Outboard well turbulence

[Graham W]

Ray, Michael,

Thank you for your suggestions.  Ray's use of the term 'release agent' sent me down a Google hole which gave me all sorts of interesting results.  Here's a clear Swiss explanation of what epoxy won't stick to https://acrylgiessen.com/en/what-does-epoxy-not-stick-to/.  This led me to sheathing tape which in turn sent me to eBay.  And it turns out that I already have some in my shed.  Described as sheathing tape, an obviously very specialist item, it costs £12.99 for a roll.  The exact same item described as Gorilla clear repair tape (which I already have) is £8.50.  The power of marketing!

I'll use Gorilla tape to make a mold in the gap between the outboard well perimeter and the ply infill.  I'll then fill the mold with epoxy, which will only adhere to the infill.  Wait for the epoxy to cure, peel away the tape, lift out the infill and the gap should be thoroughly closed, with a bit of luck.  I'll post before and after photos here in due course, whether a success or failure.

Michael's cyanoacrylate activator looks to be interesting stuff and is now very widely available.  You can get a tube of superglue with a can of activator for £4.98 from Toolstation.

[Ray S]

Graham,
Try on a lash-up first before the real thing?

[Graham W]

Definitely!

[Graham W]

I haven't got around to closing up the gaps around my infill yet but can report that in its existing state, it improves speed by around 0.25kn compared to having no infill at all.  Measured while doing 4kn with the eProp.

[Jeremy Apted]

I have removed the Sikaflex and replaced the flaps however I think there is now a better option available. I have attached a PDF which shows the current arrangement on my BC23 whereby the flaps are sandwiched between the hull and a section of marine ply which is screwed into the hull. The main problem being to maintain the integrity of the hull during the removal of the Sikaflex. Chiseling away at the Sikaflex is no fun!
The PDF also shows the arrangement on a BR17 however I do not have all the detail. It would appear that a plastic infill is used in some way, perhaps the flaps are glued to the underside.
Does anybody know how the plastic infill is used and whether it is an item which can be purchased, perhaps from Swallow Yachts?

Regards,
Whistling Kite BC23