Skagit Floor replacement. Foam or not to foam?

[aguynamedchris]

I'm going to be replacing the floor in my 20" skagit this winter and would like to hear from you who have done this before the pros and cons of using foam to fill the voids in between the stringers and the plywood that will be going down as the new floor. Also what thickness of plywood do you recommend and do you fiberglass the bottom of the plywood first so that it's watertight before it goes down? Am interested to hear any and all opinions on this subject or if it's been covered before please direct me to the post. Thanks!

[TheBronze]

You can check through my restoration page here for what I did:

[ame="http://www.classicboatclub.com/forums/showthread.php?t=2497"]Bell Boy 404 Express Restoration - Northwest Classic Boat Club Forum[/ame]

In short, I think it is a good idea to do all of the above mentioned in your post.

I went with 1/2 inch birch ply. It is a hard wood, so will be less susceptible to water penetration than regular cedar or fir ply.

I strongly reccomend using foam in the voids. If you ever have a hull breach, water won't be able to penetrate since there is no place for it to go.

For the floor, definately resin and glass, unless you want to replace it again in a few years...

If you do it this way, you will have foam on the underside of your wood, and resin/glass on the top, effectively sealing the wood and turning it into "marine grade" plywood for less.

Long version:

Fit the new wood floor.

Fit your new floor into place. Then snap lines for the stringers. Inbetween the lines, drill 1 inch holes every foot or so (where the voids are) - Before you fasten it down - you don't want any accidental holes in the hull! Once you have it all laid out, you can tab it onto the hull with 4 inch glass tape to provide an edge seal. Then fasten it down with stainless screws. I used construction adhesive on the stringers as well to provide a water tight seal. Then jack the front of your boat up as high as you can get it, use blocks, jackstands, whatever. (I'll explain this below).

Using the foam.
You want the foam to start at the stern and flow up hill to the bow. This is why you jacked the hull up. You will know you have it right when you feel that it is "juuuuust" barely safe to be in the boat. Step lightly and you should be OK. Just make sure to get in from the transom, not the sides.

Put your A and B foam parts in hot water and bring them up to temp, around 80-90 degrees. This will allow maximum expansion. Mix small amounts, 10 ounces or so, at a time. Buy yourself a 5 quart mixing container to hold the leftovers and waste. use a drill powered paint mixing stick. You can get these at Coast or Ace. Don't buy them at Home Depot, they want way too much for them.

Experiment with small amounts of foam first! Just play with an ounce or so of each part to get a feel for how it behaves. Don't worry about wasting it, you can cut it up and put it through the holes when you are ready to do the real pours.

Thuroughly mix the A and B parts with the drill mixer. I used 1 quart mixing cups for your material. Act fast! Have EVERYTHING ready and within reach before you pour the parts together. You have about a minute to work with this stuff before it goes nuts (especially at these temps). Mix for 30 seconds, then pour it in. Use a tounge depresser to scrape the foam out of the container. Start with your lowest hole. Wait for it to expand. When it starts to come back up the hole, cap it with a one ounce mixing cup. It will come up a little and then the pressure will stop it from expanding into the cup any more. This will force it to continue up the hull towards the bow. Do this over and over until you are done with a section. Then do it all over again until you are done with the boat! Left overs can be cut off of the floor with a rough wood saw. Then they can be broken down and shoved down into the open holes to maximize materials usage.

Glassing the deck.

Use vinylester resin. It is more expensive than poly, but is much stronger and more resistant to chemicals and heat.

Use 1708 biaxial cloth. It is mat and 8 ounce cloth together. You get heavy duty strength on the bottom, and smoother finished cloth on the top. This also eliminates the need for multiple laid up layers.

Once your foam is in place, get your resin and fiberglass out and cover the whole thing. It is hard to work with in large cuts, so use 36 inch by width of the hull sections. Start in the stern and work your way forward. This will help the water flow over the lips instead of getting stuck on them. Give it about a 4 to 6 inch overlap running stern to bow and allow it to come up over your floor to hull joint by the same. Do one section at a time or whatever you are comfortable with.


Is this a lot of work? YEP! Is it expensive? HELL YEP! Is it worth it? I think so. The 404 has a floor that is stronger than it was from the factory. It is water tight, I can drop tools on it witout worry, and if I get a hole in it, I know the boat isn't going to sink.

Good luck!

[aguynamedchris]

Thanks John - I appreciate the detail and quite enjoyed reading the full story on your restoration.

[TheBronze]

Glad to help. No sense in having to figure this out on your own after I went through all of it last year.

Also glad you enjoyed my log - to date. More updates are in the future for sure

I feel I should clarify a few things.

Pour foam:
Don't put your A and B parts into hot water. Put the containers holding the A and B parts in water to heat the components up.

Drilling holes for foam. I should say that when I did it, I did a test fit of my wood, snapped my lines, and then pulled the wood out of the boat and drilled my holes on workstands.

[Tim_Mattson]

Nice writing John,
I`d add to resin the floor bottom on a table updside down after taping off the new foaming holes.This way the holes are resined and ready for gluing in plugs which can be glassed over while doing the seams.
I also start pouring two holes from transom when foaming so you can learn how much it will travel....a heavy steel plate I use will slide over holes as they ooze,basically steering the foam whichever way seems best.
Use an old Makita battery drill fitted with a coat hanger bent into a "J".
Down to the kid`s laptop so no pics to show right now......sorry.
If foaming to the keel area ,a hose or drain from bow area would be nice,but structure and such do dictate what you can do.
The sump Dave H did on my old Seafair was a really nice add most every boat can use,bilge pumps work good when in bilges ,not just on a flat deck.
Seem to recall the rear would be best with two squares to flatten the humps,leaving a small central area for drain tubes.I pinned in doorskin which was then glassed over after foaming.Foam was shaped so corners drained.
TM

[TheBronze]

Thanks Tim.

As for plugs, on the 404 I just let the foam come up past the holes, then cut it down flush. Using 1 ounce plastic mixers was pretty sweet. As the foam comes up, it creates a pressurised chamber to halt the foam from going crazy. Then you just lift the mixer when the foam has set enough. This approach does require either a weight on the mixing cup or a second person (I used my son )The holes are small enough that they can bear weight and once I put the glass over them, they were sealed.

I figured that the pour foam would seal up against the wood well enough to not resin it, but there is nothing wrong with doing that in advance. Probably it would provide a more sticky surface for the foam anyway. Next time... Right!

[aguynamedchris]

Thanks again for some of these tips - I am wondering about the value of drains or sumps. My thought is that if you completely seal the floor and fill with foam doesn't that eliminate the need and added complexity of drainage?

[TheBronze]

I went through this exercies myself when I was putting my floor in. I ended up not putting any sort of drain in, figuring I can run it along the gn'ls. In hindsight, it might have been better had I ran a sump line of some sort to the bilge in the stern.

On the 404 I left a small compartment at the stern for my bilge. This will allow me to put a couple of pumps in there and have them pump out any water from rough waters (I hope not!) or washdowns, etc.

In general, I think it is a good idea to have bilge pumps no matter how tight your floor is. Just an added safety margin.

[Bflaherty]

Thanks again for some of these tips - I am wondering about the value of drains or sumps. My thought is that if you completely seal the floor and fill with foam doesn't that eliminate the need and added complexity of drainage?

Foamed or not, you're going to get water (maybe from leaks or more likely from condensation) in the bilge area. If you do not plan for a method to evacuate this water you will enevitably end up with another rotten floor or worse rotten stringers... I always laugh when I see boats fully foamed and "sealed" cause all it takes is one hit with sharp rock on a beach or a large log in the water and that "sealed" hull is now full of water with no way (other than drilling or cutting up the floor) to get the water out to repair the damage...

When I worked for ACB designing "unsinkable" fishing boats we had air tight chambers around the hull and compartments under the floor that were "foamed & sealed" but through the bottom of each compartment was a drain tube (1-1/2" pipe) with holes drilled in it to allow any moisture to drain to the aft comparment where the bilge pumps were. The idea behind foam is to displace the potential volume of water that can fill a compartment, not prevent all water from entering... It's the difference between having 5 gallons of water in the bilge vs 500 gallons...

[Lootas1]

Ya know, whatever happened with a captain going down with his ship. No foam for me. Just a band that can play "Nearer My God to Thee." Sorry, I guess that didn't really contribute anything to the discussion. As I always say (but forget to obey) "Better keep my mouth shut and be thought a fool, than to open it and remove all doubt."

[Skagitguy]

Lol ! ! !

[Outlaw]

BUMP

I may be wrong but I heard that the Coast Guard doesn't like it when you foam the bottom and seal it. they like the foam under decks and air sealed compartments. true or false?

Outlaw

[TheBronze]

That may be the case on new construction, but on older boats there are no requirements.

[Outlaw]

aw, thanks for that. I knew I heard something but can't remember if new old or both. I am old and my brain don't keep up any more. lol

Outlaw