Split the boat

I am currently replacing my transom on my 1970 19' mako The transom is completely out. I see, as I suspected, the flotation foam under the deck, seems to be soaked. For that reason and also to put a gas tank under the floor, I would like to take the complete deck assy. off the Hull. I have seen boats that have had it done. I would like to know how hard it is to get them apart. Also I would appreciate any advice on this procedure. I've never done this before so I'm guessing. Also I wonder if the foam would dry out on its own and if so will it be ok to leave or will it get soaked again? Thanks Ken

 

Ken sorry to say this ithe foam will not dry out. I dug foam out of one boatand left it laying in the sun for a year and you could still sueeze water out of it. someone may no of a way of drying it but I do not. In what shape is your deck in? that might be the more proper question for me to ask before we take a strategy on removing it.
Howard

 

Ken why do you feel it's necessary to remove the deck? I strongly do not recommend this action for a backyard DIY. The deck will be held on with a few hundred S.S. screws hidden under the aluminum rub rail (with rubber insert) and a slathering of butyl rubber, which will be still goo like after 35 years. This rubber seal can be broken with a hot knife, but considerable force will be needed to get the thing off. I use a 3 ton chain hoist for this type of work and it's rare not to damage the deck, liner or hull.

The foam is an open cell foam, common of the era and can be cut easily with a hand saw or whatever fits in the location, you could also melt it out with solvents (not recommended) You can refill the area with liquid polyurethane foam (closed cell - no sucker upper). I'd recommend a 2 pound foam, a two gallon kit (parts A & B) will make about 8 cubic feet, which is about 60 pounds of buoyancy per cubic foot. There is higher density foam available where support is more critical than weight or buoyancy.

Personally, I'd find a way of putting tanks through a hatch (which you'll make) in the current deck (5/8" ply covered in mat and polyester I think) rather then the major surgery you're suggesting. You can refoam the area where you removed the soaked stuff while you have the deck cut open for the tank(s)

Under deck tanks are a different animal then above deck ones, so think about it. They must be strongly mounted, vented, sending units for gages and have access for cleaning and repairs. There are a number of USCG guidelines that must be met for them as well.

 

Captword, PAR, Thanks. First my deck is in pretty good shape. a couple heaves in the back and a lot of screwholes but otherwise good. Next it appears that the foam is only in the sides of the boat from the stringer and up the sides. Even from the centersection where I would cut the hole to put thefuel tank I would not gain good access to the foam. Maybe I am wrong but It looks like the stringers are at least mostly blocking the foam. that is why I am considering pulling the whole deck off. I have all the screws and rivets out but It seems to be bonded to the hull. Maybe I can get enough of the foam out from a tank access hole what do you guys think? Thanks for the help! Ken

 

It is pain staking and aggravating but if you are going to remove part of the deck, i would remove it all. YOu will have fixed everything that you cannot sea and know that it is right. PAr is right about the under deck fuel tank. make sure if you put a tank under the deck that you follow uscg standards. that is for your safety and well being. if the boat already has a tank under the deck make sure you put it back like it was. One thought to ponder though if it doesnt already have a tank under the deck what about a console with a tank built into it? Depending about your area you might be able to find one of the araea builders that puts that style of console in their boats. YOu could by a console from him and just remove and switch yours. get what you want without having to remodle the boat in a MAJOR WAY.
Because of the age of the boat if it were me. If i was going to remove part of the deck. I would remove all of it as aggravating as that is. DIg all the old bad foam out. fix any bad places that are hiddeen by the deck and foam and put it back together right. If you have done it right, you should not have to wory about under the deck for a long time. DEpending on the amount of water soaked into the current foam in the boat, you might see a noticable increase in speed and economicability.
howard

 

It's unlikely that the deck cap is bonded to the hull at the flange or other wise in a 1970 boat. The sealant is sticky stuff and a one inch wide strip of the stuff on a 19' boat equals 460 sq. in. of goo holding on to the deck cap. That's plenty of holding power, enough to lift the boat less the engine as I've done on more then one occasion. I suppose it's possible that some resin was splashed around when the cap was installed. If that's the case there WILL be damage when you remove the deck. Odds are it's stuck to the foam and flange sealant.

Again I'll recommend you not tackle this project in this fashion. The problems you have can be handled without removing the deck cap. Cut your hole for the tankage (I'd recommend two smaller tanks, then one large) and hack out the foam from there. It's not pleasant work but isn't real hard, especially if you think of people you don't like while you hack away at the foam. The foam on the topsides (hull sides) shouldn't have much water in it unless the boat was flooded, so leave it alone, you'll need it if you do get swamped. You'll break the deck cap or screw it up good if you use to much force and since you're a virgin at this work you'll not know what is to much force until it snaps in half. Why make more work for yourself, do it the easier way. Replacing a bad section in the sole is one thing, but removing the cap is another animal.

Removal is easy with a hoist, but a ***** with anything else, no matter how strong you pals say they are. The hull topsides will flare or move some so this must be prepared for with internal bracing to prevent the sides from moving away from the center line as the main structural member (the deck cap) is removed. Replacing it requires careful alignment and the ability to slowly move around the cap over the hull to get the spot it'll drop down on. This most times requires some tilting, tipping a cussing.

This boat should have come with on deck tankage, a wise idea on a boat this size and wouldn't have come with a console tank another wise idea. Under deck tankage isn't all that tough, but you should log on to the USCG web site and down load the "Backyard Boat Builders" info sheet. It has guidelines for new construction in home built craft and these will apply to your modifications to the tankage. Use some thought for the hatch to cover the hole. A flange with a strip of gasket around the edge should do and screw it down. It will only need to come off if more repairs, inspection or cleaning needs be done, so make it tight. You'll need to provide some venting and filling hose, bilge blower w/ it's electrical needs, gage, sending unit w/ it's electrical needs, clam shell vents for the blower air going in and out, fittings, a bilge pump if you don't have one w/ it's electrical needs and a very solid way of attaching the tank(s) that's not to the hull bottom or sides directly. You should be able to turn the boat upside down and have the tanks stay put. Starting to get complicated ain't it? This why on deck tankage is used. They're basically fool proof and little risk of explosion, while on deck, but once enclosed in a below deck space a time bomb waiting to blow unless done correctly, used and maintained properly.

If you drop me an email I can give you the technical details for a safe installation and attach the USCG regs for you to look at.

 

PAR, Thanks for you real good advice. I don,t have your e-mail address. My address is kenness927@comcast.net I would very much like to talk to you. 860-663-2663 Thanks again Ken