What is the conversion method for determining the proper three bladed prop for a TT 46 Pro that is now turning a 10-7 two bladed prop?

Thanks

You want to drop at least one inch in diameter and/or pitch. So a 9 X 7 or a 10 X 6 should work okay.
Dennis-

Go down 1. Either go down 1" in diameter or 1" in pitch. A good standard propfor a 46 Pro engine is a 11-6 two blade prop so to go to a 3 blade prop an 10-6 prop or a 10-5 would be a good replacement. Having said that 3 blade props turning at the speeds of our RC engines are not as efficient as 2 blade props. The main reason to go a 3 blade prop is if you need a bit more ground clearance. [8D]

Close, but not quite right. Go down 1" in dia for the same pitch, or down 2" in pitch for the same diameter. A 10-7 2b equates to either a 10-5 3b, or a 9-7 3b

MAS recommends to go down one inch in diameter, and go up one inch in pitch--just what they recommend on the back of their 3 blade prop packages

Fastsky -- could you be misreading that? To me it doesn't make sense. Are you saying that MAS recommends decreasing diameter while increasing pitch? That would be a 9-8 3b to replace a 10-7 2b.

Well, I'm not fastsky, but I assume you're talking to me. Yes, that is what was on the back of the package that my last three blader was in. I had a 12 X 6 2b on it, and ended up going with the 11X7 because of the chart on the prop packaging. It was counter-intuitive to everything I'd always heard, but it seems to work just fine. My .56 saito seems to run at the same rpm's with the 11 X 7 3 b as it did with the 12 X 6 2b. Go figure.....

Sorry 2slow -- I'm getting a bit slow myself. That MAS thing is very strange. Who knows, maybe prop technology has made another jump of sorts.

The 1" up/down thing is really only close when we are starting with 2B props in the 10x6 range. I suggest downloading a prop calculator such as Thrusthp, which is free. Just search google for "Thrusthp." The program is not perfect and makes some assumptions, but overall I've found it very useful, and you can't beat free. With the program, you can compare props, see the engine load, required HP, static thrust and aprox max speed.

I have tried the Thrusthp. Its great when you can put on different props on the same engine and then record the rpms that you read with a tach. Then plug the data into the calculator to see which prop will give you more speed/power. Without the rpm numbers you really can't find out very much. My opinion.

Hey there, I downloaded the program but I don't really understand how to use it. Are you trying to match numbers is all. If that is the case then my Saito 100 that should run a 15x6 2 blade would need a 13x7 three blade. Correct yes/no?

The program is based on mathematical equations that uses the rpm, pitch of the prop, and prop type to work out the hp and thrust. Without running the engine and obtaining rpm numbers to plug into the program the program isn't very useful. You can just pick a number and change props to see which will give you more thrust at the rpm. Trouble is the engine rpm can change by 2000 rpm by simply changing from an APC prop to a Master Airscrew so for the formula to be useful, tach readings are a must![8D]

14/7 or 8

A 10-6 3B is good for the TT .46 Pro, or an 11-4 3B also works well.

Ditto on what fastsky posted. I probably should have been more clear. You must take a baseline measurement on your engine/prop. For example, your engine can turn a 10x6 APC 2 blade at 10K RPM. Punch this into Case 1. Thrust HP claims a arbitrary load of 60,000 and HP of 0.429. To find another prop that will load the engine similar at that RPM, on Case 2, put in 10K RPM and then fiddle with diameter, pitch and # of blades until the load figure closely matches Case 1. The program isn't perfect as there are too many varibles it doesn't take into account, such as engine power curves. For example, a 6x6 APC 2B at 20,000 RPM shows the same HP as a 10x6 2B at 10,000 RPM. Odds are, a TT46 will never get anywhere close to 20K RPM, so use some common sense when using the program and it will get you in the ballpark. Cheers.