1987 Larson DC-215 restoration

[Willyclay]

Second, the boat only had a little bit of foam in it .there was a big chunk up front under the lower deck which you can see in the picture. Other than that, there was only foam under the engine kickouts, which are about 1/2 cubic foot each. Will it hurt to foam in a few other sections for more floatation?​​​​

I do not believe you are "required" to have flotation foam in your boat that I believe is longer than 20ft. See the link below:

http://newboatbuilders.com/pages/flot3.html

However, I had a boat that used foam in place of structural components and that may be the case with yours also. Finally, this is a great opportunity at this stage of the restoration/rebuild to make a significant improvement to that aspect of the boat.

Your Dad's safety is probably way up there on your priority list. Good luck!

 

[tpenfield]

Keep in mind that foam is as much for strength as it is for flotation. The ABYC standard for flotation is up to 26 feet, whereas the USCG is 20 feet. Keep in mind that when the USCG set the standard, years and years ago, 20 feet was a 'big' boat.

 

[kcassells]

That's good info Ted.

 

[kcassells]

I would foam the crap out of any boat I have. But of course you should have some type of drainage and aeration system under the deck, otherwise just a coffin waiting to fail. :}

I tend to like to float if I have a hull penetration or wave that can capsize or bad following water. Just can't find any system that works ha ha ha .

 

[oldrem]

I've heard of a company that's come up with a possible solution. I think it's flotationfoamsolutions.com or something like that.

 

[sms986]

So for the floatation, I had an idea. The boat is 2900lb dry, and I estimated very generously for on board gear etc. The fully submerged boat with gear comes out to 1341lb. Safety factor of 2 brings it to 2682 lb.

Air seems to be the best way to float a boat. The problem with air is reliably encasing it. One cubic foot of air displaces 62.4lb of water, or provides 62.4lbf of buoyancy. So, that's 43 cubic feet of air that I need to encase to float two of my boats.

At work, we use 5 gallon square pails to transport small quantities of liquid chemical. These pails are extremely durable and pretty flexible. The actually capacity of these pails is about 6 gallons, or 0.8 feet. That's 49.9 lbf of buoyancy per pail of air. I can fit 6 pails under the deck on each side between the outer stringers and the hull as well as between the inner and outer stringers. That's 24 pails, 1200 lbf buoyancy. In the cabin, I can fit another 2 on each side, plus 3 up front. Now we're up to 1,450lbf.

On the gunwales, there are two spots on each side, about 6"x6"x8' that I can turn into long boxes. In these, I'll use an inner tube from an old car tire, cut and reseamed, to create 4 x 2 cubic foot air bladders in these boxes. Now we're up to 1950lbf buoyancy.

11.73 cubic feet of air unaccounted for. I measured the boat to have a total of 12 cubic feet of foam in it total. There we have it. I'll probably add additional foam in places like under the battery boxes as well.

So even if the foam absorbs water, I have these huge air bladders throughout the boat to provide the necessary buoyancy. I'll probably get fancy and cut/plastic weld the pails to make multi-cell pontoons out of them, but that's the jist of it.

The idea here is to conceal bulk amounts of air within the hull without relying on wood and glass to hold the air. Having the air in multiple cells means that if I hit something and puncture the hull, I may lose a camper or two, but the majority of the cells will still hold air.

I saw a guy somewhere say that his floatation is a swim to shore and a fat boat insurance policy. That may be the dumbest thing I've ever heard. Maybe he's on a small lake, but if not I sure hope his insurance policy is buoyant. Id rather give my dad something other than a life jacket to depend on if something goes wrong.

 

[chevymaher]

Use foam. Makes it quieter and stronger.

 

[sms986]

My first thought was to use foam, and I'm still going to put foam back in all the places it was before for structural reasons, but from what I've read, all foam will retain water and eventually become useless. I did a lot of reading and it seems like everyone who builds the boats love the foam until they tear them apart for some reason and find that the foam is a giant wet sponge. I can attest to that. All of the foam u ripped out was completely waterlogged, even though the boat was and had been bone dry. I would water that the foam played a strong role in the rotting because the worst rot was where the wood butted up against the foam. I've even seen waterlogged closed cell foam. If something went wrong I'd like to have the peace of mind of knowing that I'm not relying on potentially soaked foam to keep me afload. I don't mean to come off as inconsiderate or argumentative, I just want to explain my reasoning for using air bladders.

 

[JASinIL2006]

Foam in boats that are improperly stored will become waterlogged. Not so much a problem in well maintained boats.

 

[zool]

My first thought was to use foam, and I'm still going to put foam back in all the places it was before for structural reasons, but from what I've read, all foam will retain water and eventually become useless. I did a lot of reading and it seems like everyone who builds the boats love the foam until they tear them apart for some reason and find that the foam is a giant wet sponge. I can attest to that. All of the foam u ripped out was completely waterlogged, even though the boat was and had been bone dry. I would water that the foam played a strong role in the rotting because the worst rot was where the wood butted up against the foam. I've even seen waterlogged closed cell foam. If something went wrong I'd like to have the peace of mind of knowing that I'm not relying on potentially soaked foam to keep me afload. I don't mean to come off as inconsiderate or argumentative, I just want to explain my reasoning for using air bladders.

My sportfish was built with air chambers, with weep holes leading to a central compartment at the midship bulkhead. At that point there was a garboard drain plug to clear out any water that may get in there. The majority of the wood structure was still like new after 30+ years when I tore it apart.

 

[kcassells]

Foam installation with no drainage and aeration is the ruin of many a fine boat. Bladders come in at what cost? I have heard of cases where they simply lose their air eventually like a old balloon. Did a cursory search and couldn't find much other than for water or other liquid storage.

 

[sms986]

The beauty of air bladders is they're free for me. My family runs a tire shop, so I have free innertubes. I actually have over 100 chemical pails that I need to get rid of anyway, so that covers the pontoons. It'll be an afternoon of work, but that's much cheaper than the closed cell foam.

I know that having proper aeration and drainage is important for upholding foam packed compartments, but I can't wrap my head around how that's physically possible. Friscoboater used sacrificial cardboard on the low side as drainage, but if the boat ever had a leak, the water would run up these cardboard passages and soak the foam, holding there finitely long. Also, if water ever got in at any other spot than where the cardboard was, it would have to work its way through the foam to get to the cardboard and most likely just sit on the surface where it originally collected. Suspending plastic pontoons inside these compartments would ensure there are no closed off spots where water can collect and stay.

 

[kcassells]

Free is good!

 

[sms986]

I'm back!

So today, I got the transom out. I am REALLY concerned with this. It was done before. I can't believe Larson would have done this bad of a job. the wood transom looks like it was laid down on a bench, wrapped in CSM, and just put into place with a few dabs of resin. After that, it was tabbed in. I cut to the depth of the wood, a little less actually, all around and pried the whole thing off. Underneath, the outer skin of the transom is wavy. Probably 2mm of thickness difference. Looks like it was gouged into with a grinder.

Now what?

I have read a lot of horror stories on this lately, and I haven't found a good read on how to fill these voids.

Anyone have a similar experience?

I will get some pictures this evening.

 

[oldrem]

Those voids should easily fill in when you PB the new transom in. More important that everything be ground clean than smooth

 

[sms986]

Smooth as in?

No burrs, loose chunks of glass, or debris

Or pool table smooth the whole way across?

 

[oldrem]

Clean as in no dirt, debris, old loose glass strands etc. A rough surface won't matter when you spread PB and clamp the new transom wood to the old skin before glassing it in.

 

[kcassells]

Acetone the crap out of it he's saying.

 

[sms986]

The clean part is covered. I was just concerned about the waviness. I'll probably go over it with a belt sander and 36 grit just to smooth it up a bit before clamping

 

[sms986]

When I am grinding the old tabbing from the stringers, how much do I need to remove? Just until I get good fiberglass, or all of the old tabbing?

It's very difficult to find where the tabbing ends and the hull begins.

Also, I did a bit of work on the transom this morning. I smoothed it out and ground off the old lip. I'm seeing a TON of little drop sized air pockets throughout the entire area. If these are filled with collodial silica PB, will it compromise the strength of the bond? I'd imagine that if I put enough P. On the boat, the air pockets would act as anchors when filled with PB and cured. I am afraid of air pockets remaining behind the transom though.