Winter Blues

[MarkD 53]

Kenneth,

The shroud is around 6" to 7" long, I started out with it about 8" long but had to trim it to fit and I have not actually measured it since.  It is spaced about 1/2" off the exhaust pipe using glass rope (similar to wood stove door seal).  I actually had the material left over from a heat muff I applied to a RANs S-6S muffler. The shroud is tapered to match the pipe but straight would work just as well.  It makes heat, not enough to drive you out of the cabin but with OAT around 40F I can feel the warm air on my feet and legs and cabin temp around 60F.  I can also feel where the cold air is coming into the cabin area.  The Avid is not a real tight airframe, lots of holes and loose fitting closures. I made the shroud with flanges ( about 3/4" )  along the seam and used tinnerman nuts and sheet metal screws to hold it together so I can take it off if I have to for any reason.   The material is .015" aluminum sheet.  I made the 2" hose fittings from the same material.  I acquired the 2" aluminum foil tubing from NAPA typically used for intake heat risers. I figured if the EGT was running around 1100F - 1200F the exhaust pipe should be at least 1000F and that even a short heat shroud should give me air heated to between 120F - 150F.  It does work but I have not measured the actual air temp out.  If you have any other specific questions just ask,  I can take some more detailed pics if you need more info.

[lostman 198]

Mark, 

That sounds great. In the little cockpit of my Teenie it would probably be downright comfortable. It's not drafty like the Pursang was, although I have to say that plane was sealed up fairly well. Guess if I keep it I will look into that soon. If not then I'll apply that type of heat to the Sonerai I'm building. Then ultimately if I ever get the chance to buy/build another Avid I for sure will use it. I always wondered how much heat you could get from a short riser like that. 

Thanks for the answers. That would certainly make a difference of when I would fly. 

Kenneth

[allonsye 85]

UPDATE: 

In the mid range throttle settings the mixture control works great.  I can set the throttle for just about any mid range RPM and tweek the low pressure control valve to obtain the EGT desired ((usually 1100F to 1200F).  I try to shoot for 1150F but as you guys know EGT varies with load a bit.

One of the big reasons for doing this is so I can throttle back and fly with a friend in his CH-701.  He only cruises at around 80MPH and I was cruising around 95MPH.  If I throttled back to cruise with him at 80 my EGTs were going above 1200F. I was getting tired of passing him then doing a 360 and coming up along side again just to have to do it all again just to keep EGTs below 1200.  He was getting tired of me always showing him how slow his 701 was.

I suppose I could build up a set of STOL wings and get some 21" or 27" tires then I would have to burn more gas just to go 80.  Maybe not....

MarkD

Mark - a slightly cheaper solution than changing wings would be to change to an IFA prop.  If you could course your pitch you get that load you're looking for in a pinch and lower the egt's.  I don't think there's any more convenient or effective way of controlling EGT on the fly other than via IFA mixture or pitch control. I'll likely build a HACman this spring.  In the meanwhile the IVO works great for EGT control.

[MarkD 53]

HAC UPDATE again:

After doing some initial flight testing at various throttle settings I finally opened the orfice on the HAC circuit to .100".  I can now fly with throttle settings from 5000rpm to 6000rpm and adjust the HAC to keep EGTs between 1100F and 1200F with ease.  Fully closed the carb bowls are only vented to atmosphere and in a full power climb the EGTs are well below 1100F and I can adjust them up to an optimal 1150F if desired.  OAT was around 52F,  Field elevation 110MSL, Baro 31.00inHg.  I am anxiously waiting for warmer weather to see if I have to make any jetting adjustments.  This should also help with higher altitude field ops in N.Idaho.  The available adjustments also allow me to vary the cruise speed to match my friend in his (slow) CH-701.

This is probably old news to some of you guys but I am really happy that I now have almost infinite control of the mixture in varying load and temperature conditions.  The info from the FORUM has helped a bunch,  Thanks!

MarkD