Ive never changed a skin fitting

[colhel]

Looking at upgrading the transducers which will likely mean charging the skin fitting, possibly enlarging the hole, 2"seems to be a common size. I'm reluctant to tackle this, and probably won't as we have a launch booked for October the 24th.
Whats actually involved and how to minimise the risk? I've never changed a seacock either.

 

[Restoration man]

Not to hard really,Remove the old one , clean the sealer off , if need to go bigger buy a hole saw of the correct size , find scrap piece plywood. Drill hole in that then offer the plywood upto the old hole keep it Centralised hold the ply against the hull and start drilling till it make a groove, remove the plywood and continue drilling unsung the grove to help stop hole cutter moving about , then just stick new skin fitting in with sealer , this is where problems can start as some of the cheaper transducers (nasa ones I think )don’t like pu based sealers so that rules out sikaflex etc , other than that it’s an easy job , unless you have a cored hull and that’s different story altogether

 

[john_morris_uk]

Cored below the waterline is extremely uncommon.

 

[Restoration man]

Cored below the waterline is extremely uncommon.

not as uncommon as you might think quite a few American boats as do sailing boats

 

[Restoration man]

not as uncommon as you might think quite a few American boats as do some sailing boats

 

[DavidJ]

You mention seacocks.
I changed mine a couple of years back to plastic. No more worries about earthing or not to earth or stray currents. Available in UK from Leesan
Tru Design

 

[john_morris_uk]

not as uncommon as you might think quite a few American boats as do sailing boats

Fair enough, but can you name one production boat that has cored construction below the waterline? All the main line builders realised it was a mistake several years ago IIRC.

 

[john_morris_uk]

You mention seacocks.
I changed mine a couple of years back to plastic. No more worries about earthing or not to earth or stray currents. Available in UK from Leesan
Tru Design

Just use decent quality bronze or DZR skin fittings and ball valves and DON’T connect them electrically to anything and there’s no problem. Plastic is good as well, but they’re bulky and won’t fit in some places.
It’s all irrelevant to the OP as they are replacing an echo sounder or log transducer.

 

[Restoration man]

Fair enough, but can you name one production boat that has cored construction below the waterline? All the main line builders realised it was a mistake several years ago IIRC.

searay and bayliner both have both of used cored hulls in the past ,

 

[BruceK]

Looking at upgrading the transducers which will likely mean charging the skin fitting, possibly enlarging the hole, 2"seems to be a common size. I'm reluctant to tackle this, and probably won't as we have a launch booked for October the 24th.
Whats actually involved and how to minimise the risk? I've never changed a seacock either.

Seriously? I'd just avoid Roy altogether. The last thing you want is Seacock anywhere near your skin fittings.

 

[colhel]

Thanks, there's some very reassuring answers here, but an amateur drilling holes in the bottom of boats, I'm not convinced ?.
Next time I'm down I'll have a closer look ?

 

[john_morris_uk]

He

searay and bayliner both have both of used cored hulls in the past ,

Same manufacturers IIRC and they’ve had no end of problems with rot in the plywood.

 

[simonfraser]

Thanks, there's some very reassuring answers here, but an amateur drilling holes in the bottom of boats, I'm not convinced ?.
Next time I'm down I'll have a closer look ?

i went for my first hole a few years ago, scariest bit was lying under it ....

 

[Bouba]

 

[Bouba]

Ok...the vid is restricted try to google Beneteau cored hulls

 

[dankilb]

Thanks, there's some very reassuring answers here, but an amateur drilling holes in the bottom of boats, I'm not convinced ?.
Next time I'm down I'll have a closer look ?

Honestly, it’s no biggie. Plywood guide (bit of scrap anything with the right sized hole cut in it), decent hole saw (buy a single good quality one of the size you need versus a cheap set), make good with epoxy if required (e.g. cored hull or a hole does end up a bit messy) and the right adhesive to affix the new fitting in (epoxy, polyurethane hybrid, or silicon sealant if it’s a more ‘tender’ - e.g. Nasa - fitting).

We bought our first ‘proper’ boat three years ago. All 12 skin fittings were condemnable. We reduced down to 7. Redundant ones were ground off, bevelled, and glassed over. A couple needed moving, so new holes were cut and the old ones filled. TruDesign replacement fittings give great confidence via good instructions and general feeling ‘in hand’ that they’ll serve well.

Don’t mean to belittle the initial caution/anxiety, but it really is no biggie - and the most problematic hole(s) in your hull will always be or become the ones you’ve never touched, not vice versa.

 

[superheat6k]

If you need to expand a hole simply nest two hole saws together, with the smaller as close to the existing hole as possible. This simply sits inside and acts as a guide as the larger blade cuts the enlarged hole.

Clean the hole and its surrounds of any old sealant, paint, dust, etc. Allow any cleaning solution to thoroughly dry.

When bedding a new fitting I always use Sikaflex 291i. Apply a generous amount to the flange of the fitting and up the threaded part at least just past the hub thickness. Then place a decent bead around the periphery of the hole, and wet the internal surface with the Sika to ensure there are no voids.

Then press the fitting gently into place and press so you get a decent squidge of excess sealant right around the periphery of the fitting. But don't push it too hard home.

Affix the inner fixing retainer nut and nip it up until the squidge marginally increases. The idea is to leave an even gasket between the fitting flange and the hull ~ 1.5 - 2mm thick. Then once this is done gently remove any major excess of sealant, but don't worry about cleaning every last vestige then leave it completely alone for at least a week to allow your gasket to set.

Then nip the locknut up finger tight plus ~ 90o with a tool but don't over do it. That's it - affix the internal valve or what ever you are using and when tightening this do not allow the fitting to rotate - this bit is important or your new seal will be ripped away from its set surface. It will still seal, but its strength could be reduced.

I have never had a skin fitting leak.

 

[dankilb]

When bedding a new fitting I always use Sikaflex 291i.

Not if the OP goes for a Nasa fitting. The plastic isn’t up to hybrid/polyurethane sealant adhesives (as per the instructions, which advise silicon but I use epoxy…). Otherwise great advice and hopefully more source of confidence. A ‘must do’ job as a boat owner IMHO.

I mention this because the OP does say ‘transducers’ and Nasa are a popular (and my) choice because they’re the most affordable way to get NMEA depth and speed - inc elecromag log.

 

[dankilb]

If you need to expand a hole simply nest two hole saws together,

Genius!!Can’t believe I never thought of or even saw (excuse pun) anyone do this. I’ve always used the ply hole method (keep em and you soon end up with a set) or even a bit of scrap wedged/held behind works - but what a comparative faff compared to just popping another saw on the arbor. ?

 

[superheat6k]

Not if the OP goes for a Nasa fitting. The plastic isn’t up to hybrid/polyurethane sealant adhesives (as per the instructions, which advise silicon but I use epoxy…). Otherwise great advice and hopefully more source of confidence. A ‘must do’ job as a boat owner IMHO.

I mention this because the OP does say ‘transducers’ and Nasa are a popular (and my) choice because they’re the most affordable way to get NMEA depth and speed - inc elecromag log.

Can't see that Sika would attack the Nasa, but then that is cheap gear anyway that I wouldn't ever purchase it myself, indeed I would be questioning the quality of any under water fitting where the maker is concerned by what sealant is applied. I would not use epoxy because I like some flexibility in hull fittings. Hence the provision of a 'gasket' by my method.