delam foam removal

After looking at all the delam problems and posts, I was wondering. I have/had a book on repairing fiberglass sailplanes that suggested that you can drill a small hole in the top layer and then insert a nail that has been bent 90 degrees. Place the end of the nail sticking out of the hole into a drill and chop up the damaged foam. You then fill the void with resin. Would this work? Unadvisable? Thanks.

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Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important.
C. S. Lewis (former atheist)

Interesting idea,

However what would be the bennifit of this vs Dilling multiple mulls through the first laminate of fiberglass and the foam (Not through the second laminate), and injecting epoxy

I idea is that the expoxy wicks through the foam, and hardens with the epoxy creating a new core laminate. This sounds safer to me, (IE damaging either layer of fiberglass), and I couldn't imagine not taking out the old foam core being that much of a weight penalty.

Just my thoughts.

The point of the delam repair is to rebond the fiberglass "skins" to the foam core. Not to fill a void between the layers. The laminate gets it's rigidity by preventing the layers to move in shear.

An example. Take a few layers of sheet metal strips say 1" wide by 12" long. Stack them on top of each other. Grab each end of the stack in your hands and flex the stack. It will bend fairly easily. Now, take the same stack of sheet metal and about 1" from each end drill a hole and insert a bolt through it. Place a nut on the end of the bolts. Now, try to flex the stack again. It will be harder than before. The bolts prevent the layers from sliding along each other. The layers now work togeather to resist felxing.

The epoxy between the layers in your boat is like an infinite number of bolts binding the layers togeather. Creating and then filling a void does not accomplish the same thing. It only adds weight.

I hope this clears things up a bit.

_________________
Nick

Current Boat
In the market
Previous boats owned
'74 Pearson 30
'84 H16
'82 H18 Magnum
St. Louis, MO

I think the idea is that foam doesn't wick very well. Thorough wet out would be the benefit as well as filling the total void. I don't know the clearance between the layers. If it's at least 1/4", I think this would work. A large finishing nail or one with the head ground off would help prevent damage to the upper and lower layer of glass. I agree the weight issue would be inconsequential. If they do it for an aircraft, it should be a good idea for a boat.

_________________
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important.
C. S. Lewis (former atheist)

Another "option".

If your area of delam is rather large, and crunchy, indicating the foam is breaking up, and you really want to save the boat...adding resin in this void will add an excessive amount of weight.

A quick synopsis of a suggestion to me, carefully cut away the outer gelcoat/glass skin, in one piece. Remove all the damaged foam. Replace (cut/glue in) with a piece of surfboard foam. Patch the skin back on.

In theory I like this option. I have not researched "surfboard" foam for sources.

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hobiejohn at earthlink dot net
Fleet 297

You are not trying to get the epoxy to be wicked into the foam. You are trying to rebond the foam to the outer layers of fiberglass.

As for removing and replacing the foam that is not a bad idea. I woud think, however that you would want to remove more of the outer layer of fiberglass than is affected by the delam. This way when you glue it back on you bridge the seam between the new and old foam. (I think this makes sense.) If you don't do this, then you have two of the three layers with a seam in the same place. This just seems to be asking for future trouble.

_________________
Nick

Current Boat
In the market
Previous boats owned
'74 Pearson 30
'84 H16
'82 H18 Magnum
St. Louis, MO