Best prop for YS120 for 3D
11-18-2002, 05:47 AM
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Best prop for YS120 for 3D
I just finished an Aeroworks 80" profile Extra. I have a used YS120 on it and was very disappointed in the performance. I tried a 15 x 10 and a 14.4 x 12. Both turned about 9200 rpm's. The first would barely hold a hover and the second wouldn't even come close. It came with a tuned pipe from a 25 or so 2 stroke. I am going to try using a tuned pipe off a 60 size 2 stroke to see if there is to much restriction with the small pipe. Do you think a different prop would work or do I need a bigger motor. I don't have a good scale but will try to get an accurate weight.
11-18-2002, 06:00 AM
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Best prop for YS120 for 3D
I don't have a YS 120, but I'm flying a YS91 on a 7.5 pound plane. It hovers at half throttle, and while it doesn't leap out of the hover it does climb out with authority at full throttle.
It sounds like you should go to a larger diameter prop with less pitch. I run a 16x6 on my 91, I'd bet that an 18x6 would be the ticket for your 120.
David
It sounds like you should go to a larger diameter prop with less pitch. I run a 16x6 on my 91, I'd bet that an 18x6 would be the ticket for your 120.
David
11-18-2002, 02:17 PM
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Best prop for YS120 for 3D
On aerobatic sport planes I usually use an APC 16 x 8 prop on a YS 120. I agree with David, try an 18 x 6 or maybe a 17 x 6 APC for 3D.
Jim
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12-02-2002, 02:14 AM
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Best prop for YS120 for 3D
I finally got some time off to fly and wow! I am using a master airscrew 17x5 (it was free) and can hover at 1/2 throttle with plenty of zip to pull out. I'm going to buy a APC or wood 17x6 and think this should help even more. Thanks for all the help guys. I finally have an airplane to learn to torque roll with.
Phil
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12-03-2002, 03:55 AM
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Best prop for YS120 for 3D
I'm sorry, I took my spinner off and it wasn't a 17x5 at was a 16x6 and yes a Master Airscrew. It looks like an old prop. I'm going to try to find a 17x6. I have 3 18x6 APC props but think they are too much. I might have to cut one down.
12-03-2002, 04:24 AM
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Don't ruin that prop
I have tried several times to get more performance (vertical pull) by cutting the tips off to reduce prop diameter. I have done extensive RPM and Static thrust measurements before and after the modification. In each case the results have been the same. The cut-down prop on the same engine with the same setup will turn more RPM, but the static thrust is reduced. I don't have an explanation for this. In fact, most people will offer explanations that will support the opposite results. But I can attest to this being my "real world" findings each and every time.
12-03-2002, 04:33 AM
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Best prop for YS120 for 3D
Thanks Robert. You have been a great help. The first weekend I flew my 80" I was greatly dissapointed. Thanks to you ond others it will probably turn out to be an alltime favorite. I just recently modified a Morris Hobby Balsanova by adding larger ailerons and with a os46fx with a performance specialties muffler is looking like another good 3D plane. I'll have to add more elevator. Am looking to make the horizontal stab smaller instead of just adding elevator. By the way how do you measure static thrust?
Phil.
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12-03-2002, 06:52 AM
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Measuring Thrust
I have my engine test stand mounted on a drawer slide, and have the drawer movement limited to 2 inches back and forth. To the back of the drawer I attach a small nylon chord that runs over a ball bearing mounted pulley and drops 90 degrees toward the ground. I hang a plastic bucket on the end of the string. Start the engine and bring it to full power, and the drawer slides to the front stop. Add weight to the bucket until the drawer just starts to move rearward. Shut the engine down, remove and weigh the bucket with contents. Now you know exactly how much static thrust your engine / Prop combo has. The rolling resistance of the drawer is 2 oz, which I add to final weight. You can easily compare prop performance by seeing if you have to add a little or take out a little from the bucket for a different prop.
12-03-2002, 06:56 AM
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Re: Don't ruin that prop
Originally posted by Aerosplat
I have tried several times to get more performance (vertical pull) by cutting the tips off to reduce prop diameter. I have done extensive RPM and Static thrust measurements before and after the modification. In each case the results have been the same. The cut-down prop on the same engine with the same setup will turn more RPM, but the static thrust is reduced. I don't have an explanation for this. In fact, most people will offer explanations that will support the opposite results. But I can attest to this being my "real world" findings each and every time.
I have tried several times to get more performance (vertical pull) by cutting the tips off to reduce prop diameter. I have done extensive RPM and Static thrust measurements before and after the modification. In each case the results have been the same. The cut-down prop on the same engine with the same setup will turn more RPM, but the static thrust is reduced. I don't have an explanation for this. In fact, most people will offer explanations that will support the opposite results. But I can attest to this being my "real world" findings each and every time.
What you are experiencing after cutting tips off is quite normal. Cutting off tips is like cutting off the best part of the prop. Also reducing prop disk area will reduce thrust. Also new tips usually end up being thicker, generating unnecessary drag. What you should actually do is look for thinner prop with less drag possibly with bigger diameter but spinning at the same RPM like your old prop before you cut the tips off. And by the way - that's my goal - to design one like that.
George
propellers.us
12-03-2002, 07:47 AM
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Quit that already
Yes, I came to the same conclusion after testing several props and getting the same results every time. I have not cut a prop in over two years. Now, I just look for one in the diameter and pitch I think I need. If I can't find it, I settle for the next best size.
The Thrust measuring setup I have works great. I use a digital postal scale to weigh the bucket. Another nice feature is, you can determine what throttle setting will lift a known weight. Say your plane full of fuel weighs 10 lbs. Just put 10 lbs in the bucket and increase throttle until the drawer starts to move froward. Now check RPM and throttle setting. This is the setting at which your plane will hover, and you can see how much reserve you have to get out of trouble.
The Thrust measuring setup I have works great. I use a digital postal scale to weigh the bucket. Another nice feature is, you can determine what throttle setting will lift a known weight. Say your plane full of fuel weighs 10 lbs. Just put 10 lbs in the bucket and increase throttle until the drawer starts to move froward. Now check RPM and throttle setting. This is the setting at which your plane will hover, and you can see how much reserve you have to get out of trouble.
05-30-2003, 01:13 PM
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Re: Best prop for YS120 for 3D
Originally posted by bstfrnd2bstfrnd
I just finished an Aeroworks 80" profile Extra. I have a used YS120 on it and was very disappointed in the performance. I tried a 15 x 10 and a 14.4 x 12. Both turned about 9200 rpm's. The first would barely hold a hover and the second wouldn't even come close. It came with a tuned pipe from a 25 or so 2 stroke. I am going to try using a tuned pipe off a 60 size 2 stroke to see if there is to much restriction with the small pipe. Do you think a different prop would work or do I need a bigger motor. I don't have a good scale but will try to get an accurate weight.
I just finished an Aeroworks 80" profile Extra. I have a used YS120 on it and was very disappointed in the performance. I tried a 15 x 10 and a 14.4 x 12. Both turned about 9200 rpm's. The first would barely hold a hover and the second wouldn't even come close. It came with a tuned pipe from a 25 or so 2 stroke. I am going to try using a tuned pipe off a 60 size 2 stroke to see if there is to much restriction with the small pipe. Do you think a different prop would work or do I need a bigger motor. I don't have a good scale but will try to get an accurate weight.
06-15-2003, 01:42 PM
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The airplane is gone
Thanks for all the replies. Long story. I was flying at the club and when others are flying I try not to hover right in front of flight line. So, I went about 300 yards out and 300 yards up and was practicing torque rolls. A friend of mine (new pilot) flying his baby, a 1/4 scale extra, flew right through my tail leaving a very small piece of the vertical stab. It turn straight down. All I could do is chop throttle. Totaled. Since then I installed the engine on a 1/4 scale Pitts and fly a 15x10. Not great vertical but flys very realistic.
