RE: [omc-boats] How to check stringers/foam?

From: Tom Paquette <tpaquette@...>
Date: Sun, 2 Jul 2006 21:06:52 -0400

Thanks Dave,


I like the added braces idea. Sound like I’m on the right path then.


What weight of foam did you use do you remember? It comes in 2lbs, 4 lbs
and 8 lbs etc. I was thinking 8 lbs but have not called the mfr yet to get


The rest is kinda the path I’m on.


And YES I guess it is a little insane but I grew up with this particular
boat and I learned to ski, fish and drive with this boat.


How could I not restore her. I owe her and my dad my love of boating……and
soon my own son will get the same opportunity. Once we get her back


I assume Haig is a close relative of yours as well….


I really appreciate the input.



Charlotte, NC



From: owner-omc-boats@... [mailto:owner-omc-boats@...] On
Behalf Of David A. Avedesian, PE, RPA
Sent: Sunday, July 02, 2006 2:54 PM
To: omc-boats@...
Cc: David Avedesian; 'Haig Avedesian'
Subject: RE: [omc-boats] How to check stringers/foam?


Tom of Charlotte, NC:


In some ways you are way ahead of my thought process. When it came to me I
was trying to ensue that the foam was level with the underside of the floor.
I was not trying to get the foam to expand up to the floor.


I put the foam in first. I made it as level (straight line from edge to
edge) as possible. I had the boat level but I was not trying to make it
perfect because I don’t think it is possible. I pulled a string from edge
to edge and if it was ” above the foam, I was happy.


Note: Some of this maybe a repeat. I then wet all six sides of the precut
floorboards. I tried to have the least amount of seams. Not because I
thought a seam was weak, but because it would be easies to ensure that the
floorboard were straight from edge to edge. The West System is very strong.
It will strengthen any seam on the floor.


Once I felt I had a good base, I lay the wood on the foam and placed a 4’
level across the boards. The boards were supported and there was no rise or
dip. I felt that if I had a solid enough base and the boards rested on the
foam without any ‘rocking’ then I should be good to go.


On any other design note, the primary cause of water getting into the bottom
is due to the fact everything is either screwed or bolted into the
floorboard. I spent time and effort creating a system that would be epoxy
the floor prior to the carpet being over laid. I would then bolt the seat
plates to a bracket that was epoxy to the floor. I have a backing plate
epoxy into the floor for everything that I would secure to the floor. This
way I was not come back and making holes in the floor.


There are less expensive methods such as using bedding compounds such as
3M-4200 or 3M-4200 for every penetration into the floor.


As for foaming under the front section where the floorboard exists, the
first suggestion would to roll the underside with epoxy. This will give you
some protection in the future. Then in small batches run the foam up under
the floorboards.


On another note, this would be an easy time to have a built in gas tank made
or you could mold out of fiberglass an in-floor ski locker. I took the gas
tank approach and it has been great. With over 27 gals, we have an average
run time of ~4.5 hours. This surely beats carrying three 6-gal red tanks.


I hope this has been helpful. If you go the gas tank approach, please
contact me. I would like to share some lessons learned.


I would like to add some other design considerations. I have a 115 hp
Yamaha on my transom. The boat is rated for 130 hp. In 1985, 115 hp was
the largest that Yamaha made. However, you don’t have to be Einstein to
know that over time that is a lot of stress on the boat.


I installed some supports into the transom and boat before I put the floor
back in. Up high under the rear deck I put two corner knees that would hold
the top of the transom to the sides of the boat. Under the floor and on
either side of the bilge well, I added two more knees to tie the bottom of
the transom to the bottom of the boat. Also, similar to the original
design, I epoxy a 2x2 spruce stud across the entire back of the transom just
under the motor well. This stud was also tied into the sides of the boat.
The final consideration was a transom plate that I ordered from Land & Sea
( <> ) (603-329-5645).


Perhaps I have over done the supports. However, which one of the above
approaches is the best, I could not say. I am pleased with the final
results. I also am convinced that my refit will last longer than the
original design. Will I be around in 50 years? No. But my 1965 Sweet 16


By the way, what we do for these old boats. I am convinced that what we do
can not be explained as normal behavior.


Good luck,


David Avedesian

Silver Spring, MD


PS: Haig: I thought you would enjoy reading this tread on the Sweet.



-----Original Message-----
From: owner-omc-boats@... [mailto:owner-omc-boats@...] On
Behalf Of Tom Paquette
Sent: Sunday, July 02, 2006 10:52 AM
To: omc-boats@...
Subject: RE: [omc-boats] How to check stringers/foam?


Thanks David,


I have an outboard. So in that respect I think my task may be somewhat
easier to attack. But removing an engine is removing an engine….


I removed the rear seating section using a sawsall type saw cutting along
the seam. The transom was dry rotting. That wood has been removed. I then
removed all the floor as it was rotting in places as well.


So What I have now is an empty shell. Except the front seating section
which I dug out with a crowbar and a shovel using extreme care not to put
pressure on the hull. The rest I cut out with a knife style keyhole saw I
picked up at Lowes for around $10. I still have a small amount to dig from
the front.


Here is a photo of current state. As you can see the front area is still
damp as I dug out from under the front this am.


The dark areas in the middle are where there was more resin applied during
the original building.


The bar clamp I put in place before removing the rear section to ensure the
upper hull stayed somewhat in proper dimension.


Note if you look close there are two small bolts glassed into the hull to
hold motor mounts. Wow a 14’ boat with an inboard that would be


Anyway, Where do I go from here? Sound like you made sure the hull was
level. Then poured in foam. Can you detail a little more your method of
“leveling” the foam? Sound like you went slow and hacked out any high
spots. How did you ensure a final level surface for the floor support (Ie.
No voids under the wood..).


I was thinking of building a jig section from the future floor. A 4 foot
piece that I would bracket on the sides using framing above to hold in
place. I was going to staple plastic onto the under side of the jig so the
foam would not stick to the jig. Then I assume the foam would expand out
past the section rather than pressuring the floor or hull.


Any and all thoughts would be highly appreciated.



Charlotte, NC






From: owner-omc-boats@... [mailto:owner-omc-boats@...] On
Behalf Of David A. Avedesian, PE, RPA
Sent: Saturday, July 01, 2006 6:54 PM
To: omc-boats@...
Subject: RE: [omc-boats] How to check stringers/foam?




I have a few questions first in order to understand your application.


Have you removed a section of floorboard? Or have you cut hole into the
floor and use the hole like the opening of a mine. You have reached into
the hole and ‘mined’ as much wet foam as you can by reaching into the hole.


I am really asking you to describe what your condition is right now.


Yes you want to be concerned about over and also under foaming. Over
foaming can push up the floorboard. Under foaming will leave voids of


The method I used was a complete floorboard replacement. We foamed in
batches. As we mixed a new batch we would overlap and over foam the area.
Once the foam had set, we would pull a string from edge to edge and then
using a cheap steak knife, we would cut the foam down to the height of
finish floor minus the thickness of the new floorboard. In my case, my new
floorboard was ” marine plywood.


A few questions and a few directions,


David Avedesian

Silver Spring, MD




-----Original Message-----
From: owner-omc-boats@... [mailto:owner-omc-boats@...] On
Behalf Of Tom Paquette
Sent: Saturday, July 01, 2006 10:28 AM
To: omc-boats@...
Subject: RE: [omc-boats] How to check stringers/foam?




I have one question.


I have removed the foam and hull is now empty and dry. I kept a few edge
spots for height determination. I plan to pour a little new foam beside
these spots level it with them and pull up the last few pieces of old foam.


Once I glass the new floor to hull following the sealing methods you
prescribe… HOW do I know how much foam to pour into the chamber?? I know I
have to have a couple of pouring/release holes. How many holes do I
need?? Is it possible to over foam and crack or deform the hull?? Or am
I being over concerned….



Anyone who has done this part your advise would be highly appreciated.



Charlotte, NC


From: owner-omc-boats@... [mailto:owner-omc-boats@...] On
Behalf Of David A. Avedesian, PE, RPA
Sent: Friday, June 30, 2006 10:14 PM
To: omc-boats@...
Subject: RE: [omc-boats] How to check stringers/foam?


Zach in Seattle:


If you have water in the foam, the floorboard is bad. OMC did not protect
the wood floor from the bottom. The wood is open or raw.


My suggestion for the easiest and best method is as follows:


* Make a mark a straight cut line two inches from the side of the

* Then draw a cut line about two inches in front of the bilge well

* A cut line between the front and back seats.

* Using a hand skill/7" circular set the saw blade for a 1/2" cut and
saw cut the floorboard.

* Remove the floorboard and send it to 'heaven'.

* Using a claw hammer’s claw, remove the foam and send it to

* If you have any mildew/mold, wash the inside of the hull with
bleach and water.

* Then rinse and dry the inside.

* Note: When I removed the foam, I decided to make a custom fit
stainless steel gas tan to fit down in between the stringers. I made the
tank 8 feet long x 11 inches wide with a varying depth of 7 inches in the
front to 4 inches in the back. The new gas tank held 27 gallons of fuel
and place the weight as low in the center of gravity as possible. It has
worked great and freed up valuable space in the back of the boat. The trim
on the boat greatly improved. The down side of this option was the tank can
be very expensive. For me the benefits out weight the cost.

* By leaving the two inch edge on the side of the boat, it becomes
easy to rematch the floorboard height within the boat.

* Use the finest grade marine grade plywood (5 ply) you can buy.

* Cut the pieces to fit the void created by removing the old floor.

* ‘Paint’ all six sides of the new floorboards with epoxy. This will
seal the floor from moisture in the future.

* Re-foam using the highest density closed cell foam system under the

* The floorboard does not touch the boat stringers.

* The floorboard is supported by the foam. The foam becomes part of
the structural support of the boat.

* The floorboard ‘floats’ above the stringers.

* The floorboard is ‘hard’ at the edges to the boat.

* Use one layer of tri-axial fiberglass cloth and epoxy the new floor
board in place.

* Sand and paint the floor a dark gray interior paint.

* ‘Float’ a carpet over the new floorboard.


When you take hundreds of pounds of water out of the basement of the boat
and you hit the gas, the boat just want to jump out the water. She can not
be on plan with in 12 feet. Now that is a boat.


If you would like to view the finished product, I sent my Sweet 16 to my son
in Seattle, WA. In fact, he is almost out on it every week on Lake Union
and Lake Washington. The boat is all white with a black rubrail with a 115
hp Yamaha. If you see the boat, my son’s name is Greg.


Good Luck,


David Avedesian

Silver Spring, MD






-----Original Message-----
From: owner-omc-boats@... [mailto:owner-omc-boats@...] On
Behalf Of Zach Stanley
Sent: Friday, June 30, 2006 11:57 AM
To: omc-boats@...
Subject: Re: [omc-boats] How to check stringers/foam?


This is a topic that has had me waking up at night screaming! I know that
our boat is waterlogged. It has sat low as long as we've had it - about
three years - but also lists to the starboard side. Also, the boat has been
in the family since new and everyone has commented how "the boat just kept
getting slower and slower" and "harder to pull a skier out", etc. Makes
sense now that the boat is dragging some extra weight around.


My question is... will replacing the foam using conventional methods now
give the boat structure as the original injected foam did. I would love to
hear comments about regained performance - or hull-flex post foam repair.
Pictures of the repair process would be great. Perhaps a section on the
ultimate site should be devoted to this subject with tips and photos since
it is such a common problem. Someone had mentioned cutting large holes in
the floor at intervals to scoop out the foam and re-fill the cavity while
leaving the floor basically intact. I think I will try this if the floor
itself can be saved. If that person has any pictures or further tips I
would love more info. I feel very fortunate to be involved with such an
informative group - thanks guys!


1970 Seasport 155

Seattle, WA





> ----- Original Message -----

> From: "Andy Perakes" <aperakes@...>

> To: omc-boats@...

> Subject: Re: [omc-boats] How to check stringers/foam?

> Date: Thu, 29 Jun 2006 20:49:12 -0400



> I haven't tried this, but another thought that would be a lot less

> destructive (if it works): Remove one of the bolts holding the seats down

> and try sticking a pipe cleaner (the fuzzy wires used in arts & crafts) or

> some other object that might show moisture into the foam. I'd recommend

> trying one of the front bolts as both my rears were rusted in place and

> ripped the lock nut out of the plywood when I repaired my seats 2 years

> (both fronts came out easy). As I said, I haven't tried it yet, but its

> quick and easy enough to be worth a try before cutting holes in your floor

> (though that's probably the only way to be 100% sure....but then how many

> holes do you cut and where?) Good luck!


> ----- Original Message -----

> From: "David A. Avedesian, PE, RPA" <david.avedesian@...>

> To: <omc-boats@...>

> Sent: Thursday, June 29, 2006 6:56 PM

> Subject: RE: [omc-boats] How to check stringers/foam?



> > Kenneth:

> >

> > I own a 1965 Sweet 16 outboard model.

> >

> > Generally there is never a question regarding whether you have water or

> not.

> > If you have water under the floor boards, the boat is very heavy and

> > very low in the water in the stern.

> >

> > I believe the easiest and effective way to check is to use a hole-saw

> > perhaps 3" to 5" in diameter and drill through the floor in the center

> > front of the rear combing.

> >

> > The floor board is about 1/2" thick and there is nothing under the

> > line of the boat from a structural point of view.

> >

> > As soon as you remove the round plug, you will know by the odor. The

> second

> > way to determine is to push your finger into the foam. If it squeezes

> > water, than you have a problem.

> >

> > I have found that when it comes to water under the floor boards, you

> > never be sort-a-pregnant. It will either be zero or flooding.

> >

> > If you are dry, then mix up a small amount of epoxy (West System is what

> > have used) and a layer of tri-axial cloth. Tri-axial is strong in three

> > directions and you can use one layer.

> >

> > This may be more information than you wanted but I have asked this

> question

> > a couple of times. If you would like more, feel free to ask.

> >

> > David Avedesian

> > Silver Spring, MD

> > Near Your Nation's Capital

> >

> > -----Original Message-----

> > From: owner-omc-boats@... [mailto:owner-omc-boats@...]

> On

> > Behalf Of Kenneth Fingerlos

> > Sent: Thursday, June 29, 2006 4:21 PM

> > To: omc-boats@...

> > Subject: [omc-boats] How to check stringers/foam?

> >

> > I've seen a lot of traffic on this list about the state of the foam and

> > stringers underneath the floor.

> >

> > Does anybody have any sage advice as to how one would go about checking

> the

> > status of such things? In particular, can it be done without cutting

> holes?

> > and if one has to cut a hole, where should such be cut to maximize the

> > benefits and minimize the problems?

> >

> > Thanks,

> >

> > Kenenth

> >

> >

> > -----

> > To get off this list send mail to omc-boats-unsubscribe@...

> >

> >

> > -----

> > To get off this list send mail to omc-boats-unsubscribe@...

> >


> -----

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