daven

My Feedback: (1)

I went to the field with high hopes of getting a few high speed test runs in with my newest seeker.

With a new "last year" nelson turning a 8 3/4" x 9W at close to 19,500 I thought I was in for a very fast flight. Took off at what I felt a Rich setting, and made a few passes. The Radar quickly picked it up, and after about 4 passes in the 145-148 range, I said "screw this" and landed. The fuel trail on the bottom of the plane was slightly darker than I like, but not bad.

Figured I switch to a bigger pitch prop and richen her up a hair. The plane still turned 19,300 with a 8.8x9.0 prop but the speed was nearly the same as the previous flight.

I don't think I had ever seen such poor perfomance on props that I know work at those RPM readings. Another local racer tuned up one of his quickees with a 8.8 x 8.75 in the mid 19,s and his speeds were in the low 140's. Whats up with this??? The planes did seem slow, so I don't believe it is bad readings from the gun.

It was very humid today, with a temp right around 60 degrees. Not sure where the pressure was, but I believe it was low.

Any ideas? What would you change in this type of weather to speed them up? I would guess raising the head, but curious to what you think.

colesifer3d314

My Feedback: (9)

u know dave, as i remember when we would go fly the giant scale racers we would have days where the unlimiteds would run in the 230mph range and days that they would only get into the 210 range...the weather has alot to do with how ammotor runs...to me thats what i gatherd from what the giant scales use to do...im prolly talking out of my ***** but im just tryin to help.


Cole

Mluvara

My Feedback: (10)

Dave,

I've seen many effects of humidity on props and I'm just now starting to be able to log actual data on some aircraft with it. But, nevertheless, my personal experience has been that in humidity, I need to run a narrower blade as the motor bogs down. Thin, dry air allowed more blade area.

I don't believe though that you would be able to gain much speed in conditions that are not prohibitive to speed. Heck, if everyone is running the same speeds, then it's probably a wash.

Michael

daven

My Feedback: (1)

I agree that it levels the playing field, but if you could lower or raise the head or sleeve and gain some speed back, that would be helpful to know (and a nice advantage).

Whats odd, is I don't see much of a difference when its hot and dry versus hot and humid, but when its cold and humid they really don't seem to go.

I know I'm leaving air pressure out of the equation here, I'd be curious to hear someones opinions on how that effects these things also.

ALbert.S

Must be the density of the air Dave.Better go down in pitch Cold dense air in the winter hot thin air in the summer Well I think you have all the secrets now!!!! Try a 9.5 X 7.5 on those cold days

daven

My Feedback: (1)

Als solution to every engine problem ( the 9.5 x 7.5 NN )

I would agree with you about going down in pitch, but it just seems tough to do when the RPM's are up in the low to mid 19's.

If thats the solution, great. Any other ideas?