Dynam Spitfire

[FLY BOY]

Greetings from the Pacific NW  :D

My winter build this year is the Dynam Spitfire. This build is going to be pretty cut and dry. Being well informed in Dynam war birds, Only a few mods are going to take place. For starters I'm throwing out the stock motor and ESC. Not fast enough and the stock 3 cell motor DONT LIKE a 4 cell pack behind it. Surging and vibration will kill it in around 4-5 flights. Instead I'm opting for the Dynam 4 sell KV650C motor and a 50 amp ESC most commonly found in the SU-26. The motor is also 5mm's longer so trimming for spinner clearance not needed. The only trimming will be in the batt bay. Its all plug and play and will bolt right up. The other advantage is, I will be able to select a number of prop sizes until I find the one thats going to work the best with out ground striking the prop and getting the most speed. I'm thinking an APC 12x12 single blade is going to be my best bet. Single blades work best on any plane for speed and performance. Sure wont look as sexy while on the bench, but dog fighting and racing around the poles is what we do here for fun. Next all hinge surfaces will be reinforced with nylon hinge tape, landing gear raked forward as far as possible, And a set of DAVE BROWN shock absorbing tires to complete the build. And if I find the motor swap is not fast enough to stomp the competition, Plan B is to swap in the P51 strega motor next winter which is going to require a lot more time, energy, and reinforcing.  The Dynam Spitty and P51 Mustang are perfect matches for the Strega motor swap because of there flying weight, and stock prop size. Why not just buy one those 980mm speed demons you ask? Because there 980mm's of twitchy. The bigger they are, the easier they are to fly, and I dont recall a Spitty or P51 war bird in there line up. If MRC had speed demons in the 1250mm class I would be all over it. My bank account would be empty, and I would be divorced, HA!
HAPPY LANDINGS FROM THE PACIFIC NW  :cool:

[FLY BOY]

RE: Dynam Spitfire

Greetings from the Pacific NW  :cool:

The Spitfire build going better than expected. The Dynam KV650C Motor bolted right in. Had to make a couple more mods, so here's my update.

In order for the nose cone assembly to fit the upgraded motor, had to use my prop reamer tool to make the center hole bigger in the nose cone mounting plate so that it would fit the bigger cowlet. I did this so as to stay with the factory 3 blade prop for now. The look is cool, and as expected, the 5mm longer motor gave it perfect clearance between the nose cone and fuse. Also chose to up grade the control horns. Because of the higher speeds and pulling more G's in the turns, Threw out the factory horns that glue in, and went with the kind that screw in to a backing plate on the other side of the control surfaces. 

Because the upgraded motor wont need to work as hard to turn the factory 3 blade prop, Its going to use less batt power which equates to longer flight times. And yes it will be much faster to. My expectation is a min of 10 minutes per flight, and maybe 15 minutes per flight using the Admiral 4s 3000mah pack. Will let you know after all the test results are in.  :D

Happy Landings from the Pacific NW.

[fhhuber]

RE: Dynam Spitfire

The prop itself requires the same power to turn the same RPM regardless of what is turning it...

Its possible the motor may be in a slightly more efficient RPM range, but the % energy savings won't be huge, since we generally run in the 80% to 90% efficiency range.

I've been flying my Dynam Spitfire and P-51 with the stock motor, stock prop, stock ESC on 4S 3000 to 4000 (didn't carve the foam in the Spit for bigger than 3300) No issues...
Well over a year on the Mustang and 4S. I haven't had the Spitfire as long. The motors are fine if you balance the prop and spinner... and put longer screws in the Mustang firewall. (haven't needed longer screws for the Spitfire) The Mustang spinner was BADLY out of balance... Spitfire wasn't too bad.
Wattmeter says there's ample margin for the ESC's max current rating... (been over a year since I took the reading so I don't remember the exact amp demand)
Since both use the same 3715-890 kv motor, same prop and same ESC... I don't foresee issues with the Spitfire.

***************

The 3720-650kv... you could go to the APC 11X9 4-blade. There was a series of Spitfires with 4 blade props. Slightly higher calculated pitch speed than the OEM prop with the OEM motor+prop on 4S for both motors.

[farmflyer]

RE: Dynam Spitfire

The prop itself requires the same power to turn the same RPM regardless of what is turning it...

Its possible the motor may be in a slightly more efficient RPM range, but the % energy savings won't be huge, since we generally run in the 80% to 90% efficiency range.

I've been flying my Dynam Spitfire and P-51 with the stock motor, stock prop, stock ESC on 4S 3000 to 4000 (didn't carve the foam in the Spit for bigger than 3300)  No issues...
Well over a year on the Mustang and 4S.  I haven't had the Spitfire  as long.  The motors are fine if you balance the prop and spinner... and put longer screws in the Mustang firewall. (haven't needed longer screws for the Spitfire)  The Mustang spinner was BADLY out of balance... Spitfire wasn't too bad.
Wattmeter says there's ample margin for the ESC's max current rating... (been over a year since I took the reading so I don't remember the exact amp demand)
Since both use the same 3715-890 kv motor, same prop and same ESC... I don't foresee issues with the Spitfire.

***************

The 3720-650kv... you could go to the APC 11X9 4-blade.  There was a series of Spitfires with 4 blade props.  Slightly higher calculated pitch speed than the OEM prop with the OEM motor+prop on 4S for both motors.

fhhuber your right about the spinner on the mustang I finally changed mine out and the one on the spit balanced fairly easily. 10 or so flights on my mustang on 4s stock set up no signs of trouble yet. Have not tried 4s on the spit yet but am glad to hear of your success with this set up.

[FLY BOY]

RE: Dynam Spitfire

Greetings fellow flyers,  :cool:

I'm very happy to hear about your success running a 4s in your spits and stangs. I cant figure out why that I, and a whole lot of other people had durability issues with the motor. Kudos to you!  :D 

On the prop thing, Its been to my experience through trial and error that an under propped motor uses less energy. Example is my T-28. In factory form my flight times were around 8 minutes. When I changed to a more aggressive pitch, I gained more speed, but flight times were reduced, and I had more heat in the electronics. Cooling mods were always required when doing this. I got so aggressive with the prop at one point that my flight times were reduced to 5 minutes and the batt and ESC became a hand warmer on a cold day. They got that hot even with a cooling mod. In my playing around and learning, when I went to a less aggressive pitch, I lost speed, but flight times were increased, and the batt and ESC stayed cold as ice. At one point I was getting 15 minutes of flight time from the T-28, but performance suffered greatly. My 4s KV650 motor in factory form can handle a 13x6 single blade. My Dynam Corsair has this same motor upgrade, but has a 14x12 prop and this plane screams through the sky. Flight times are 7 minutes, electronics are luke warm at best. Even though a single blade dont look as good, they offer the best performance because of less drag. I'm pretty sure I'm going to end up with a 12x12 prop on my spitty. Any longer blade runs the risk of ground striking the prop on take offs and landings because of clearance issues. Depending on performance and flight times, I may not choose to change props at all. Food for thought.  :)

[FLY BOY]

RE: Dynam Spitfire

Greeting from the Pacific NW  :cool:

Today we have clear skies and sunshine. Just took the spitty off the cg balancer, and out the door to maiden her today. I will have to say that no lead was required in the nose. I set up the balancer at 75mm, slid the plane into the balancer inverted with gear down, perfect, slightly nose heavy, put the gear up and rechecked, still perfect. slightly nose heavy. Taking a little lead with me to the field just in case I dont like how she feels. I'm running the KV650 motor with the factory prop to start. Dynam 50 speed controller, and the Admiral 4s, 3000 mah batt pack. Cg came out perfect. Will post some pics and hopefully a video of the maiden if my video guy shows up. Looking forward to posting my results later today. Wish me luck. always nerve racking on a maiden.  :D

[Alpha]

RE: Dynam Spitfire

Good luck, Fly Boy! Can't wait to see your pictures and video!

[ryramZ]

RE: Dynam Spitfire

Greeting from the Pacific NW  :cool:

Today we have clear skies and sunshine. Just took the spitty off the cg balancer, and out the door to maiden her today. I will have to say that no lead was required in the nose. I set up the balancer at 75mm, slid the plane into the balancer inverted with gear down, perfect, slightly nose heavy, put the gear up and rechecked, still perfect. slightly nose heavy. Taking a little lead with me to the field just in case I dont like how she feels. I'm running the KV650 motor with the factory prop to start. Dynam 50 speed controller, and the Admiral 4s, 3000 mah batt pack. Cg came out perfect. Will post some pics and hopefully a video of the maiden if my video guy shows up. Looking forward to posting my results later today. Wish me luck. always nerve racking on a maiden.  :D

Cool! Hows your throws? Any expo? I go 30% on maidens sometimes 20%. Spits can be pretty pitchy. The 3000 sounds like a great choice for weight balance and duration.

Regards
Ryan

[Pheonix]

RE: Dynam Spitfire

The prop itself requires the same power to turn the same RPM regardless of what is turning it...

Its possible the motor may be in a slightly more efficient RPM range, but the % energy savings won't be huge, since we generally run in the 80% to 90% efficiency range.

I've been flying my Dynam Spitfire and P-51 with the stock motor, stock prop, stock ESC on 4S 3000 to 4000 (didn't carve the foam in the Spit for bigger than 3300)  No issues...
Well over a year on the Mustang and 4S.  I haven't had the Spitfire  as long.  The motors are fine if you balance the prop and spinner... and put longer screws in the Mustang firewall. (haven't needed longer screws for the Spitfire)  The Mustang spinner was BADLY out of balance... Spitfire wasn't too bad.
Wattmeter says there's ample margin for the ESC's max current rating... (been over a year since I took the reading so I don't remember the exact amp demand)
Since both use the same 3715-890 kv motor, same prop and same ESC... I don't foresee issues with the Spitfire.

***************

The 3720-650kv... you could go to the APC 11X9 4-blade.  There was a series of Spitfires with 4 blade props.  Slightly higher calculated pitch speed than the OEM prop with the OEM motor+prop on 4S for both motors.

fhhuber your right about the spinner on the mustang I finally changed mine out and the one on the spit balanced fairly easily. 10 or so flights on my mustang on 4s stock set up no signs of trouble yet. Have not tried 4s on the spit yet but am glad to hear of your success with this set up.

I have been running 4-cells on my spit for some time now without issues.  Of course, I change out the ESC to a Gecko 45 and put a shim under the read gear servos to prevent nosing over.  It really flies well.

[FLY BOY]

RE: Dynam Spitfire

Greetings fellow flyers, and MRC Crew,  ;)

Maiden went well, She powered right up and took right off. I believe it was pilot Ryan that said, Shes light on her feet, YES she is!!! 3 feet of runnway and she was up. Very little down trim was required. Throws set to manual specs. Took her high and flipped on the Hobby eagle gyro, PREMO, hooked up right the first time, and the gain set to the 11 o clock position. PERFECT as expected. After flying around easy, and slow for the first few min, Flipped gyro off and throttled up to full. High speed low pass showed 58mph on the pocket radar. Was expecting more but she flew good and stable, did seem a little bit tail heavy, but was very close. NO up pressure was needed while inverted. Turns well, almost unlimited vertical, lots a power in a climb for sure. Sounds good to on the low fly by. after 6 mins, turned the gyro on and landed. checked batt power. Way good, hanging around at 3.95 per cell. Satisfied with elevator, and rudder throws for now. Ajusted more throw into the alerons at control horn clasps. added 1/2 ounce of led in the nose, Put in a fresh batt, set timer for 10 mins and went for it. Much better snap roles now, still a little sluggish in the role but way better. Loops, climbs, inverted, hammer head stall turns, High G turns, very nice, very stable. Flew all out full throttle until the timer started beeping. Turned on the gyro and brought her in. Over all very happy. I was hoping for more in this conservative set up, but I have plenty of room for ajustments. 1/2 once of led in the nose made the most difference, better suited my flying style. After 10 mins of all out full throttle flying, batt pack in the 3.65 per cell range. Electronics cold.  Going to make the following ajustments. Not fast enough yet for racing around the poles. Going to an APC 12x12 singal blade. My goal is 70 mph, I dont think the air frame can handle much more than that, Its not a strega by no means. Ajusting all control surfaces for more throw. Going to stabilize main wing mounting to fuse. Rake the landing gear a little more forward. a little tippy with 1/2 once added in the nose.  See you on the next sunny day, Rain forcasted for the next week.  :shy:

[FLY BOY]

UPDATE: Scraped project. no matter how far forward I rake the landing gear, She flips on her nose 9 out out of 10 landings unless its a perfect landing or put CG slightly tail heavy. Hate tail heavy.