The shape of the water ballast for a through hull transducer

[windypatrick]

Folks ,

I am installing a B&G Vulcan system (partial over kill...possibly) on my 1998 MAC 26x. I've been offline because there is soooo much danged work to be done before we drag it down to Puerto Vallarta this Christmas. I've refurbished the trailer entirely, the electrical has been robustly upgraded, I have the mast off and I am updating it, and I've rebuilt the centerboard, sanded , surfaced, epoxied and bottom coated and side painted the beast.

My question: I am putting two transducers in. One has a little paddlewheel sensor and requires a through hole in the hull (which gives me pause). I plan to install it in the last 40" aft near the transom, as there the little paddlewheel won't hit the trailer. I crawled the aft section and I notice that the water ballast appears to be in three flues at the aft-most part of the boat . It appears to run forward 7 feet before they share a common volume. Other than further forward, is there any water in the flat spaces between those flues? Yep, trying to avoid drilling through the hull and the Ballast.

Another part of me is thinking, build a PVC enclosure for the paddlewheel and bolt it on the transom. Ugh, maybe I should do that.

Thoughts?

[DaveC426913]

My paddlewheel is installed on the transom at the waterline.

As for transducer, when I installed one years ago, I was given instructions to install it near the bow. I would think you'd be able to install it forward of the ballast air valve. Hopefully, it will be forward of the ballast too.

I glued a short section of 4" PVC pipe to the hull - trimmed to snug fit the hull curvature - then poured some baby oil (linseed oil?) in there, and set the transducer in that, then covered it up. The baby oil acts to make the hull effectively transparent to sonar.

[Russ]

I would vote for mounting it on the transom. I don't like putting holes in the hull.

For inside, non-paddlewheel transducers, simply bed it in a large glob of silicone caulk avoiding air bubbles. I've been doing it this way forever and it works great.

[Be Free]

I would vote for mounting it on the transom. I don't like putting holes in the hull.

For inside, non-paddlewheel transducers, simply bed it in a large glob of silicone caulk avoiding air bubbles. I've been doing it this way forever and it works great.

+1 on both recommendations. I don't like underwater holes in my boat.

[windypatrick]

Thanks gents, this is helpful!

[Jimmyt]

If it's built like the M, it should be hull as long as you aren't in the ballast tubes. Pick your spot and get someone to tap on the inside while you're underneath with your hand on the spot. You should be able to tell by feel if it's one layer. As a precaution, send a 1/8" bit through first to verify its only one layer. This will allow you to easily fill the hole with epoxy if you had too many beers before doing the tap check. The bottom is likely pretty thick in that spot, FYI.

Should you put a big through-hull in the bottom? Your boat, your rules. If you can transom mount it where it won't get torn off during steering. boarding or docking, that would be my preference. You've already thought about trailer damage; but what about beaching damage? If you beach stern-to, hard to know which spot might be less damage prone.

If you can't do a good transom mount, I'd get a tube of 4200 and stick it in the hull. You spent decent coin getting that stuff, so time to get it put in and start enjoying it. Boats get through-hulls everyday. We have odd boats, so we hesitate when putting holes below the waterline. We are the minority. Even if you change your mind later, patching that hole would be relatively easy. Make it so you have easy access from the interior.

The way that sensor is made, it appears you are more likely to tear it up without creating a leak - assuming you aren't going to skid the bottom across a steel rail or rock ledge.

If I were to put it in the hull, I'd probably offset it from centerline a bit; on the off chance that I accidentally grounded. I have some thin water in my sailing grounds. Not too far, so it doesn't hit air when you're pulling a Highlander, but enough to give some room to take the grounding without hitting the sensor first.

We want pics when you get some breathing time. Sounds like you're doing big things!