How many people are using baffles on their cowled glow engines?

Me, for one. Nothing elaborate, but I started by closing off one of the two intake vents on either side of an Extra type cowl, leaving open the one directly in front of a side-mounted two-stroke. That worked so well I did it again on a Sukhoi with a YS 1.20. This time with a radial type cowl I just cut a circle of 1/16" plywood to fit the opening, and removed the wood directly in front of the engine. I did this as part of the original set-up, so I don't have any before/after comparisons. But the big opening on the stock cowl looked like too much wasted airstream.

I've had a look at a couple of pylon racing compression cowls, where the engine has very little clearance all the way around, except for a narrow slit in front of the cylinder with a horn-shaped inlet (to compress the incoming air), and the hot air exits not so big either--but still proportioned to the inlet. The principle involves keeping the airstream very close to the cooling fins so that no air is wasted.

I used to travel to Puerto Rico, where the company provided quarters in a sea-side high-rise condo. We were on the 16th floor, and normally kept the front door and patio doors both open to the breeze. If you stood right in the doorway, it was very impressive how much wind there was, compared to moving around in the calmer interior spaces.

Hello Major,

I have done as you and had good results.

I now go one step further and ad small pieces of balsa to the opening that lead to the cylinder and head. Nothing fancy. I give them a quick coat of ca for fuel proofing. I try to get all the air thru the fins where it does the most good. I have been rewarded with engines that even with an accidental lean run don't quit.

When I was a kid we would crack the window over our beds and on the opposite side of the house put a fan in the window drawing the air out . You would get a low volume, high velocity rush of air to cool you off. Same idea as a whole house fan before the need for A/C.

When you channel airflow around an engine, make sure the exit side has adequate size to remove the heated and expanded air.

For a radial engine where a cooling slot is provided in front, make sure it can get out the back...just like a real one.


George

Strangely enough I was reading an article on this about a week ago and I thought I was doing it fairly well with my cowls. How wrong I was! The article is at http://www.supercoolprops.com/articl...ed_cooling.php but the thumbnails for the photos are broken links so just open them in a new window.

Strueth! After reading Supercool's article I can see I've been doing it all wrong.

...and just when you thought sticking the fins out in the breeze gave the best cooling.

How does the saying go? "There are more things in heaven and earth, Horatio...?"

Wow! That was some fancy machining. I'm a believer in full scale type baffles on model planes.

Here is a another link I like.

http://www.avweb.com/news/columns/188945-1.html

I would really like to do a 1/4 scale Super Chipmunk with a OS 3.20 pegasus and scale baffles in the cowl. The smooth running, the sound and smoke capability would be.......... That's my scale dream machine.

Nah! Stick the pots out in the breeze. They'll look better...