What Density Foam Should I use in my 92 Brendella

[Carlg802]

I am currently in the process of restoring my 1992 Ski Brendella Super Comp. I am not sure of what foam density I should use (2lb or 4lb). I was hoping someone on here could provide some guidance on whether the foam used is structural, or just purely for flotation purposes. 

Thank you for your suggestions, 

Carl from VT

 

[DvarianDan Johnson]

My recommendation is to NOT replace any foam.  Remove the old and clean up the space below deck . The foam is only for flotation in the event ever needed. From my chair that’s why you have insurance. Mine has been without foam for years . 

[RobHazelwood]

40 minutes ago, DvarianDan Johnson said:

My recommendation is to NOT replace any foam.  Remove the old and clean up the space below deck . The foam is only for flotation in the event ever needed. From my chair that’s why you have insurance. Mine has been without foam for years . 

I remember we had a very odd problem once but essentially but essentially had a big bow wave, put it one way… it would have been a very bad/expensive day without any flotation. 

[Dano]

The foam is there for more than flotation. If you look at how these old boats were made the foam is sandwiched between the hull and the floor. Essentially acting as a core material making the  relatively thin fibreglass hull stronger, more rigid,  distributing forces across greater areas,  while also providing support for the floor.  In the boats I’ve seen with the floors pulled up there is very little structure that would provide any support for the hull with the foam removed.  I would replace with new foam and enjoy your ride.  Keep a dry bilge and it will last forever. It’s also a great safety feature. 
 

not sure what rating you need but you can check with skidim.com or skiboatpartsonline.com I’m sure they will both know exactly what you are looking for. 

[DvarianDan Johnson]

My foam below deck was not uniform or for any structural support whatsoever. It was poured in haphazardly and randomly and did not even reach the flooring where it was poured. The boat if not pulling a skier is on the lift . Not the least concerned about it being absent . Have also seen recent Malibu restorations where is was all removed as well, as can get soaked over time and cause problems. The only traffic these days about foam is all negative. 

[BraceMaker]

I'm in the do or don't crowd.  While I buy the concept of both structural and floatation arguments I have also worked on enough boats where it was completely waterlogged, poorly installed to begin with, and not well bonded to he surface and plenty of photos of boats "with foam" taking a nap on the bottom

 

[Carlg802]

Thank you all for your suggestions. @Dano My boat is built without a lot of other structural support, so I agree that foam will be necessary. I will contact both of the websites you recommended and see what they think about the density. 

On another note, does anyone have any suggestions on decking materials/brands? I want to use something like Sea Deck but have no experience with the product/ ease of installation. 

[Ski2000]

Should post this over on Correctcraftfan. Those guys rebuild old boats and have done everything you are talking about. They love hearing about any old ski tug living a second life. 

[03RLXi]

Way outside box thought............. if you want subfloor floatation but don't want to risk foam getting soggy long term how about fill the void with capped plastic bottles before rebuild the floor? Low/zero cost. Might be noisy though.  

[Jody_Seal]

 amazon pool noodles bulk cheap 12 pack

[BraceMaker]

15 hours ago, 03RLXi said:

Way outside box thought............. if you want subfloor floatation but don't want to risk foam getting soggy long term how about fill the void with capped plastic bottles before rebuild the floor? Low/zero cost. Might be noisy though.  

While that's probably a bit on the hillbilly end you could probably do that and pour foam around them which would reduce weight/cost of the foam considerably.

Another thing to consider is that if you're in there it wouldn't be terribly complex to install drain bulkheads through the stringers into the bilge, pretty typical on sail boats you don't fill them with foam because that has weight and not too uncommon to have pumps to move water around for ballasting so you could insert bulkheads and sealer the inside of the pocket then glue down the floors and have essentially air float.

[ReallyGottaSki]

I can remark Pre '86 supremes have the bulk of foam in the extreme bow and in the gunnels. very little below floor, just a couple 2x4 strips

One doesn't have to make it float like a Whaler met a chain saw, just make it recoverable.

Any coosa used in the new construction  will also add substantial floatation volume.

And pool noodles under the floor can be strung with nylon rope to make them removeable 

[DW]

You can add some vertical supports (as simple as a 2x2 ) to reduce any floor sagging.