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PostPosted: 26 Jul 2016, 11:01 
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Has anyone seen a setup where the support ribs are run perpendicular to the keel where the pockets between the ribs was filled with poured foam that wasn't water logged? Every restore build I've seen on here has involved pulling water logged foam out of these areas and I've found that my 2yr old build has water logged foam in this region now too.

Do the longitudinal rib setups have the same water logging issues? I drilled through my foam lower deck and everything was water logged despite my best efforts to keep the boat covered all the time. I cleared the channels of foam and installed grille covers over the drilled out areas but I'm thinking ahead to my 16' Tracker III restore and I'd really like to keep the voids filled with foam but not if they're just going to add 100lbs of water down the line and not provide adequate flotation in the event of a catastrophe.

Pulled my seat mounts off just to check the foam under them & that seems dry - so the saturation is only in the lower deck (beneath the side console) but that would be where I'd want foam (if nothing else but for sound deadening reasons) on the 16'. I know I can cover the lateral channels with piping & elevate the floor, add drains into the channels from each forward compartment and seal everything forward of the rear livewell so the water has to shed off the deck via the drains to get to the transom - but any water accumulating in the boat will have to drain to the rear and build up past the foam level before triggering the bilge should I take it fishing in the rain (as I love to do) so unless my sealing job along the aft most rib is perfect the foam will still be exposed to water.



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2002 Alumacraft 1436LT w/ 1984 Mariner Tiller Converted to Remote & 55# Minn Kota Terrova 12v (removable)

1985 Bass Tracker III - restoration posting coming soon w/ 1988 Mercury 60hp 2-Stroke & 55# Minn Kota Terrova 12v shared w/ my 14'


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PostPosted: 26 Jul 2016, 11:33 
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Location: Central FLORIDA - The Sunshine State -
is there a way you can make the area that you say will wet the new foam accessable?
meaning, in a couple of years, it would be easy to access that area to replace the foam
if needed...... just a thought.





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Last edited by Johnny on 29 Jul 2016, 09:31, edited 1 time in total.


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PostPosted: 26 Jul 2016, 11:53 
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I don't want to use the building foam because it will break down if exposed to gasoline. Also - by using expanding foam it provides support to the thinner aluminum hull they used on the riveted Tracker III's back in the 80's and should cut back on some of the wear & tear occurring at the rivets. I used the 2 part urethane foam in my 1436 build, but I did not line the cavities with anything, so the foam is quasi-attached to the hull (I intentionally didn't clean/sand etc. the paint and now most of the visible foam has separated from the boat).

Your point on the liner is well taken - I could lay a very thin painter's plastic in there after clearing out the old foam before pouring the new - this wouldn't add any weight and it would put a barrier between the new foam and any temporary water flowing underneath due to shortcomings in sealing any of the corners & joints in the new floor. Just need to test & make sure the 2 part urethane foam doesn't react to the painter's plastic, not that I expect it would.

I'm planning on using all aluminum on this build & I want the finished product to be as permanent as possible (other than the occasional touch up for the non-skid paint) so I need to figure out this water-logging issue as accessing the foam will require drilling out the rivets and will be very time consuming in the future. I'm going to try do everything I can to minimize weight such as using lighter gauge aluminum for some of the decking, including the main floor section, as it will be supported from underneath by the foam.



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2002 Alumacraft 1436LT w/ 1984 Mariner Tiller Converted to Remote & 55# Minn Kota Terrova 12v (removable)

1985 Bass Tracker III - restoration posting coming soon w/ 1988 Mercury 60hp 2-Stroke & 55# Minn Kota Terrova 12v shared w/ my 14'


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PostPosted: 26 Jul 2016, 12:19 
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onthewater102 wrote:
Has anyone seen a setup where the support ribs are run perpendicular to the keel where the pockets between the ribs was filled with poured foam that wasn't water logged? Every restore build I've seen on here has involved pulling water logged foam out of these areas and I've found that my 2yr old build has water logged foam in this region now too.

FWIW when I tore my '97 Starcraft apart I was stunned - in a good way - that the foam in the stern, in the 2 aft-most 'pockets between ribs' as you've termed them, had dry foam :D !

Technically I think it depends highly on the quality and type of foam that the company used. Some foams may absorb water on the skin level, but everything I've read on the 2-part foams, like that sold by US Composites, states that as long as the structure isn't physically compromised, e.g., cut into or penetrated by a knife, sharp object, or saw blade, or broken off (which exposes the non-closed cell core) then the outside skin won't absorb any more than 10% of it's weight over its lifetime.

Some foams must not be truly 'closed-cell' upon curing, or possibly sheds or loses it's water repelling/absorption properties as it ages (due to hot then freezing temperatures, collapsing the foam cellular structure), as there is just way too much water-logged foam out there ... especially in tin boats! But I do know that Boston Whaler didn't use closed-cell foams until 1986 or so that is because prior to that timeframe, closed-cell foams were far too expen$ive to use for routine boat production use.

Now all boats sweat (due to condensation of thermal temperatures, i.e., think of a glass of iced tea or a ccccold adult beverage pool-side in a glass at one of Jim's BBQs) ... but I find tin boats form condensation WAY MORE than any frp boat I've ever owned.

Example - The live well on my present Starcraft, a rectangular water-tight formed structure foamed in place at the beginning of the bow deck area. For live wells in saltwater use, a well with square corners will KILL baits like pogies and mackerel, so I use a 30 or 55-gal cut-down drum in the stern ... but I digress. Thus I reserved to use my old live well as 'dry storage' and I put a new thermoplastic water-proof hatch (with 3/8" full diameter O-Ring) seal) over the top of the well area to make it truly water-tight.

Well the 1st time I opened that hatch after install ... surprise, surprise and everything inside was damp - and yet we had no recent rains! There was even some standing water in the lowest corner, all there due to condensation. I added a thru-hull vent (3/4" pipe) from the inside of the well to the vertical structure of the bow deck and PRESTO ... now all condensation is gone, as that 'dry' area can now vent to the surrounding atmosphere. Note I also added a small screen on the inside end so bugs won't think that they now found themselves a new dry home ...

As a tip, I added an 8" round inspection port towards the front of my cockpit deck floor and I removed the center aft seat base and replaced it too with another inspection port. Believe me, any opportunity I have ... I leave these wide open on warm days to vent out the bilge. Just don't break a leg :shock: by stepping into them!



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#1) 1st tin rebuild, 18' Lund viewtopic.php?f=21&t=36583
#2) 25' Parker refurb from EMPTY hull http://www.classicparker.com/phpBB3/vie ... p?f=15&t=6
#3) 16' V-tin rebuild viewtopic.php?f=21&t=36465
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#5) 16' Starcraft entirely NEW Transom Skins viewtopic.php?f=3&t=37548
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PostPosted: 26 Jul 2016, 12:36 
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I used US Composites 2# 2 part foam in my 14' (not rated for structural applications). The area I drilled into was ~ 1" thick, basically from the top of the rib to the bottom of the original floor, so perhaps the cellular structure was degraded by supporting the FRP flooring & it's a fault in my design & not the foam.



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2002 Alumacraft 1436LT w/ 1984 Mariner Tiller Converted to Remote & 55# Minn Kota Terrova 12v (removable)

1985 Bass Tracker III - restoration posting coming soon w/ 1988 Mercury 60hp 2-Stroke & 55# Minn Kota Terrova 12v shared w/ my 14'


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PostPosted: 26 Jul 2016, 12:49 
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onthewater102 wrote:
I used US Composites 2# 2 part foam in my 14' (not rated for structural applications).

Wow, surprised to hear that! I added below what their FAQ on their foam states - emphasis added. Looks like anyone using their foam or a similar foam must be sure there are limber holes or drains in the hull to ensure any water into the bilge cannot become trapped.

14. Is this foam water resistant? Source = http://www.uscomposites.com/faq_foam.html

Yes, but with the following caveat. The foams that we sell are considered closed-cell, which means that each cell that makes up the foam structure is completely closed off from surrounding cells which prevents it from acting like a sponge. It is completely safe for this foam to be in contact with water for hours/days/weeks and even months with no adverse effects. However, it should never be submerged in contact with water permanently. Over a period of years the water contact can begin to soften the foam and cause it to lose its closed-cell status. This foam is designed primarily to be used as an insurance policy in case of damage/holes that could cause a vessel to lose buoyancy. Pinhole sized openings would essentially have no effect on the foam since the amount of exposure is so minimal but you should always make repairs as soon as possible to keep the foam effectiveness as good as possible. This will be the case with all after market closed-cell polyurethane foams and even manufacturer installed foams.



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#1) 1st tin rebuild, 18' Lund viewtopic.php?f=21&t=36583
#2) 25' Parker refurb from EMPTY hull http://www.classicparker.com/phpBB3/vie ... p?f=15&t=6
#3) 16' V-tin rebuild viewtopic.php?f=21&t=36465
#4 Procraft SV14
#5) 16' Starcraft entirely NEW Transom Skins viewtopic.php?f=3&t=37548
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PostPosted: 26 Jul 2016, 13:42 
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My foam supported FRP floor doesn't feel any less solid than it did originally - but that doesn't mean that the stress of supporting loads on the floor isn't causing small failures in the cell structure where poor draining rainwater could seep in over the course of a few days.



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2002 Alumacraft 1436LT w/ 1984 Mariner Tiller Converted to Remote & 55# Minn Kota Terrova 12v (removable)

1985 Bass Tracker III - restoration posting coming soon w/ 1988 Mercury 60hp 2-Stroke & 55# Minn Kota Terrova 12v shared w/ my 14'


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PostPosted: 26 Jul 2016, 19:20 

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I am using Secure Set foam for my rebuild project. It is used to set fence posts. Now it is used to fix the foam flotation under the seats. So far I am sold on it.


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PostPosted: 27 Jul 2016, 08:35 
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That is a 6lb density foam - three times the density of what I used but still an expanding urethane foam. It will cost more to obtain the same coverage, add three times the weight to the boat but it will be much, much harder. Also provides a bit less flotation in the event of an emergency (~56lbs/cuft vs ~60lbs/cuft).



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2002 Alumacraft 1436LT w/ 1984 Mariner Tiller Converted to Remote & 55# Minn Kota Terrova 12v (removable)

1985 Bass Tracker III - restoration posting coming soon w/ 1988 Mercury 60hp 2-Stroke & 55# Minn Kota Terrova 12v shared w/ my 14'


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PostPosted: 27 Jul 2016, 13:14 

Joined: 27 May 2016, 10:06
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Greetings onthewater102,

Excellent topic and one that anyone modifying a boat should carefully consider. I had an issue with waterlogged pink foam sheets under the floor of my jet jon that equated to literally 100s of pounds of additional weight. My solution, which has yet to be proven, was to add a layer of geogrid between the floor and the first layer of foam hoping that the grid would separate the foam from the floor, allow any water a path to follow to the back of the boat and perhaps encourage drying by adding an air space. I appreciate DaleH's advice re: encapsulating the foam with a layer of plastic. I wonder if a combination of geogrid and encapsulating the foam in a heavyish gauge plastic bag that could be sealed would be a viable option? Red house wrap tape has proven to be a long lasting product, perhaps it could be used to seal a heavy gauge bag of foam? hmmmm #-o


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PostPosted: 27 Jul 2016, 13:45 
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Hmm, geogrid is that honeycomb material you lay out as you're filling behind a retaining wall correct? Does it actually produce linear channels for water to flow through our just a grid of air pockets?

Thinking along those lines though you could lay that fiberglass sheeting material used for roofing sheds or fluted poly sheeting under the foam, but either way you wouldn't have the foam directly against the bottom of the boat supporting it against flex that will ultimately result in leaking rivets.



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2002 Alumacraft 1436LT w/ 1984 Mariner Tiller Converted to Remote & 55# Minn Kota Terrova 12v (removable)

1985 Bass Tracker III - restoration posting coming soon w/ 1988 Mercury 60hp 2-Stroke & 55# Minn Kota Terrova 12v shared w/ my 14'


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PostPosted: 27 Jul 2016, 18:55 

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You're correct, one of the uses of geogrid is behind the large retaining wall systems you see on the side of highways, etc. The grid I used is intended to help collect liquids, gases, etc. from under large pond liners and allow it to be draw away, so yes the system I used will allow water to flow between the grid. The material is really quite rigid and the grid pattern small so I'm not concerned with loosing support between the floor and rigid foam above it as its much more rigid than the foam. With that said, flex and loosening rivets wasn't a concern I considered because my boat is welded. It may be a concern for those that are running a riveted hull however and well worth taking into consideration.

Have a look at the various plastic sheet base materials used for the transition between a floor's surface and tiles. There may be something there that will act as a barrier and transfer load that you're more comfortable with. It would be fairly easy to line the floor with the material then pour a 2 part foam over it. Something like this might work for you:

tile backing.jpg


I may have misunderstood your original post. Is your hope to identify a system to stiffen the bottom of the boat or are you looking for a system to prevent the foam supporting your floor from becoming waterlogged, or both? I'm strictly thinking from an angle of preventing the foam from becoming waterlogged and may well be completely missing the nail's head.

I like your idea re: fiberglass corrugated roof sheets. The material is quite rigid, certainly more rigid than some foams, and I think it would transfer load between the bottom of the boat, a layer of rigid foam and your flooring as long as the layers were properly fastened and in contact with each other ??????


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PostPosted: 27 Jul 2016, 23:11 
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I'm always looking for the best of both worlds if I can find it. The boat I'm going to be working on next is riveted and thin skinned by modern standards so I want to make sure I've done what I can to try and prevent loosening the rivets over time while not adding useless water weight to the boat over the same interval.



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2002 Alumacraft 1436LT w/ 1984 Mariner Tiller Converted to Remote & 55# Minn Kota Terrova 12v (removable)

1985 Bass Tracker III - restoration posting coming soon w/ 1988 Mercury 60hp 2-Stroke & 55# Minn Kota Terrova 12v shared w/ my 14'


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PostPosted: 27 Jul 2016, 23:38 
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Hmmmmm.. I obviously don't have all of the answers.

When I did my 1652 G3 flooring, I put the Blue foam in. But, I put the sheets in between the aluminum supports very loosely. My thoughts were to allow an area for the inevitable water to find its way out to the bilge.

richg99



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PostPosted: 28 Jul 2016, 09:15 
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When we put new decks into frp boats, we'd rip suitable plastic tubing in half and lay them perpendicular to the keel, then foam in-place using that 2-part foam. Where the half-pipes served as limber holes and drains direct to the bilge.


Limber Drains.jpg
Limber Drains.jpg [ 41.45 KiB | Viewed 679 times ]

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#1) 1st tin rebuild, 18' Lund viewtopic.php?f=21&t=36583
#2) 25' Parker refurb from EMPTY hull http://www.classicparker.com/phpBB3/vie ... p?f=15&t=6
#3) 16' V-tin rebuild viewtopic.php?f=21&t=36465
#4 Procraft SV14
#5) 16' Starcraft entirely NEW Transom Skins viewtopic.php?f=3&t=37548
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