Keel cooling design for electric inboard

[yabert]

I have the chance to have low heat lost with our electric catamaran and I think about installing keel cooler on our boat.
I estimate the heat lost at 300-600W during cruising and up to a max of 1500W for few minutes.
So, to keep salt water out of the boat, have a single cooling circuit with a single pump, I think about building keel coolers (one on each hull/each motor).

I thought about building it from 5052-H32 aluminum, but I realized that SS316 can be nice too, if not better.
Thermal conductivity is way worst with SS than Aluminum, but SS is stronger and will not corrode.

Please let me know what you think about my design.
The main principle is to clamp the cooler to the wood epoxy Cat via two 1'' holes.
Thickness is only 1’’. Overall length is 18’’.
If the design is good, I still have question:
-What sealant or rubber used underwater (salt water)?
-If I use rubber washer around the 1’’ holes, is it best to put sealant around the cooler to fill the gap?

 

[yabert]

Example of integration near electric motor.

 

[yabert]

The design is inspired by this Vetus keel cooler

 

[BlueBell]

Have you considered forcing sea water through copper tubing wrapped around the motor?
It could be fed from a bow through-hole only flowing water while making-way.
No exterior plumbing, drag, or vulnerability.

OR

Set up a radiator in the cabin and capture the heat!

 

[yabert]

Have you considered forcing sea water through copper tubing wrapped around the motor?

No.
The Leaf motors I will use come with a nice coolant circuit optimize and integrated to the motor, so I think to reuse it.

 

[BlueBell]

-What sealant or rubber used underwater (salt water)?
-If I use rubber washer around the 1’’ holes, is it best to put sealant around the cooler to fill the gap?

Yes, and leave the fitting lose, lightly finger tight leaving more sealant than the gap requires.
3M 5200 or equivalent.

 

[kapnD]

As long as you’re using 316L, I’d not worry too much about running salt water through it.
A quick rinse with fresh water at the end of the day will keep corrosion at bay, and it should run cooler than a closed loop coolant system.
No mention of a thermostat?

 

[yabert]

316L, I’d not worry too much about running salt water through it.

It's not about corosion, it more about all the stuff who can cause problem between SS and epoxy/wood (and destroy epoxy/wood).
Stuff I have in head: rock, sand, marine life, salt crystal, SS cooler itself and any other thing who can cause problem.

No mention of a thermostat?

Not really need as pump will be on when motor is on and the controller temperature monitoring will throttle down the current in case of over heating.
Motor controller will be in the cooling loop to.

 

[yabert]

3M 5200 or equivalent.

Thanks for the tips.
But from what I know, 5200 is a permanent sealant (non removable without damaging something) and that can cause problem if I need to remove the cooler.

 

[jehardiman]

The design is inspired by this Vetus keel cooler

FWIW, I would follow Vetus's lead and use bronze rather than Al or 316. Better heat transfer and less fouling.

 

[montero]

All keel coolers doesn't look interesting to me .I need low drag , longitudinaly ribbed , big surface , bottom stucture integrated , aluminium keelcooler .

 

[montero]

So it must be designed before hull structure is done . Retrofitting is always compromise . I consider some keel cooling but it's not applicable to current cat design because it's difficult above water surface.

 

[yabert]

I would follow Vetus's lead and use bronze rather than Al or 316. Better heat transfer and less fouling.

Sure bronze is best in this application, but I don't see how I can design and build it at low cost.
Maybe starting from bronze sheet metal, but how well this can be weld?

 

[yabert]

All keel coolers doesn't look interesting to me

It's why I plan to design mine

 

[montero]

Somewhere on the forum someone wanted to use extruded profile aluminum. Jet Boat or something. Rather freshwater use.