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  • July 18, 2025, 05:45:51 PM

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11
Open Forum / Re: 2025 Nats Qualification Groups, scores and final reports
« Last post by Rusty on Today at 07:30:38 AM »
Interesting discussion.   

I feel you guys may be the last of the builder's era.  If local clubs are any indication of the future, it is not bright.  I belong to 2 clubs.  (It was 3 clubs, but 1 closed Monday.)  The biggest club is about 150 members.  Out of that, there is maybe 3 builders.   I have pushed people to build, by giving them the kit and parts to make it.  One person, a doctor took the offer and built (with a lot of help) a House of Balsa P51, 60 size.  He converted it to electric.  It took about a year. He was successful and I flew it for him.   He was very, very proud of his accomplishment.  I have given kits to 3 other people and none of those ever started the kit.   The reason is they give is WHY?  Why spend the time doing all that work, when they can buy a plane ready to fly and go fly.   I explain that building and fly are two very different tasks.   Building gives one a deep satisfaction and pride when they fly a plane they made.  If you never built one, you cannot know that.  Convincing people to try it, is nearly impossible.   They make stupid excuses that programming the receiver and transmitter for their new FOAM ARF is more difficult than building.  Bull Hockey!!!   I know programming and it does give satisfaction, but not what you get building.   And, as I explain to them, that very ardent task of programming cheats them out of reallyl learning to fly, because they are programming SAFE receivers that virtually fly the plane for them. 

What does it mean to us?  It means the hobby as we love it,  is dying.  Eventually, you will have to confront people like I describe and their demand to fly ARFs or you won't have many competitors.   

I still think you guys that are here now, should consider, just for the hell of it, changing your rules as Sparky suggests.  That would truly get the most out of you, who are the last of the best.   
12
Open Forum / Re: Team trials location and dates?
« Last post by Doug Moon on Today at 07:14:14 AM »
One day with Tuesday being the rain date.

Mike,
You making that drive?
13
Gettin all AMP'ed up! / Re: Lippo to Li-Ion
« Last post by Ken Culbertson on Today at 06:52:01 AM »
or see Igor about a prop.
Unfortunately it is time to approach the finance committee.

Ken
14
Stunt design / Re: 2 blade and 3 blade prop adv & disadv
« Last post by Will Moore on Today at 06:50:18 AM »
Dennis - I noticed my 3 blade used more energy, motor got warmer during short trials...oversized for the motor I think

Dan, The beer sounds really good......having some and reflecting on the moments  -  good advise, thank you

Kieth, you are in alignment with Igor, for different reasons..and I suspect the same thing..

Igor...appreciate your insight.  Valuable.  Normally I would use a 10" 2 blade prop.  The 3 blade I have would work, I think,
        if I cut it down to  10".., or slightly less. Seems to have a higher pitch than my 10/6 wood prop. Would that be wise? It started 
        out as an 11" 3 blade.  would cutting down to 10" change any of it's dynamics substantially?

Appreciate all of your comments
15
Gettin all AMP'ed up! / Re: Lippo to Li-Ion
« Last post by Igor Burger on Today at 02:33:57 AM »
Folks say you should reduce the low-voltage cutoff in the ESC.  Voltage drops more during a flight with a Li-Ion battery than with a LiPo.

Exactly, that is also reason why the LiIon combo needs MORE voltage head room than compared LiPo. Wheather LiIon can replace the LiPo in particular setup is question of that volatge head room. Motor will need pull hard when pulling nose up, so lower voltage can limit that boost. If there is enough head room it will be covered, if there is not enough, especially on end of the flight, it will loose speed. This problem is magnified by string sensitivity  of active timers. Solution is motor with more KV but it will also need more amperes.

In any case, LiIon 6s battery has end voltage like 5S Lipo battery, so it will always run at lower efficiency, fortunately it has more capacity.
16
Stunt design / Re: 2 blade and 3 blade prop adv & disadv
« Last post by Igor Burger on Today at 02:18:25 AM »
There are 2 reasons for 3 blade props. The first and most important on electric model is they have uniform gyroscopic moment. Our experimets show 2 blade rigid prop (carbon or wood) can damage those subtile bearing really quick. Bearing cannot be large on electric motors, especially not that which is inside the drum. Reason is induced current from rotating magnets in outer ring, so there are typically one large bearing on open side of the motor (out of the magnetic field) and two tiny inside. Imagine those micro balls inside and all is clear. 2 blade props strongly vibrate and it kills bearing quickly. Standard IC engine constructed to withstand vibration have no big problems with it, but still, I used piped LA.46 with 12x3.5 2 blade full carbon prop and it made visible free play in shaft plain bearing after may be 100 flights.

The other reason is smaller precession. Moment of inertia is smaller especially because of mass distributed on shorter blade close to center of rotation, so precession is smaller at the same RPM.

Disadvantage is clear: little lower efficiency. There is always possible to make equivalent 3 blade prop, but result always come to smaller RE number  and therefore little lower efficiency (equivalent 2 blade prop has either wider blade, or larger diameter running at higher velocity - RE is in both cases higher). That efficiency is more visible on props smaller than 12" at less than RPM 10 000. That means 11" props need pitch maximally 5" to be in good efficiency (>10000rpm). 12" is safer. 6" pitch is good only if diameter at least 12" or more (9000rpm).
17
Gettin all AMP'ed up! / Re: Lippo to Li-Ion
« Last post by Howard Rush on Today at 12:09:28 AM »
or see Igor about a prop.
18
Open Forum / Re: Team trials location and dates?
« Last post by Mike Palko on Yesterday at 09:21:30 PM »
Are the TT a one-day event on Monday?  I too may need to revise my calendar

One day with Tuesday being the rain date.
19
Open Forum / Re: 2025 Nats Qualification Groups, scores and final reports
« Last post by SteveMoon on Yesterday at 08:49:09 PM »
What Keith said!
20
Open Forum / Re: 2025 Nats Qualification Groups, scores and final reports
« Last post by Brett Buck on Yesterday at 06:31:15 PM »
I do not think I can answer how judging in those categories was handled.  The best response I can come up with is "Not well!"  Yes, there were issues.


   OK, fair enough. It's pretty obvious where the issues might arise, and your post hit the nail on the head.

     Brett
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