Winter build project: Wolfgang Matt’s ATLAS

Oi that's my baby that is! It is also a triumph of ascetics over aesthetics.

I found myself pondering or is it wondering over cooling. I wanted keep the sleek lines as much as possible. In the image I knew it definitely needed a slot here. Not so much for the motor but air flow over the ESC which is behind the firewall. A fair bit of air will exit anyway via the retract bay anyway. However, the motor is still enclosed hence the holed spinner. (Modellsport recommend not using a spinner - but then it wouldn't be a Curare!) I do have an exit hole on the underside of the fuselage just behind the wing trailing edge, not that big I have to add but it is early days yet to find out if more cooling is required.

However, some have said how balsa makes a nice cosy warm environment so you may have to take that into account.

Of course you don't have to fly it flat out...

PhilF51 wrote: Modellsport recommend not using a spinner - but then it wouldn't be a Curare!

Modellsport are correct...the original Curare always flew with a domed nut, not a spinner.

As for cooling, exits behind the wing are not going to do much since all the cooling air is going to be swirling around the retract opening. I assume the Curare came with an opening and plastic covers, but these Atlas's don't and won't need them.

Butchery took place:



It was intended to be a little narrower and then to flare as it meets the retract area, but the balsa and sanding sticks, didn't play nicely, or rather I was looking specifically at one area while not realising how much I was taking off elsewhere :blush:

Chris001 wrote: Talking of being in the air Mike, how did the Blue Angel perform on the 11x10?

The weather was not that conducive to testing, so I only flew with the 11x10. I'm not convinced it's any better than the 11x8.5, but more testing in calmer weather is necessary. I think the prop unloads a fair bit in the air (or I was flying more at lower throttle settings) since the flight times were about the same.

Ah! Chris, I see now from the image your issue. It appears the air could exit via the retract bay. Of course it has to get in first. I am sure you don't want to break up those sleek lines so give the slotted spinner a try first.

It's tricky Phil, from what I've read, air will always take the path of least resistance, which becomes an issue when you are wanting to direct it somewhere. For an electric motor ideally the cooling air will be passing through it from the front, but by the nature of our planes with spinners and cowls we block off a lot of this potential cooling air.

The motor being so close to the front limits the options, as far as I can see, to gracefully direct the air onto the motor. In the case of the Atlas, you can open up the area towards the rear of the motor and hope the air will circulate, or go full monty and do what Mike did with the Blue Angel, which had 2/3 of a nose ring and a channel direct to the motor.

I also didn't want to increase the drag by carving out the cowl, with the cowl as it was, the air would hopefully have been smoothed over and around the retract bay, now it is funneled directly into it with all the retract gear and a brick wall at the end.

This is partly why I like the design of the later pattern planes like the Aurora, because you can keep to the original lines and yet still take advantage of an air intake at the front to cool the motor. But I'm learning loads on the Atlas build so hopefully when the time comes to build the next one I can undertake something a little more challenging to build. :woohoo:

In the back of my head I can hear Chirs H saying, 'just glue the thing together and fly it'

Chris001 wrote: I also didn't want to increase the drag by carving out the cowl, with the cowl as it was, the air would hopefully have been smoothed over and around the retract bay, now it is funneled directly into it with all the retract gear and a brick wall at the end.

When I looked at your cooling mod I couldn't help thinking that it looked more like an air intake than an exit. I'm no expert and could be completely wrong but I wonder whether the channel you've created from the front of the cowl is going to do more harm than good.

AlanF wrote: When I looked at your cooling mod I couldn't help thinking that it looked more like an air intake than an exit. I'm no expert and could be completely wrong but I wonder whether the channel you've created from the front of the cowl is going to do more harm than good.

You've made two fundamental errors/assumptions/misconceptions, Alan. The first is that you assume the air molecules know the difference between an entrance and an exit and the second is that you assume British molecules form an orderly cue for the exit.

The truth is that molecules will simply move from areas of high pressure to those of low pressure, and they will do so in a very disorderly fashion unless you have millions to spend on wind tunnels in order to see what it is doing.

With our models we just cut holes and hope for the best and all holes will be of some benefit for cooling