Hard spots on hull (bedding question)

[joe_nj]

Re: Hard spots on hull (bedding question)

There are many methods to float stringers, one method that no one has mentioned is to use a high density closed cell foam between the plywood and the hull. /QUOTE]

Isn't this the stuff that they use to make swimming pool noodles? Would you suggest cutting up a pool noodle for spacing material?

I'd like to know what pb (peanut butter?) and pl abbreviations mean and what they're composed of.

 

[rickryder]

Re: Hard spots on hull (bedding question)

Hi Joe,
PB would be a mixture of fiberglass resin,cabisil (a thickening agent) and chopped strands of fiberglass.
PL is PL adhesive that you get at Home Depot Lowes or your local lumber yard. It used as a sub floor adhesive mostly.

Where ya at in NJ? Sussex Co. here.

 

[barbosam]

Re: Hard spots on hull (bedding question)

Joe, I've never used the pool noodles myself but I don't see why they wouldn't work. Like I said, just test for compatability with the resin. Poor a couple teaspoons on a piece of the foam and let it cure, If there is a reaction, it should eat right through the foam within an hour or so. The foam is just a filler to keep the wood off the hull. It also acts as a backer for the fiberglass 1) to make it easier to lay the glass and 2) to prevent what happened to GracieBell, the glass pulled under the stringer "most likely" due to shrinkage. The noodles may be a little too soft to be a an effective deterent of number "2)" but thats not a big deal, if you use the correct amount of hardner you "should" not see much shrinkage.

 

[GracieBell1]

Re: Hard spots on hull (bedding question)

I have also read about people suspending the stringer on a few spacers and filling under it with expanding foam. Then shaving a 45 degree angle to soften the bend for the glass. Any opinions on that. It may work for me since I am scabbing the stringer and it will be easy to hold off of the hull.

 

[rickryder]

Re: Hard spots on hull (bedding question)

Most of the Great Stuff foam is open cell and will absorb water....just put some 1/4" wood spacers under your stringer and tab in some 6" pieces of csm and let it set. That will keep your stringers off the deck and hold them in place so you can remove the shims and start your glass layups.

 

[barbosam]

Re: Hard spots on hull (bedding question)

From the great stuff website...
"There are two key differences between latex foam and GREAT STUFF? polyurethane foam sealant:

Latex foams are typically "open cell" and, as a result, can take on water. In fact, the same properties that allow you to wash latex foam off your hands with water also mean that the cured foam can absorb water. This can cause wood rot or deterioration in areas where wet latex foam is next to wood, such as a window frame. In contrast, GREAT STUFF? is a closed-cell foam. It forms a water-resistant outer skin when cured."

The miscoception is that flotation foam will absorb water. This is not exactly true. It can "trap"water due to the very large size of the cells that tend to form. Also it does not really bond to surfaces like a resin does and therefore can allow water to seep in between the foam and the adjacent surface, again "trapping"it.

I don't think that the foam would be any more of a weak link than the plywood you are using. If you are encapsulating the whole structure and water still manages to get in then the foam will not make your situation any better or worse, your wood will be vulnerable either way.

 

[rickryder]

Re: Hard spots on hull (bedding question)

Thats why I bedded my stringers in peanut butter no water getting in there

 

[Yacht Dr.]

Re: Hard spots on hull (bedding question)

If stringers/bulks are glassed right..no water should get in there ..

When you say bedded stringers..are you talking about Structual PB..or Fairing PB..

If your Foaming..yes there is a weak link when water gets to it..it brings the humidity up in that box...and it will have a harder time evaporating compaired to an open box with no foam..

Again..foam or not to foam...there are pros and cons against them both.. you have to decide for your application..

YD.

 

[rickryder]

Re: Hard spots on hull (bedding question)

When you say bedded stringers..are you talking about Structual PB..or Fairing PB..

resin cabisil and 1/4" chop strand fibers.... it's the oops! recipe Would that be structual?

 

[Yacht Dr.]

Re: Hard spots on hull (bedding question)

resin cabisil and 1/4" chop strand fibers.... it's the oops! recipe Would that be structual?

Yup

YD.

 

[barbosam]

Re: Hard spots on hull (bedding question)

Yacht doctor, I think you may have read gracie's post wrong or I may have misled you when I called it "flotation foam". My post was in response to gracies question about using "Great Stuff" foam to suspend the stringer off the hull instead of using a high density closed cell structural foam which is a common technique in composite structures. In that case the foam would be encapsulated with the stringer itself. If water gets through the encapsulation (lets just say it wasn't done right, as you say) then the wood will eventually rot either way.

Just trying to clarify, hope that helps.

 

[ondarvr]

Re: Hard spots on hull (bedding question)

Unless you're using epoxy the Great Stuff foam will be disolved by the resin.

 

[barbosam]

Re: Hard spots on hull (bedding question)

Ondarvr it looks like your right! After a little research it seems that the canned polyurethane foam is not the same as the two part polyurethane we use for floatation. The two part is compatible with polyester but the "great stuff" is not. I never played with the canned stuff and resin before.

hhhmmm, interesting!