My idea for permanent delam repair

I searched for this idea on the forum and all I could find is that Coral Reefer did this just to his bows. I'm thinking about using 4lbs per foot expanding foam ( http://www.uscomposites.com/foam.html ) to fill the entire hull. 

My boat is a 1973 16ft, and I'm not in it for racing. My research found that the boat weighs about 320 lbs and according to wiki it has a max capacity of 800lbs, so I'm assuming that with a total weight of about 1200lbs it will become a submarine. With water weighing 62.4lbs per cubic foot that tells me there is roughly (very roughly) 19cubic feet total in both hulls. So rounding up to 20 cubic feet, which to me sounds ridiculously high to me,  if I use 4 pound cubic foot foam that would add 80 lbs to the boat. if the boat does in fact have an 800# rating then I am only loosing 10% of my carrying capacity.

So if I put my wife on a diet or make her swim it is basically no real difference. 

Really my question is has anyone ever tried this or can anyone think of any flaws with my logic? 

Does anyone know the volume of a hobie 16 hull?

 I am planing on fixing the delam with epoxy first, this is just to add more structure to a 38 year old boat and to keep further delam from happening.

Before anyone mentions water absorption, my boat is stored on a trailer and if your boat leaks that much then your probably carrying more than 80 of water in your hulls by the time the race is over anyway.

Hopefully your wife won't read this and divorce you and take your boat.

I can't remember where I saw the thread from a guy who did this. He seemed to think everything was fine with it. He only filled the bows back to the front pylons since that was the only place he had delamination. Said he had experienced no problems with the boat. Wish I had bookmarked it. Interested to see what everybody else thinks. I need to strip my boat down and rework the hulls this winter. Is there a lighter foam that might work?

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Big Dan
1982 H16

Hot Flash #68984

The guy that did this in his bows told about it here: viewtopic.php?f=14&t=14169&p=80578&hilit=Expandable+foam#p80578

I'd be interested how that's holding up for him, he said he did it 3 years ago and it was holding good but that was two years ago I think.

As far as lighter foam, there is a 2lb and 3lb per cubic foot densities. But the 2lb foam sounds like it is easily compressible and if you stand on a spot on the hull that is getting weak and it compresses then you will probably start cracking the fiberglass. And even though the 3lb foam would probably work, they recommend the 4lb for under the deck. Either way it is 20 to 40 pounds difference. On a 320+ lb boat that seems like a negligible difference.

Just because it will sail with 800 lbs doesn't mean that it is a great idea

Now I can't say I have not loaded a hobie or two down... and will do it again.. But the more it weighs the slower you go... You don't point as high... and it really slows ya down headed downwind...

The difference between having 320lbs or 400lbs of crew on a hobie 16 is huge in terms of performance in most conditions.. When it is really blowing more weight is great... But you won't get the same advantage from the way you are wanting to add weight....


Besides that.. your old delaminated hulls are going to leak... and the foam may not let it out all that great...

I would keep it light (as possible) and just do a typical delam repair..

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www.thehobiewayoflife.com

The 320lb boat weight that you reaserched is for new boats. Your 1973 boat almost certainly weights more than that. For starters, the older boats were made differently and weighed more right out of the mold, so around 340lb would be more likely. But then after almost 40 years, the boat is likely to have gained several more pounds.

In any case, if you fix the delam properly, there is no need to fill the boat with foam. Filling the boat with foam adds very little to the hull structure, only dead weight. Adding dead weight to the bow of a Hobie 16 = bad idea.

Also the claim of 800lb payload on a Hobie 16 is ludicrous. The boat might be able to float that much weight, but it sure won't sail. Figure about 1/2 that for a realistic max capacity, and closer to 300lb for optimum performance.

sm