spinner or no spinner for better cooling?

[ryan_m]

I've been running a motor with no spinner for a while now, it's mounted on a 3dhs 91" Yak 55. The cowl curves around the front more than most other Yak's I've seen, and if I used the 3dhs suggested spinner (4") it doesn't leave a whole lot of room for air to enter the cowl and cool the motor, especially if it's baffled. There is about 3/4" gap between where the edge of the spinner and the edge of the cowl are. So I've left a spinner off and figured the motor would get more air over it this way. I've got another thread on here somewhere asking about motor temps, and how hot is ok, and right now I'm in the ok range (330 degrees max with temp sensor mounted at back/top of one of the cylinders). But it hasn't gotten into summer heat yet, and the plane has only been flown in 70-75 degree temps, not the 100 degrees we often see here in the summer. And I have an alarm setup when it hits 325, so I can back out of whatever maneuver I'm in and let it cool down. It is interesting to see how quickly a motor heats up and cools down with the telemetry readings on various moves.

Anyways, a full scale pilot was looking the plane over and suggested that a spinner would actually really help cool the motor better. He said there is a nasty turbulent area right in front of the prop from the flat plate/prop bolts that are exposed there and that a spinner would actually help it run cooler despite appearing to allow much less airflow since the air would flow right in smoothly. He said that on one of his full scale planes he can't even fly the motor without a spinner as the motor overheats rapidly. So it's got me thinking I should add a spinner, but I don't want to spend 50-100 bucks to try one only to find it doesn't help at all.

So what do you guys think? Will a spinner help any? The motor is an EME70 twin. Thinking if I did do a spinner that it should be a 3.5" one, not a 4". What is everybody's preferred brand of spinner if I do add one?

 

[nebwake]

That is interesting. Get a head temp sensor and try it out both ways. I have a yak 55 that i am maidening soon also so very interested in how this goes.

 

[stangflyer]

I've been running a motor with no spinner for a while now, it's mounted on a 3dhs 91" Yak 55. The cowl curves around the front more than most other Yak's I've seen, and if I used the 3dhs suggested spinner (4") it doesn't leave a whole lot of room for air to enter the cowl and cool the motor, especially if it's baffled. There is about 3/4" gap between where the edge of the spinner and the edge of the cowl are. So I've left a spinner off and figured the motor would get more air over it this way. I've got another thread on here somewhere asking about motor temps, and how hot is ok, and right now I'm in the ok range. But it hasn't gotten into summer heat yet, and the plane has only been flown in 70-75 degree temps, not the 100 degrees we often see here in the summer.

Anyways, a full scale pilot was looking the plane over and suggested that a spinner would actually really help cool the motor better. He said there is a nasty turbulent area right in front of the prop from the flat plate/prop bolts that are exposed there and that a spinner would actually help it run cooler despite appearing to allow much less airflow since the air would flow right in smoothly. He said that on one of his full scale planes he can't even fly the motor without a spinner as the motor overheats rapidly. So it's got me thinking I should add a spinner, but I don't want to spend 50-100 bucks to try one only to find it doesn't help at all.

So what do you guys think? Will a spinner help any? The motor is an EME70 twin. Thinking if I did do a spinner that it should be a 3.5" one, not a 4". What is everybody's preferred brand of spinner if I do add one?

Hmmm.... that is very interesting. I would tend to put a little trust in a full scale pilot I think. I myself have zero knowledge of what you are speaking regarding cooling with or without a spinner. I have often wonder it, but never really investigated that aspect. That being said, I would really like to hear how it turns out for you. As for spinners, I may have a little relief for you. Spinners are really not all that terribly expensive. From what I have seen that is. A couple of links for you to look at. I've purchased this brand numerous times and found the quality very good, durable and very economically priced. Same spinners that are offered by many other big company vendors. Though you may have to do your own slotting for the prop as I have, they look really nice and help dress up the nose of a plane. Slotting is really pretty easy too. Hope this helps just a little for you.



http://www.r2hobbies.com/89mm-3-5-inch-rc-plane-carbon-fiber-propeller-spinner.html

http://www.aliexpress.com/item/RC-M...k-plate-3K-Surface-Processing/1220923437.html

http://www.ebay.com/itm/1-piece-3-5...540?pt=LH_DefaultDomain_0&hash=item19ff5aa744

 

[Naughty Monkey]

Another thing on the round cowls is they tend to move the prop out farther from the cowl to help with airflow also

 

[SleepyC]

The thing I have always heard is you do not need to much of an air entrance surface area to get proper cooling as long as the exit is 3X as large. In fact some of the better baffled airplanes have smaller air entrance holes. (Think the race planes with the tiny little square cowl inlets. Personally I would think a spinner would help push the air to the sides and into the motors fins. And since the spinner gets wider to the back this could cause a compressing effect by speeding the airflow up sending faster moving air to the motor.

Now again this will only work if you have 3X the surface area in the air exit zone...

 

[nebwake]

Another really good place for inexpensive and very high quality spinners is PAU and their no limitz line. The fiberglass ones are much cheaper than carbon and dont weigh any more than carbon.

 

[ryan_m]

Thanks for the tip on the PAU spinners, I ordered up a 3 1/8" one, hopefully it will fit a Falcon 24x9 prop. That ought to leave plenty of room for air to get in still... I'll be sure and update the thread here with results of how much better/worse it does in cooling as soon as I get it mounted.

Anybody got tips for cutting the spinner? Never had to do one from scratch before, always been able to enlarge existing holes if needed. I suppose it's much the same process though, just lots more enlarging!

 

[Naughty Monkey]

Another really good place for inexpensive and very high quality spinners is PAU and their no limitz line. The fiberglass ones are much cheaper than carbon and dont weigh any more than carbon.

+1 on the No Limitz, and I almost like the look of the silver ones more than the carbon

 

[TazmanianDevil]

I fly a Krill SU 29 37% and there was a time that I flew it with and without a spinner.
There is a huge difference for the spinner. Didn't know that till I went back to fly with that especially in a very hot day we had.
Use a spinner.

 

[ryan_m]

awesome, thanks for the info Tazmanian Devil! I have a silver one just like that on order.