16' Model KL Alumacraft

[FirstRealBoat]

Hello all,

I have a 1960 Alumacraft Model KL with an 18HP Evinrude. Plywood floor, so I am not walking on ribs and a bow mounted trolling motor. What I am interested in learning is how much foam to order? I want to put the pour foam under the floor, hate to swamp the boat and lose it. Right now there is NO flotation in the boat. The factory seats were taken out by PO.

This is a solid boat, I use gluvit on all seams and rivets on the inside of the boat and some goop on the outside, just as added peace of mind. I will have two batteries (65 lbs each) and one 6 gallon gas tank. I have been looking and just don't under stand the formulas for how much I need to order. 2 quarts? One gallon?

Thanks for reading

 

[Woodonglass]

You need to post the measurements of the distance from the bottom of the plywood floor to the hull and the length and width of the boat in inches. You can then calculate cubic inches and convert that into cubic ft and then you can estimate how much foam to order.

 

[FirstRealBoat]

You need to post the measurements of the distance from the bottom of the plywood floor to the hull and the length and width of the boat in inches. You can then calculate cubic inches and convert that into cubic ft and then you can estimate how much foam to order.

Sounds good, I will measure for sure tonight. But off the top of my head, under the floor is 2.5" in the center following the contour of the hull to 1". 48" wide in the back and 40" wide in the front at one spot. Then the floor is 40" going down to 10" wide in the bow area.

Total surface area is about 1 1/2 sheets of plywood.

 

[Woodonglass]

Heck, then I'd use the Pink Or Blue slab foam from Lowe's or Home Depot and cut it to fit.

 

[FirstRealBoat]

Will that be enough to ensure I don't sink if swamped? We have some large wake boarding boats that don't care who is around them when flying by......it worries me.

 

[BWR1953]

Ya gotta have enough foam installed to displace water which weighs about 62 pounds per cubic foot. And you need to do the math for your boat and equipment to figure out how many cubic feet you'll need. Not having enough means that the boat will sink anyway.

And the foam has to be distributed correctly as well. Can't just put it in haphazardly. The pic will give you a general idea.

 

[bonz_d]

I believe the recommendation is 1 cubic foot of foam for each 62lbs of boat weight. Therefore a 620lb boat would need at least 10 cubic feet of flotation. Not trying to float the water just the hull and all it's gear.

 

[FirstRealBoat]

I believe the recommendation is 1 cubic foot of foam for each 62lbs of boat weight. Therefore a 620lb boat would need at least 10 cubic feet of flotation. Not trying to float the water just the hull and all it's gear.

The boat is 300 lbs, actually 265 Just adding to make sure. Wood and screws is about 60#'s, motor is 65#'s or so (18HP Evinrude) add two batteries @ 130#'s then the fishing gear and gas tank 100#'s. With me @ 300#'s (yes I'm a fat arse) Grant total of 655#'s without me an 955#'s with me.

11 Cubic feet would cover the boat with a little extra. I will be in a live vest, so I don't count.

 

[jbcurt00]

Gas and wood are lighter then water, so they help a little w/ the total, but it'll never be said:

Dang I wish I hadn't put so much flotation foam in my boat.

So more truly is better.

Blue/pink rigid foam insulation has about the same float properties as pour in foam~60lbs of flotation per cubic foot. A 2inch thick, 4X8 sheet will yield about 5.33333 cubic feet, and float approx 320 lbs. You need just over 2 full sheets of 2" thick insulation

 

[FirstRealBoat]

Gas and wood are lighter then water, so they help a little w/ the total, but it'll never be said:


So more truly is better.

Blue/pink rigid foam insulation has about the same float properties as pour in foam~60lbs of flotation per cubic foot. A 2inch thick, 4X8 sheet will yield about 5.33333 cubic feet, and float approx 320 lbs. You need just over 2 full sheets of 2" thick insulation

Thanks, that is kind of what I was looking for. I didn't know that the pink/blue foam was that good a floating. Will it absorb water? Does it need to be sealed?

Thanks

 

[Woodonglass]

Nope, the Pink/Blue stuff is Totally 100% waterproof and will NEVER absorb water. Don't need to seal it with anything. Really good stuff to use for flotation with ONE exception. Gasoline will eat it like Hungry Relatives at Thanksgiving!!!!!

 

[FirstRealBoat]

Hungry Relatives at Thanksgiving!!!!!

Bwhahahah....Nice. I'm usually that hungry relative...haha

Thanks, looks like a trip to Lowe's will be in order soon!

 

[bonz_d]

Nice to see you've come up with an answer that will work for you. Now enjoy the work and then the rewards.