bulkhead installation ??
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bulkhead installation ??

  1. #1
    Senior Member $uperJoe's Avatar
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    Default bulkhead installation ??

    in a general rule of thumb kinda situation, i have read that the wood used for a bulkhead in a vessel shouldnt actually touch the outer fiberglass structure of the boat. this is because as the boat flexes the wood will not and it will crack the hull from stress. it should be mated to the outer structure with a few layers of glass mat and resin.

    few questions

    1 is this actually correct
    2 how big is the gap area (noted with the pink arrow)
    3 how far should the connecting glass and resin spread over the new bulkhead and hull? and is it small pieces to larger overlapping as on top, or is it large followed by smaller support as on bottom?

    i attached a picture to help illustrate my question if i didnt explain my concern correctly

    just trying to get my head around this so i can knock it off the list of things to research for when it comes time for a new floor in my boat
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    Senior Member Sanger-Spectra's Avatar
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    You are right, bulk head should not touch, you will proably get some different responses on this so I will describe how I did my day cruiser. One good thing to do is to encapsulate the bulk head in glass before installing, you can just use cloth for this no need to go crazy with the heavier matt. use a couple layers of matt and set the bulk head in and then two layers of matt to finsh up. No need to stagger the width, a good trick is to feather the edges of the matt, grab about 1/2 of matt and pull it out, this will allow the matt to flow out really nice at the edges. I went about 4 to 5 inches onto the bulk had and then to the hull. here are a few pics, the painted pic will show how nice the glass lays down when you feater it out. I did do two final resin coats and 1 sanding coat. if you are not going to see them no need for that. This was with poly resin. On the under deck picture, you can see I added soem Y shaped bulkheads, the reason is that almost every Spectra I have seen has about a 1/4 to 3/8 dip just infron of the cabin. I used a piece of 1/2 plywood encapsulated in cloth as a base for the bulk head on the side and the top deck, may have been over kill but I felt comfortable that this would eliminate the possibility of the bulk head transfering thru.
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    Last edited by Sanger-Spectra; 01-26-2013 at 08:04 PM.

  4. #3
    Senior Member $uperJoe's Avatar
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    Quote Originally Posted by Sanger-Spectra View Post
    You are right, bulk head should not touch, you will proably get some different responses on this so I will describe how I did my day cruiser. One good thing to do is to encapsulate the bulk head in glass before installing, you can just use cloth for this no need to go crazy with the heavier matt. use a couple layers of matt and set the bulk head in and then two layers of matt to finsh up. No need to stagger the width, a good trick is to feather the edges of the matt, grab about 1/2 of matt and pull it out, this will allow the matt to flow out really nice at the edges. I went about 4 to 5 inches onto the bulk had and then to the hull. here are a few pics, the painted pic will show how nice the glass lays down when you feater it out. I did do two final resin coats and 1 sanding coat. if you are not going to see them no need for that. This was with poly resin. On the under deck picture, you can see I added soem Y shaped bulkheads, the reason is that almost every Spectra I have seen has about a 1/4 to 3/8 dip just infron of the cabin. I used a piece of 1/2 plywood encapsulated in cloth as a base for the bulk head on the side and the top deck, may have been over kill but I felt comfortable that this would eliminate the possibility of the bulk head transfering thru.
    that does look very nice. in the last pic it that the inside of the transom? it looks like you have 4 stringers. is that correct

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    Senior Member md-11mike's Avatar
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    Quote Originally Posted by $uperJoe View Post
    that does look very nice. in the last pic it that the inside of the transom? it looks like you have 4 stringers. is that correct
    Like what Sanger Spectra did. When you are going wood to wood (bulkhead to bottom of boat keep it tight. If the boat is old and already shrunk all you need is about 1/4 in along the hull sides and deck. Some guys get carried away with huge gaps. Seen as much as 3/4 which is way to much.
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    Senior Member johnf's Avatar
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    Looks good!!! Must be replacing bulkhead with 0-gravity or while the hull is upside down??

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    Quote Originally Posted by johnf View Post
    Looks good!!! Must be replacing bulkhead with 0-gravity or while the hull is upside down??
    yea someone else complained that the boat was upside down to long so I flipped a couple of them. But 0 gravity is nice cause the resin doesnt drip as bad as it does at 1 positve G or normal gravity

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    Senior Member OFFSHORE GINGER's Avatar
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    All Great advice but no one mentioned using a fillet which is a coved shaped application of thickened resin , and Cabosil ( peanut butter consistency ) that is used to fill in all voids , and gaps which also gives your fabric something to roll into which can be done using a hobby stick when applying the thickened resin or putty .
    Last edited by OFFSHORE GINGER; 01-27-2013 at 03:23 PM.

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    Could you bed the bulkhead in like you do for a stringer? Or would that put a stress point on the deck?

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    Senior Member OFFSHORE GINGER's Avatar
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    Joe , this is a staggered layup that i normally do along the perimeter of bulk-heads & transoms sometimes more................... depending on the boat , and just curious what type of boat are we talking about , and how about some pics .
    Last edited by OFFSHORE GINGER; 01-27-2013 at 04:15 PM.

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  13. #11
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    Quote Originally Posted by dobber View Post
    Could you bed the bulkhead in like you do for a stringer? Or would that put a stress point on the deck?
    Ha Ha Ha , are you stalking me ............................................. & yes you can bed the bulk-head in like you would do a stringer and welcome to the forum .................................... & what took you so long ?

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    So the bulkhead can touch the bottom of the hull, and fit tightly but at the sides and top you want a 3/8" or so gap. Am I understanding this correctly? This is how I have mine trimmed up, but I do not have it glassed in yet.

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    Quote Originally Posted by OFFSHORE GINGER View Post
    Ha Ha Ha , are you stalking me ............................................. & yes you can bed the bulk-head in like you would do a stringer and welcome to the forum .................................... & what took you so long ?
    I'm slow. lol.

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    i used a sheet of 1/2" foam to get the shape. much easier to cut and trim than wood/cardboard. i made it tight to the bottom of the hull and stringers, but gave a 1/8" gap or so on the sides of the hull and the top. 2 layers of mat and resin on the inside and out. feels like a whole new boat. no stress cracks on the hull or deck so far.






    Last edited by ka0tyk; 01-27-2013 at 05:10 PM.

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