Interesting. Last night my son was showing me desktop computers immersed in mineral oil as a cooling solution. I’m guessing it’ll be heavy to have the battery box filled with mineral oil, but a custom aluminum box just large enough to hold the vesc outside the battery box might be a good option. If backpack builds have any heat issues, this might be good. Anyone built a backpack assist/efoil and have any issues with overheating?
See an example of that in this thread
The backpack idea has been around for a year or two but I don’t recall seeing anyone post many details of a successful build. I know there are a couple people who have done it with some success but they haven’t taken the time to post much. It’s the least represented form factor on the forum.
For the oil solution, I don’t think you need to fill the box, just 2-3cm of it sloshing around the bottom
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Not trying to dampen your enthusiasm but you started this thread asking for critique so you have left yourself open😉
You seem to trying to incorporate a very diverse set of approaches into a single build. It might work out but you might spend a lot of time trying to address things once you get it going.
From what I understand you are starting out full efoil (powered all the time with the motor) with what is a small motor and battery for that type of foiling so you will not have much time on the water before you need to recharge or swap battery for a spare.
Then you want to foil assist with same setup (use motor to catch wave etc). You have a relatively big board and foil to pump so you are dependent on battery and motor and you might find that rig challenging to handle in sizeable waves.
You are now expressing interest in a backpack build. This type seems to be more for someone who has advanced wave foiling and some pumping skills and only use minimal motor power for their session. They are after a feeling of pure (non motor assisted) riding.
It’s great to consider and investigate all the options and I applaud you for that but at some point I think it would be prudent to settle on a foil method for your first build and build a rig that will optimize your experience. 
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You’re totally right to call me out, I may be asking for something that might not be possible. My thoughts were that this setup could be used:
- on my bigger board for short efoiling sessions for about 20mins (max of 30 mins) like the foil assist+.
- then transition it to more of a foil assist use (first on the same large board and then moving to a smaller board)
- the backpack idea may be too much to consider right now, I was just curious if this build might be able to transition to a backpack. It would be cool to move the weight off the board for a more natural feel of the board and foil.
However, maybe it’s too optimistic to think it’s even posible that this system could work as a jack of all trades. I’ve seen @Jezza (pretty much my exact weight) mention he is able to go out on a pretty small board. He obviously has experience and skill that I don’t, but I’m hoping I don’t outgrow my first build too quickly once I get a bit of time under my belt. Maybe it’s inevitable that I’ll want dedicated builds.
A backpack is very simple, along with “box on board” are possibly simplest options,
Marine sealant for the heatsink to box, and thermal paste for heatsink to ESC. It seals very well with very little chance of leak, just make sure the heatsink to box interface is an inch wide or more.
Here is a picture, high quality marine sealant better than epoxy I think for heat cycles (advice from someone here)
.Tips for mounting Flycolor x-Cross 120A - #5 by Jesserosco
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