Show us your cowl exit air pics

[rate1]

Kicking this old thread back to life, just to say no cooling issues with my set-up. This while running a brand new DA70 with only two thanks thru it before flight.

 

[49dimes]

Just an update too..... I have not flown that much during the summer but did get some temp testing on a couple of hot days where it was in the lower 90's. Full power up-lines to heaven produced an engine cylinder temp of 282 degrees.
Long hover (a bit over a minute) produced 297 degrees. Extended harrier's about 290-295. Engine never goes over 300.
It would probably on the hottest of days say 98 to 102 OD temps but I don't fly when it is that hot. Now that nice flying weather is here ( 70's to low 80's) I need to get some more temps. @Alky6 did a similar set up on a 40 twin and temps where very similar. @jaybird also has a similar set up and would like to know if the temps are running similar as well.
Hands down this has got to be one of the better cooling methods for non round cowls and not having to carve out the cowl bottom.

 

[stangflyer]

Just an update too..... I have not flown that much during the summer but did get some temp testing on a couple of hot days where it was in the lower 90's. Full power up-lines to heaven produced an engine cylinder temp of 282 degrees.
Long hover (a bit over a minute) produced 297 degrees. Extended harrier's about 290-295. Engine never goes over 300.
It would probably on the hottest of days say 98 to 102 OD temps but I don't fly when it is that hot. Now that nice flying weather is here ( 70's to low 80's) I need to get some more temps. @Alky6 did a similar set up on a 40 twin and temps where very similar. @jaybird also has a similar set up and would like to know if the temps are running similar as well.
Hands down this has got to be one of the better cooling methods for non round cowls and not having to carve out the cowl bottom.
View attachment 43185 View attachment 43186 View attachment 43187

Very nice Kelly. I've been contemplating the air exits on the Yak. I too don't want to "hack" up a cowl. Especially since it will be brand new. The old Yak cowl had a couple of the vents hollowed out so air would pass through them. I'm probaby going to take the time to open all cowl vents. Have to admit it looks pretty cool when done properly. Depending on the motor I use, I want to do a little more elaborate baffling such as you've done on yours.

 

[49dimes]

Very nice Kelly. I've been contemplating the air exits on the Yak. I too don't want to "hack" up a cowl. Especially since it will be brand new. The old Yak cowl had a couple of the vents hollowed out so air would pass through them. I'm probaby going to take the time to open all cowl vents. Have to admit it looks pretty cool when done properly. Depending on the motor I use, I want to do a little more elaborate baffling such as you've done on yours.

Mine is oriented for air exiting at the bottom of the cowl. The most important thing is getting inlet air to go no where else but across the cylinders and behind the cylinders. Look at @Alky6 what he did. His is like what I would do with a round cowl but he did it with a smaller Extra cowl. Still gets the job done efficiently!

 

[stangflyer]

Mine is oriented for air exiting at the bottom of the cowl. The most important thing is getting inlet air to go no where else but across the cylinders and behind the cylinders. Look at @Alky6 what he did. His is like what I would do with a round cowl but he did it with a smaller Extra cowl. Still gets the job done efficiently!
View attachment 43189

Very nice. I figure the Yak will be the longest in progress plane I've had, so really going to do this one up right. Love those baffles.

 

[Alky6]

Just an update too..... I have not flown that much during the summer but did get some temp testing on a couple of hot days where it was in the lower 90's. Full power up-lines to heaven produced an engine cylinder temp of 282 degrees.
Long hover (a bit over a minute) produced 297 degrees. Extended harrier's about 290-295. Engine never goes over 300.
It would probably on the hottest of days say 98 to 102 OD temps but I don't fly when it is that hot. Now that nice flying weather is here ( 70's to low 80's) I need to get some more temps. @Alky6 did a similar set up on a 40 twin and temps where very similar. @jaybird also has a similar set up and would like to know if the temps are running similar as well.
Hands down this has got to be one of the better cooling methods for non round cowls and not having to carve out the cowl bottom.
View attachment 43185 View attachment 43186 View attachment 43187

I had to steal the idea from somewhere! I did finally see what the bottom of yours looks like in a photo you recently posted in another thread. Well done!

Mine is oriented for air exiting at the bottom of the cowl. The most important thing is getting inlet air to go no where else but across the cylinders and behind the cylinders. Look at @Alky6 what he did. His is like what I would do with a round cowl but he did it with a smaller Extra cowl. Still gets the job done efficiently!
View attachment 43189

Interestingly, that square scale air inlet below the crank bypasses a TON of air. On my old system on the EF78, just closing that hole off lowered the cylinder temps by almost 20 degrees!! I will also add that your idea of getting the air around the entire cylinder has made jetting easy and engine performance very predictable. No more burbles anywhere in the rpm range that seemed like you couldn't tune out. Very, very happy with the results.

 

[Alky6]

@49dimes what did you use to make the transition piece from the cowl inlets to the baffles? That looks like it was a ton of work!

 

[stangflyer]

@49dimes what did you use to make the transition piece from the cowl inlets to the baffles? That looks like it was a ton of work!

No kidding, right?

 

[49dimes]

@49dimes what did you use to make the transition piece from the cowl inlets to the baffles? That looks like it was a ton of work!

A 6"x 12"x1" solid balsa block. Was a wee bit of sanding but I had made templates of the cowl inlet opening and center offset for the propeller drive hub. Believe it or not it was not that hard to do. There was a day when I actually built airplanes!

 

[Alky6]

A 6"x 12"x1" solid balsa block. Was a wee bit of sanding but I had made templates of the cowl inlet opening and center offset for the propeller drive hub. Believe it or not it was not that hard to do. There was a day when I actually built airplanes!

Whoa! That's a wee bit o' work! Growing up machining and working with metal all the time and thinking that, while expensive, aluminum machined like through a horn. Balsa... well that has to be the easiest ever! Really used to hate wood. Now, well, I kinda enjoy it. Screw something up, just a glue another piece on and sand it off. On the contrary, have some machining ooops, better throw it away and start over - hours of lost time. Yep, coming to appreciate wood.