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A trip to the doghouse. Woof.


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Sorry if I am ignorant.  Why is the doghouse even needed?  My 75 F just has baffles and no doghouse.  As long as I use common sense on climb out I have never had a cooling issue.   Was there a major change to the cowl airflow design in later years?  What years have the doghouse?

 

 

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5 minutes ago, TTaylor said:

Sorry if I am ignorant.  Why is the doghouse even needed?  My 75 F just has baffles and no doghouse.  As long as I use common sense on climb out I have never had a cooling issue.   Was there a major change to the cowl airflow design in later years?  What years have the doghouse?

Earlier models and later models didn't have the doghouse.  The doghouse was developed to enhance engine cooling, but was later dropped because of cost.

I asked Bob Kromer (I think that's who it was) at the last Mooney summit why Mooney did away with the doghouse and he said it was a cost saving measure.

My C's doghouse is in pretty good shape;  it does a great job of cooling even on those really Hot-lanta days.  While I don't like it's added complexity, I can't argue with it's effectiveness.  I'm not sure if the fixed cowl flaps were a result of the doghouse effectiveness.

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The doghouse was agreat attempt to control airflow though the cylinder's cooling fins.  Based on the materials and production technology of the day, it worked pretty well.  Without digital CHT readings for each cylinder nobody real knew how good it could be.

A few modern steps evolved....

With shaped parts made of fiberglass, and seals made of silicone rubber, combined with computer modeling on top of 50years of Mooney experience.  See the photos of what David has been putting together...

When it really evolved the cowl flaps got eliminated for the M20R.  Cowl air is used to cool the surface of the exhaust pipes...

Basic observations I have made...

Best regards,

-a-

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  • 9 months later...

Thread update - I really pressed the shop during annual to do as much as they could to tighten up my dilapidated doghouse baffle, after I maxed out on what I could do on my own with RTV caulk. My climb CHTs have always been too hot in summer despite adequate peak fuel flow, and in cruise #2 always ran 30 degrees hotter than the rest despite being one of the richer cylinders.   A likely result of these temps was I had to pull two cylinders for IRAN at 900hrs SMOH during annual, so the baffle was getting pulled apart anyway.   I wanted them to address the hard to reach areas around the starter and alternator, particularly on the prop side, and replace the disintegrating front seals.   Below are some pix of the results.  Too early to tell if it worked, because now #2 and #3 are running very hot during re-break in.  

Fingers crossed that this will hold me until Sabermech's cowl mod is ready to go however...

 

baffle1.jpgbaffle2.jpgbaffle3.jpg

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Alex, check and see if your seal around your starter and alternator is as tight as Dev's.  In the event you have the seal from the original starter and generator there will be a huge gap based on the old larger dimensions.....

Dev,

Nice work!

Snap a photo of the new rubber seal with the cowl in position.  My C had a tendency to get this right 50% of the time.  The old stiffer rubber made it an extra challenge.

Best regards,

-a-

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7 hours ago, carusoam said:

Alex, check and see if your seal around your starter and alternator is as tight as Dev's.  In the event you have the seal from the original starter and generator there will be a huge gap based on the old larger dimensions.....

Dev,

Nice work!

Snap a photo of the new rubber seal with the cowl in position.  My C had a tendency to get this right 50% of the time.  The old stiffer rubber made it an extra challenge.

Best regards,

-a-

 

I don't. There is quite a bit of gap around both. Also some splits in the top of my doghouse.

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