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Wolfgang Matt Joker

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Ian Bagshaw26/11/2017 09:29:54
39 forum posts

I have just acquired a 60 size Joker in need of renovation. Does anybody have a PDF plan of this plane? or could advise as to the CofG right thrust & down thrust?

Many thanks

Ian

Denis Watkins26/11/2017 09:44:25
2983 forum posts
141 photos

To help the guys to help you Ian, this is the spec

And there is a free Joker 25 Plan on outerzone, which shows the C of G, and would be the same position as the larger

5295.jpg

Construction

 

Wolfgang and Günther Matt

Type

 

F3A-Model
This airplane was especially constructed for the new turnaround pattern.

Wing span

 

178cm

Fuselage

 

152cm

Weight

 

3.9kg

Engine

 

Webra 61 Racing LS

Radio Control

 

Futaba Robbe CM Rex

Edited By Denis Watkins on 26/11/2017 09:47:31

Edited By Denis Watkins on 26/11/2017 09:50:27

Bob Cotsford26/11/2017 12:01:30
avatar
7408 forum posts
419 photos

When I get a chance I'll see if I've still got the instructions from the Marvic Models Joker I had some years ago, it didn't come with a plan as it was a pre-built fuselage and foam wings. From memory I think it was just one degree of each.

Ian Bagshaw26/11/2017 12:21:30
39 forum posts

Many thanks

David Foley26/11/2017 13:18:57
56 forum posts

Go to one of the on line C of G calculators and a good place to start is 25% MAC.

This is as far foward as you should go. Move aft as needed. I usually work between

25-35%

Denis Watkins26/11/2017 15:19:03
2983 forum posts
141 photos

Or, look at the plan above, and see the C of G in the centre of the wing.

David Foley26/11/2017 16:11:07
56 forum posts

It may no workout on the 60 size in the same place.

Stuart Z27/11/2017 07:13:42
avatar
311 forum posts

Hi Ian,

You mentioned that you were looking for the down and side thrust also. I don’t know which Joker you have, however I had the (I think) Marvic one years ago and I believe the side and down thrust was built in at manufacturing stage. I have the DSM Joker 40 (still after all these years) waiting for build time. The kit is stashed deep in the loft but I have a copy of the instructions to hand and they do not detail an actual side or down thrust but say,”Final down-thrust and Right-thrust angles can only be found after test flying”. So again I suspect there is a “built in to fuselage” value to be added to depending on the powers of the engine.

I know in the build instructions, in this case, it tells you to displace the engine mount 3/16ths to the left (looking from the rear) to allow for right thrust.

HTH

S

Ian Bagshaw27/11/2017 09:38:58
39 forum posts

Thanks for all the advice

Ian

Ian Bagshaw27/11/2017 16:00:00
39 forum posts

I found an old post giving the CofG as 161mm from the leading edge which looks about right as a starting point. I've just set the whole fuselage level on the bench and with an incidence meter on the horizontal stabiliser levelled to zero the Firewall is pointing upwards....which I cant believe is correct.

It's not going well......

Bob Cotsford28/11/2017 12:04:37
avatar
7408 forum posts
419 photos

Found the Marvic instructions and that too recommends 161mm back for the CofG at the wing root and an engine mount offset of 3/16". I don't remember how long the cowl is on this, but for a 4" length that would be 3 degrees or for a 6" cowl 2 degrees. Specs are wingspan 66", area 850 sq in, wing incidence + 1/3 degree, weight 8lb.

Ian Bagshaw28/11/2017 12:09:07
39 forum posts

That's Brilliant Bob many thanks

It doesn't happen to mention where the thrust line is on the Firewall does it? the one I have has no markings. or engine mount as yet.

Thanks once again

Ian

Bob Cotsford28/11/2017 12:37:45
avatar
7408 forum posts
419 photos

Sorry Ian, it doesn't. I've just looked again and it does state right on page 1 "Downthrust and rightthrust have been set on F1 to about 1 1/2 and 2 degrees respectively". If you have a cowl the best way would be to set the fuselage up level on a flat surface with the cowl in place and measure the centre of the spinner location above the surface, then transfer that height back to the fuselage F1 location. The engine mount centre needs to be about 1/8" above this if you use 1 1/2 degrees of downthrust.

If you would like the Marvic build and trimming books just PM me your address and I'l pop it in the post. It might take a couple of days as I'm reliant on my daughter running errands for me for another two weeks.

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