My boat has four thru-hulls, all of which are of unknown age and flush-fit on the external part of the hull
- i.e., the thruhull mushroom head
is buried in epoxy
so there is no 'bump' and drag is minimised. Sorry, I have no pics of this.
They appear to have been epoxied or glassed in, and even the hollow tube is very narrow so there may be a layer of epoxy
inside the thruhull as well. The flush fit is, I have been told, a racing
thing to reduce drag - she is after all an old race
boat (Jim Young Rocket 31). I am assuming there is a rebate the thruhulls are fitted into, and then this is all epoxied in to create the flush-fit on the outside of the hull
. The hull is strip-planked red cedar with dynel. All thru-hulls appear in reasonably good condition, but because they are of unknown age my confidence in them is not as high as I want.
Because they are unknown age (possibly never changed in the thirtyone years since she was built, at the pending next lift
for antifouling etc I want to replace them.
Thing is, I have never replaced thru-hulls like this. I have only ever done ones that are a straight forward fit and the mushroom head
standing proud (you know - just fit them into a hole with backing plate and sealant
So, here is the first question - how the heck will I remove them? Do I grind out the epoxy to get to the thruhulls - sounds a bit rough, but probably doable. Smash them out - that sounds wayyyyy too rough so I doubt that would be right. Use a hole saw to cut away the epoxy - which might make sense. Or something else. I guess another option might be to drill out the thru-hull to the full size of the thru-hull shaft/tube, leave the mushroom head buried in the epoxy and just do a standard fit?
Second question - should I redo the flushfit using the rebate, or accept the mushroom head standing proud of the hull and accept the (probably minimal) increase in drag?
Hope my explanation makes sense - sorry for nil pics. I've googled etc but finding nothing. Help!