Raising boat deck

[hawaii1982]

Hey, new to the computer thing. So far have not found any topics regarding this issue but if anyone has any information to help me out please let me know your ideas. I plan on raising the deck in my 18ft gulfstream. The original side stringers come up only 8" from boat hull and are partially rotten but not all the way. I plan on raising another 8" to complete a "wet deck" for fishing rough ocean waters. Would I be able to just use 8lb to replace the 2lb I removed and instead of raising stringers just pour over them, it seems the 8lb is so solid that it would not matter. I'm not that worried about having a stringer to screw my deck into, possibly just glassing over the rock hard 8lb foam. Any info would be greatly appreciated. Thanks, Josh

 

[craze1cars]

Re: Raising boat deck

You posted this quesion in an area dedicated to propeller discussion...and your question has nothing to do with propellers at all....

If you would like useful responses I suggest you post your question over here in the Boat Restoration & Hull repair section:
http://forums.iboats.com/forumdisplay.php?f=22

 

[steelespike]

Re: Raising boat deck

Welcome, as suggested the hull repair section will be more help.
Not unusual for newbies to get in the wromg area.I'm sure the guys will get you setup.
Does 8 pound foam refer to its actual weight per cubic foot?Seems like that would add a lot of weight right at the top of the boat where it could change handling negatively.

 

[ezmobee]

Re: Raising boat deck

Thread moved...

 

[Cadwelder]

Re: Raising boat deck

Josh.....Welcome to the Dry Dock.

First off raising a deck that much changes the center of gravity of your boat, I wouldn't suggest it, the deck height was engineered the way it is for a reason.

But if you do change it, you'll need to extend (replace if rotten) the stringer system of the boat. Don't just pour in some foam. The deck needs to be attached to the stringers as it is a part of the boats structure.

 

[Bondo]

Re: Raising boat deck

Josh.....Welcome to the Dry Dock.

First off raising a deck that much changes the center of gravity of your boat, I wouldn't suggest it, the deck height was engineered the way it is for a reason.

But if you do change it, you'll need to extend (replace if rotten) the stringer system of the boat. Don't just pour in some foam. The deck needs to be attached to the stringers as it is a part of the boats structure.

Ayuh,... I agree with CW,...

Maybe ya just otta start with a hull that better fits yer Needs, as that 1 sure don't....

 

[hawaii1982]

Re: Raising boat deck

Thanks for the response, the boat I am working on is completely gutted except for remaining stringers. I am currently installing the new transom for an outboard motor. Nothing going back into this boat is going to be "factory specified". Just curious if stringers really needed to be attached to deck or if they could be held down by other force ie 8lb dense foam. There would be about 6" of space between deck and stringers.

 

[Cadwelder]

Re: Raising boat deck

Just curious if stringers really needed to be attached to deck or if they could be held down by other force ie 8lb dense foam. There would be about 6" of space between deck and stringers.

Well you know the answer now, but still don't recommend raising the deck that much.

 

[Bondo]

Re: Raising boat deck

Thanks for the response, the boat I am working on is completely gutted except for remaining stringers. I am currently installing the new transom for an outboard motor. Nothing going back into this boat is going to be "factory specified". Just curious if stringers really needed to be attached to deck or if they could be held down by other force ie 8lb dense foam. There would be about 6" of space between deck and stringers.

Ayuh,... The Stringers are supposed to be bonded to the hull, 'n are supposed to support the deck...
When it's all tied together, it creates strength, through structure...
The deck, Don't hold the stringers down, per se'...
That's backwards...

Yer Idea, throws All that out the window...

 

[hawaii1982]

Re: Raising boat deck

Ok, sounds like the stringers will be raised then. What about the 8lb pour foam to replace the old stuff that was in the hull? Anyone have any experience changing to a denser rated foam? Not sure what they used back in 73' but it mostly waterlogged....

 

[Bondo]

Re: Raising boat deck

Ok, sounds like the stringers will be raised then. What about the 8lb pour foam to replace the old stuff that was in the hull? Anyone have any experience changing to a denser rated foam? Not sure what they used back in 73' but it mostly waterlogged....View attachment 91581

Ayuh,... It's a Stringer Drive,..??

You really, Really otta reconsider this project...

 

[hawaii1982]

Re: Raising boat deck

Yes it was a stringer drive. Going to convert to outboard, using a bolt on motor extension mount. I plan on reinforcing hull, not sure yet what size mat I am going to use. Just want to beef everything up for rougher water.

 

[petermarcus]

Re: Raising boat deck

If the old foam was 2 pound, you're sacrificing buoyancy for strength. A cubic foot of foam is going to weigh more and float less than the old stuff.

Basically, a cubic foot of water weighs 62 pounds. A cubic foot of 2-pound foam will float 60 pounds of boat/hull/engine/equipment if you swamp the boat. 8-pound foam will float 54 pounds of that stuff (so, about 10% less). If you plan on making your boat even more heavier with more glass and resin, adding more wood in the stringers (and glass and resin), adding more deck (and glass and resin) to cover the wider beam, then replacing 2-pound foam with 8-pound to make it more rigid...it seems you're going backward in safety, not forward. I'm not even addressing the center of gravity changes that raising the deck and changing the entire drive system will cause.

The How-To's in the sticky at the top of this forum have a pretty cool foam calculation thread (#6, I believe). It doesn't address structure too much, but it does address safety.

 

[Cadwelder]

Re: Raising boat deck

Yes it was a stringer drive. Going to convert to outboard, using a bolt on motor extension mount. I plan on reinforcing hull, not sure yet what size mat I am going to use. Just want to beef everything up for rougher water.

Have you looked at this thread?
http://forums.iboats.com/showthread.php?t=469836

 

[hawaii1982]

Re: Raising boat deck

Looks like I have my work cut out for me, however my transom will be 1 7/8 thick and I am installing a Custom made full span motor mount which is going to distibute weight more evenly. Also motor weight will only be 400lbs. The transom will be glued in this weekend, any suggestions? Will be posting pics as well.