sigflyer_us

Folks,
Would somebody please post a picture of the square cowling cutout on the lower half of the cowling as described in the instruction manual? I would also like to see a picture of the baffle installed on the lower half - I'm nearing completion and I want to get the baffle right. I'm using a DA 150.

Thanks in advance.

-Curt

0tter

My Feedback: (39)

Not a composite, I have a pic of a 37% Godfrey baffling. I have made a similar set up for a 33% Extra. Both are made of 1/32" maple ply. You can soften it with water and form it to the desired contour. In this case, the pieces are connected together with epoxy and some balsa backing at the corners. I have seen some where it is carved from one or more balsa blocks for each side. Depending on the fit, some peices my need to have a screw together assembly to allow close fit and reomval of the cowl.

Regarding the cut out in the bottom of the cowl I think the general rule is 3:1 (exit volume to intake volume), correct? I have seen many applications that do not fit this rule. Perhaps on larger engine installs the ratio is less??

On a side note, how would one achieve this ratio (if true) with say a Shukoi or Corsair where the intake is huge? Big cut out or block the intake?

cnbhome

My Feedback: (2)

The real secret to venting the hot air is a lip that creates an aerodynamic vacume for the air to flow into. If you only make a hole, especially in the cowl where it is still curved and creating a positive pressure area it is tough to get the hot air out. The comp-arf exit has a slightly moulded lip on it but I have found that on hot days it is not enough. I simply cut it off and reglued it on, using some glass and CA and make the angle about 45'. That creates a bigger vacume on the bottom of the cowl and gets the air out. On the baffels some simple light ply arranged to make the air go through the fins is all you need. A block across the top of the engine each side and in front of the cylinders. Nothing fancy is needed.