Foam OR No Foam?

[kmorin]

Just a topic to get the discussion going about foaming aluminum hulls/voids in hulls.

FULL DISCLOSURE: I'm a No Foam builder, having never put anything but air or bottled gases into voids in any hull I've built. So appropriate amounts of "salt" (or salty language) should be liberally used to digest my remarks.

And Please Remember: hosting my regulation conflicting ideas and their supporting 'reasoning' it is not advocated by AAB.com or anyone here; these are my ideas and are posted on a (semi) public forum as opinion not as agreement, advocacy, or an advancement of these statements by our fine host; welder.

First we need to get the regulations out here because they may come back to confuse the argument if not included here. It is my belief, and I'm not very well versed in this subject, that the CG/DHS/boat cops' regulations treat boats longer than 20' LOA and those shorter than 20'LOA as two separate classes.

It is my understanding that the longer boats (>20'LOA ) don't require 'level when swamped' testing but those shorter than 20's do require this testing? It would be nice to know if this understanding is correct? but, unfortunately, I probably won't follow the regulations in this particular matter anyway.

It is the level when swamped testing that initially drives the 'need' for a material inside the voids to displace water. A material inside the voids that displaces water, keeps the entire metal hull from filling so that the final volume of water inside the swamped boat does not weigh the same as the metal boat. In fact, the displacing material has to displace the weight of both the metal hull and the material (foam) itself in order to keep the buoyancy force high enough to float the swamped boat.

I think we're mainly discussing boats longer than 20' and welded and those with welded decks and foam installed below the deck. At least that is the primary focus of my remarks; if your's are aimed at other boats either in size or construction it would be helpful for you to mention that in any reply(?)

The hull seams of any welded boat are supposed to make the sheet/plate/shapes into to one piece of metal. Therefore weld integrity is important and the primary factor of integrity I'm referring to is the full fusion between welds as the fusion between plates to provide a structural bond is over done and is almost never a failure point.

However, leaks in hulls are not rare if the welds are not air pressure tested.

My argument is this: if a builder pressure tests the 'sealed deck' and all the hull seams for weld integrity- why would anyone need to put a "water displacer"/foam inside that volume. Because it has been tested at greater than normal pressure differences - water will never get into this volume even if the boat is filled from the deck to the gunwales.

Foam costs money, takes labor and materials; air doesn't.
Foam breaks down; air doesn't.
Foam adds weight to a boat: air doesn't.
Foam can absorb water and therefore increase the retained displacement: air doesn't
Foam can foster crevice/poultice corrosion sites; air doesn't.
Foam is not 'needed' unless the voids fill with water; How is that going to happen?
Foam is a poor substitute for decent welding testing/repairing; why accept a poorly done job?

OK, I know lots of major name, (otherwise) high-quality builders use foam, but then dozens of these same builders refuse to strip the mill scale from the interior of their boats too, and we've seen over and over what those bilges come to in a few seasons; posted right here at AAB.com.

To Foam or Not To Foam? that is the question.

We're (I'm) not discussing the riveted, press formed Lunds, Starcrafts that are 16' long and have no voids but only covered areas that are not sealed as these are not welded boats. We're not trying to discuss the short welded skiffs either but they may be a logical part of our argument?

Cheers,
Kevin Morin

[Fisherman]

I'm not advocating foam or no foam, but I do want to pose a question that needs to be addressed: what happens when an air/sealed deck boat hits something and the compartment is ruptured? I can see this as being one of the main arguments against an air chamber. Maybe multiple air chambers would lessen the possiblilty of sinking though.

[kmorin]

Fisherman, great question & top of the list to discuss.

Fisherman, do you (or anyone) have pictures? I don't even have any reports/stories? Anyone seen a hull at sea ruptured? How about on the beach? I've seen some tearing of unknown alloys in river jet sleds, but I've yet to find a Cold Water/Pacific/S'Streak/Woolrich/Specmar/Munson Mfg/Winginghoff/Rocksalt/Glaciercraft or even any home built with actual holes in the hull?

I'm completely willing to see those ruptured hulls but just haven't found them. So my idea that water 'never' gets in the under deck area is just based on my experience here in Cook Inlet in Alaska -surely not a wide view of welded boat use or durability.

I've seen cracks from;
poor framing;
poor design;
poor welding; and
ill-placed trailer rollers with heavy duty truck straps; (I even did this one myself once).

But none of those cracks was due to the hull being holed from collision or rock impact, and all these cracks resulted in taking some water but none of them resulted in the entire bottom flooding.

Is there anyone with one single instance of a sealed deck boat flooding from keel to deck? I just haven't heard about it: but.... I'd sure be interested to learn more; especially if it were something that was documented in a survey or an article some where?

I figure I'm never too old to learn, but I just don't know of any holes-in-the-hull types of failures. [I sure know from repairing plural dozens of boats built with foamed in bottoms (with my own hands) about those results.]

funny story:
I was a young (er) builder making set net skiffs and a fisherman who was considered a 'colorful' guy had ordered a skiff but needed it delivered about 70 miles away from the Kasilof River where I built to his 'beach site' on the West Side of cook Inlet. He'd bring me back in his jeep ( Super Cub terminology in bush AK) so I agreed to deliver the skiff to Silver Salmon Creek.

It was a nice morning in late June and the Inlet was flat, the sun out and the kicker was new so the trip was just sitting there for a while letting the ebb take the skiff and I south as I made a steady westerly with the kicker.

I pulled up on his beach and walked up and down a bit to find the site, I knew his neighbors well and it was fun to just walk the beach and see the other skiff's sites. I put the skiff on the sand and the skipper came over to 'park her' on the beach where his other boats were pulled up.

I had no idea he'd prepped a corduroy int he sand so when he said he wanted to take her for a spin and then beach the skiff a little farther away- I of course agreed. He swung off the beach put the boat on step and ran out a couple hundred yard and did some turns and got a feel for my beach shaped hulls.

Then, on step at full power, he turned to the beach and just steadied down on a single heading no turns. We got a couple hundred feet from the tide line when I expected he'd pull up the kicker and let the skiff drop off step.

Full throttle we kept approaching the sand and I'm in the eyes of the bow ready to jump over and pull her the last few feet in the few inches of water to the beach. Now I look back and the skipper is completely straight faced and has his eyes on the beach and is not looking at me.

I ducked under the gunwale, sitting down on the bow deck so I won't get blown overboard and die when he hits the sand and we come to an abrupt halt with my teeth trying to make a dental impression in the 2" pipe at the sheer.

As he got within two boat lengths of the sand, he shifted to neutral killed the engine and reached back of the cowling and pulled the kicker up and locked it, then ducked down to hold the console for what I was sure was a crash.

The logs were buried about 80 to 90 % in the beach so they were not noticeable from my last glance as this maniac slammed the boat into what i was sure was sand and rocks. But since the skipper had done this hundreds of times before with other boats, he was sure of the boat sliding up the beach.

The bottom centerline of these skiffs has a 2" x 2" x 1/4" 6061 angle welded over the keel seam for wear and beaching. This angle hit the first log and the boat simply slipped out of the water up to the next log and so on.

When we stopped about two or three boat lengths up the beach from the water, the skipper jumped up and laughed uproariously at me "You should have seen your face!!! (laughter) "Your eyes were as big as saucers!" (laughter)...

I think welded aluminum boats will bounce off anything they hit, well before their bottom is ruptured.

Cheers,
Kevin Morin

[Fisherman]

Nope, no pictures, no stories. Just adding to (maybe???) the discussion. The more I think about it, I probably prefer multiple sealed chambers for floatation.

So Kevin, what are you thoughts about adding floataion chambers/sealed deck on boats larger than 20? Think it's a good idea? Too hard to get enough floatation? What if a guy has a inflatable life rafe on board, is it really needed?

[spoiled one]

Excellent experience, Kevin. You have a way with words. I felt as if I were white knuckling right next to you! I have seen some river sleds that have opened up, but never a blue water, alloy hull compromised. I saw a 30' GC, like mine, after it hit a well marked can opener rock at 30+ knots. It took off one lower unit, broke the outboard bracket, and badly damaged the other lower unit. I understand that they were able to limp it back to port on one motor. The keel was creased pretty good from the stern forward about four feet, but the hull was still water tight. Pretty impressive if you ask me. A tupper ware boat would have ended up on the bottom.

[Chtucker]

The Kvichak that I saw pictures last year had a 12x12" patch put on from hitting a rock somewhere in Alaska. They just got the boat up on plane and went into Whittier to be hauled out.

That stabicraft that got run over stayed afloat as well.

The one boat that I looked at had foam in it had some stray current corrosion as well as "white powder" in spots around the foam. No idea what was behind it all.

Duckworth foams I believe. If I was ordering a Duckworth, I would ask them to save the foam for someone else.

[JETTYWOLF]

I didn't read every single detail, jus as Kmorin probably doesn't escavate thru each of my Florida Trout fishing video's.

So I may have missed something, but my question is "Then Why?"

"Then why" do well respected companies use foam?

Ya know this is a can of dead worms? This is a well beaten topic.

[kmorin]

Capn' Dave, I couldn't agree more with your question. So here are some reasons that occur to me.

Why? Why do major boat building firms use foam?

I'd like to learn why (too) because I've never done it and maybe I should call and suggest the owners add some foam?

I don't think it's a can of dead worms, what if welded boat buyers, here, start asking WHY? and what's their cost savings to have an air tested void instead of foam installed void? " Don't you guys air test anyway?" so .... " WHY add foam?"

What happens if the ABB.com readers starting asking for, or refusing to buy, without acid etching or mechanical cleaning of the mills scale inside their new boats? whoaaa....!

What if owners start to ask for MTR's with their boat? major whoaaaaaa.....!
(Cap'n Dave how many owners on here even know what an MTR is? Or the history of why a set of these documents might be important?)

[If that had been common practice the West Coast's "5083 fiasco" of 10-15 years past would have been averted while at one or two boats.]

What may happen..... is that better practices of building could become common place and we won't hear about guys buying a four year old boat with corroded bilges and soaked foam under a welded deck?

How long ago was it that "frozen snot" (term by L. Francis Herreshoff- not me) and dead-plant-parts (cellulose) were the only way to build boats? Education of the boating buying community is why these questions are not a 'can of dead worms' but should be part of regularly held discussion.

How long ago did people, like many of our Forum members and readers, learn about welded aluminum boats? a couple of decades- recent history. Why? Because we're all still learning there may be reasons we don't already know about lots of aspects of metal boats.

How many posts do we see where people still confuse #1 galvanic, #2 stray current (electrolysis), and #3 crevice or poultice corrosion events? They're here on the site, today. If the owners, as a group don't even understand what these forces are: the reason to discuss foam is that its a topic in the same area. It's not well established as a need but, like corrosion that could be avoided, its used commonly.

Surely there is an almost uniform, industry-wide failure to install hardware with isolation bushings and washers. One builder was just reported to use foam to mount tanks, on another thread/topic and the owner reports that tank is corroded in the way of the foam........

Why indeed? Why would that builder use a quickly cheapo, foam pack to bed a tank? Don't know but I'd like the AAB.com reader/member to know enough to AVOID that builder's boats so they don't get 'stuck' with the results we've seen in photos here.

When your question(s) of reel build/design and material quality become widely discussed (I know you're not holding your breath either) and eventually become understood; reels may/will/perhaps/could conform to higher standards. The 15$ Walmart 'weekend special' trout rod and reel special is part of the market but it may not be considered the 'right tool' for the job on the deck of the Jettywolf.

But why are these products made? Lots of reasons, so foam is used for 'some' reasons too.
I just can't find them spelled out and want the AAB.com members to ask themselves, like buying quality hook and line gear, why they should be involved?

Cheers,
Kevin Morin

[Fisherman]

This is maybe slightly off topic, but I think you guys will find it interesting. I was once talking with a boat salesman and one of the selling points he hit was that his boats had foam in them. He said it did two things: 1) made a quieter ride and 2) made the boat float higher in the water.

I still smile to myself about that line.

[jj225]

Sound insulation. Helps to dampen that "tinny" or "slap happy" sound that alum. boats make. Have been told by more than one builder. Some will spray it in while others use blocks.

[goatram]

Sound insulation. Helps to dampen that "tinny" or "slap happy" sound that alum. boats make. Have been told by more than one builder. Some will spray it in while others use blocks.

Tinny boats aren't made of 1/4 plate with 3/16ths" sides

[welder]

That's why my boat gets such good fuel mileage, it barely in the water due to all that foam.


If you do have foam in your hull, I hope the manufacture did it right, used the right type of foam and left water ways from bow to stern so IF water did get below deck it could drain out.The foam does quite the hull noise down and get this.... That foam is HEAVY for what it is.

[Chaps]

My Edwing 21 had a "sealed" hull but after owning it a few years I began to notice I could hear water sloshing around below decks if I shook the boat when it was sitting on the trailer. The boat had no drain plug so got out the drill and put a 1/4" hole in the transom and sure enough out drained about 2 gallons of brackish water . . . curious as to where it might be leaking I tapped the hole and screwed in a hose barb so I could apply some air pressure (just a little, didn't want to pop the deck plates) and I found air escaping up at the bulkhead separating the below decks anchor locker from the rest of the hull. The builder had not fully welded in the plate . . . and apparently did not pressure test the boat before delivery. No real harm done since the hull is easy to drain using the plug now in the transom but like many things "air tight" needs to be verified. I'd hate to think what a mess I'd have had if the hull had been filled with foam and had the same leak in the bow locker

[jj225]

Sound insulation. Helps to dampen that "tinny" or "slap happy" sound that alum. boats make. Have been told by more than one builder. Some will spray it in while others use blocks.

Tinny boats aren't made of 1/4 plate with 3/16ths" sides

Actually, that quote came from a NR dealer when discussing the OS model.

[Gypseas]

So if you have foam in a 24 fter would you scoop it out and get rid of it even though it doesn't seem to be wet or show any signs of corrosion.
I could use more storage anyway and not sure if the little foam it has would keep it afloat when you consider the weight of the aluminum plus 1000+ lbs I/O.
cheers

[kmorin]

Fisherman, I'd have to qualify all of what I had to say about the design of air voids or chambers with a review of where will the boat be used and what will it do? If it will load four tonnes of fish and run back through the surf, the likely hood of swamping seems much greater than a sport boat that never hauls more than a fraction of the total displacement.

Finally, what are the costs versus lifetime performance of the different methods of attaining a safe mode? These items would make a pretty long list of considerations.

If I were building for an offshore boat that was open, no cabin and I was using regularly where I had to take whatever weather was out there, and that includes being far enough out that you can't out run changes- then building in voids seems like a good idea. If the voids were designed in(?) welding them tight (with vents) seems the best practice in my experience.

But with that said, where is the void located? If the void is ONLY the bottom then the same sea that will swamp or poop a skiff will also roll it turtle because the boat will become vertically unstable when filled. If all the air is under the water on deck, and the water filling the topsides above the deck is heavy enough to hold the entire boat down; I'd say the likelihood of turning turtle is pretty strong/highly likely. Now what? cling to the upturned bullet-proof hull?

What good would that void, foamed filled or otherwise, do if it resulted in the boat rolling, but staying at the surface? I know its better to stay afloat than to sink completely but I'm just saying that voids are a full discussion in themselves.

So if I were designing an open ocean, open skiff I'd use the topsides gunwales as a major air void to insure the boat remained upright as much- as possible- when swamped. This means that a set of voids under the deck and under the gunwale would combine to keep the boat afloat while the bottom's air void worked (buoyancy) to lift free the decks draining out the scuppers or freeing ports.

If the boat were covered, even if it were a smaller boat with a cabin, and I needed to provide level flotation I'd work on a cabin sealing scheme. If the cockpit/after deck is all that can flood, then the amount of water is much less to 'lift' and drain. Its possible a raised after deck and a decent high coaming at the cabin with a good door might be enough for the worst case with a cabin or covered boat.

The comparison of the overall design and the use would influence my choice about where to put them and what size of voids. I don't really favor wet bilges in any but the smallest boats if I can find some way to avoid that condition. But you do have to remember the 'righting moment' is no longer positive (keeping the gunwales up) when the air void of the bottom is held down by a filled topsides.

Also along these lines you'd have to consider the size and flow of the scuppers if you're considering a design that may reasonably expect to be swamped and recover.

Cheers,
Kevin Morin

[Katoh]

Our last boat an 18' CAT was foamed filled in both sponsons, and this did save our hides once. My partner in the boat, had decided to install two automatic bilge pumps, one on each side, and I agreed thinking its a good idea. But when he installed them the outlet came close to water line. The one way valves he installed where just rubbish, and we found with a couple of guys at the bow these outlets where actually below water line and letting water into the hull. A combination of errors from above and some incorrect wiring saw both sponsons fill with water. Now the boat was always a pretty wet boat, wasn't really well balanced properly and the scuppers like on 90% of smaller craft would actually let water in from time to time.
By the time we had realized that we were full of water was too late but the foam did keep us afloat and aloud us to get back to the ramp, and trailer the craft. I have to say the foam did save our hides.
The boat I am rebuilding now was not built with foam at all, it did have some 2part pour in stuff around the tank and tank well, were poultice corrosion ran rampant where it was in contact with any aluminum. I have read that this practice of foaming in tanks is now strongly discouraged.
Even though this boat has a fully welded in floor, extremely large scuppers, and each frame in the hull is fully welded to the bottom plates with only a small drain hole each side of the keel line, leading to the motor well and the bilge pump. I still would feel better if something was there also. I looked into ping pong balls, PET bottles, foam balls, the best one I found where urethane balls 3"dia used in sewer ponds, but so expensive and could not find a distributor here in Oz.
I have taken option 2 and simply bought a compact life raft (Pacific 6 person) and will install 2 much larger pumps in the hull.
Cheers

[speedboats]

Remember that you do not have to float all the weight that the vessel displaces (or weighs on the trailer). You only have to get the overall relative density of the vessel to less than 1. Gas has a relative density of 0.72 hence it floats on water. Now while 100 litres (26.5 USgal) may weigh 72kg (160 lb) when on the trailer it is actually of benifit to be trapped inside the tanks when the boat is swamped (it will support 28kg (61 lb) which is about the weight of the tank)

Aluminium has a relative density of 2.7 (depending on the grade), so 100kg of Al will only weigh 63kg (139 lb) when underwater. This is with the consideration of fresh water and as we all know brine is significantly more dense (heavier).

Foam as used in squabs will also contribute to the positive bouyancy of a swamped boat (assuming closed cell foam was used, not the cheap open cell stuff which will eventually allow water to displace entrapped air)

A persons relative density changes when considering a lung full of air or empty.

For our river jet boats we don't use any form of floatation as we prefer our boats to go to the bottom and stay (makes finding it for recovery much easier!). However this flies in the face of ABYC and Australian standards which require that a vessel must float when swamped. To overcome this we fab air tanks and fix into the foredeck area and either side of the engine (inboard jet). I've considered expanding foam to fill the void under the coamings and reasoned that water will rarely get up in there and if it did it could drain easily (gravity), but as yet cannot bring myself to do it for fear of the corrosion issues that may entail

[Sculpin]

Really great thread Kevin. I am learning lot's reading this stuff. I am a no foam guy because of everything I have read on here about corrosion issues and weight issues. Keep it up as I want to learn more.

[StabicraftMarine]

When we first entered the US market our small boats were exempt from foam but a reclassification has changed this and made life a lot harder. We were classified as an inflatable I believe, now not.
It is part of the reason we don't market as many sub 20 foot hulls up your way.

We have used 2-part foams which were a nightmare. They made an absolute mess and took too long to cure. We now use foam shaped to the profile of our pontoons and cut to length onsite. It is much, much cleaner and faster. I'm sure you would be able to give someone dimensions and have something cut to suit up your way. It does help with sound deadening but that can be achieved without filling complete cavities. With strategic placement of proper sound deadening, you don't need much and you don't always have to have it in wet areas. I am not a sound engineer but I have spoken to a few, it is about finding resonance and placing dense, vibration absorbent mats to it.

It is not in our DNA to fit foam but some contracts require it. We subscribe to Kevin's idea of proper construction and maintenance. What Kevin was saying about the location of trapped air is one of main selling points. The majority is trapped above the resting water line in our design. Should the cockpit flood there is ample displacement in the pontoons to keep the boat level and afloat. Our pontoons are pressure checked for leaks before shipping and we expect our owners to check them periodically as well as nothing can be taken for granted long term.

We don't rely solely on them. The 659 that was run over is testament to that. Our boats all have welded and sealed floors to add to the total buoyancy.

Personally I thought the idea of empty PET bottles, ping pong balls and the like in floor cavities was genius but after a good thought they are only of benefit to a poor hull and in the event of a big rupture (say submerged container or reef) how much help would they really be? If your hull turned over with a sizable hole I suppose a spotter plane might see a sea of ping pong balls easily. Maybe buy yellow ones as they may be easier to spot in white water. Nothing will ever be infallible but maybe many compartments in strategically spread locations around the boat would be best.

So cynical today - my apologies.
Tim.

[speedboats]

Was going through old pics, found this one of a boat I built in '08. The sides as well as the underfloor were sealed and pressure tested meaning you could completely fill 'er up and she wouldn't turn turtle but still retain the outside shape of a traditional hull and not look to 'boxy' as some of the pontoon boats do...

[Wantry]

I've yet to find a Cold Water/Pacific/S'Streak/Woolrich/Specmar/Munson Mfg/Winginghoff/Rocksalt/Glaciercraft or even any home built with actual holes in the hull?

I have.

Winninghoff. Not the owner's or capt's fault. But a real bad docking that led to a crease that led to a wee leak that led to a small water intrusion that then froze, thawed, froze, etc.

Not so much a hole as a small leak that built up over time and did not sink the LITTLE GIRL, by grace of god. Welded over and never a problem again. would have been worse had there been foam.

Ice in a gap in aluminum is Satan. when it's trapped behind foam it's ninth circle of hell.

Seriously censors, did I just type LITTLE GIRL?

[kmorin]

Wantry......." that led to a crease that led to a wee leak that led to...... a small water intrusion that then froze, thawed, froze, etc."

are we on the same topic? The discussion was about foam to avoid sinking when the hull was holed in use. So that would include running over something, or onto something that breached the hull catastrophically so there was water inside and the boat sunk- except for the saving grace of foam being in the breached/holed/ruptured/torn open hull.

I don't see that there's too much correlation to a "lead to this; that lead to that; which lead to....and then there was a bit of water in the bilge" circumstance?

I guess, by your post, you've not heard of a actual hole in these hulls mentioned either?

When I was building full time in the '70's and 80's I used to keep a .357, loaded with wad cutters, at the shop so I could have the customers demonstrate for themselves the hull's strength. I'd take them out back and hand them the pistol and ask them to run off a few rounds into the three or four plates set up for this purpose. It would go through 1/8" but barely through the 3/16" and was fully stopped by 1/4" at about 30 yards. (5086) They'd take the plates home and look at them for a week or two, but that plate with the bullet stopped cold inside a stretched pocket of aluminum usually brought the fisherman back to buy a welded metal boat.

The reason for my statement is the boat is floating so even the entire mass at the full momentum of the moving mass coming down on a really sharp immovable object is usually (98% of the boats) less than the force needed to hole the average welded aluminum. If you add to this the glancing nature or angle of incidence of the impacts afloat, well there are just aren't any incidents of a production boat or even any homemade welded boats being holed. Swamped, rolled over, driven over by other boats, hurled by the wind and waves, driven over by land vehicles, and lots of other damage, but no record of any hull holed afloat that I can find.

It's a sucker bet.

cheers,
Kevin Morin

[welder]

I've yet to find a Cold Water/Pacific/S'Streak/Woolrich/Specmar/Munson Mfg/Winginghoff/Rocksalt/Glaciercraft or even any home built with actual holes in the hull?

I have.

Winninghoff. Not the owner's or capt's fault. But a real bad docking that led to a crease that led to a wee leak that led to a small water intrusion that then froze, thawed, froze, etc.

Not so much a hole as a small leak that built up over time and did not sink the LITTLE GIRL, by grace of god. Welded over and never a problem again. would have been worse had there been foam.

Ice in a gap in aluminum is Satan. when it's trapped behind foam it's ninth circle of hell.

Seriously censors, did I just type LITTLE GIRL?

Yep, you did, pumpkin.

[welderbob]

I believe in the void concept.BUT! We build a flat bottom workskiff. The whole 20'er is made of 3/16" 5086. There are three compartments with the theory that any one compartment can be flooded and the boat will stay afloat. So my customer runs over the top of a sunken steel tug at low tide. He creases the bottom and the dent stops at the bulkhead It opens a small hole that cause two compartments to leak. Luckily the trailer was close by. The water was still leaking out an hour later when he got the boat to us. Because of that incident we now put rigid board foam in the two aft compartments. The foam sits on top of the frames and doesn't lay on the aluminum.
Welderbob