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Old Apr 10, 2009, 11:13 PM
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Twistaholic AMA 134406
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USA, TX, Teague
Joined Jul 2007
6,443 Posts
Kickin it off...

Engine talk....

TT40 Engines
46 AX ...the standard. Run a 12.25x3.75 on this combo for max performance. 12x4 is ok too.
For a 4 stroke Hot Rod....Os 70 to a Saito 82 with a 14x4, 13x4
OS 61FX for 2 stroke max performance with a 13x4
Waldo's 61 ...."OS 61FX 13x4 and 13x10 for a hoot"
Plow's 61......."I like the OS 61FX/MAS 12 X 7 S2 Series (Scimitar) prop."

TT60 Engines
Ya know, this is a 60 but I dont know anybody runnin a 60
4s choice...OS 91 FS with a 14x4, 15x4
2s choice...OS 91 FX with a 14x4, 14x6
Crazies choice.... up to 125 4 strokes with a 16x4

All of these prop recommendations (of mine) are based on WIDE blades. Run a APC "W" blade or a MAS K-Series prop. Stay with a low pitch. This plane is not a speed demon and I have heard stories of them breaking in the air. High speed flutter is a major possibility also so keep your speed as such.

This is just some basic prop philosophy (IE:just MHO)

Props can be compared to the gears in a car for easier understanding.

Some props are built for speed and some props are built for power.

4 strokes and 3D (hi-alpha) flying have brought on the advent of basically "wider" available blades. These have a wider profile from the front (leading edge) to the rear (trailing edge)

Master Airscrew (MAS) are called "K-Series" props
APC uses the term "W" and will sometimes use the word "Wide"
Generics usually use the term "Wide"

The diameter of your prop is applicable to YOUR aiframe, landing gear, engine specs, etc. but the performance you want OUT OF the prop to make the airframe do what you want is a relationship to "pitch".

Think of it this way....

1st gear......a #4 pitch of the "WIDE" variety.
2nd gear.....a standard #4 to #6 pitch prop
3rd gear......a #6 to #8 pitch pitch prop
4th gear..... a #8 to #10 pitch prop
5th gear (overdrive) a #12 pitch prop

Things to keep in mind. 1st gear doesnt have much speed, but you get there quick! Remeber you ALSO SLOW DOWN JUST AS QUICK! The massive blade profile on these type props also have massive air CATCHING abilities when slowing. This same profile also harnesses the massive torque provided by our 4-strokes in order to hang your plane motionless in the air.

A torque monster motor (todays 4-strokes) really shines with these fat blade props and 3D flying. You want immediate power and power to do massive tricks (like hanging on the prop and flying on the prop in hi-alpha, to pull out of a spin, etc) so it becomes a match made in heaven. You dont particularly want the speed and you dont get it with this high torque low RPM set up.

2nd gear is a compromise....and most the time a happy one. Little speed and a little power. Longer roll out with a #6.

.....usually moving to high RPM 2 strokes at this point...

3rd gear is getting out of our catagory (of TwisTing) and more into sport. Moderate speed.

4th gear gets us to the Warbird catagory. 8's and 10's. Looong rollout. High speed. As is true with the 4Wide on braking, the opposite is obviously true here. With an 8, 10, 12 your prop braking will be virtually nil.

5th gear overdrive....speaks for itself

Waynes Prop Load Factor (PLF) chart is invaluble, as are the other tips in his post...FOUND HERE

Structural changes
Reinforce your rear fuse areas shown n the piccy's
Also reinforce your landing gear block with some tri stock or something.
Go with a sullivan tail wheel from the get go, or eventually the tailwheel will snag and tear your rudder off.
Battery mounted behind wing saddle (maybe not at first )
Below are some pics of a hatch that you create right behind the wing. This allows you easy access to the area you need to beef up. This also allows access to where your battery will (eventually) be. It becomes nessessary to mount the battery in this area in order to achieve a perfect balance for engines in the 5-60 2c range and for 4c engines in the 70-80 range.
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Last edited by Dad_Roman; Apr 17, 2011 at 01:45 PM.
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