mikes68charger

My Feedback: (34)

So Im building a crazy 130in BF109 and like all other water cooled war birds Im having issues with cooling. Because of its tight cowl my motor options are very limited. Flew the test model with a DLE111 and it was ok, but very weak.

The width of a DLE111 is all I got, Or I would go with a DLE170 or DA150 but they wont fit, to wide. In Germany were there are a few this size the motor chose are the amazing 3 cylinder 4 stroke motors which for this bird would cost $4800 way out of my price range.

So I went with a DLE222, it fits tightly, and has the power and weight needed. But Cooling is channeling, Tried a few things, Took a compress blade off a gas powered leaf blower and attached it behind the spinner trying to get it to force air over the cylinders and out the bottom, but it works great until I put the spinner cone on the back plate, then it cant get the air in the motor.

So what Im thinking of doing now, is 2 options.
1. Use a very small and light Black and Decker 40v leaf blower, put the blower assembly in the fuze on the CG, have a air intake door on the bottom, that will open when I turn the fan on with my TX, that way I can turn the fan on once on the runway so it down sound odd, then have it pump the air from the fuse into the cowl, with an aluminum shroud to for the air over the motor, before modifications the blower weighs 3.5 pounds, not sure if that incudes the battery as I just ordered one for testing last night. With 2000mah I can get 10-15min so I would use 4000mah for 2 flights before needing charged.

2. Use a 7.5in race car fan from Jeggs for $80, build an aluminum shroud around the motor, attach fan, then build another shroud on the fresh air side, to help the fan only pull outside air, not sure I will be able to get enough air from the scale side sand scoop and top gun mounts to feed the fan Well.

3. Use an 115mm edf fan, mount it to the motor box and try to get it to blow over the heads., but I was told EDF do not like to work with restrictive tubes, and because Im only working with 3in or so for a tube to bring air from the motor box, to the motor.

I will get some pictures tonight, but just wanted to know if you guys had any thoughts on my thoughts or alternative ideals, the good thing weight is not such a issues as it will already be over 55 pounds and need an LMT1 Cert.

larry@coyotenet

My Feedback: (21)

It always come back to having enough intake of cooling air and exhaust of heated air. Doesn't matter if you use a fan it still needs to draw air into the fan from somewhere and the best place is the front of the cowl. I have seen more great scale planes meet their end because the builder just doesn't want to cut a hole in the cowl for cooling air. We can't duplicate a liquid cooled plane with a radiator using air cooled engines unless we increase the openings for the cooling air. An old saying is "you can only shove a grand piano through a knothole so fast"
Larry

mikes68charger

My Feedback: (34)

I agree, but the ME109 is not like a P51 with some forum of air intake factory. Even cutting a large opening in the front of the cowl would only cool one side of heads, I got 4 heads to worry about, and only cooling the 2 on the bottom with a hole in the bottom next to the spinner would only help the bottom 2 heads.

mikes68charger

My Feedback: (34)

Ill take another photo tonight inverted to show spacing between cowl and motor.

That is why I think the leaf blower ideal is great as it will pull the cool air from under the fuse and pump it across the heads to then vent out the bottom.

larry@coyotenet

My Feedback: (21)

The best way to cool an inline twin, which you basically have two of, is to baffle the engine so that the air goes from one side of the engine through the cylinders and out the other side.
Look at the way a Ryan STA is cooled, it had a four cylinder air cooled inline engine. Looking at your picture I just do not see any way of cooling the top cylinders without some scoops or something that would be non scale. An inverted inline twin of some kind is what you always see in big 109's.
Larry

av8tor1977

My Feedback: (6)

Just a wild ass thought since you are open to unconventional ideas.... I wonder if multiple wraps of copper tubing around the cylinders, routed to a radiator would work. Walbro makes small impulse fuel pumps that could be used to pump the coolant. Thermal paste used on the tubing would be beneficial.

Just a thought.

AV8TOR