what size prop for my twist 3d
04-12-2005, 12:37 AM
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what size prop for my twist 3d
i have a twist 3d with a OS Max .46 fx engine on it. What size prop should i try on this plane? Im running a 11x5 prop now and it does alright . Thanks for the suggestions.
04-12-2005, 06:33 AM
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RE: what size prop for my twist 3d
The recommended prop-size should be in your manual.
Anyway, A Twist 3D should not go very fast, and a prop with lower pitch and higher diameter, as the one you have, should match good for your plane.
If you plan of experiencing, you can calculate the loadfactor like this: Diameter X Diameter X Pitch.
Your Prop give loadfactor 605. If you change it to a 10x6, it gives loadfactor 600 - almost the same.
High Picth gives better pull - high diameter gives higher maximum speed.
Physicians could probably write pages - more accurate than me
Pal
Anyway, A Twist 3D should not go very fast, and a prop with lower pitch and higher diameter, as the one you have, should match good for your plane.
If you plan of experiencing, you can calculate the loadfactor like this: Diameter X Diameter X Pitch.
Your Prop give loadfactor 605. If you change it to a 10x6, it gives loadfactor 600 - almost the same.
High Picth gives better pull - high diameter gives higher maximum speed.
Physicians could probably write pages - more accurate than me
Pal
04-12-2005, 08:05 AM
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RE: what size prop for my twist 3d
Rule of thumb: Higher pitch smaller diameter = Speed, Low pitch large diameter = power. 3D guys like the large diameter props and low pitch for maximum power and prop wash. Go to a W prop and increase the volume of air thrown past your control surfaces.
04-12-2005, 08:07 AM
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RE: what size prop for my twist 3d
a W would be nice....I use a 15 x 4W on my .91 four stroke and a 16 x 4W on my Saito 100, but I never see them smaller than the 14 x 4W but if you can find a 12 x 4W that would be great....
a buddy of mine runs a 13 x 4 on his OS .46 but I think that is over propping it just a tiny bit, but it does fly very well on a UCanDo....
a buddy of mine runs a 13 x 4 on his OS .46 but I think that is over propping it just a tiny bit, but it does fly very well on a UCanDo....
04-12-2005, 08:16 AM
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RE: what size prop for my twist 3d
If you use the formula calculating load-factor, a 13x4 gives a factor of 676, which is 12% more than the 11x5. This probably give less RPM, and decreased max power.
A rev-counter should be the best solution to determine the best prop-size. If you reach, but dont exceed, the recommended max RPM, then you have the optimal prop size.
Anyone knows of any (cheap) gadget to measure RPM on these engines?
Pal
A rev-counter should be the best solution to determine the best prop-size. If you reach, but dont exceed, the recommended max RPM, then you have the optimal prop size.
Anyone knows of any (cheap) gadget to measure RPM on these engines?
Pal
04-12-2005, 10:04 AM
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RE: what size prop for my twist 3d
Not bashing you theroys but whats on paper cannot be acuratly applied to real life IMO. Prop loads in tables look good but are rarly right on. Air density, humidity, wind, and Altitude play multiple roles in all calulations. In some instantces a YS .63 will run better on a 14x4W than a 13 x4w and tach the same, the difference is altitude among other things where the plane resides. I can get a 14X6 to tach equal to a 13X4w on the same plane and engine. The difference is power vs speed. A digitial tachometer is a must when trying to get optimal rpms out of you props and deciding on which one to go with. Also spool time is greatly affected when the diameter of the prop goes up and the pitch goes down or as the pitch goes up and the dia goes down. Its a delicate balance but one you will have to pinpoint as your favorite when you get close to optimal rpms. I had to play with 3 differnt props before I settled on my favorite for all out 3D.
04-12-2005, 04:46 PM
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RE: what size prop for my twist 3d
I suggest you buy a 12x4 apc and a 12 1/4x3 3/4 apc prop - fly it with each one and use the one you like best and keep the other as a spare.
04-12-2005, 05:07 PM
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RE: what size prop for my twist 3d
It depends on what you want to do. If you want thrust for 3D an APC 12.25x3.75 or an APC 11x3 will produce the max thrust. The larger prop may not have enough ground clearance. The 11x3 will run close to the redline, rpm wise, but I ran one for a couple of years will no ill effects on the .46fx.
