Thorp Air Command - T18.net

Is anyone using a 3 blade prop? If so who is the manufacture, what kind of performance numbers are you getting, why a 3 blade, gnd clearance?

Pretty much explains some advantages of 3- vs 2-bladed props here:
http://hartzellprop.com/faq/technical-questions/

Spanky

I have a 3 blade CATTO on my RV-8. It's nice and smooth, but sometimes it gets a slight vibration as if one blade has flexed a bit in cold weather at about 6000 ft. It comes and goes, sometimes I don't experience it for more than a year...Otherwise, it's great. The static 2050 RPM is a bit low. The same aircraft had a 2 blade CATTO when it was powered by a turbocharged Mazda rotary engine. It was great too.
My T-18 has an 'olde' style Ted Hendrickson 2 blade wood prop, 68x68 (O-290G), it's great. Static RPM is above 2300, 2660 MAX RPM @ 6000 ft. Ted has retired, but I think the modern wood prop maker's 2 blade offerings would be fine.
My future choice would be a 2 blade WhirlWind ground adjustable carbon fiber blade prop. In fact, 2 T-18s in my area have them. Additionally, I just ordered W-530 blades from WhirlWind for my Yak-55.
The Sensenich version is more expensive, but has a nice pitch setting system that uses pin gauges provided with the prop.
I think the 3 blade prop looks cool and the 3 blade sound is nice, but I also think the 2 blade prop is more efficient in cruise and possibly top speed. The 3 blade is good for initial thrust & climb if the pitch and blade area are not too great, which they are in the case of my RV-8.

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Scott Emery
EAA Chapter 326
T-18 N18TE

Thanks Scott, what dia Whirlwind would you get. Sensenich prop is 72" not sure of the ground clearance for those not so good wheel landings. I had a 68"X68" wranikie prop for my 150 hp which was good but now I have 30 more hp and new another prop.

I would ask Bruce Finney, he has a T18 convertible (?) with an O-290g and a Whirlwind. I think Whirlwind has 2 different hub diameters and different blade length combinations that can take you from 68" up to more than you want.
I think short gear T-18s should maybe stay with a 68" prop.
I have another T-18 friend with a Whirlwind on a 160 HP O-320. He does not post, but he does like his Whirlwind.
My wife has an RV-4 with the Sensenich carbon fiber ground adjustable, it was ordered at 70".
My CATTO 3 blade easy absorbs 180 HP and is 68" diameter.
I think large diameter gives better acceleration, but a slightly reduced diameter gives more top speed.
It's a moot point in a T-18, they sit low and need a short prop?

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Scott Emery
EAA Chapter 326
T-18 N18TE

It all depends, which gear do you have, short or long? If the short gear stick with a 68" dia. I measured my clearance with the short gear in the level attitude to be 6". The long gear legs are 4" longer, I now have the long gear on my plane and have about 10" of clearance with a 68" Whirlwind prop.

Whirlwind has two different hubs and two different length blades so you can get a 68", 70" or 72" dia. mixing and matching hub and blade length, i.e. small hub and short blade = 68", large hub and long blade = 72", any other comb = 70". This prop was originally designed for the RV series of 2 place airplanes so it works just fine on the Thorp.

What I like about the Whirlwind is that it has an airfoil shape all the way to the spinner so it is more efficient also being adjustable you can tweek it for climb or cruise or in between what ever your preference. With the Whirlwind and new pressure recovery wheel pants, from Team Rocket, I have gained 5 to 10 mph cruise speed over the wood prop that I had before.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA