First off hello..This is my first post here. I did some looking around and it looks like some of you may be able to help me? A little background of my project. I'm building 2 sets of transom lights for my boat. The first set is 24 3watt Ebay LED's in each light. Each string will run off a Flexblock at 48v in series, 12 LED's. The second set is 4 Lexeon M 12watt each led. My question isn't about powering. I'm using the following light enclosure. It's 6063 Aluminum. These lights will be in saltwater. I embedded the LED's in thermal epoxy then attached the rectangle tube to the u channel where the lights are embedded with thermal epoxy to transfer the heat. Water will run behind the led to cool. That is my theory..I am going to prime and paint the aluminum to protect it. It may take away from the heat transfer, but I have to protect it somehow.
NOW....I'm trying to figure out how to waterproof the LED's. I purchased some MG encapsulating epoxy and was thinking of filling the channel shown. I'm afraid of the epoxy cracking. Or water leaking in where I would drill the wire to power the LED. Will the encapsulation fill the void and keep out the water. If I was able to machine and install a lens I would, but I can't. Any suggestions are welcome. Thank you

 

I don't know why the pictures are not showing up??

 

There was a long thread on this forum not long ago regarding this topic. Might be helpful. If you can't find it, let us know. I'm sure it'll turn up.

 

I believe that the forum software will not allow a user to post pictures until he has made some minimum number of posts.

Suggest that you check the light output of the LEDs before you mount 72 watts worth. That is both a lot of light and a lot of heat to dissipate. LEDs are a lot more efficient than incandescent lamps and they have to be kept from getting very warm because heat hurts their efficiency and lifetime.

If you mount the LEDs in epoxy it will be difficult to heatsink them, so you would have to reduce the current -at that you would probably want to spread out the LEDs. If you very good at casting large objects in epoxy you might get lucky with the cracks. And then maybe not.

A commercially made waterproof lamp housing might be your best option. You would be assured of a good seal and you could heatsink the LEDs to the metal housing. Probably would be a good idea to be careful and experiment before doing anything "permanent".

Suggested reading: https://en.wikipedia.org/wiki/Thermal_management_of_high-power_LEDs

 

Thank you. I think I read the thread from a while ago that your talking about. He put the light in his tub and the potting cracked. My design is a little different than his in the means of heatsinking. I also never got an ending out of it. Did he ever get it to work?
DickCappels. I know 72w is a lot. I mounted them in Thermal epoxy (arctic silver) to transfer the heat to the aluminum. The current is at 700ma with the driver I am using. I have 2 designs with LED's that I'm wanting to try. The first is (26)-3wleds and the second is (4)-12w leds. The four 12watt leds are brighter than the 26 3watts. Cost wise the 12watt leds are $80 for 2 lights and the 3w are $25 for 2 lights. The 12w are much better quality. Here is a thread I started in another forum. Maybe you can see pictures here. http://www.candlepowerforums.com/vb/showthread.php?393796-Will-this-setup-work-with-this-driver

 

Do you think he is using a sold block for his heat sink? Looks like he made 2 slits for the water to flow behind. If you click on his about he says he machines a solid block for his heat sink and has a warranty of 2 years?? https://loomisled.com/shop/2-24-led-flush-mount-boat-transom-lights-12-14-5-vdc-charging-battery/

 

Yes. most likely he is using a thick piece of aluminum to draw the heat away.

I did not see thread you mentioned (about cracking). My comments relating to the difficulty is based on my own experience and that of others. Some people get consistently good results. Some of us just can't seem to get it right.