Author Topic: 1/2a Pathfinder Electric (Read 4335 times)

Andrew Borgogna · « **on:** February 10, 2011, 06:17:21 PM »

Well the new electric 1/2a Pathfinder is coming together. The assembly is just about finished, and I am getting excited about flying it. I would also like to say I did the framing but that would not be true. My good friend Larry Renger purchased the plane with the framing complete. He then gave it to me when I mentioned it would make a great electric project. Anyway I covered it and made the modifications to mount the electric motor. Today I hinged all the control surfaces and soon I will be painting it.

This will be the test plane for the new KR hardware that is on the way. I will let you all know how things work out.
Andy

Dennis Adamisin · « **Reply #1 on:** February 10, 2011, 06:34:15 PM »

The PF is a great design - you're gonna love it!

Larry Renger · « **Reply #2 on:** February 13, 2011, 08:54:58 PM »

I have seen this model, and Andy is going to have a delightful model to fly! I think the power system is closer to .09 than .06, but the weight seems acceptable. And the model is definitely of the correct size for a .061. It will even fly well with the .049s it was intended to use.

I am still racking my brain on how to define an acceptable system to fit into our 1cc class. I want the electrics to have an equal footing with the wet systems, but not dominate. The idea is to have the builder and flyer be the controlling factor in victory, not the hardware.

Should I set an area limit on the planes? A weight limit? Battery capacity limit, or Watt maximum? There are a lot of ways to do the specs, but what is most reasonable?

Wet motors are limited to .061 or .049 twin. However, a twin .049 electric equivalent would totally blow away any other possible setup. I only allowed .049 Wet twins because they are almost impossible to get to work right. That is NOT the case with equivalent electric systems.

Dennis Adamisin · « **Reply #3 on:** February 13, 2011, 10:52:38 PM »

I think the answer is to limit to 250 sq (max) 7" prop and 50' eye to eye lines. That controls the power conversion (prop) and hemisphere (usuable airspeed)

Mike Anderson · « **Reply #4 on:** February 14, 2011, 10:18:35 AM »

Jim Renkar has been using a 6" prop limit (that is the ONLY limit) at his 1/2A contest. He tried changing to a 7" limit one year and the flyers were not happy - especially the electric flyers that had been developing equipment to fit the 6" rule - so went back to a 6" prop.

My original setup for 6" props will fly a 200 sq. in. plane through the beginners pattern (everyone flies the beginners pattern) on 42' lines.

Dennis Adamisin · « **Reply #5 on:** February 14, 2011, 03:51:26 PM »

Quote from: Mike Anderson on February 14, 2011, 10:18:35 AM

Jim Renkar has been using a 6" prop limit (that is the ONLY limit) at his 1/2A contest. He tried changing to a 7" limit one year and the flyers were not happy - especially the electric flyers that had been developing equipment to fit the 6" rule - so went back to a 6" prop.

My original setup for 6" props will fly a 200 sq. in. plane through the beginners pattern (everyone flies the beginners pattern) on 42' lines.

Ya know a 6" prop is probably closer to the capabilities of 1cc gas too. (good call Mike!)

Mike Anderson · « **Reply #6 on:** February 14, 2011, 04:32:06 PM »

I ended up with a 7" APC cut down to 6" - tested a LOT of others. By the way, my setup is a 2-cell with Kv of 2200, 50 g. motor. The little 850 mah batteries weigh 50 grams and do an easy beginners pattern length flight - plane probably draws around 10 amps in the air. A lot of people are using 3-cell setups - but that would be too easy.

Larry Renger · « **Reply #7 on:** February 15, 2011, 10:33:56 AM »

Thanks for the input guys! I think that not only 6", but only 2 blades. For twins, the props can't have more swept area than a 2 blade 6" prop.

6" prop 28.3sq.in. swept area
make that a 3 blader and you drop to 5" diameter
For two props you would be allowed 4.25" diameter

And so forth. I'll think about it!

Andrew Borgogna · « **Reply #8 on:** February 15, 2011, 01:56:37 PM »

Not to change the subject but the Pathfinder is ready to fly, but I am having a big problem with the CG. With the 1400ma battery located where the gas tank would normally go the plane is nose heavy. No real supprise there, but where to locate the battery to improve the CG is not obvious. I really hate to add lead to the tail to balance the plane but I really don't see any other option.
Andy

John Cralley · « **Reply #9 on:** February 15, 2011, 05:41:46 PM »

Andrew,

Same problem that I faced with the S-1 Ringmaster when I wanted to use electric power for it. I cut into the outboard wing root, beefed it up some and installed a plywood plate located just in the lower half of the wing. A pair of velcro straps hold the battery in place. Works fine for me and only messes up the aerodynamics to a minimum degree. Actually since the rather large mass of the battery is more or less centered at the CG this location may improve corners somewhat. For this application, I fortunately had the bell crank located on the inboard side so it did not interfere with the battery location. You may still be able to do this modification depending on the thickness of the wing and the bell crank mount. It might also be possible to do the modification on the inboard side without interfering with the lead outs.

John

Dennis Adamisin · « **Reply #10 on:** February 15, 2011, 07:54:33 PM »

Andy:
I am using the 3S x 1300 and while it seems nose heavy it does not fly that way. Push the back back as far as you can (even notched into the LE if you can) and give it a go...

Larry:
I understand your rationale for the 4.25" props, but those are awfully small, How about letting them run 5"? That is still a pretty substantial difference in thrust.

I have a Brodak Twin Mustang with 6x4's because I could get them in opposite rotation. The pitch is low so I have to run 3 cells to get enough RPM. under those conditions it is probably comparable in thrust to the single 7" prop on the Pathfinder. Hmmm, just what I need, another project..!

Larry Renger · « **Reply #11 on:** February 16, 2011, 10:27:17 AM »

What about 2 smaller batteries on either side of the fuselage? Run them in parallel. Or can the battery be mounted vertically? What about a hole through the fuselage and the battery is horizontal and parallel to the wing? The flow would join with the wing and have pretty low drag that way! You could even put a rounded shield ahead of it to smooth out the flow.

Or, go to a 4s pack and a smaller prop to keep the Watt level the same.

On the subject of setting an equivalent, how about 5" props cut to 4.5". That way you compensate slightly for the smaller allowed prop.

Of course, just setting maximum battery capacity is the simplest of all criteria. Say 14.5 Watt-Hours (1300mAh 3s pack, 975mAh 4s pack or equivalent), use them however you will.

jim gilmore · « **Reply #12 on:** February 19, 2011, 09:02:44 AM »

While 6" is the right prop to be considered 1/2A. The mostly flew better on 6-2 or a cut down 6" prop. Though I always used the same fuel I flew my fow 35 on. Though I did try the davis deisel converson. And it would use the 6-3 or 6-4 easily.

Dennis Adamisin · « **Reply #13 on:** February 19, 2011, 09:40:49 AM »

Both of my twins use a single pack with a Y-harness for the power AND another Y-Harness to the single timer. I think on 1/2A a single pack is viable because the current is low and the harness is not too heavy. However on a full size stunter it is a little less clear - the case can be made for two small packs ilo 1 large pack.

The common element between IC & ECL is the prop thrust, so prop size limit is a direct hit. The IC guys will select the engine and nitro content that delivers the best combo of power, performance, and reliability. Ditto the ECL guys, who will select the best cell count and smallest/lightest practical mah.

I will try the PF with the 7x5P trimmed to 6". That should let me downsize the motor from the 2210 to a 2205 and relocate the pack a little forward to compensate for the 11g weight save...

Andrew Borgogna · « **Reply #14 on:** February 25, 2011, 12:26:28 PM »

Dennis
I have replaced the original motor with a Arrowind 2210/25 and I have installed an APC 7x5 E (tractor) prop. I just was not getting enough thrust with the original motor. Can you tell me what current or how many watts you set your motor at launch time? The original motor was set to 132watts @ 12amps with the 7x5 and that didn't get it done in terms of thrust. I could run the motor up beyond that setting and get the power but the motor was getting hot and it was beyond the max rated continuous current of 12amps. The 2210/25 only specs a burst current of 15amps for 60 S, but does not spec a continuous current.

Anyway, any help would be greatly appreciated.

Andy Borgogna

Dennis Adamisin · « **Reply #15 on:** February 25, 2011, 03:54:06 PM »

No idea what the watts are - given prop needs a given RPM to provide the thrust we need to get the job done. What motor did you change FROM? It's possible that if the motor was too small for the prop OR if the kv rating was too low to generate enough RPM you could have fallen short on thrust.

I have not even tach'd it, just fly/adjust/fly (took two flights to get it where it is). I set the Hubin FM-0c for max rpm then turned it back a little - I get a 4.3 sec laps (50' eye to eye), could probably fly a little slower if I had too but it flies nice at this speed!

I originally tried it with a 6x4 (Renkar rule 6" prop) but there was not enough thrust. Went to the 7x5 and the bird came alive. Since I have some RPM in reserve I think I could clip back to 6", turn up the RPM a little and do OK with the paddle blade 6x5.

Pusher 7x5 really helps on birds this size...

Andrew Borgogna · « **Reply #16 on:** February 26, 2011, 11:40:24 AM »

Dennis
The original motor was a Hobby People 2208/09 the Kv is 1920. I think it would have been OK with a smaller prop and let it rev up. With the 7x5 it just was overloaded and getting hot. I currently have the Arrowind motor timer set to max power and it uses 1222ma of battery capacity over a 5 minute run. The motor is cool and the battery is cool, and the thrust seems to be what is needed for first flight testing. The all up weight of the Pathfinder is 17 ounces, I think with a higher quality battery I can get the 1400ma capacity with less than 4.4ounces of weight. But before I spend any additional money on batteries I want to see how it flies. The only real concern I have is the power consumption is 85% of the total battery storage for a 5 minute run. That's more than I would like to see, I want to see what the usage is unloaded. Now if we could just get some decent weather to do the test flights I could get that information.

Thanks for your help Dennis.
Andy

Dennis Adamisin · « **Reply #17 on:** February 26, 2011, 12:43:32 PM »

Power consumption was measured on the ground? If so you will find that the FLIGHT loads are much lower. I agree that a test flight or three will let you zero in on a comfortable battery choice.

Let the games begin!

Andrew Borgogna · « **Reply #18 on:** February 26, 2011, 03:03:56 PM »

Dennis
Yes the measurement was made on the ground. Hopefully tomorrow I will get some flying in.
Thanks again.
Andy

Dennis Adamisin · « **Reply #19 on:** February 26, 2011, 07:02:40 PM »

Andy:
I got thinking (uh oh) I normally use around 1000 mah, while I never run it very long on the ground I have seen others post that static current drain is around 20% higher then in-flight You said you used 1222, or about 22% more - that is almost too perfect!

I am OPTIMISTIC about your success tomorrow! Meanwhile I have to snow blow another couple inches of "Partly Cloudy" (grrrr)

Andrew Borgogna · « **Reply #20 on:** February 27, 2011, 07:12:58 PM »

Well Dennis I did get in a flight today and it used 1137ma which is exactly 81% of 1400ma. That's close enough for government standards. The power was very good, but it is nose heavy and very slow on the controls. I will be moving the battery back on the plane to get the CG right, it should be a real winner.
Thanks
Andy

Dennis Adamisin · « **Reply #21 on:** February 27, 2011, 07:19:57 PM »

T'rrific!

I am unclear - are you using the 1400 NOW or is that the pack you wanted to go TO? Any thing you do to lighten the bird will also let you slow it a down a little and use fewer MAH - etc.

Andrew Borgogna · « **Reply #22 on:** February 28, 2011, 11:35:40 AM »

Dennis
I am currently using a 1400Mah battery and the lap times are right around 5 seconds. I say right around because I was not timing the laps, and I was told the lap times. The line tension was very good both at level and 45 degrees. I am planning to locate the CG at the main spar line by moving the battery back. The plane also was listing with the outboard wing down. Because of the CG I didn't want to take it inverted to see if it is a aero problem or a weight problem. So I am going to locate the battery on the bottom of the wing centered on the fuse.

What is your all up weight on your Pathfinder? Mine is 17 ounces which seems heavy to me for a 1/2a size plane but as I said before it's built as light as I can build. What is weight of your battery? That seems to be the only difference that might be affecting the weight of my plane. On second thought you covered your plane with in film and I covered mine in polyspan and three coats of clear dope. I really don't think there is much difference in weight between the coverings.
Andy

Dennis Adamisin · « **Reply #23 on:** March 01, 2011, 03:15:11 PM »

Just weighed in - the PF is 15.0 oz, of that, 3.3 oz is the 3Sx1300 pack.

Andrew Borgogna · « **Reply #24 on:** March 02, 2011, 11:41:29 AM »

Dennis
Took the plane out yesterday with the CG where it belongs and well the plane is just too heavy. It corners well and does rounds OK, but anything overhead it not so good. The only place to save weight is with the battery so I went to local hobby shop and found 1300mah batteries that weight 3.7ozs that represents a 2.4oz weight savings over the 6.1oz 1400mha battery. That takes the overall weight of the plane from 18.5ozs to 15.9ozs, why I got 17ozs the first time I weighed it and now I get 18.5 I can't explain other than how I was holding the plane. Anyway the new battery should make a big difference, my major concern is battery capacity for the full pattern. I am going away for the weekend so the next test flight will be next week.
Thanks for your help.
Andy

Dennis Adamisin · « **Reply #25 on:** March 02, 2011, 03:06:18 PM »

and don't forget the pusher prop! BIG help overhead...

Andrew Borgogna · « **Reply #26 on:** March 02, 2011, 06:03:55 PM »

You are right Dennis, I completely forgot about that. I also changed prop hubs and saved another .3 ounces. Every little bit counts.
Andy

Dennis Adamisin · « **Reply #27 on:** March 02, 2011, 07:20:11 PM »

Wow, .3 oz out of the prop hub will be a big help on your CG issue. Also did you seal the hingelines? I used 'kote over/under hinges to achieve that.

Larry Renger · « **Reply #28 on:** March 03, 2011, 08:29:31 AM »

Heinlein also said: "Never try to outstuborn a cat"

Dennis Adamisin · « **Reply #29 on:** March 03, 2011, 07:06:05 PM »

Quote from: Larry Renger on March 03, 2011, 08:29:31 AM

Heinlein also said: "Never try to outstuborn a cat"

Heinlein had LOTS to say about cats:
"If you would know a man, observe how he treats a cat."

"Anyone who considers protocol unimportant has never dealt with a cat."

"Cats have no sense of humor, they have terribly inflated egos, and they are very touchy."

"How you behave toward cats here below determines your status in Heaven."

"Women and cats will do as they please, and men and dogs should relax and get used to the idea."

Dave Adamisin · « **Reply #30 on:** March 03, 2011, 09:33:33 PM »

Cool Dennis but you forgot: "cats get all their pull from pushers"

Andrew Borgogna · « **Reply #31 on:** March 04, 2011, 05:40:01 PM »

I knew Larry had met my cat Benson, but how did the rest of you find out? "My name is Andy and I am a cat owner" and everybody reply "Hi Andy". OK enough about Benson he is perfect and he knows it.

The 7x5-EP props are on the way from APC, I hate it when the cost of the two props is less than the shipping and packaging. I will be back home on Monday and on Wednesday I will be able to go flying. Don't ask me what's going on Tuesday, and Larry don't say a word!

I am hoping for some good flights on Wednesday.
Andy

Andrew Borgogna · « **Reply #32 on:** March 09, 2011, 11:58:47 AM »

Dennis
Went out and put a flight on the 1/2a PF with the new battery and the pusher prop. Big difference in ever respect. The plane does the wingover solid on the lines and does all the inside stuff quite well, but outsides are loose on the lines. This is an aerodynamic issue not a power to weight issue. Larry and I checked the control surfaces and there are some adjustments that need to be made. Also I am currently flying without tip weight, the original configuration had the battery on the outside of the fuse and tip weight was not needed. Now with the weight centered on the CG under the wing tip weight is needed. How much tip weight are you using, if any? With VSC coming up next week I won't be flying the PF will be hangered for a few days. Anyway reducing the weight and going to the pusher prop all had positive results, I think following trimming this will be a good flying plane.
Andy

Larry Renger · « **Reply #33 on:** March 09, 2011, 04:01:13 PM »

I totally agree with Andy. The model is now at the point where trim is the issue, not the mechanical/electrical setup. It looked very solid for most of the flight regime, and it was clear that trim is now what needs work. Both the flaps and elevators were not aligned to each other (Andy didn't do the basic construction, so he is absolved of this one). Once those are aligned, he needs to recheck the flap to elevator setting. The tip weight is close, but not on the money yet. A few more flights, and the only problem with the model will be the pilot!

Dennis Adamisin · « **Reply #34 on:** March 09, 2011, 10:07:17 PM »

Quote from: Andrew Borgogna on March 09, 2011, 11:58:47 AM

Dennis
Went out and put a flight on the 1/2a PF with the new battery and the pusher prop. Big difference in ever respect. The plane does the wingover solid on the lines and does all the inside stuff quite well, but outsides are loose on the lines. This is an aerodynamic issue not a power to weight issue. Larry and I checked the control surfaces and there are some adjustments that need to be made. Also I am currently flying without tip weight, the original configuration had the battery on the outside of the fuse and tip weight was not needed. Now with the weight centered on the CG under the wing tip weight is needed. How much tip weight are you using, if any? With VSC coming up next week I won't be flying the PF will be hangered for a few days. Anyway reducing the weight and going to the pusher prop all had positive results, I think following trimming this will be a good flying plane.
Andy

Sounds like SUCESS is within reach - WAY TO GO!

My battery is on nearly dead center, and I have 1/4 oz tip weight. I say add some til you got too much, then back it off a little. Larry had FAR more experience than the res of us in making small ships really fly, this will be right in his wheelhouse.

Some notes for NEXT VSC; a Wee Duper Zilch for OTS and a Pinto (I think) for Classic!

JohnPrator · « **Reply #35 on:** March 10, 2011, 07:14:04 AM »

I know you all already know this but I put my battery in the wing and it is a 3S 1300, and should the ground pop up too soon this is what can happen!

Rather than try and rebuild this plane I ordered another one and plan to try and re-enforce the area better and put some type of cushion up there in hopes that it will prevent, or at least lessen the damage should I do this again, and the odds are in my favor that I will do it again.

Author Topic: 1/2a Pathfinder Electric (Read 4335 times)

Dave Adamisin