SailNet Community banner
1 - 6 of 6 Posts

·
Banned
Joined
·
250 Posts
I have 2" holes in my hull for the transducers. The B150M that goes to my plotter decided to quit. I can easily just swap in another next haul out, but I have been mulling the Garmin GT23M or similar scanning type transducer. Most of the water I plod is on the shallow side. The beam angle of the B150M is pretty narrow in shallow water, and while yes, I ultimately just need the depth info of what is immediately below my keel, having a larger picture for situational awareness to compare against charts could come in handy. Some of the shoaling around here can be a surprise. If I go this route, I'm faced with a 1" threaded stem on the GT23M for a 2" hole. Aside from glassing over the hole and redrilling it the proper size, is there a proven way to sleeve or collar the 1" stem? I have some ideas in my head such as a large backplate epoxied to the inside of the hull with a 1" hole and copious sealant. The backface of the GT23M transducer is wide and itself could be sealed against the outside of the hull since I think my deadrise is within tolerances to not need the fairing block.

This is just my initial thinking out loud. I may just end up swapping in a new B150M since that's worked for as long as I've had the boat and is the easiest and least expensive solution. But I am curious about what one does, aside from reglassing and drilling a new hole, when putting an undersized stem into a hole in one's hull...
It’s called a helicoil. A threaded chunk with a threaded hole in it. Most are aluminum so bury it in Epoxy or it will sacrifice its self. Add a zinc nut on the inside on top of real fastener. It’s possible to 3D print the piece in a 20% poly carb in black white or grey and then bond it permanently to the hull. Kinda easy 20 minutes in software called fusion 360 and off to a local printer. Fusion 360 is free on the internet. When designing in a ASA or Poly Carb you’ll have to allow for .009% shrinkage. So when you draw both threads inside and outside tell the software to increase all dimensions by .009 %. The part will thread in tight. The part printed in ASA will be as strong as cast aluminum.
 

·
Banned
Joined
·
250 Posts
Den, well familiar with helicoils on the smaller fastener scale. That's a fantastic idea for this application (and an excuse to someday get a 3D printer for my own additive manufacturing bright ideas). In this case it wouldn't need to be threaded on the inside since it just needs a properly sized inner diameter for the threaded shaft of the transduced to pass through, which is subsequently mechanically "clamped" by the nut. But this could be a very clever method to make a larger hole a smaller hole below the waterline on this scale, especially since in this case, inside the hull also has a 3/4" thick ply backing plate for added strength as a part of the transducer mounting location.

Stated conversationally, not trying to be a smarty pants, but wouldn't putting a zinc nut on the inside of the boat be utterly useless as an anode? It won't be in the water...
Quit making fun of my nuts.
I’ve have a couple soft metal parts left in my bilges where anything could have a current through it. In your house your stainless steel sink attaching your brass elbow is a zinc nut. 20 years from now your zinc nut will fail. Zinc nuts hold just about every switch in every marine dash. On a transducer made from machined aluminum I use nut which comes with it and a zinc lock nut.
If you decide to buy a printer buy the Prusa 3+ about $800.00 US as a kit from Czechia. They Chinese copies are getting better but not really a work horse. The materials used in Prusa are superior. Their new XL is $2,000 and above the casual use. For boats stick to ASA and poly carb. Learn his to use the printer with PLA. PLA is made from corn and biodegrades. You’re in for a shock if you think 3D printing is easy plug n play. Each item takes a different approach. I’d go as far as running a 2” corse thread into the boat to increase the Epoxy bonding surface. Also the hole has some cell loss. So in fusion 360 pick the thread for the transducer place in a cylinder add the outside thread. Increase all dimensions .009% and bond this threaded hole to the hull.
The corse thread will double my surface bonding area and prevent vibration a straight thin seem won’t.
 

·
Banned
Joined
·
250 Posts
Just the opposite. It would be the strongest repair possible. A solid threaded hole in carbon fibre vs a fibreglass patch!?
Easy and fast yes. Thread it in with a bolt in the sensor hole with a coat of systems west, paint it primer and bottom paint. Thread in the sensor in bedding compound and connect.
It’s the correct mechanical repair in just about every material for a stripped oversized or damaged hole.
I’ll take that bet.
For tricks I’m going to run the project on a 3D slicer program which will estimate the cost in poly carb.
 

·
Banned
Joined
·
250 Posts
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
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.
 

·
Banned
Joined
·
250 Posts
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
My bad well then you know when you tear something out the fibreglass is weakened. Poly carb is used for formula 1 suspension parts. It handles higher temps than fibreglass, waterproof, UV resistant 10X, oil, has no worries. A 1/2” wall to assure good bonding to a ragged edge. Not a shaft for a rudder or prop but equal too cast aluminum. I don’t like any hole drilled through fibreglass left unsealed. Bedding compound in excess doesn’t cut it.
My senders have threading most their length. Knowing fibreglass structure is a one time thing I only trust Epoxy and nothing else for any repair. Structurally it will be the strongest through hull in the boat. 3D printing used in manufacturing boats use similar methods even inserting metal while printing like the Hanse Yacht 38’ experiment. There are thousands of marine sailboat replacement parts available to print in ASA, Poly Carb, TPU, Nylon and TPE.
At the end of the day I don’t have to sleep on her so no worries.
 

·
Banned
Joined
·
250 Posts
Den, so every hole in your hull is threaded to receive the threads of every through hull (transducers, seacocks, discharge, etc)? Thats an impressive set of taps to do that! Or did I misunderstand you?
Nope wish it was though. Mine are installed just like ones in question.
However I would sleeve any hole I opened to replace an item. Even if it was 2mm wall sleeve.
Through hull is it’s own sleeve but when you grind one out you loose material. The new fitting goes easy.
I print them 1.5 mm larger snug.
A raw unprotected hole is not protected from water migration with extra mounting goo.
 
1 - 6 of 6 Posts
Top