deck repair boat building question

[starcrafttom]

Hi, This is really a general question on rebuilding decks as the boat in question is a non-cdory, but I wanted the advice of the many talented / gifted boat builder, repair experts here on the pub. So now that the a$$ kissing is out of the way here's the problem.

So my fathers 44 Atlantic has some rot in the forward deck. Seems that the windless, which was mounted thru the bow pulpit then thru the deck, leaked and has caused a large area of rot. None of the thru deck holes where over drilled and back filled with epoxy. The deck is your typical fiberglass sandwich with a balsa wood cord in between. We have cut several large holes ( 1 inch to 8 inch) to expose the rotten wood and dig out much of it. It has been drying for a few weeks now while dad has been rebuilding the bow pulpit in my garage. Turned into project in and of its self.

So the accepted way of fixing this problem is to cut out the top of the deck skin over the affected area, which is going to end up being a area of 4 to 6 square ft, digging up the rotten wood and then replacing the balsa followed by re-glassing the skin back in place. My question is this. With the 6ft cable camera my father has and some long rods we should be able to dig out all the rotten wood with out cutting out the deck any more then we have already. This would just leave the job of filling the void, which is the meat of my question. Would it be a good idea to fill the void of several square feet with some thing other them balsa core. I ask because when I had the raised deck added to my 22 ( which made it look like a newer model) they filled the space between the decks with A,B foam. I was wandering if this would be a doable project ? what are the plus and minuses of using two part foam? or even using one of the house hold construction type foams found at home depot? I wonder if the foam would provide the support needed to walk on? I don't think their is much strength in the wood core as there is in the design of fiberglass sandwich around it.

So good idea ? bad idea? Off my rocker again? lets hear it.

 

[thataway]

Tom, You are correct that the strength is in the glass and thickness, not the core itself. There are two part pour in place fairly high density foams which will work--but you had to get them well back in the voids, and withdraw the tubes as the foam is applied, with a cartridge gun. Foam expands with enough force to break aluminum thick wall masts, so you have to judge just the right amount and allow vents for it to come out of. My personal preference is to take out the bottom of the deck area, and put in new core from there. This leaves the molded non skid intact.

I hope to have a little more time later--if you were to post some photos it would help. I am very familiar with the Atlantic 44 and 47--great boats! Yes, deck core rot is a issue with all most all of those boats.

 

[lloyds]

I had some delam and rot in the core of an old ranger sailboat I had. I stripped off the glass on the inside around the area and just glassed it all back to the original shape. Left the top surface intact.

 

[starcrafttom]

Bob, The problem with going in from under is that the rotted area over laps the chain locker and the front cabin. trying to glass both sides of that would be a pain. I cant fit in the chain locker to do the work. No way the old man will fit. Between that and the head liner that is already installed It may be easier to go in from above.

I really want to figure out a way to use the foam if there are no problems with doing so. I understand that if too much is used or its used to fast with out a out let for the extra then it could bulge the deck.

With the large holes we already have in the deck that may not be a problem. Iam worried about the long term use of the foam. Seems to me that any thru deck holes for bolts could be under cut and epoxy filled then redrilled just like balsa. Would the foam and the epoxy work together?

 

[Sunbeam]

I have always removed the deck or underside skin when making a repair like this, so I haven't tried the other methods.

One possible problem is that normally you take some care in prepping the skin(s) so that you get a good bond with the new material. That's because it's the bond between the three (skin/core/skin) that makes the cored structure strong. No bond = no strength.

For example, I cut off either the top or bottom skin, then before proceeding with laying in the new materials, I grind/sand all the irregular bits of old core off (it never just comes out perfectly clean), and then solvent wash it and vacuum. I want it clean and relatively flat. Then I go in with new core (mushed into a bed of thickened epoxy) and the new skin (some folks save the old skin and then grind about 2-3" on either side and then tab the joints with fiberglass tape. This can allow one to plan seams for the smooth strips between non-skid, say, which can make fairing/re-finishing easier.)

Now, your deck skins may be strong enough, or your area may be small enough, that you can get along fine without a perfect bond (or maybe you can figure out a way to get one), but it's just something to think about.

Another thing is that - at least on the jobs I've done - I always end up finding more wet stuff than I thought or it goes into a different spot than I thought it would, etc. So that's another reason I just bite the bullet and get it over with (i.e. cut the sucker off and go from there). Also I have a mortal fear of having to do the job over again if it fails :cry, so I want to be SURE it's going to work. That probably leads me into a bit of "go with what I know" vs. experimenting, admittedly.

One tool that makes it a lot easier for me is a Fein Multimaster (or one of the other similar tools). FAR less dust, very controllable, and much less likely to cut skin (human type). The E-cut blades take out core like butter.

I've used both foam (sheet) and balsa core. I slightly prefer balsa, but they are both good, I think.

 

[thataway]

Tom,
I understand the issues on the Atlantic about access--and that this may not be practical. The two part foam does have good adhesive properties, and should not be a major issue. Yes, you should undercut and epoxy any bolt holes. This also increases the strength. You may want to go with a completely different on the top when you re-glass it--such as rolled on 2 part LP with glass micro beads, walnut shells etc. Vs trying to replicate the original non skid (another option is cabosil thickened gel coat.

We have made coolers with poured in place foam, and fiber glass; and they were very strong.