Curing a slow and hot Rocket: CHTs

[cduster]

I've recently picked up an early SN Harmon Rocket 2 and as is always the case, "new to me" airplanes always end up slower, thirstier, and hotter than the rest of the fleet. I'll be spending the next few months, or years, taking her from what she is, to what she should be. In order not to flood this thread with too many variables, I'll make multiple threads with known issues.

Currently CHTs are quite limiting and I think some of that may be instrumentation (MGL iEFIS), some is the poor baffle sealing, and some is the very limited exit area. I'm running down a bunch of possibilities in the instrumentation department, and we've spend a bunch of time and a few tubes of red RTV sealing up the obvious leaks. As for the cowling exit, the lower cowling is nearly flush with the bottom of the fuselage. I'll try and attach some pictures.

Are/were the factory HR2 cowlings nearly flush, or did they have something more similar to other RVs with a 4" or so deep "tunnel" to duct the air out?

[Robb]

which Rocket did you buy?

[Gt-401]

I have seen some rockets with larger inlets, but for most the stock size is big enough. Smoothing out the exit airflow seems to be very effective mine has a fairing on the firewall and motor mount to help the air turn the corner as it exits the cowling.

[cduster]

Originally Posted by Robb

which Rocket did you buy?

N86WR, SN 011 Its a beautiful plane that just needs a little TLC to bring her up to speed.

She had a large piece of flattened out hose clamped in between the exhaust stacks right about where the air exits the cowling. I removed that and trimmed a tiny bit of uneven material from the trailing edge of the lower cowling today. It will be tomorrow before I get any real numbers, but it sure seems to have helped a good bit. I'm guessing that the flattened hose represented about 9 square inches of obstructed exit area. Is there any need to tie the exhaust stacks together?

On another note, the LH upper landing gear intersection fairing has seen better days. It looks like a homeless place kicker used it for a shoe for the entire 2018 season. It really sticks out since its just about the only thing on the plane that isn't really nice. The crankcase vent exits flush with the belly at the left gear leg and I see where it is sucking oil all the way down the outboard side of the gear leg, so I'm guessing that it has the airflow really jacked up in that area. Does Mr. Harmon still supply these fairings?

All of the gear leg fairings are split in the rear to facilitate removal, but when installed, the gaps are unacceptably large. Are there any tricks to neatly pull them together?

https://doc-10-28-docs.googleusercon...c3x1x6R2CpGAEX

https://doc-10-28-docs.googleusercon...c3x1x6R2CpGAEX

[cduster]

Originally Posted by Gt-401

I have seen some rockets with larger inlets, but for most the stock size is big enough. Smoothing out the exit airflow seems to be very effective mine has a fairing on the firewall and motor mount to help the air turn the corner as it exits the cowling.

Did you cover and smooth the area around the lower engine mount cross bar? I'd love to see some pics of that if you have them available.

[f1rocket]

The two most effective mods to improve cooling are to smooth out the top side of each inlet on the inside of the cowl and to add a plenum. There is plenty of air coming in, it?s just that too much of it is escaping.

It has been my experience that none of the outlet mods are needed once you redirect the inlet flow.

[sailvi767]

Come over to BQ1 for lunch tomorrow about noon and we can have two Rockets there! I am working on my temps also. Test flight to lunch for BBQ!
George

[cduster]

Originally Posted by sailvi767

Come over to BQ1 for lunch tomorrow about noon and we can have two Rockets there! I am working on my temps also. Test flight to lunch for BBQ!
George

Durn, I?d love to fly over there and check out your rocket, unfortunately Hurricane Dorian has us way behind at work. Maybe I can catch up with you some time in the near future. BQ1 is awesome by the way.

[vfrazier]

What Randy said, plus the stuff on this page:

http://vincesrocket.com/Additions%20...2010-27-04.htm

Scroll down to the "Summer heating woes" section.

[Robertcropdust]

I was the second proud owner of 86wr. Private message sent.