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Old Mar 06, 2012, 09:17 PM
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United States, AZ, Lake Havasu City
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SuperPacer 20/Dirty T Birdy 20 Conversion

Hi All,

This is not a build log, but more about highlights of my effort at converting these two planes to electric. Both are retractable tail draggers powered by Lightning .25s which I just tested with an APC 10x6 glow prop and got 400 watts at 35 amps which is what I was shooting for. I will try E-9x7, and 8 in the next few days.

Both planes are scratch built and at this time, the Super Pacer is being prepped for painting, while the DTB still needs a wing to be framed and retracts installed.

The reason for the funny name for the Dirty Birdy, is that it is built from both Dirty Birdy 20 and Tweety Birdy 20 plans. The Dirty Birdy 20 is Dirty Birdy 60 plans shrunk down, while the Tweety Birdy is an actual Joe Bridi/Great Planes kit from the 70/80's (took me a while for that to sink in, right doxilia? ) I liked the lighter built up Hor Stab and shorter ws but wider root of the wing of the Dirty Birdy 20, but the simplicity of the Tweety Birdy fuse.

The one setback at this time is I may have to use a 10" prop, I will not have as much ground clearance as I would like, so if the 9" prop in higher pitch numbers don't get the watts I need, I may extend the gear legs up to 1". I am not happy with the wheel wells on the SP, so I may have to rebuild that area anyway.

I also decided to freeze work on the DTB until I have actually test flown the SP, so that If I need to make mods such as going to a higher power system such as a Lightning .32, then I will not have to re-do a bunch of work. I don't need rockets, but I want them to perform as if they had OS .25s which I originally planned to power them with.

Below are a couple of earlier pics taken. The one the left is the SP and the one on the right is the DTB. Will update with latest pics later.

SpadCat
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Old Mar 07, 2012, 05:37 PM
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Prop Test Results

Tested 3 different sized APC props and below are the results:

9x6E 285 Watts 26A

9x7.5E 320 Watts 29A

10x7.5SF 457 Watts 42 amps At 3/4 throttle, it dropped to 400 watts and 36 amp

I will do static pull tests later. The pull of the 10x7.5 is quite strong.

SpadCat
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Old Mar 07, 2012, 06:43 PM
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SpadCat,

Thanks for this thread. I had an original Super Pacer with a Supertigre .15. I'd love to build one for electric. I think the wing was constant chord, and the plan was full size, but the fuselage plan was reduced. What kind of plans are you using?

Retracts are a great idea.
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Old Mar 07, 2012, 10:12 PM
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Originally Posted by Zoomer-Ron View Post
SpadCat,

Thanks for this thread. I had an original Super Pacer with a Supertigre .15. I'd love to build one for electric. I think the wing was constant chord, and the plan was full size, but the fuselage plan was reduced. What kind of plans are you using?

Retracts are a great idea.
Hi Zoomer-Ron,

This is my 2nd Super Pacer and was also my first pattern style ship after learning to fly on an Ugly Stik. I was doing fast rolls low to the ground, got dis-con-boober-ated and did a split "S" right into the ground . It was Goldberg retract requipt and OS .25 powered. Great flying model.

The wing is constant cord and very easy to build.

SpadCat
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Old Mar 08, 2012, 08:57 AM
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Sweeeet. Thank you for the .pdf file.

Sorry about the crash. Been there, done that, got the T-shirt.

I always liked the side view of the fuselage, with the dorsal fin coming out of the canopy. What canopy are you planning to use?
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Old Mar 08, 2012, 12:08 PM
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You are welcome. That is for tiled plans.

I tried to upload parts list and a .pdf that you can burn to disk and have a full sized plan printed out, but the files were too large. I will try to find the link so you can download them if needed.

That crash was a long time ago, so I am over it now. . Did not get a T-shirt though!

For the front of the canopy which is mounted on top of the battery hatch, I am using a modified canopy I used on my scale combat ships. I have several of them and since they are already paid for, I might as well use them. The aft portion is shaped from blue foam from the plans.

Tower has a more true to form canopy. Here is the link: http://www3.towerhobbies.com/cgi-bin...?&I=LXJ934&P=7


That dorsal fin is pretty cool, and also really helps with knife edge flight. It might be the first use of a flat plate fuse design for that purpose, but I could be wrong.


SpadCat
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Old Mar 08, 2012, 08:28 PM
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Cute pair of electrocutions. The glow size brought back fond memories of my OS25 powered models - my favourite lump in oily days - blowing past most 40 powered models.

Idle thoughts... Have you figured out the boring stuff? A battery hatch, for one. Refueling an electric can be tedious if your battery hatch doesn't allow quick pack swaps. Some RC gear re-arrangement around the new drivetrain to maintain the CG may be neccesary. UC - are longer legs needed to deal with a longer e-prop.

If you already gave sorted that boring stuff out - good on you, and my apologies. Looking forwards to your progress with these neat models

D
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Old Mar 08, 2012, 09:58 PM
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Quote:
Originally Posted by Dereck View Post
Cute pair of electrocutions. The glow size brought back fond memories of my OS25 powered models - my favourite lump in oily days - blowing past most 40 powered models.


Idle thoughts... Have you figured out the boring stuff? A battery hatch, for one. Refueling an electric can be tedious if your battery hatch doesn't allow quick pack swaps. Some RC gear re-arrangement around the new drivetrain to maintain the CG may be neccesary. UC - are longer legs needed to deal with a longer e-prop.

If you already gave sorted that boring stuff out - good on you, and my apologies. Looking forwards to your progress with these neat models

D

"Electrocutions"...I like that.

OS is what I powered my first Super Pacer and with the new birds, I was going to use an OS .25 with mousse can until I decided to try the E-conversion. If I do not like it, I will just tear out the motor and install the OS engine as originally planned.

No apologies needed. I appreciate any and all comments.

I built a hatch on the bottom of The Dirty Birdy, since it is hard to hide hatch lines on top (at least for me) and it will be no problem to turn it over on a stand to change batteries. I built the Super Pacer per plans with hatch on top. Smaller planes are not as much of a handling problem in this situation as large planes are. Both planes have a slightly extended battery bay so the nose is about a 1/4" longer than plans. Did not want to change the overall geometry much. There is plenty of room for 3s 2200 lipos and I could go to larger lipos if needed for either balance or higher power requirements.

I did a test of the SP's CG with the components in place and it is balancing slightly nose heavy, but that will change as I Monokoat the wings and paint the fuse. Right now the total weight is 2.7 lbs which I am pleased with. It will be interesting to see how much weight is added with the finish applied.

The 10" E-prop is giving me 1.25" ground clearance with wings level. Like to have a little more, but since this is a tail dragger, with proper take off and landing technique, should not be a problem. If it is, I will just have to rebuild the bottom of that section of wing to accept longer legs.

Thanks,

SpadCat
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Old Mar 10, 2012, 12:00 PM
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Retract Wheel Well Problem Solved

After doing a dumb thing and burning out the first set of Super Pacer e-retracts due to an incorrect hookup, I decided to go ahead with mechanicals I had on hand. Got the whole system in and working (forgot how much fiddling one has to do with linkages) when the set of e-retracts for the Dirty T Birdy came in. After a bit of thought I decided to tear out the mechanicals, ordered a 3rd set of e-retracts, and installed the new e-retracts. I was sure glad to get rid of the mechanical retract servo and associated linkages.

The next main problem I had to resolve was the wheel cut out in the left wing leading edge sheeting. I did a very nice job on the right wing, but maybe it was too late at night as the left was not done very well. It came out too large after trying to sand a slight oval shape out. There was no problem with the operation, but did not like how it looked. Easiest way out was to just leave it that way, as who looks under a wing. But it kept on bothering me, so after running various possible solutions through my head, last night I came across the one that should work. I got a piece of leading edge sheeting, cut out a round hole of the right size, glued it on top of the original sheeting, placing it so that there was proper clearance for the wheel. I used light spackle to fill in beneath the overhanging edge of the top sheeting, tapering it to the back wall of the wheel well. After the glue and spackle dried, I sanded the top sheet down so that the only material left was on top of the fill in spackle. I will then reinforce the area with a thin coat of epoxy.

I think I have more time invested in the retracts than framing up the whole airplane, but now I feel much better and can continue with the finish process.

SpadCat
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Old Mar 15, 2012, 11:28 PM
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Here are a couple of photos of the pre-covered wing with just a little more work to be done, and the other one is after covering. It has been a number of years since I used Monokoat, so had to relearn some techniques. Just need to do the tips and I am not sure if I will paint or cover with film at this point.

SpadCat
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Old Mar 17, 2012, 06:55 PM
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Here is the fuse almost ready to prime. Need some touch up work on it and on the canopy turtle deck. The canopy is just sitting there and will be finished later. I will be using the WOW LS2 undercoat system. The tail feathers will be Monokoated.

SpadCat
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Old Mar 24, 2012, 03:54 PM
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Here are the latest pics. Fuse is primed. Canopy just sitting there and hatch needs a little sanding to fit perfectly.

Tips are blue foam (except for the ply tip ends) and so is the turtle deck. It is a somewhat of a challenge sanding when mixing balsa and exposed foam.

I actually like the color white of the primer coat, but will stick with the original idea of Navy blue and I am thinking a bit of red.

SpadCat

PS My wife said she likes the white, so I may change the scheme.
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Old Mar 25, 2012, 08:36 AM
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Boy, that looks great.
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Old Apr 06, 2012, 02:04 PM
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Ready to Fly!

The Super Pacer is finished but not done....just need some color trim work on the fuse and was hoping to fly her later this afternoon, but it is very windy.

Weight came out at 3 lbs 3 oz and CG is just a hair behind the recommend forward point with the battery at the forward point in the compartment and 2 inches remaining to the rear so I can pull the CG a little more aft if needed. I was aiming at an AUW of 3 lbs, so I am very pleased at the weight as I put no effort into weight reduction and just relied on my original calculations with the electronics being much lighter than nitro and vintage radio gear and mechanical retracts.

I was concern with the clearance of the 10" prop, but I think it will be ok.

I learned a lot about painting mixed materials of balsa/foam. What time and effort I saved in making the canopy and wingtips out of foam, I lost in painting prep. Next time it will be a lot easier and the results will be better. I tried the LS system, but ended sanding most of it off. Nothing against the system, but there is a learning curve and at 30 bucks for 8 ozs is a lot of dollars to just experiment with (along with a heck of a lot of work in removal), but I see the possibilities with the system and am confident I can work out the proper application technique for a great finish.

I am not sure I like the red tips, the other side is all white and will change one side or the other. The red is only tape.

Below are a couple of photos and will report on the maiden flight, hopefully soon.

SpadCat
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Old Apr 07, 2012, 08:26 PM
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Maiden Flight eSuper Pacer

Had 3 six minute flights. Take off was less than 50' and climbed out very steeply, tracks beautifully on the ground (hardly know it is a tail dragger) and in the air. Rolls are crisp and stops where you want it. Quite fast with gear down, but gear up and you think it went "on the pipe" if it had one. Slowed down for perfect landings (it will make you look good) and roll out was straight with no ground looping tendencies. Taxis like it has nose gear and no problem with prop ground clearance.

The motor and battery were not hot (it was 85 degrees here this afternoon).

Awesome plane and well worth the effort to convert to electric. Highly recommend this conversion.

SpadCat
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