Not dumb questions
05-29-2006 | 09:00 AM
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From: Charleston, SC
Not dumb questions
I have a couple question that I know someone can answer.
1. If I charge my tx and rx batteries today and can't fly but can 4-5 days later, will it be safe to fly without putting them on the charger?
2. I have an Avistar Select with OS 40 LA and it seem to take forever to get it off the ground. Running the 10x6 that came with it. Would performanace improve with a 11x5 or 6 prop or will I have to buy a larger engine for it.
Thanks for any and all replys,
Old Man Jim
1. If I charge my tx and rx batteries today and can't fly but can 4-5 days later, will it be safe to fly without putting them on the charger?
2. I have an Avistar Select with OS 40 LA and it seem to take forever to get it off the ground. Running the 10x6 that came with it. Would performanace improve with a 11x5 or 6 prop or will I have to buy a larger engine for it.
Thanks for any and all replys,
Old Man Jim
05-29-2006 | 09:19 AM
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RE: Not dumb questions
Assuming you are using the batteries that came with the radio, which are usually nicads, they should still have most of their charge 4 or 5 days later. A voltmeter with a load, such as this one, http://www.towerhobbies.com/products/towp1181.html , is helpful for confirming that the battery is ok. And if you're in doubt about the charge, put it on the charger for an hour or so to top it off.
Moving on to props, an 11x5 should give you better takeoff acceleration than a 10x6. However, it's only going to help a bit. The OS LA engines are good basic engines, but they are not power houses. If you want your Avistar to takeoff and climb significantly faster, you may want to eventually upgrade to a .45 size ball bearing engine. However, try the prop change first and see what you think.
Moving on to props, an 11x5 should give you better takeoff acceleration than a 10x6. However, it's only going to help a bit. The OS LA engines are good basic engines, but they are not power houses. If you want your Avistar to takeoff and climb significantly faster, you may want to eventually upgrade to a .45 size ball bearing engine. However, try the prop change first and see what you think.
05-29-2006 | 09:32 AM
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RE: Not dumb questions
Thanks Chuck. I have .46FX in Nexstar that im not flying at at the moment. If prop change don't work i will swap out. It looks like the 46 will fint same mount. However I know it is heavier so will have to add weight to tail I guess.
Thanks again.
Old Man Jim
Thanks again.
Old Man Jim
05-29-2006 | 09:32 AM
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RE: Not dumb questions
If I were going to switch to an 11 inch prop it would be 11x4; possibly 11x5. Using a free program called ThrustHP (do a Google search if you want to download it) it appears you'd gain about 2 pounds of static thrust at 12000 rpm by going up in diameter. I have read on RCU that the program is pretty optimistic about the numbers but it should at least be ok for comparison.
For 10x6 vs 11x4 @ 12000 the calculated numbers were 4.32 and 6.32 pounds. Even if the real numbers are more like 3.5 and 5.5 you still have an idea of the difference you might see.
Ideally you should check the rpm with the 10x6 and with the other props you try and plug in you actual numbers.
For 10x6 vs 11x4 @ 12000 the calculated numbers were 4.32 and 6.32 pounds. Even if the real numbers are more like 3.5 and 5.5 you still have an idea of the difference you might see.
Ideally you should check the rpm with the 10x6 and with the other props you try and plug in you actual numbers.
05-29-2006 | 11:26 AM
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RE: Not dumb questions
ORIGINAL: old n slow
I have a couple question that I know someone can answer.
1. If I charge my tx and rx batteries today and can't fly but can 4-5 days later, will it be safe to fly without putting them on the charger?
>If it was my plane, I would recharge them 1st. Batteries will lose
>power just sitting. The amount a battery will lose will depend on
>many different things, but for a ball park you can ESTIMATE about
>.1 (point 1 ) -> .2 (point 2 ) volts per day.
2. I have an Avistar Select with OS 40 LA and it seem to take forever to get it off the ground. Running the 10x6 that came with it. Would performanace improve with a 11x5 or 6 prop or will I have to buy a larger engine for it.
>The LA series engines are not powerhouses. What I suggest
>to people is to run a 10" prop on a 40 engine and an 11" prop
>on a 46 for general sport flying. I feel an 11x5 or 11x6 tends
>to load most 40 engines, while a 10" prop does not allow a 46
>to really perform. As with anything there will be exceptions.
>
>As for your question about the engine, I would suggest getting
>a ball bearing 46. It will provide noticeably better performance
>and if you are worried about flying too fast, that is why the
>throttle is there. Some USER FRIENDLY engines I can
>recommend from personal experience are:
>OS 46AX, Thunder Tiger Pro 46 and the Evolution 46NT. By
>user friendly, I mean that 99%+ are going to run great right
>out of the box, minimal break in is required before being able
>to fly them and very little (if any ) "fiddeling" is needed to keep
>them running great.
Thanks for any and all replys,
Old Man Jim
I have a couple question that I know someone can answer.
1. If I charge my tx and rx batteries today and can't fly but can 4-5 days later, will it be safe to fly without putting them on the charger?
>If it was my plane, I would recharge them 1st. Batteries will lose
>power just sitting. The amount a battery will lose will depend on
>many different things, but for a ball park you can ESTIMATE about
>.1 (point 1 ) -> .2 (point 2 ) volts per day.
2. I have an Avistar Select with OS 40 LA and it seem to take forever to get it off the ground. Running the 10x6 that came with it. Would performanace improve with a 11x5 or 6 prop or will I have to buy a larger engine for it.
>The LA series engines are not powerhouses. What I suggest
>to people is to run a 10" prop on a 40 engine and an 11" prop
>on a 46 for general sport flying. I feel an 11x5 or 11x6 tends
>to load most 40 engines, while a 10" prop does not allow a 46
>to really perform. As with anything there will be exceptions.
>
>As for your question about the engine, I would suggest getting
>a ball bearing 46. It will provide noticeably better performance
>and if you are worried about flying too fast, that is why the
>throttle is there. Some USER FRIENDLY engines I can
>recommend from personal experience are:
>OS 46AX, Thunder Tiger Pro 46 and the Evolution 46NT. By
>user friendly, I mean that 99%+ are going to run great right
>out of the box, minimal break in is required before being able
>to fly them and very little (if any ) "fiddeling" is needed to keep
>them running great.
Thanks for any and all replys,
Old Man Jim
05-29-2006 | 12:12 PM
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From: Marana,
AZ
RE: Not dumb questions
I woudn't trust the batteries after a week, personally, I would cycle them - or at least put a good slow charge on them before flying.
As far as the engine/prop issue.... try an APC 10x6 or 10x7 prop before anything else. Not sure what came with it, but I've noticed that there's some difference in performance between props (ie: master airscrew vs. APC). Within certain limits - more pitch&same diameter=more speed, more diameter&same pitch=more thrust. Play around with different props to see what you like. They're cheap enough to experiment with. [8D]
As far as the engine/prop issue.... try an APC 10x6 or 10x7 prop before anything else. Not sure what came with it, but I've noticed that there's some difference in performance between props (ie: master airscrew vs. APC). Within certain limits - more pitch&same diameter=more speed, more diameter&same pitch=more thrust. Play around with different props to see what you like. They're cheap enough to experiment with. [8D]
05-29-2006 | 01:43 PM
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From: Sarnia, ON, CANADA
RE: Not dumb questions
Before I comment on the choice of engines and props - I would like to know how much the AC weighs...[
]
It is possible (mayby) that you have made this bird a tad too heavy, or are you taking off from a grass strip that needs to be cut..., is the engine tuned properly - what is it's top end?
There are lots of reasons for a slow take off - Can we have some more details?
]It is possible (mayby) that you have made this bird a tad too heavy, or are you taking off from a grass strip that needs to be cut..., is the engine tuned properly - what is it's top end?
There are lots of reasons for a slow take off - Can we have some more details?
05-29-2006 | 02:04 PM
#10
RE: Not dumb questions
Hi!
Go with a 11x5 or 11x6 APC. I have used both of these props on numerous trainers with the OS LA.40 -.46,and and these props are what you should use. The OS LA .40 is also a much better novice engine than the more powerful OS .46 FX or AX ball bearing engine as it provides calm steady power at lower rews ...and that is what newcomer needs...not explosive power the way a .40-.46 ball bearinged engine deliver. Here many newcomers make a misstake and think a .46 engine better...It's not!
And forget about the argument that you can always throtte down ...it's isn't so easy when you are a novice...You need steady, reliable power delivered calmly, not power delivered in an explosive way in a bucket!
Regards!
Jan K
Sweden
Go with a 11x5 or 11x6 APC. I have used both of these props on numerous trainers with the OS LA.40 -.46,and and these props are what you should use. The OS LA .40 is also a much better novice engine than the more powerful OS .46 FX or AX ball bearing engine as it provides calm steady power at lower rews ...and that is what newcomer needs...not explosive power the way a .40-.46 ball bearinged engine deliver. Here many newcomers make a misstake and think a .46 engine better...It's not!
And forget about the argument that you can always throtte down ...it's isn't so easy when you are a novice...You need steady, reliable power delivered calmly, not power delivered in an explosive way in a bucket!
Regards!
Jan K
Sweden
05-29-2006 | 04:11 PM
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From: South West Rocks N.S.W., AUSTRALIA
RE: Not dumb questions
Hi old n slow,
I think that describes me too[]. If you remove the baffle from the muffler you will find the 40LA produces more than adequate power with a 10x6 the change in db is v small. I believe an 11xanything will bog the motor down.
Cheers,
Colin
I think that describes me too[
]. If you remove the baffle from the muffler you will find the 40LA produces more than adequate power with a 10x6 the change in db is v small. I believe an 11xanything will bog the motor down.Cheers,
Colin
05-30-2006 | 04:44 PM
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From: San José, Costa Rica
RE: Not dumb questions
I have had three os 40 LA and I lke the little buggers (I also have irvine's 53' adn 72's and a os 50 so I do like others as well) are uncimplicated and albeit not as powerfull... just remember ti back off two or three click from max rpm's whe tuning and they won't overheat
For this size engine I liek to use master airscrew SCIMITAR style props, the give you a better performance without the added weight and stiffness of APC's so if you're willing to try prop changes first try the Scimitar you'll like them
For this size engine I liek to use master airscrew SCIMITAR style props, the give you a better performance without the added weight and stiffness of APC's so if you're willing to try prop changes first try the Scimitar you'll like them
05-30-2006 | 05:00 PM
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From: Charleston, SC
RE: Not dumb questions
Hung a 11x5 on it and it was off the ground in about 30 ft and I did lean it out slightly after the first flight. Ran 3 tanks of fuel thru it this morning. Overall performance seemed to improve a little also. But if it goes bonk i still have the 46Fx on standby.
Thanks to all who answered. These forums here are fantastic.
Jim
Thanks to all who answered. These forums here are fantastic.
Jim
