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Drill below water line?
http://www.hobie.com/au/en/forums/viewtopic.php?f=11&t=39485		 Page 1 of 1
Author:  Chexone [ Thu Oct 27, 2011 5:10 pm ]
Post subject:  Drill below water line?
Humminbird wants me to drill little holes for clamp screws on the outside of the hull, at least one which needs to be below the water line to hold the temp sensor below water... does drilling holes below the water line sound like a bad idea to anyone else?

Of course, there'd be a screw in the hole and i'd fill it with silicone, but still...

Any advice would be greatly appreciated. Thanks!

Image
Author:  fusioneng [ Thu Oct 27, 2011 6:06 pm ]
Post subject:  Re: Drill below water line?
Chexone:
Instead of drilling a hole under the waterline ( I wouldn't do it), can you drop the sensor into an unused scupper hole, maybe with a rubber plug to hold it in place. This way it would be easily removed and stored with the unit inside. As long as the end is touching the water it should be accurate enough, or just do like I do stick your finger in the water to check the temp ( LOL)
Bob
Author:  stobbo [ Thu Oct 27, 2011 7:06 pm ]
Post subject:  Re: Drill below water line?
:shock: I wouldn't if I were you!

I think you WILL end up creating a problem. The issue will be sealing any hole you make because of the difficulty in finding a sealing material that you can 100% guarantee will adhere to the polyethylene and therefore give you a reliable seal - poly is not like wood, fibreglass or steel: it is much more difficult to find things that will bond to or seal in contact with it.

Even if you do manage to get a reliable enough seal:
1. a hole below the waterline is likely to affect the resale value of the boat.
2. you will probably always have a nagging doubt in your mind "oooer ! is that seal holding???!!?!".
3. anything hitting the outside of the hull in the vicinity of the seal could compromise the seal...
4. if the seal goes it is highly probable that you WILL sink.

From personal experience it is not nice to be a long way offshore and suddenly find your boat half full of water. If you are bobbing about in choppy water, unless you have fitted a through-hull bilge pump, there is no easy way to bail out the hull without opening a hatch - which lets water in - and will let even more in if the boat is settling in the water due to it losing buoyancy.

...there must be another way ! (My fishfinder reports water temperature via the transducer shooting through the hull dunno how accurately but IMO I would prefer to suffer from inaccurate temperature readings than a hole in my hull)

Could you attach the required sensor to e.g. the rudder or rudder stock so that it can be held securely in place without necessitating holes in the actual boat ?
Author:  Chexone [ Thu Oct 27, 2011 7:13 pm ]
Post subject:  Re: Drill below water line?
Thank you guys. Yes, there must be another way, including just sticking my finger in the water :lol:

I actually don't care that much about the temp... I just figured I'd try to do the best install I could, but drilling the hull below the water line?? You guys convinced me not to.
Author:  fusioneng [ Thu Oct 27, 2011 9:12 pm ]
Post subject:  Re: Drill below water line?
Chexone:
If it were me I would mount the transducer to the bottom inside of the hull (nowhere near the mirage drive, "can interfere with transducer reception"). I would then glue the end of the temp probe right next to the transducer (inside the hull), then cover the whole works with clear silicone (big blob, like a whole tube). This silicone will keep any gear banging around from damaging things and also insulate the temp probe so the temp probe should read the water temp through the hull (probably within 5 degrees). This way you only have one wire going to your main unit (if the temp probe is attached to the transducer). If you ever want to remove, the silicone peels off fairly easily if needed. If mounted inside the hull it will still be more accurate than my sticking my finger in the water :lol:

Bob
Author:  Chexone [ Thu Oct 27, 2011 9:24 pm ]
Post subject:  Re: Drill below water line?
Thanks for the good idea fusioneng. :idea:

I think what I'll do is cut a short piece of PVC and put it around the transducer and temp probe, and fill that with silicone. That should make a nice tight protection. I wonder how long a big blob like that will take to dry.
Author:  Chexone [ Sun Oct 30, 2011 10:28 am ]
Post subject:  Re: Drill below water line?
So I finally ended up dropping it in a scupper hole. It's easily removable if I need the hole for something else, it's fairly non-intrusive and I'll get 100% accurate temp readings.

Only downside is a 1/2" hole and 3 tiny screw holes on the top deck (not below the water line!) and I've siliconed them well, so it should be nice and watertight.

Thanks for the suggestion guys!

Image
Author:  marcosailfish [ Mon Oct 31, 2011 8:32 am ]
Post subject:  Re: Drill below water line?
Chexone,
Marine Goop seems to work better on the Poly than Silicone. If you use silicone then tighten down the fitting so it is about 1/8" from the hull and wipe away the excess. Let it dry for a couple of days then tighten again. You essentially are making a silicone gasket. Adhesion will be irrelevant then.

Johnny
Author:  Chexone [ Mon Oct 31, 2011 9:35 am ]
Post subject:  Re: Drill below water line?
Good to know, thanks. I have noticed that it doesn't stick very well.

I actually already ordered some goop but haven't received it yet. I'll use that from now on.

Modifying the yak is a lot of fun. There should be a sticky best practices post on here for newbs like me. :D
Author:  kayakman7 [ Thu Nov 03, 2011 4:21 am ]
Post subject:  Re: Drill below water line?
lexel adhears very well to poly

made by sashco and sold in ace hardware, amazon, ect...

and the clear stays clear and flexible forever! i've been impressed by this stuff

still wouldn't drill holes below the waterline, lol

j
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