Foam in between inner and outer hull 23' Inboard

[tmtmv]

Has anyone injected foam between the inner liner and outer hull? The boat could use the stiffening effect of this I'm just worried about distorting the contour of the Hull.

[strick]

The factory will put some foam here and there in key places in between the outer hull and liner. Why do you think that the hull needs foam injected throughout the entire hull/liner?

strick

[BigLew]

Strick,

I was wondering the same thing. The boat wasn't designed to be foam filled, like a Boston Whaler is. If it were to be filled with foam, it would seem to follow there might be some real problems as a result.

[tmtmv]

The foam would act somewhat like a core between the 2
If you take your hand and as run it down the side of the boat slap the hull and listen to the noise and also feel the flexing of the hull. I have run the idea by a couple of boat builders and they think it is a great idea. My first concern was that it might cause an osmotic problem but since air freely covers both outer surfaces I don't believe
it to be a problem. I'm going to try it around the chase where the fuel vent and gas fill goes.

[deepsushi]

I fail to see what your going to accomplish by injecting foam between the hull and liner? Don't you think that a 30 year old boat would of already shown any ill effects from flexing over its 3 decades of use? I have been reading this site almost from its inception and I can't remember ever reading about any hull issues inherent in Seacrafts.

I would be more worried about creating a hard spot by injecting foam and actually creating a problem leading to gel coat cracking and or liner / hull damage.

The hull on both my 1979 18 and 23 inboard deflects quite a bit when I push on it. However, I don't see any ill effects from this flex.

If you want a foam filled (and water logged boat) sell the seacraft and buy a whaler...

[Islandtrader]

I have to ditto the last post. My 21 has no liner and flex's when pushed on. The hull has over 1700 hours of running time on it. When stripped down for restoration there was not one gel coat crack due to flexing. The majority of the gel coat cracks came from stress of added on items.

[cdavisdb]

Think twice and then several more times before putting foam in any boat, especially a Seacraft. It is possible to do it right and possible to do it very very wrong and screw up your boat. Further, foam attacts problems down the road that are hard to fix. In a seacraft, you don't need it. Assuming the decks and transom are solid, the flex you see is a non-issue. If you drill holes in a seacraft hull, you will find some places with a lot of glass and others where the hull is quite thin. Moesley was a genius at putting glass where it was needed and not otherwise. Potter followed his lead quite well. My old 20 ft seafari had a places in the bottom which were quite thin, just like a 25 Bertram (I've cut transducer holes in both). Both boats were tanks that would handle far more abuse than I could dish out. I just cut a bildge pump discharge in my 25 seafari back near the transum. The hull at that point is less than 1/4 inch thick. The boat is 37 years old and you have to look very hard to find any stress cracks in the gel coat.
Make sure your decks are solid and don't worry about it.

Connor

[BigLew]

"I'm going to try it around the chase where the fuel vent and gas fill goes."

FWIW- If you do that, ask yourself objectively what do you gain verses assuring yourself one nightmare of a job when (not if) there comes a time that you will want or need to replace the fill and vent hoses? This would be just one question for starters.

Another more general question would be, How will it affect air circulation and venting of gas fumes in the event your fuel tank develops a pinhole leak due to foam having been used to wedge it in its comartment in the hull." On this topic search this website regarding tank replacement and you will find many, if not most, were caused, at least in part, to foam holding moisture in contact with the aluminum tank with corrosion of the aluminum being the result.

Just my CAUTIONARY (as a friend) 2 cents. Good luck.

[77SceptreOB]

....On this topic search this website regarding tank replacement and you will find many, if not most, were caused, at least in part, to foam holding moisture in contact with the aluminum tank with corrosion of the aluminum being the result.

Yep, See below....caused by a "foamed in" fuel tank.

[Bushwacker]

. . My first concern was that it might cause an osmotic problem but since air freely covers both outer surfaces I don't believe it to be a problem. I'm going to try it around the chase where the fuel vent and gas fill goes.

Tom, don't do it! "Better" is often the enemy of "good enough"! You CAN get osmotic blisters on the inside if that foam gets wet and holds water. In fact, since there is no gel coat on inside, it can blister from the inside easier than outside! I'm convinced that foam in boats is generally a bad idea because it can add a lot of weight if it gets wet!

The early SeaCraft's had NO foam in them! It was only added when the USCG started requiring positive flotation in the late 60's. Any foam in a Moesly or Potter SeaCraft is only there for flotation, none of it is structural.

Like Connor said, Moesly knew what he was doing and tried to put the beef only where it was needed. He was a pilot in WWII and with over 13000 hrs in all types of planes, and spent about 15 years after the war converting surplus aircraft into executive transports. He understood aircraft construction, how much weight hurts performance, and his boats reflect that understanding. His philosophy was to build it very stiff but as light as possible, and then take it out and beat the hell out of it (in the offshore powerboat races in the early 60's) to see if anything broke. Nothing broke, and he literally blew away all the competition in his class for several years!

If you'll study the Boating Magazine article on the Seafari 20 in the Literature section, particularly the cross-section showing the stringer arrangement and the lay-up schedule, you'll see that Moesly truely was a genius when it comes to designing a stiff light hull. The 4 stringers were put in about half-way thru the lay up, so they're an integral part of the hull. The bottom panels are naturally stiff where there is a vertical step, and the stringers are attached near the center of the panels to provide extra thickness and stiffness where it's most needed. The inner liner (consisting of about 1/8" glass + 1/2" balsa core + 1/16" glass) is then bonded to the top of the stringers, creating an I-Beam that's about 12" tall! This structure is so robust that Potter was able to change it from 4 to 2 wider box stringers in about 1973 with no ill effects, evidently as a cost-savings change. Because of this design and construction, hull failures are virtually unheard of in a SeaCraft. The weakest link on these boats is the "Nut on the wheel"! About all you need to worry about is an ignorant previous owner that may have drilled holes in the cored deck, gunnel or transom without proper sealing, allowing water intrusion that will rot the core. As long as those areas are solid, you're good to go! Denny