BWC Flying Fish I/II – Enclosed Centerboard Case Narrowed, GRP Walls Bowed Inward

[Toky]

Hello everyone,

I own an older BWC Flying Fish [I/II] and am having a problem with the enclosed centerboard case. The centerboard has become very difficult to move and can no longer be pulled out freely because the case has become too narrow in several places.

The inner GRP walls of the centerboard case are visibly bowed inward. There appears to be foam filling behind these walls. The material looks similar to polyurethane expanding foam or construction foam. However, I am currently unable to determine whether this foam was installed originally by BWC as buoyancy foam or as part of the double-skin construction, or whether it was added during a previous repair.

The restriction does not appear to be caused merely by dirt, paint, or isolated resin residue. It looks more as though pressure from the foam-filled cavity behind the walls has permanently pushed the GRP surfaces inward into the centerboard case.

My questions are:

Are similar deformations of the centerboard case known to occur on older boats of this construction?

Could old, damp, or incorrectly applied polyurethane foam exert enough pressure to deform the GRP walls in this way?

Could the problem instead be caused by delamination, frost damage, or a previous improper repair?

How would you open up this part of the structure without completely separating the upper and lower hull shells?

Would it make sense to open the cavity locally from the cockpit, remove the foam, realign the centerboard case using a straight former, and then rebuild the area with a suitable core material and new laminate?

I do not want to simply grind the walls thinner from inside the centerboard case, as I am concerned that this could weaken the structural and watertight GRP layer. Forcibly spreading the walls apart or heating the cured laminate also seems risky.

I would particularly appreciate hearing from anyone who has repaired this kind of boat, a similar double-skinned hull, or an enclosed foam-filled centerboard case. Photographs of the original construction, old shipyard documentation, or information about typical weak points would also be very welcome.

Thank you very much for your help and advice!

Best regards,

Toky

 

[HelmutSheina]

Cannot speak specifically of centreboard cases, but that cheap crumbly brown two part urethane foam has too many issues on boats to be of much usage.

It readily absorbs water, which negates its use as a flotation aid; and crumbles apart, blocking the passage of limber and pump inlets. Plus it can easily deform and destroy structures due to rapid expansion prior to curing.

A lot of early sailboards were made of it, coated in a thin plastic skin. A pin hole in the skin led to a huge repair job. Or another very expensive wreck on the pile.

I would imagine your best option would be to build a new case.

 

[Toky]

Cannot speak specifically of centreboard cases, but that cheap crumbly brown two part urethane foam has too many issues on boats to be of much usage.

It readily absorbs water, which negates its use as a flotation aid; and crumbles apart, blocking the passage of limber and pump inlets. Plus it can easily deform and destroy structures due to rapid expansion prior to curing.

A lot of early sailboards were made of it, coated in a thin plastic skin. A pin hole in the skin led to a huge repair job. Or another very expensive wreck on the pile.

I would imagine your best option would be to build a new case.

Thanks for the introspective, I will try to open it and check it from inside

 

[Toky]

Cannot speak specifically of centreboard cases, but that cheap crumbly brown two part urethane foam has too many issues on boats to be of much usage.

It readily absorbs water, which negates its use as a flotation aid; and crumbles apart, blocking the passage of limber and pump inlets. Plus it can easily deform and destroy structures due to rapid expansion prior to curing.

A lot of early sailboards were made of it, coated in a thin plastic skin. A pin hole in the skin led to a huge repair job. Or another very expensive wreck on the pile.

I would imagine your best option would be to build a new case.

I am planning to separate the deck/cockpit shell from the lower hull to gain access to the centreboard case. Do you have any advice, or do you know of a guide or forum thread explaining the best way to do this?