Keel cooling design for electric inboard

Is there other sealant than 3M 5200 who will perform well underwater and for long time?

 

Yes, bronze and copper alloys can be welded with an ordinary D.C. stick welder. Costly, but maybe worth it.

 

I don’t understand all the negativity about 5200.
It is an excellent, high performance adhesive/sealant, perfect for underwater applications, especially those where sealant failure could have disastrous results.
It remains pliable in all conditions, and, contrary to naysayers, can be removed when necessary with a little diligence.

 

Maybe...
A bit like food cook with bronze cooking pot is better than food cook with SS cooking pot
In some application, I bet bronze can worth it, but I think I will stick with SS for the conductivity difference over 1/8'' of material.

Still, I'm not sure about best solution to sealed the hull holes.

 

Sure, I understand it's an excellent sealant and I have use it.
It's simply that I don't want to destroy the wood/epoxy hull if someday I need the remove the stainless steel cooler.

But as you wrote, it's maybe worth the challenge to remove it to never be challenged with water ingress. I will think about that. Thanks

 

From a sealing perspective i's just another two trough hulls to do. Every manufacturer of boat goo has a product it recommends for this application. The market is clearly dominated by Sika 291i and 3M 5200, with regional variations in percentage distribution.
I don't see a need for a rubber washer, just do it like any of your other trough hulls.

As for the wood epoxy hull, the recommended procedure is to isolate the wooden core with epoxy.

Bronze is better at transferring heat then stainless. Stainless is also susceptible to different types of corrosion related to it beeing oxygen starved (the backside wich is contacting the hull). Best two materials for this application are bronze and titanium. From a design standpoint you need more baffles inside to maximize the heat transfer area. Or you simply do what others have done and use a long pipe bent to a U shape. The extra drag won't matter at the speeds you're considering (unless you want to race).

Bronze can be TIG and acetylene welded without major dramas.

 

Lot of good info in your post. Thanks.
I'm now convinced that good sealant will ensure proper sealing. It will be a pain to dismantle, but with a bit of luck I will never have to dismantle it.

 

Ask online price for a laser cut plate at Sendcutsend... I think SS316 is a bargin

Alu 5052: 15$
SS 316: 40$
Brass: 104$
Copper: 127$
Titanium: 184$

They don't offer bronze and I don't see where I could have bronze part laser cut.

 

I'm not suggesting this as an actual avenue to persue, but...

Assuming an uncored fiberglass hull, how much area would you need to build a heat exchanger into the skin while keeping temperatures to a safe level?

 

Yes, I 've also think about that. Sure I would do an ''internal'' cooler if I had an aluminum boat, but with my wood epoxy Cat, I don't think it's good.
Internal cooler is best as there is no holes in the hull, but is it really possible to pass some heat through 1/2'' of wood/epoxy? Sound like a good insulator to me.

 

Bronze is as relatively easy to weld or braze. You can buy rectangular tubes and fabricate the cooler. Aluminum is a terrible idea for a cooler. Also, it is much more difficult to work with. Wood is an insulator and would not conduct heat efficiently. I don't know what the hull of your boat looks like, but there are options that create little drag. For example, a long narrow tube along the keel. A skeg can be converted into a heat exchanger too.

 

Why aluminium is so bad as have better than bronze heat coductivity easy to weld and machining .It's also very light if we compare to bronze.
Thermal Conductivity of Metals and Alloys: Data Table & Reference Guide https://www.engineeringtoolbox.com/thermal-conductivity-metals-d_858.html

 

Because of electrolytic corrosion. Further, it is not easy to weld. It requires specialized equipment and to be either indoors or the area tented to keep the Argon gas from dissipating.

 

I've think at this.
In fact, I have to rebuild both rudder and I thought about building them in aluminum to integrate water cooling inside. Rotating action and possible damage to rudder/cooling kill the idea.
I also have to rebuild mini keel, so I thought about integrate some cooling inside, but, another time, possible damage kill the idea.
Then, I have to fill the holes of the daggerboards as I will not need them anymore and they take lot of space in the hull. What about building two compact ''daggerboards'' in aluminum with cooling circuit inside?
They will be higher than keel, so damage are less risky and they will contribute to maneuverability of the boat.

Umm!, lot to think about, but at the moment I consider external coolers and mini keel (no daggerboard) a simpler idea and I don't see huge disadvantage (maybe 6'' more draft?).

 

Aluminum is not ideal because of electrolysis. However, if that is your choice, there are several locations that could work. Making a daggerboard heat exchanger would put it at the most vulnerable place though. To start with, have you calculated the surface area you need for the worst case scenario?