1974 del magic build foam question

[Jake222]

So I’ve been keeping up with restoring a boat lately. It’s a 1974 Fiberglass Del magic. It looks exactly like a Glastron to note. Done new stringers and transom and getting ready to put 2lb density foam in it. I am not sure how much it needs as I still need to do the calculations. But I already have the cc foam. Ready to pour. My plan is to pour then cut channels along the stringers about 2” wide out from the stringers with a large knife going down to the hull for drainage. I was wondering if this could cause me any problems with the closed cell and cutting it to make channels. If I don’t end up having enough for the whole under the I plan on using sheets for the rest of more pour. It’s an 80hp Merc 1978 on there to note.

 

[Scott Danforth]

skip the channels. most of the time the foam is intended to be a structural part of the hull.

add the floor, drill some 2" holes to pour the foam in, then fill the void under the floor.

then after the foam has cured, plug and glass the holes.

 

[Chris1956]

Yes, you do not want water under the deck in contact with the foam. However, I would set the hull level and pour in the foam. After the foam has set, use a long knife or saw to trim the foam level with the stringers.

Now install the decking with stainless screws and glass it. Make sure to seal the foam inside the hull completely.

 

[Jake222]

My concern is that blocking the runaway points for water being able to drain along the bottom of the center stringer.(that’s why I have a drain plug right?) I know everything is going to be sealed but how can I be sure that some water Won’t get under there?

 

[Jake222]

So what your saying is that I should fill all of the under deck after putting in the floor. The way it’s setup is 3 stringers front to back so only 5 cavities. I like this idea but I’m wondering if the foam should go all the way back to the drain plug. Probably shouldn’t worry being it all foam I just don’t see the need for the plug in that way as I don’t want to trap moisture.

 

[Jake222]

I can remember taking the old foam out and it was in sheets. Also debating use if sheets again. Maybe it wasn’t as structural as I though. But some the bottom sheets were stuck to the hull

 

[Chris1956]

A lot of boats have a well in the read of the deck to trap any water. This well will have the drain plug, and will be sealed from the rest of the boat, so the deck is completely waterproof.