Aquabird - Electric Build - Page 10 - RC Groups
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Jan 04, 2013, 12:26 PM
We shall serve the Lord
kingsflyer's Avatar
You are correct that heat buildup in the lipos is not much of an issue. In fact, some EF-1 racers actually pre-heat their packs before a race to get them above 100 degrees F.

However, heat buildup in the ESC is a real killer. There are a number of ways to cool your ESC. The one you described of providing airflow through the airframe is the preferred method. You can also attach a larger heatsink to the ESC and mount the sink through the fuselage in the outside airflow. This allows you to seal the area around the heatsink and keep water out of the fuselage.

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Jan 04, 2013, 01:51 PM
Slip the surly bonds...
Sopwith Mike's Avatar
Water cooling would be very effective, much better than air cooling.

But any thoughts? No.
Jan 04, 2013, 02:03 PM
Registered User
Trevorh's Avatar
Originally Posted by Sopwith Mike
Water cooling would be very effective,
Thanks Mike, that's exactly what I am trying to avoid!
Jan 04, 2013, 03:23 PM
eye4wings's Avatar

You did say water cooling!
Maybe not such a daft idea when you read the blurb about safety margins and so on... maybe one of the 100A water cooled jobs would run really cool with water non-circulating and air fins attached? Sort of dual cooling.
Jan 04, 2013, 04:10 PM
Registered User
Steve Merrill's Avatar
The Aqua Bird is an airplane, not a boat, so I think air-cooling is the best option.

I always go with a higher than needed ESC. i.e. if I know my motor is going to pull about 20 amps, use a 30 amp ESC. This way cooling is not so much of an issue. Still, I always try to have cooling air. The main rule of thumb is double the size of the air exit hole, vs the air entrance. Perhaps on this model, the air exit should be out the top to the fuse. Try using some of Sparky's plastic parts, he sells air ducts just for this purpose.
Jan 05, 2013, 09:18 AM
Registered User


I use the heat sinks from modelaero on most of my seaplanes. Also would advise you to waterproof the esc. Simple matter sealing the ends with a hotmelt glue gun. After that you can then mount esc to a cut out on fuse,wing or where ever you want to mount it. Make cut out and again use glue gun to seal it in. Foolproof and waterproof. donnie
Jan 05, 2013, 03:35 PM
parkcityskier's Avatar
I would use Corrosion X intead of completely sealing up the ESC. If you ever want to use the ESC in another application, having some airflow through the ESC cover will keep it cooler. I treat all my water use ESCs with the stuff and have never had a problem, once done.
Jan 06, 2013, 04:09 AM
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Trevorh's Avatar
Thanks for the tips guys. I must admit my usual practice to date (on both land and water planes) has been to try to leave the ESC hanging on its wires so that air can circulate freely around it. I've been using the HobbyWing brand of ESCs for a while now and have never had any heating issues with them. The larger capacity ones come with switched-mode (as opposed to linear) BEC feeds too, which is also helpful in avoiding heat build up.

I have heard lots of people recommend Corrosion X. Does anyone know whether it is significantly different from the more common brands of sprays in the UK, e.g. WD40?
Jan 06, 2013, 02:17 PM
parkcityskier's Avatar
I'm not sure what is available in the UK but WD-40 definitely will not work for our purposes. If there is a boat or marine shop available to you I would suggest asking them about what might be available for waterproofing electronics.
Jan 07, 2013, 04:29 AM

I delayed in responding to your question about weight so I might ask my friend, the owner of the Aquabird I've flown. He didn't build it, didn't remember weight exactly and was unable to place his hands on his notes for the plane. In any case... it was 120% version, 72 in. span sheeted foam wing, and powered by an OS Max .61. Together, we estimate the weight at about 9 and 3/4 pounds. If he comes up with the actual numbers I will post them.

Last edited by tonystro; Jan 07, 2013 at 04:30 AM. Reason: correct grammatical errors
Jan 07, 2013, 06:19 AM
Registered User
Trevorh's Avatar
Thanks for taking the trouble to look into that Tony. That sounds a very reasonable weight for the size. It must have been an impressive beast!
Jan 07, 2013, 07:26 AM
Registered User
Trevorh's Avatar

Cockpit Thoughts

I took the Dremel to the detergent bottle yesterday. It looks like the 'canopy' is an excellent match to the width of the fuselage at the base of the fin and should need very little trimming.

Since I was planning to 'black out' the canopy, the fact that the fin goes right through the pilot's seat hopefully won't be too obvious!
Jan 07, 2013, 08:27 AM
What could possibly go wrong?
nickchud's Avatar
Trevor, for waterproofing I think silicon grease from Maplin is a good solution. They say it "Lubricates, waterproofs, insulates and preserves electrical and electronic equipment".

Your pilot won't be able to see a thing, even if you don't black out the cockpit!

Jan 09, 2013, 05:20 PM
Registered User
Originally Posted by kingsflyer
Though the Aquabird has anhedral on the inner wing sections, it has a lot of dihedral on the outer panels. This will act to help stabilize the plane in upright flight.

On top of that I chose the flat bottom airfoil on the winglets to get maximum lift when wing is banking. Without the winglets, the model will not be as stable.

The weight of my model is 6lbs 10oz. with 6S 5000mA batteries.

I have no cooling opening for the motor or 80A ESC. The current draw is around 45A.

Trevorh, Your model at the weight you will probably end up with will make it a floater. I still have concern at the location of the aileron servos. If you going to stick with it, then when time comes to cover the wing, I would suggest to you to cover the floats and the bottom of the wing only. Then place the wing on the surface of the water to see if any water is seeping into the wing in the servos location.

I am enclosing the pictures of the Aquabird prototype. As you can see it had V tail. I did not like it. The model was unstable in pitch. After takeoff the model would start oscillating up and down badly. I am pretty sure that the elevators were inside the turbulent air coming off the wing. For this reason, I changed the tail to Y arrangement.
Jan 10, 2013, 03:37 AM
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Trevorh's Avatar
Thanks Laddie, as always a very informative and interesting input.

I think I'll follow your lead and not bother with any cooling air through the fuselage.

I also like the idea of a flotation / leakage test before covering the top of the wing. It would also give me one last chance to chicken out and move the aileron servos!

One of the reasons I have deferred building the floats is to see what the weight is likely to be and then take a view on whether I should reduce them in section at all. At the moment, I am thinking that I could perhaps reduce the width by half an inch or so. Any thoughts?

On the pitch stability front, moving the tail up on top of the fin also moved it back a fair way so much of the improved pitch stability may be simply down to increased tail moment.

I do like the colour scheme on that prototype though - particularly the eyes! Maybe it looks even more attractive at the moment because I'm grappling with job of modifying the rear end of the fuselage to blend into my detergent bottle cockpit.

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