Author Topic: Seafire AMA E-Profile (Read 3829 times)

john vlna · « **on:** April 06, 2013, 08:35:29 PM »

I finally cleared the bench and am getting back to my electric AMA profile Seafire. It is an all foam project, well almost; there are a few wood and carbon fiber parts. I use 3/8 pink construction foam for projects like this. The AMA size is just a big version of my 15 size plane, photo attached.

I laminate two pieces for the fuselage and run an arrow shaft down the center. 1/16 ply Fuselage doublers are used to stiffen the front end. The wing spar is also an arrow shaft. The gear is mounted in the wing with standard gear block. The gear area is also re-enforced with a carbon shaft.

The most unusual feature is the KFm-2 stepped airfoil. It performs something like a Clark Y section and is commonly used by RC modelers.

Power will be a Turnigy 3648 or 4250 on 5 cells. I use simple Aluminum angle pieces to mount the motor, this allows easy motor changes to see which works best. Most of the construction techniques are similar to those used with balsa model as show in the attached construction photos.

john vlna · « **Reply #1 on:** April 09, 2013, 05:41:04 PM »

The Seafire on wheels, first coat of paint

john vlna · « **Reply #2 on:** April 10, 2013, 10:03:48 PM »

It's beginning to look like a carrier plane. The color scheme is from the Korean war , albeit loosely interpreted. Paint is flat latex from Home Depot.

Wayne J. Buran · « **Reply #3 on:** April 11, 2013, 04:40:20 AM »

John, are you going to have it ready for Brodak's?
Wayne

john vlna · « **Reply #4 on:** April 11, 2013, 03:10:08 PM »

Wayne,
Yes I'll have it at Brodak's. It would be legal in sportsman since electric and glow are combined. but I will not enter it. I fly the AMA events, and we aren't offering the AMA electric classes.

john vlna · « **Reply #5 on:** April 13, 2013, 07:21:28 PM »

I had hoped to get in the air this week but it looks like next week at this point. But I am getting some of the components on.

Bob Hudak · « **Reply #6 on:** April 14, 2013, 08:11:42 PM »

John,
What prop and Esc are you using in this setup?

john vlna · « **Reply #7 on:** April 14, 2013, 08:47:10 PM »

Bob,
I have two primary options, both use the Dynam 80A esc and 5 cell batteries

Motor 1 is the Turnigy 3648 850 Kv with APC 10 x 8R

Motor 2 is Turnigy 4250 1000Kv with APC 9x6R or 9x7

Flight tests will determine the best setup. The 3648 was used on another plane, converted from glow, but was too heavy to use the 5s battery so high speed suffered.

john vlna · « **Reply #8 on:** April 14, 2013, 08:56:34 PM »

I forgot to mention, the 4250 with 10x8 also is a possibility with a 4s battery

john vlna · « **Reply #9 on:** April 15, 2013, 06:18:25 PM »

Naval planes don't normally have nose art, but this is a model.

Peter Mazur · « **Reply #10 on:** April 16, 2013, 04:01:01 PM »

I know about the Sea Vixen. What's a Sea Vixon?
Pete

Joe Just · « **Reply #11 on:** April 16, 2013, 04:57:17 PM »

A gay Vixen.
Joe

john vlna · « **Reply #12 on:** April 16, 2013, 05:58:02 PM »

Just to broaden your education

" The word "Vixon" is not in the dictionary but it is used as a slang word for "Sexy Beast" which is often found on the Valentine's Day heart candies. "

Source: www.urbandictionary.com/

Peter Mazur · « **Reply #13 on:** April 17, 2013, 07:26:58 AM »

Yup, I am educated now. Maybe I never heard of it before because nobody ever called any of my airplanes a vixon. Or ever called me that, either.
Pete

Mike Anderson · « **Reply #14 on:** April 17, 2013, 09:39:25 AM »

At least not to your face ....

john vlna · « **Reply #15 on:** April 17, 2013, 03:23:04 PM »

Pete maybe because MO-1's are not Vixons, now maybe a Corsair or Bearcat....

john vlna · « **Reply #16 on:** April 21, 2013, 05:32:48 PM »

Flew the Seafire this weekend. The slider was not operational, just wanted to get the balance for high speed setup. Looks like it will be a good flier. Weight came out 46oz, but I may have more battery than required.

john vlna · « **Reply #17 on:** April 29, 2013, 08:56:27 PM »

Some pictures from the first days flying. Had it out last Sunday, but conditions were very windy and variable, and I didn't get much flying in. I really like the servo slider release though. Sliders can be a problem but the servo release is very positive. Just need to spend some time trimming.

I also really need to get busy on a handle. I also flew my class I and have to use both hands on the handle during high speed, so the electronics must be integrated in, a separate RC TX just won't do.

john e. holliday · « **Reply #18 on:** April 30, 2013, 05:52:03 AM »

Great pics and thanks for the report. Now it sounds like the weight room if a Class I takes both hands to fly.

Mike Anderson · « **Reply #19 on:** April 30, 2013, 11:48:16 AM »

A vixEn (with an 'e') :

vix·en (vksn)
n.
1. A female fox.
2. A woman regarded as quarrelsome, shrewish, or malicious.
[From dialectal alteration of Middle English fixen, from Old English fyxe.]

A vixOn (with an 'o') is not an actual English word - but from the "Urban Dictionary":

vixon: Sexy Beast. Often found on the Valentine's Day heart candies.

john vlna · « **Reply #20 on:** April 30, 2013, 12:01:02 PM »

Doc,
Yes it does look like I'll have to do some body building. It is electric and it even surprised me. The scary part is I was only running at about 75% of the available power and it is still under the 3.5 lb electric weight limit.
john

Mike Anderson · « **Reply #21 on:** April 30, 2013, 12:06:37 PM »

So which motor is mounted and prop are you running at present? And can you measure current and get an idea of what kind of power you are using?

john vlna · « **Reply #22 on:** April 30, 2013, 01:13:20 PM »

Mike,
I am using a Turnigy 4250 1000KV, battery is a 2250 mah 5s 65c, esc 60A. On the ground with a 9x6 Zinger Pusher it draws 40-44 A @16K. I have not measured the draw in the air yet. The motor is fully capable of maxing 60+ amps with more prop for the short time high speed takes. I only flew it once and as I said it surprised me, so we didn't get a high speed. I am having some back problems so I did not want to fly it again. I've attached a spec sheet

John

john vlna · « **Reply #23 on:** April 30, 2013, 01:16:24 PM »

P.S.
I think the motor will take 6s, I will try that some time this spring, would probably make it a classII. I will also convert to 2.4 when I get some handles made.

john vlna · « **Reply #24 on:** May 06, 2013, 10:20:20 AM »

Flew the Seafire at Huntersville. The trim was all wrong on the first flight, and I missed the landing. The wind was also about the worst I have flown in in over 60 years of CL flying. I was using my stunt motor, (850Kv). On the second fight something went wrong with the motor, it made a horrible noise. I checked it out on the ground but it seemed OK. The third flight I got through high speed and it seized up. Lesson: I should swapped out the motor, but I am not sure that is legal in carrier.

Mike Anderson · « **Reply #25 on:** May 06, 2013, 10:48:15 AM »

You can swap out motors or engines without restriction. The restriction is on more than one person using any particular engine (or motor, I guess) in any single event. That does not restrict you from using an engine in profile and someone else using the same engine in Class 1 (for instance).

Mike Anderson · « **Reply #26 on:** May 06, 2013, 11:01:15 AM »

Quote from: john vlna on May 06, 2013, 10:20:20 AM

...... I was using my stunt motor, (850Kv). On the second fight something went wrong with the motor, it made a horrible noise. I checked it out on the ground but it seemed OK. The third flight I got through high speed and it seized up. Lesson: I should swapped out the motor, but I am not sure that is legal in carrier.

Most likely cause is shaft flexing allowing the magnets to crash into the stator - I bet you will find magnets loose, shifted out of place and or broken when you open it up.

Shaft whip is much more likely when the motor is rear-mounted - there were some early posts which analyze this a couple of years ago (probably in the e-stunt forum). I went through 3 Scorpions in very short order when we were building and debugging our first e-powered Skyrays three or four years ago, before we figured out that the rear mounting exacerbated the problem. Also, my problems often were happening while using glow propellors - something probably due to the RPM's range and the harmonic resonance frequency of the nose causing amplified vibration at certain RPM. Pete M uses glow APC pushers, with no apparent problems however. He DOES front mount his motors though.

Peter Mazur · « **Reply #27 on:** May 06, 2013, 11:29:41 AM »

I use a glow APC 10-8P prop (after careful balancing) without problems on my AXI motor for Skyray. When I try glow props on my Scorpion I often get severe vibration problems. I have much less vibration with the lighter electric props, but there are fewer sizes to choose from. And solid, front mounting is important with each.
Pete

john vlna · « **Reply #28 on:** May 06, 2013, 03:23:53 PM »

Yes, I think it was the magnets, we will see when I open it. My last AMA profile used a front mount, this model does use the rear mounting. I have used rear mounting on a lot of different model, not all carrier, without any problems. I was using the APC 10 x 8 glow pusher. The rc guys tell me that the Chinese do not use good epoxy, while I wouldn't rule out shaft flexing, with front and rear ball bearing it doesn't seem to me that it would be easy for the rotor to loosen a magnet due to prop loads. During high speed we are basically straight and level.

PS I am using really cheap motors and this one in particular is over several years old, could it be that cheap doe not last forever?

Mike Anderson · « **Reply #29 on:** May 06, 2013, 03:51:51 PM »

It isn't prop load or the epoxy - the shaft flexes at certain RPM. In rear-mounted motors, the motion is not adequately damped out by the bearings and this can allow the magnets to contact the stator. It physically just knocks them loose. It is worse on motors that are 'long and skinny' than those that are 'short and tubby'. Stunt flyers find it manifesting itself in tight turns, when the model rotates the motor mount/firewall, and the prop tries to keep going straight. I think that most of the stunt flyers went to front mounting, and were able to dispense with the extended shafts and external ball bearings that were an attempt to overcome this same problem.

When we were going through this with Scorpion, I sent my first motor back, they re-glued and tested 'at 2000 Watts' (not sure what kind of test they mean) and the magnets didn't come loose. On the first run with a propellor - I think it was a wood, 11-7 pusher, when I throttled back to idle and then up again, a noticeable sound (like a rattle or scraping) was made. I immediately shut down and landed and several of the magnets were visible in the opening between the bell and the base plate - indicating that they had slid rearwards. Sent it back again with a couple of diagrams of what I thought might be the problem, that the rear-mounting allows more shaft whip than front mounting. They recalled all of that model motor, and redesigned it with a large ball bearing supporting the rear of the housing. That fixed the problem. When I got my new-model motor back, I also redid the front end so that the motor was front mounted and it never made any more noise.

I had posted those drawings on Stunthanger, in the E-power forum, but I think that those postings were lost in the 'Big Crash'.

(edit - found a copy of the drawings)

john vlna · « **Reply #30 on:** May 06, 2013, 06:00:00 PM »

Mike,
Interesting info, in this case here is what must have happened.

On the first landing, although I didn't hook, I did land on the deck. there was a lot of vertical wind shear, typically back east, lots of trees around our fields. I apparently hit harder than I thought, the shaft had a slight bend. It had to happen on the first flight because on the second I landed in the grass and the ground was very soft(wet), and the motor was already making noise. It also seemed to run OK . The back end of the rotor ground against the the back of the stator rim. Perhaps in the air the additional flexing made the Everything else looks fine.

I have never bent a shaft on these motors is stock configuration, but when I rear mount one I have to replace the shaft. This one came from HeadsupRC. They are 5mm. Generally it is easy to bend an electric motor shaft. I probably should get some drill rod and make my own, but it hasn't been a big problem. The additional flexing in the air is probably why it ground tested OK.
John

john vlna · « **Reply #31 on:** May 10, 2013, 09:38:45 AM »

After further analysis, I think the problem at Huntersville was the flexing mechanism Mike suggested. Rich Schneider and I both checked the motor over after the first flight. I don't think it is possible that the shaft was bent on flight 2, yet I had the problem. Also high speed was OK on flights 2&3. The only thing left is that the prop I used on the second flight caused some kind of resonant flexing when I throttled down. I did change it after flight 1, because I did land hard and chipped the tips. Even thought I landed in the grass I probably bent the shaft at the end of flight 3. It is easy to do as I mentioned before.

Before it flies again, I will convert to a front mount.

john vlna · « **Reply #32 on:** May 18, 2013, 08:44:18 PM »

I have finally gotten around to building a handle. After Huntersville it was obvious that for competition an integrated control system is needed. . The handle follows the same design as others that has been posted. The radio is the Hobbyking 2ch car, available from the USA warehouse for $20 http://www.hobbyking.com/hobbyking/store/__15141__Hobby_King_GT_2_2_4Ghz_2Ch_Tx_Rx_USA_Warehouse_.html

For electric power the only mod needed is to reposition the trigger. The car radio has the trigger centered at mid-throttle. Electric power systems need to see low throttle when power is turned on. This is easily done by moving an internal spring. I left the wheel alone; it also is normally at mid-range. This is adequate to operate the servo controlled slider release.

Power is a 3s Lipo. The little dvm shown measures the battery overall voltage and each cells voltage, it has an alarm that warns when a cell goes below a preset level