How to re-core a curved surface

[kpgraci]

Since I'm thinking about it...

I don't know when I'll get to it, but I have a soft spot on the curved portion of the front cabin. It's not a major structural issue yet but will need to be repaired one day (this winter).

I plan on attacking it from underneath so to not have any topside visible repairs.

One thing I don't understand is how to re-core a curved surface, especially one curving in several directions at once, fore-aft, and side-side like.

Strips of plywood? Something else?

 

[wetass]

Since I'm thinking about it...

I don't know when I'll get to it, but I have a soft spot on the curved portion of the front cabin. It's not a major structural issue yet but will need to be repaired one day (this winter).

I plan on attacking it from underneath so to not have any topside visible repairs.

One thing I don't understand is how to re-core a curved surface, especially one curving in several directions at once, fore-aft, and side-side like.

Strips of plywood? Something else?

Buy balsa or foam with a scrim backing and kerfs already cut in it. The other way would be to lay it up with coremat (but that may end up getting too heavy).

 

[RON20406]

Ken, if the damage is not structural where the core has completely degraded but rather simply wet, I would dry out the core over the Winter, inject the area in Spring with CPES followed by thickened epoxy(if needed). Otherwise, simply cut off the top skin over the degraded area, remove the degraded core, replace with new core and re-in stall the top skin, fair and paint. This is not a difficult project. There is no benefit, in my opinion, to performing the removal underneath since it is always more difficult to work with fiberglass/epoxy overhead working against gravity than doing it from the top. And you have the added benefit of trying your skill at gelcoat spraying/painting your repair which will undoubtedly prepare you for similar projects in the future. We all try to avoid repairing blemishes to an untouched area, but as your vessel ages it becomes necessary. I remember visiting the Metropolitan Museum of New York and saw the last two guitars played by the master Andres Segovia displayed in a case. If the average person saw one in a garage sale they would consider it junk and move on to the tarnished expresso pot for $3.00. Those well worn instruments played the most beautiful music in the world. Good luck and good sailing, Ron P.S. How's that for a diversion?

 

[RichH]

Buy balsa or foam with a scrim backing and kerfs already cut in it. The other way would be to lay it up with coremat (but that may end up getting too heavy).

ditto Klegecell and other kerf-cut core material is easiest way to do this.

 

[kpgraci]

There is no benefit, in my opinion, to performing the removal underneath

I suppose if I cut out the entire section as a unit (using one of them vibrating tools) and only had a seam to 'repair' that would be quite doable. I need to re-do the non-skid also (the po painted over it) so the entire deck will be patched and painted prior to that anyway.

I was going to do this last year in my planned winter haul-out, but the weather was so nice I sailed all winter instead, never found that stretch of 'bad' weather that justified any down time.

 

[tommays]

I would be of the OPINE that there is BIG benefit in not cutting up a deck with gelcoat and non-skid that is in good condition

 

[kendall]

I agree, if the deck surface is in good shape, going from underneath is a good plan if the area is easily accessible.
Since gravity fights you, I've only done small sections that way.

Easiest way I've determined has been to cut the core materials into strip or small squares, then working in small sections at a time, butter the underside of the deck,(faster) or the back of a square with thickened epoxy and press it in place, the epoxy will hold it in place fine. (fill areas for through bolted hardware with cloth and resin)
I feel the advantage to that method over using sheets of core material is that every square is isolated, so if somehow water does get in, it's going to be contained in that square.

 

[mitiempo]

Kendall's idea is a good one. But if you use balsa, probably the best choice, the kerfs in it can be opened up and resin let in which accomplishes the same thing.

kpgraci

Whether you do the recore from the top or bottom you will not have a neat seam and you shouldn't. The glass on each side of the cut has to be ground back and biax or similar used to tie the deck together - Probably 1" to 2" each side of the cut.

 

[RON20406]

Ken. whichever way you decide is best for your boat, remember you will not get the ultimate saturation of the epoxy into the substrata when you work from underneath since gravity is working against you. On the other hand, if you're dead set on not scarring the exterior of your boat, underneath may be an option. Whenever I repair something, I always make my decision on what would be the ultimate repair rather than what is the most convenient. I guess it's a personality type. Good luck and good sailing, Ron

 

[mitiempo]

Vacuum bagging is the best way to assure a good bond from below, especially if the area is larger.

 

[tommays]

I went with a high tech squeegee as i was not seeing that much cloth hang out upside down and hold a vacume and infuse that much area

 

[djplatt@cogeco.ca]

If the area is small why not just fill it with epoxy and cloth in layers? Not sure why replacing the core is important here? Am I missing something?

 

[tommays]

Its light and as stiff as solid

 

[25yearslater]

Hey KP I've got 4+ sheets of 3/8" baltek balsa left over from my deck core replacement if you're interested.