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As my bulkhead project is in its final stages in my San Juan 28 'Enterprise', i need some advice. I have pulled out every piece of wood on the interior and used as templates for new Jorbet Marine plywood. All pieces are installed with stainless wood/fiberglass screws and bolts. i am now looking at some rough cuts as i walk around the galley. My question is can i fill and fair the gaps which meet the cabin roof with marine grade fiberglass body filler? i plan on taping straight clean lines on the bulkheads and cabin roof before i begin working with the material. Even though the deck is 100% firm, i want to know if i will have any problems with the deck naturally flexing especially while under sail. This seems like a decent option for me, rather than going the painstaking route of cutting 1 3/4 pieces of oak trim to conform the the cabin roof.
 

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Is your mast deck or keel stepped?
You need to insert something soft, like closed cell foam to avoid a hard spot. Even though the deck is 100% firm, it still flexes and you don't want a hard spot holding it up and stressing the glass.
 

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this is our tabbing to the deck


foam inside...
 

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you can see the foam here
 

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finished bulkhead


not the prettiest...still need to paint and trim and install cabinets and the such but its way sturdy and no hard spots so to speak...the foam was just packed in then initial tabbing to keep it in place then laid up after that....

you can see the hull liner in the background...mine was firmly attached to the hull there so I tabbed to liner...I know its not the best solution but since we did major tabbing elseewhere compared to stock tabbing I think Im ok

im hoping it is...
 
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Discussion Starter · #6 ·
How firm does closed cell foam get? Is it sandable when cured? the rig is deck stepped and has a solid oak compression post which is original and intact
 

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How firm does closed cell foam get? Is it sandable when cured? the rig is deck stepped and has a solid oak compression post which is original and intact
Insert the foam and cover it with wood trim or such. A picture would help us to better understand and provide the proper advice.
 

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Use core foam like Airex or Core-Cell, not the closed cell stuff that gets used for upholstery
 

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Use close cell foam but it doesn't have to be anything expensive. I have used Ethafoam in the past. All it is there for is to space the bulkhead from the hull/deck so there are not any hard spots. When finished the tabbing on both sides of the bulkhead takes all the loading.

You don't have to use foam at all really. Morris Yachts uses a spacer, tabs one side, and then removes the spacer before tabbing the other side.
 

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^^^^x2 a lot of tabbing is done this way...or removed this way like you say

the worker said he preffered doing it this way...I thought foam would keep a better line to fillet and stuff.

originally a lot of boats simply use wood spacers....tab one side...remove then tab other side...the air gap is there and the tabbing does its job

foam is just a simple way of keeping that line if you will and cushion a bit...more than likely over time it will just desintegrate with the heat and all

when real question I have always wondered is about filleting...in essence the fillet is harder than the tabbing so really you kind of are making a hard spot but its thin...the tabbing should flex a bit but be strong....dunno just always wondered...well see what happens on my boat at least jajaja
 

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Flexing enough will weaken and break glass fibers. You don't want any localized flex - the tabbing should be strong enough to prevent this.

Foam does make filleting easier. The filleting is mainly there to create a curve for the tabbing. I have sometimes cut the foam in a trapezoidal shape to make for less filleting and easier tabbing.
 

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yeah on my boat the tabbing is massively stronger than original...I guess its the wording I find tricky and especially to newcomers when how tos say that you need an air gap...or foam which can move and compress but then the fillet itself can be brittle and crack and then that is covered with layered glass

in any case...it can be confusing to many...

the filleting indeed is basically a curve made easier for the glass to bond...basically its a joiner...too much emphasis is put on the fillet in my humble opinion versus say the gap between hull and bulkhead and how you tab...

peace
 

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The goal is to keep the bulkhead away from the hull/deck so there are not any hard spots.
 

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yes however if you think about it...the actual fillet is a hard spot...
 

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it is a little bit but it's not nearly the same as the corner of a piece of plywood.

The goal is to spread and taper the load area, which fillets and tapered tabbing do
 
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yes however if you think about it...the actual fillet is a hard spot...
If it was in one spot only yes it would be a hard spot, but it is spread evenly around the bulkhead edge. Tabbing is also a hard spot if done properly - thick enough, say 2 layers of 1708. It has to be if strong enough. As long as it isn't localized to small areas it is not a problem.
 

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I agree guys...Im just being the devils advocate cause for newbies this topic is very frustrating as when reading how tos its hard to ignore some obvious contradictions that unless explained well kind of bother you.

while yes a peak of plywood against the underside of the deck will obviously create a hardspot so will a badly tabbed thin bulkhead that is epoxied(like how some tos explain) to the hull and then tabbed on each side...

you wil start to notice especially on thin hulled boats a clear vertical line where the bulkhead is attached, especially if your boat is known as being flexible or known for OIL CANNING

on very sturdy and robust boats you can be a bit more lax on your preffered method.

like all things there are many ways to skin a cat...

some guys bed theor bulkeads in 5200, some use foam, some wood and remove, some use expandinf foam, some simply go straight to hull

in the end there are many ways...some better than others but mostly dependant for me at least on your boat and hull construction etc...

cheers

hijack over
 

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I agree guys...Im just being the devils advocate

some guys bed their bulkeads in 5200, some use foam, some wood and remove, some use expanding foam, some simply go straight to hull

in the end there are many ways...some better than others but mostly dependent for me at least on your boat and hull construction etc...

cheers

hijack over
In other words if you have a thin badly built boat you should take care and use foam to install the bulkkhead properly but a well built boat allows sloppier work?:D
 

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nah now your taking me out of context....jeje

but in a way you could say yes old boats were in fact builty sloppier(early glass boats) than those today so I guess this conversation can be dragged on forever! JAJAJAJA

sorry OP.

back to your boat
 
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