right.

Thanks in advance for any comments!!

JR

[Carl]

I did remove and replace with boat on land. I'd think that was worse than in the water were the boat sits without any induced twist from being blocked up. Not that it made much difference as mine was shot and not holding much in any position.

Removing was easy as it was mostly just pull the crumbling bits out. I used marine ply to make the new one. Behind the motors the wood was still sorta ok...I used those as templates laying over the new wood. Used overall measurements to help place and make sure panels were deep enough. Then got to cutting. A few trial fits had me make a few extra cuts, grind a bit. I left some of the original tabbing for placement and to clamp wood in place. When happy I gave a good coat of epoxy all over. A day later a light sand then put in place tabbing it in. Afterwards I put a few strips of cloth over the top to reinforce and seal the top.
It was one of those projects I overthought and overthought and was never able to get started. Once started it all kind fell into place.
A little long or short...no matter, your tabbing it to the hull. Big radius to hull giving some flex. So if longer or an edge catches on something...trim and fit again till right. It would have been a better job to have done with tank out for better access...but at that time the fiberglass tank was a forever tank. The following year the tank was pulled out as it was lunch for the ethanol.

[Ironworker]

I'm doing this project now. My boat is in the water. I'm using 3/4" Bluewater 26 Coosa. Its time consuming but otherwise not too bad. I'm using cardboard to make templates then cutting 1/8" soft plywood as templates. Once they fit, I'm cutting the Coosa. I'm putting a layer or two of topstrand mat on my bulkheads for good measure.

I'm joining two sections of coosa at the bottom of this bulkhead with one there to support the deck supports.

[Tony Meola]

Jack

I used 3/4 inch choose also the old pieces were used as a template.

Actually you can get away with 1/2 inch choose and you will be fine. We used one big piece. A 4 x 10 sheet covers the width of the hull.

[DanielM]

Jack

I used ¾” Coosa board in my boat. It’s not a B31 and the back bulkhead in my boat does not provide any support to the flybridge. So I don’t know about the support needed in a B31, but it sounds like other guys have used it.

My cabin is teak so we laminated teak veneer on the inside and decided to try something Capt. Pat mentioned on here on the outside. We epoxied Formica laminate on the outside. Capt. Pat called it ‘instant fair’ basically scuffed it and painted it to match the cockpit as I remember. Anyway it came out looking pretty good.

My boat has a design flaw that allows drainage from the flybridge down on to the aft cabin bulkhead. It had rot when I purchased it originally and I replaced the bulkheads with marine teak veneer plywood. Unfortunately I didn't fix the original design flaw well enough and I wound up with rot in the upper corners again after a few years. On the second time, while I feel I did a better job to limit water intrusion, I also opted for Coosa board to avoid any rot issues in the future.

[jackryan]

Thanks for the advice on this project. I've purchased a sheet of 3/4 inch coosa for the bulkhead material. It's not going to be possible to use the old bulkhead as a template, so my brother found a good video from Boatworks Today on how to create a template for the new bulkhead:

https://www.youtube.com/watch?v=6OKPIvNE-Ss

Have any of you guys used this process to create a template? It looks pretty straight forward.

JR

[Ironworker]

Jack,

I have built a couple and will post up some pics. I also have my templates if you want them. The two sides of the boat are different.

I used 3/4" Coosa. I bonded a second layer at the bottom to support my deck floor supports. I'll post up some pics.

BTW, I'm going to slightly modify mine with a 3" sched 20 PVC to hold a 10' harpoon.

[Ironworker]

Jack,

Regarding the template. I used luan which is 1/8" soft plywood, which worked pretty well. I think the 1/2" sheet foam for the exterior of a house may be easier to work with.

BTW, the two sides of the boat are slightly different. Based on what I was told these bolts were built with two half molds then joined together the molds were a little different.

Here are pics of mine and I through in a photo of the support along the transom. I've got some heavy loads back there hence the 1" stainless square tubing.

https://www.dropbox.com/sh/gj8uhzs5f8rs ... CIOka?dl=0

[Snipe]

Jack I used 3/4” coosa laminated with 1708. Made the templates with 1/4” luan strips and cardboard and hot glue gun.

[John F.]

Crows Nest has DD 8.2s, and to get them to fit the engine boxes were lengthened about 11" and the bulkhead was mostly cut away. She's been that way for way more than 20 years and is fine so I don't know how much that bulkhead does structurally. The part in front of the tank is intact.

I replaced that bulkhead in my old B31 using Capt Patrick's lattice strip and glue gun technique illustrated by Snipe above. I've used that technique on a few B31 projects. It works great

And Snipe - wow. Great work

[jackryan]

Guy's as usual, outstanding stuff. The pics and description will help immensely! Snipe, obviously the best way to do this would be to do it without the engines in, like yours. The process will be slightly complicated by the fact that I will still have the engines in. I'm going to use the hot glue gun technique as well.

While I'm at it, when you guys reinstalled the deck, what did you do to help direct the water on the deck out through the scuppers? A buddy of mine had the yard fabricate fiberglass tubes that were about the shape of the scupper holes and epoxied them into the bottom of the cockpit panels. I'm sure there are some good ideas on how to address this out there.

JR

[Carl]

BTW, the two sides of the boat are slightly different. Based on what I was told these bolts were built with two half molds then joined together the molds were a little different.

Yes and no to the split molds info.

Yes they used split molds but they bolted the molds together before starting the layup. Once molds were together the layup was done like a boat in a one piece mold. The part that differs is when done glassing the hull, the molds were unbolted and separated to release the hull. If not done in a 2 piece mold the shape of the hull would not allow the hull to come out. Think about the reverse flare on the chines.

[Ironworker]

Very interesting Carl. I was told about the 2 piece molds by a guy who has refurbished over 30 B31's. Lots of history to these old boats.