Thorp Air Command - T18.net

I will admit, I could probably hunt through the NLs/archives to find what propeller people have used in the past to get the best cruise speeds out of their 0-290's, but I am confident some knowledgeable folks out there can answer this question right off the top of their head.

What is the best cruise propeller pitch and length and/or manufacturer for an 0-290?

Thanks in advance for the help.
Ryan

I am having Craig Catto from Catto propeller build me a prop for my O-290 GPU. Once I gave him all the specs and mentioned that I wanted as much cruise as possible without sacrificing too much climb, he suggested 70" X 75" (I have the longer landing gear)

Catto props is known for building props for racers! When I was ordering my SABER 4" prop extension, Saber inc. highly recommended Catto.

It is supposed to be finished up in the next couple of weeks. I can post some pics if you wish once it arrives.

I have never heard anyone say they didnt like their Catto prop, so I'm sure you will be pleased. I want the same performance you describe above out of my airplane, so I would be extremely interested in your performance numbers with the Catto prop. If you would rather just email that info, my email is "johnryanallen"at symbol hotmail dot com.. I would enjoy seeing some pictured of it as well.

@Ryan - I will get those performance numbers to you once I get this bird finished. It won't be long now.

I was recently reading through some of John Thorp's old letters and saw that he put ( I believe) a 68" Length with a 82" pitch on his 145 HP O-290 GPU. He was able to get 200mph at 2850 RPM. (I would have to find the letter to confirm those numbers, but i am pretty sure they are correct). Thorp was not afraid to push the O-290 at high RPMs. It also seems that he was not concerned with a serious cruise prop as the climb in a t18 has never been something to worry about. It will climb!

I don't know what John's empty weight was on his T18, but I am pretty sure he built that as light as it could possibly be made (He was a utilitarian at heart). This is just proof the the O-290 is a fabulous engine for the t18 and you can still get those fast numbers with the right prop.

Prop is right but John Thorps airplane had a 180hp 0-360, 82" pitch on an 0290 would not work out so well.

_________________
Lee Walton
Houston, TX
N51863,N118LW
KEFD

whoops, my bad. I guess that's what happens when you read late at night. the details get all mixed up. thanks for setting the record straight Lee.

@Ryan - I attached a PDF of the archive t18 letters (Hope I'm not breaking some kind of rule by doing this...I don't think so). Anyways, in the last part of this archive you will find all kinds of submissions of t18ers using the O-290 and what type of prop they were using and the numbers that they were getting. This is a really valuable resource and should give you an idea as to what range (length & pitch) of props can be used. It looks like the most pitch used on a O-290 for cruise performance in this archive is 76". Hope this helps.

You can open the file and do a word search ... such as "Pitch" and you should be able to find all the references really quick rather than skimming through the 400 pages.

good info Dean....I had to chuckle at the part in the NL's that says asking someone about their choice of prop is like asking who is the prettiest girl.

Never mind if she's pretty...does she have money !

RB

I recall an old man once told me, "You can marry a rich girl as easy as you can marry a poor one!".....I sure do wish I would have listened to that man!

Running a 68 x 73 prop on a 0-290g Thorp since 1978. At 2350 rpm we get a cruise speed around 155 to 160 mph. It's an M76. It was rep itched many years ago. Climbs at 1,000 fpm fully loaded.

Brent Schultz
N6CM
KAJO

Old thread dig.

What takeoff distances are people getting with cruise props? I have a 68x68 demuth and it seems to take half of a 3400ft runway to get airborne. I'd like more top speed (140mph at 2500) although that distance seems a little long on takeoff for my taste. Not much runway left to shut down if there is an issue on takeoff.