Author Topic: Pathfinder 1/2A Size. (Read 2103 times)

Dennis Adamisin · « **on:** September 17, 2009, 02:04:05 PM »

From the Brodak kit. A very good build, excellent die cutting except for some of the plywood. I converted to Taildragger because I thought I might be a simdgen lighter and simpler. Weighs 14.5 oz RTF. Intend to fly it wtih a 6x4 prop to abide by the famous "Renkar rule" and also that keeps it in the spirit of 1/2A. Will fly on .008 x 52' lines, hopefully Saturday!

Power system is still experimental, includes Arrowind 2210 motor, 3Sx1100 pack, 18A Arrowind (simple non-governing) ESC & Will Hubin FM-0c timer. I think I need to turn the 6x4 at about 12,500 to get a usable lap time on .008x52' lines - and I SHOULD have enough battery. We'll see

I will put in the Post your Set-up thread when i get it locked down a little more: RPM & battery usage...

Mike Anderson · « **Reply #1 on:** September 17, 2009, 02:28:44 PM »

The Renkar Rule has been changed to 7" props:

http://stunthanger.com/smf/index.php?topic=14098.0

Just out of curiosity, what is the Kv of your motor?

Leester · « **Reply #2 on:** September 17, 2009, 03:54:42 PM »

As usual looks really good Dennis. Where are these motors from (company) .

Dennis Adamisin · « **Reply #3 on:** September 17, 2009, 05:29:29 PM »

Mike:
The kv is 1560. There is also a 1300 wind available. Frankly THAT midght have been a better choice for a 7" prop!

Leester:
The motor is made by Arrowind, their website is at:

http://www.arrowindhobby.com/

Check out their batteries - they have a fairly broad selection of "C" ratings, pack configurations, and capacities.

Crist Rigotti · « **Reply #4 on:** September 17, 2009, 08:39:00 PM »

Dennis,
That's one good looking "1/2A" Pathfinder. Keep us posted as to how it goes.

Alan Hahn · « **Reply #5 on:** September 18, 2009, 07:25:47 AM »

Quote from: Mike Anderson on September 17, 2009, 02:28:44 PM

The Renkar Rule has been changed to 7" props:

http://stunthanger.com/smf/index.php?topic=14098.0

Just out of curiosity, what is the Kv of your motor?

Yes I too was surprised by the change. Jim R. had mentioned to me that someone wanted to fly with a 7" prop, and I mentioned that that should entail a 10 point penalty, (like flying with an 061 vs a 051 or smaller engine). But somehow the penalty didn't make it into the flier.

I find it disappointing, because I think it is basically true, that 1/2 a engines very rarely (if ever) run props larger than 6".

Oh well, I'm flying a Baby Skyray and a Blackwidow anyway this year!

John Witt · « **Reply #6 on:** September 18, 2009, 09:00:05 AM »

Dennis, that plane is really neat. Excellent colors too. I have been mulling over building a 1/4A plane to fly on 20-25 foot lines in front of my house. I live on a cul de sac that is about 80 ft in diameter. Something like the Pathfinder at about 1/2 your size would be cool, perhaps with some kind of park flyer motor.

I once had a tiny Berkeley L-19 model with a Cox .020. My brother and I would fly it half in the front yard and half in the street. I think we had more fun with that plane than almost any other we ever had. The .020 was a marvelous motor.

John

Archie Adamisin · « **Reply #7 on:** September 18, 2009, 09:39:54 AM »

If the Renkar rule has been changed to 7", that really puts glow 1/2 A's at a disadvantage. I would suggest that they stick with the 6" rule to keep them close to equal even though the ECL power systems still will outdo the glow 1/2A's on virtue of cost, weight, & power.

Can't wait to see how the Baby PF goes. It ought to really scoot. That motor should be able to use the 7 x 4 no problem. Might consider the 7 x 3.5 GWS swept tip prop as it pulls really good.

Archie Adamisin
Muncie, Indiana

jim gilmore · « **Reply #8 on:** September 18, 2009, 10:49:06 AM »

OK, let me get this. You find it dissapointing that a typical 1/2A stunt plane like the pathfinder can be flown on gas with a 6 inch prop. but for electric you need a 7 inch prop to get the same power ?

Dennis Adamisin · « **Reply #9 on:** September 18, 2009, 12:11:08 PM »

Jim:
I don't think that's quite what was meant. The spirit of using a 6" prop on an electric keeps it in the same realm as 1/2A gas. Allowing 7" for electric - that's like using an .10 instead of a .049. The only thing that MIGHT be up for grabs is the battery size - and that is pretty easy to fix.

I will stick with 6" props (at least for starters) in an effort to duplicate the best that a IC 1/2A could do. This set-up should easily turn the 6x4 at 16000 RPM which (I hope!) will be enough. I have some info suggesting it will only have to turn 13,000 or so.

Frankly the 7" prop for electric is almost cheatin...

jim gilmore · « **Reply #10 on:** September 18, 2009, 04:42:00 PM »

I understand that it is an attempt to quantify performance as being equal. It's just that in my opinion if the plane can be flown on gas at a certian weight than using electric and the same weight and speed would seem to be close to the same .
There is a limitation on electric that will often make them apples to oranges in what the limititons are. So stick a 3 blade 6" or cut down 7" prop on it.

Alan Hahn · « **Reply #11 on:** September 18, 2009, 06:13:34 PM »

Jim,
Flying stunt with a 1/2a, while not super difficult, is a challenge. This is primarily due to most of us pulling out the 1/2A stuff a week (or day!) of the contest. These engines are temperamental, sensitive to small amounts of contamination, and make their power at high rpms. At these rpms, the props are pretty inefficient. However prop size is basically the only "universal" denominator of 1/2a these days.

Allowing a much more efficient 7" prop means that electric becomes almost a no-brainer. I think what most of us are concerned about is that 1/2a is fun, and I for one, would hate to see it turn into a turn-key electric only event.

jim gilmore · « **Reply #12 on:** September 18, 2009, 06:45:44 PM »

I do not see running an aircraft that is the same weight and size on gas with a 6 " prop or on electric is different ? The battle between diamond frame bicycle was that recumbents were using reduced frontal area so they banned recumbent cycle from bicycle competition. But The is a question of the same sized airframe and using a power source. I would think that what ever power source that can fly the same sized airframe and with them it would seem to be apples to apples. Sure maybe There is a different complaint ? That 1/2A gas is too difficult as opposed to electric so

That is why I suggested 6" 3 blade or cut down 7" 3 blade. to get a little more from an efficient diameter if you cannot get the rpms in an electric motor.

Alan Hahn · « **Reply #13 on:** September 18, 2009, 06:55:39 PM »

You can always get the rpms, if you need them.

One difference---I believe---is that even without a governor, the electric can hold power better than a 1/2a motor. So with glow you have to fly fast enough to carry speed into the vertical maneuvers. Of course you need to do some of the same with electric, but I think (we will see!) less so.

I have been making some in-flight glow engine rpm measurements that personally I find pretty interesting. Once I get the results in better form, I plan to post them in the engineering forum.

jim gilmore · « **Reply #14 on:** September 19, 2009, 07:59:21 AM »

I hope to see a run down of what this setup costs, and what all I would need if I choose to go electric.

William DeMauro · « **Reply #15 on:** September 19, 2009, 06:11:04 PM »

I saw this plane fly today and was today impressed with it. Watching a 1/2a fly on 50' lines was very impressive. This plane was doing 5.0 second laps(correct me if I'm wrong) with a 6x4 prop. This power setup defiantly was equal too or better than any wet powered 1/2a glow powered system i ever saw. One thing I know for sure it will be a lot more reliable. Due to the limited number of batteries and Dennis having too much fun with it, I didn't get to fly it. Maybe next time I will get that chance.

Archie Adamisin · « **Reply #16 on:** September 21, 2009, 10:16:03 AM »

I can't believe that it flew on 50'. I have a couple of VA's, (2) KK upgraded Cox TD 049's, a Norvel 049 & 061, and a Cyclon 061. I think the only one that could replicate that type of performance is the Cyclon, but it would be screaming!!! I was saving that for a blast around 1/2A combat plane, but after running it once, I had to rethink my sanity & reflexes. LOL
Great job on the Lil PF. Can't wait to fly that one!!

Archie Adamisin

Dennis Adamisin · « **Reply #17 on:** September 21, 2009, 11:30:22 AM »

Flew it one more time after you left. I wanted to get more airspeed so I substituted a 7x5 for the 6x4. Lap time dropped to 4.5, manuvers were EASY. Unfortunately with the bigger prop I am out of battery. I might still try a 6x5.5, but expect I will need a bigger battery in place of the 1100.

The PF is a real good flyer tho, and the CORNERS are sensational!

Alan Hahn · « **Reply #18 on:** September 21, 2009, 12:26:35 PM »

Quote from: Dennis Adamisin on September 21, 2009, 11:30:22 AM

Flew it one more time after you left. I wanted to get more airspeed so I substituted a 7x5 for the 6x4. Lap time dropped to 4.5, manuvers were EASY. Unfortunately with the bigger prop I am out of battery. I might still try a 6x5.5, but expect I will need a bigger battery in place of the 1100.

The PF is a real good flyer tho, and the CORNERS are sensational!

I was talking to Jim R. yesterday at his 1/2a contest, and I think we will get the 6" Renkar rule reinstated. Just to refresh everyone's memory, the rule is for the size of the prop for electric models, not a manhood test.

Dennis Adamisin · « **Reply #19 on:** September 21, 2009, 01:12:51 PM »

Quote from: Alan Hahn on September 21, 2009, 12:26:35 PM

I was talking to Jim R. yesterday at his 1/2a contest, and I think we will get the 6" Renkar rule reinstated. Just to refresh everyone's memory, the rule is for the size of the prop for electric models, not a manhood test.

Hmmm, how can I say this delicately, what is the rule for... .020???

jim gilmore · « **Reply #20 on:** September 22, 2009, 10:17:43 AM »

Just out of curiositry, throwing a wrench into the works here, If i were to used an .049 with adavis desil conversion. I would not be allowed to used a 7x2 or even a 6.25 x4

Alan Hahn · « **Reply #21 on:** September 22, 2009, 10:57:59 AM »

Jim,
You can use whatever prop you want on an IC engine, as long as the engine is a half-a (another Renkar Rule is that 1/2a is 051 and lower. 061's have a 10 point penalty-- (actually it is 051 and smaller get a 10 point bonus).

You shouldn't get to wrapped up in the "Renkar Rule". The only place and time it is used is in the Chicago Suburbs in mid September! Another point is the contest name is "This is only a hobby" 1/2 a contest. Another Renkar rule is that it has to be fun.

As a side note, the 6 inch prop rule was simply derived to set some type of parity between electric motors and 1/2a glow. I took it to be a challenge. Problem is trying to define a relationship between an IC engine and an electric motor. A six inch prop sort of fits the bill, even tho it could be turning at 30k rpm (some Fora's can do that I think).

Otherwise you could be flying the Strega and calling it half a!

Dennis Adamisin · « **Reply #22 on:** September 22, 2009, 11:51:46 AM »

Actually when I first heard of the the 6" prop rule for electric 1/2A it struck me as pure genius.