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Frog Jackdaw conversion to electric

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david humphris01/03/2017 18:47:37
2 forum posts

I have inherited a 1960's Frog jackdaw with diesel power (2.46 cc ED racer) and wish to convert to Electric power and use Futaba 35 radio control.

Any help as to suitable motor/batteries/esc, etc would be a great help as new to RC models.

Cheers,

David.

GONZO02/03/2017 09:51:17
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1249 forum posts
13 photos

Typical RC power in the past was a Frog 349(3.5cc). Power of engine 0.2bhp, 9,000rpm on a 10X5. Two engine tests on this site **LINK** So, as a starter for electric I would go for a motor that can turn a similar prop at similar revs with a power o/p of a bit more say at least 250W. A 3 cell lipo (nominal voltage of 11.1V) will do with a capacity of 2000mAh to 2,500mAh and a 'C' rating of 25C. You will also require a speed controller(ESC) that is rated for 40A(playing safe). Just a very rough indication of what may be needed. But, I guess that as your new to this it doesn't mean that much. Plus, I guess you don't have any test gear like a Wattmeter, Voltmeter and a rev counter to enable you to safely test and asses your chosen setup. Others may be able to offer you a specific setup. IIRC Paul Jefferies on this forum built one not long ago and powered it variously with a Frog 349 and a PAW 19. I believe he found the rudder response a bit 'lacking'. Comparing the Jackdaw with one of its contemporaries, the KK Super 60, of a similar span then the Super 60 has a greater dihedral angle on the wings giving the rudder more effect via a greater yaw/roll couple than the Jackdaw.

Peter Christy02/03/2017 10:24:37
1517 forum posts

Gonzo: Good info, but regarding the dihedral, the Jackdaw was designed as "aileron ready" from the outset - unlike the Super 60.

I've built quite a few Sub-Minis (half size Super 60s), and unless fitted with single-channel, I reduce the dihedral on them to about 2/3rds. This improves the handling with a proportional rudder no end!

Several of my fellow club members back in the day flew Jackdaws with bang-bang rudders, and never seemed to complain of lack of control authority.

I actually prefer it to the stock Super 60, as it is less "wallowy"! I don't think David needs to worry about it.

Excellent advice on the power side! And I agree about a 2.5cc being a bit marginal for it. It would fly (we used to fly Super 60s on ED Racers!), but it would not be sprightly!

--

Pete

Nigel R02/03/2017 10:27:32
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2977 forum posts
471 photos

For reference;

http://outerzone.co.uk/plan_details.asp?ID=4367

Some big servos shown on that plan!

Denis Watkins02/03/2017 10:30:51
3804 forum posts
52 photos

You are right guys, they flew on 5cc, or a .30 in new money

Gonzos electric set up is spot on

Lovely plane too

Colin Leighfield02/03/2017 14:23:33
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5919 forum posts
2481 photos

I have still got my Jackdaw, though haven't flown it for many years. I bought it ready built in 1976 from a work colleague who said it was originally built and flown by Dave Wright. Dave is a member of our club and he confirms that he built and flew one, so it could be his! The plan shows the wing with and without ailerons. It was my first proportional radio plane and I flew it with rudder, elevator and throttle on the OS30. No ailerons and it flew beautifully. Personally I prefer it to the Super 60, great model though that certainly is. It was designed by (Chris)? Olsen and that gives it a lot of credibility, must fly mine again one day.

GONZO02/03/2017 14:59:07
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1249 forum posts
13 photos

I placed a copy of 'Radio Control Big 4' on Outerzone **LINK** If you download it you can read all about the development of the 'Mercury Galahad', 'Frog Jackdaw'​, 'KK Super 60' and the 'Veron Viscount'. Its a very interesting read in its own right and gives a good picture of how things were back in 1962. I thoroughly recommend it.

Colin Leighfield02/03/2017 18:12:32
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5919 forum posts
2481 photos

I remember when one of the mags built a Jackdaw not long after it came out. They decided to set it up as a multi with reeds, probably Orbit? They converted it to tricycle undercarriage and fitted a Frog 349 "Vibramatic" diesel (unfortunate choice of name! It was a rear induction engine, I don't think it was a rotary valve, might have been a reed valve)? When they reported on the tests, their attempts to fly it were stymied by engine vibration playing havoc with the reeds in the radio! I think they found a solution eventually, can't remember what it was though.

GONZO02/03/2017 18:26:34
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1249 forum posts
13 photos

IIRC the Frog 'Vibramatic' diesel was a 149. a rear reed induction version of the Frog 150(??). The Frog 349 was in fact a rear rotor induction motor and did have a bit of a reputation for vibration, especially if you took the revs up a bit.

Colin Leighfield02/03/2017 20:39:22
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5919 forum posts
2481 photos

Hi Gonzo, you are right. There was something odd about the induction though so I've just looked it up and found that it was a kind "of inside-out" rotary drum valve, the air intake was vertical and looked similar to the 149 Vibramatic. Peter Chinn reported .318 BHP and very good torque, so it could swing decent sized props. Funny how in those days a 3.5cc motor to me was huge! It's a tiddler now, isn't it?

GONZO03/03/2017 10:21:30
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1249 forum posts
13 photos

Trainer power now starts at 0.45 where as in my time back in the 70's it was a 0.20.- 0.25. I know the Frog 349 well, a marine RC version was my first engine back in 1960. Still got it but converted to aero and 3 others to keep it company. The Frog 349 was best suited for use as a marine engine.

david humphris03/03/2017 15:49:48
2 forum posts

Hi, Thanks to Gonzo and others for advice on electric conversion of Frog jackdaw, much appreciated!

I notice on the Plan that there is considerable downthrust angle on the IC motor-presumably this would apply to electric motor also? Also is location of battery critical. probably just under wing for easy access would be good but would lower down be better?

Cheers,

David.

Steve Hargreaves - Moderator03/03/2017 15:59:34
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Moderator
6716 forum posts
189 photos

Your electric motor will weigh a lot less than the equivalent IC engine David so usually the battery needs to go quite well forward to keep the CoG in the right place & yes a similar amount of downthrust will be needed.....the need for downthrust is not dictated by what energy turns the propeller....wink 2

If I was you I'd obtain all the parts needed for the conversion (motor, adaptor, prop, ESC & battery) then remove all the IC paraphernalia (engine, tank, throttle servo etc) & then add the new electric bits to the airframe until it balances. This will tell you where they all need fixing.

A battery hatch will be worth creating to allow battery swaps without having to remove the wings every time....

Peter Christy03/03/2017 16:09:53
1517 forum posts

Yes, stick with the designed downthrust. The Jackdaw has a flat-bottomed wing, and a bit of incidence between the wing and the tail. The downthrust will reduce trim changes as the power is varied. The model doesn't know if its got an electric motor or an IC up front. All it knows is thrust and subsequent speed!

Regarding the battery, the vertical location isn't very critical, and higher may be better (less pendulum effect!).

As its a fairly heavy item, you will probably need to get it fairly well forward to get the correct C of G. I haven't got the drawings in front of me, but most models of that era were designed to balance on the main spar. Before deciding on a location try a few experiments (just stick the battery to the fuselage with sticky tape or rubber bands) to determine the optimum position for the correct balance point. Then figure out how to mount it in the same location inside - not forgetting ease of access! You might get away with a hatch in front of the windscreen area, where the fuel tank would have been.

Best of luck, and lest see some pictures! The Jackdaw was one of my favourites of that era. I keep getting tempted to build one for testing radios.... wink

--

Pete

GONZO03/03/2017 16:18:13
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1249 forum posts
13 photos

Keep the down thrust for starters. Be aware that an electric conversion is likely to give you tail heavy problems due to the electric motor being lighter than the IC. So get RC etc forward and retain an ability to move the power pack forward(possibly quite a bit). You could do a trial run by strapping items on with 'lacy bands'. Spend some time reading the educational info about electric flight on this site before buying anything. Then come back and ask. I also strongly advise that you obtain some essential test gear so as to avoid letting out the 'magic smoke' from some of your newly acquired electric flight components:- Wattmeter(essential), rev counter(essential), voltmeter(optional). Oh, and watch your fingers etc. its easy to get caught out. Electric doesn't stop it just draws more current and keeps on 'chopping' with those nice sharp electric props!crying 2

Steve Hargreaves - Moderator03/03/2017 16:50:55
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Moderator
6716 forum posts
189 photos

Yes Gonzo makes a good point...do all your testing with the prop removed......a simple error can result in that prop spinning at a few thousand RPM with detrimental effects on any soft fleshy bits that get in the way.....

Peter Christy03/03/2017 16:54:07
1517 forum posts

Another thumbs up for Gonzo there. You need to be particularly careful when setting the fail-safe!

--

Pete

GONZO03/03/2017 17:03:20
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1249 forum posts
13 photos

Steve, He will of course have to have a prop on the motor when he does his full power current draw and rev checks. Just have the model well restrained and keep he's 'pinkies' away from the 'bacon slicer' at the front.

Peter, FS isn't an option as he is using 35.

David, if the ED Racer is any good you could probably sell it on the 'bay and finance a lot of the parts for the electric conversion.

Peter Christy03/03/2017 19:02:39
1517 forum posts
Posted by GONZO on 03/03/2017 17:03:20:
Peter, FS isn't an option as he is using 35.

Ah! Missed that! Could be PCM, though?

Witnessed a near miss a while ago with someone who was setting up a new model. Thought he had everything set right, switched off Tx to check failsafe, and it went to full throttle! Luckily no harm done, but a salutory lesson nonetheless!

--

Pete

Erfolg03/03/2017 20:48:21
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11316 forum posts
1121 photos

Having read the link Gonzo provided, I am surprised that RC models managed more than the one flight. Consistent control must have been unusual, however skilled.

In my opinion, what ever the original set was, you would be far better served just to adhere to the current norms for proportional RC set ups.

I have a VS Tomboy, trying to fly it as any normal modern RC set up was a disaster, Dutch rolling always to a crash. Several experienced and in one case a well known RC expert flyer, ended with an arrival. If you let them fly just like a FF model of yesteryear, with minimum inputs, they will fly with something approaching control. I modified my model by taking out almost all the dihedral, moving the CG to 30% chord and lengthening the nose to facilitate the CG (modern electric motors are much lighter than many old RC motors).

In short best forget how they were set up and flown. Yesterday was a different world.

I do fancy a Galahad, so very functional looking, almost Germanic or French Steam engine philosophy

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