[colemj]

With that transducer, it is possible to do like you suggest with an inside glassed backplate and a 1" hole drilled through it and still be safe. The transducer width will span the 2" hole by quite a lot, and the two 3/8" mounting bolts 7" apart will make it strongly fast to the hull. There won't be a safety or structural issue with this, as long as you get the backing plate well-glued/glassed to the inside hull and fill the 2" hole from the outside with thickened resin before drilling the 1" hole.

However, the right way to do this is to glass it over as suggested above. A 12:1 bevel is the "correct" way, but really is overkill for glassing a thruhull hole inside and out. Particularly so for this application. So if you can't get 12:1 because of deadrise curve, chine, or some other reason, don't sweat it. Like mentioned, this is a fast and easy job.

It doesn't look like there is a good way to make a bushing for that transducer that would be quicker or cheaper than the two options above.

Mark

 

[colemj]

You could just glass in the hole and mount transducer in the inside if hull is solid fiberglass.

Aren't there optional transducers for the unit you're thinking about getting many other manufacturers have choices of transducers you may be able to find something with the same operating parameters that actually fits the opening!

This is a specialized CHIRP transducer that is more than just a depth sounder. It can't be mounted inside, and other manufacturers sell the same one (with different plugs).

Mark

 

[colemj]

No way would 3D printing a helicoil-like converter be easier or cheaper or better than either the OP's original thought, or just glassing it over and remounting.

This is being way over-thought for such a simple thing.

Mark

 

[colemj]

Carbon fiber would be the wrong material here because of the metal fittings that need to sit in it and the water. The OP would need to buy a printer, figure out how to use it, design the part, and make it. Then insert it. A glass repair could be done in 30 minutes and be as strong as the rest of the hull, and not a mechanical repair. No comparing the ease and cost difference, even if you believe one approach is better.

A helicoil isn't even the best mechanical repair for anything. The best would be to repair the hole so there was no structural, physical, or material difference with the rest of the piece, redrill, and retap. The reason this isn't done in most mechanical cases is that it is either not possible because of the material, or extremely inconvenient.

Mark

 

[colemj]

Every street light in your town is bolted into helicoils or is a burial pole leaning.
Thread inserts in all industries are common. Your cell phone prolly has 3.
I think you just like to get angry.
Poly carb will bond to the hull with its alike Epoxy. The receiving hole will equal cast aluminum without the possibility of corrosion.
The 3D society is way friendly and patient that you imply.
In software the insert would cost 2.40 Canadian if the hull is 3” thick. Likely it’s 2” in poly carb.
On a group called Cults 3D you can link to 3D artists world wide. You can get a quote for any 3D part in any material. The owner is looking at a Fat 22$ bill plus postage for two inserts in poly carb. ASA and Nylon great marine plastics would not be appropriate.
In every corner of the planet is a 3D printer networked. Its jam packed with leading engineers. The very ppl who build the boat you sail are on it.
18 of these printers are at leading Yacht Clubs. Hinckley Yachts has one in their office. All for private use.
A fibreglass patch is equal to hammering in a cork. Would indicate zero knowledge of fibreglass.

I'm not angry at all, and don't think that any of my postings indicate that.

I didn't question polycarb. Your original suggestion was carbon fiber, which would be a poor choice leading to problems.

Yes, I understand that lights and other things are designed with threaded inserts. However, a threaded insert used as a repair for something not designed with a threaded insert is a compromise over the original design, otherwise it would be designed with an insert. You are comparing apples to oranges in your argument - a designed insert vs a repair using an insert.

The fact that there are a lot of 3D printers around, as well as yacht builders having them, is a non-sequitar. Go ask Hinckley Yachts how they would approach this problem.

A fiberglass patch is far from being equal to hammering in a cork. Else you would have to declare that building the boat itself was compromised. I don't need to detail my fiberglass knowledge and experience, but I'd bet a donut it far exceeds yours.

Mark