'Mediator'

[David Ramsden]

Thought you might like to see this.
Inspired by George Aldrich (Peacemaker) and Steve Lange (Le Fish).
Traditional build. 4 channel, 54" span. under 30oz. (<9.5 oz/sq ft)
There's a Design post and three Build posts on the DSSC website **LINK**

Edited By David Ramsden on 17/01/2021 22:21:01

[Jonathan W]

Looks great and the unusual colour scheme really works, on which I read some comments in your build postings.

How about doing a plan article for RCME? It will make a nice change from the usual suspects!

[Robin Colbourne]

David, the Mediator cetainly looks a novel design. As Jonathan says it would make a nice change to the usual stuff and we need more VTPR models that don't call for large chunks of EPP or pre moulded parts.

I look forward to a flying video when circumstances allow.

[GeeW]

David

Sorry for the thread drift.

DR400 glider on the DSSC blog-site...any more information available please very nicely?

Thanks in advance

Gordon

And now back to the scheduled program.......

[David Ramsden]

Thanks for the compliments Jonathan and Robin. She's not been test flown yet so thought's of future plans are a bit on the premature side. Not sure my drawing skills are up to it either!

GeeW I think you are talking about my last design the DR420. If you go to the DSSC website there's five posts about that one starting with design news on 4th September 2020 and ending with test flight news on 9th October. I'm waiting to fly her again as well as a maiden for the Mediator.
**LINK**

[Mike T]

David, that looks absolutely superb! .

I read your posts on the DSSC website and very much agree with your comments re 'fuselages' - who wants to fly a broomstick with a plank? This design has bags of character and as for a plan, I'm all in favour, and from what I can see, your drawing skills seem well up to it! *

Looking forward to your report (and pics) of the maiden!

*Please, please save us from another Hawk - or a Mustang!

[David Ramsden]

Posted by Mike T on 19/01/2021 00:44:45:

David, that looks absolutely superb! .

I read your posts on the DSSC website and very much agree with your comments re 'fuselages' - who wants to fly a broomstick with a plank? This design has bags of character and as for a plan, I'm all in favour, and from what I can see, your drawing skills seem well up to it! *

Thanks for your compliments and enthusiasm Mike! I'm flattered.

Evidently lots of people DO want to fly a broomstick with a plank, ready made out of plastic too! I have no interest in that. I guess that makes me an old timer although I don't feel old at 62.

If she flies as well as she looks then maybe I should consider contacting RCM&E about publishing a plan although I'm not convinced there would be much interest given the choices that most aeromodellers seem to make these days. Might be better to just supply the plan free of charge myself although I don't know anyone with a big enough scanner and folk won't have a big enough printer.

Anyway. Back to watching the weather forecast!

David

[Gary Manuel]

Fuselage looks superb.

Wings look superb.

Rear end looks superb.

The only issue I have with it is that the wings and tailplane look like they are from 2 different models. A tail with similar shape and proportions to the wings would make a much nicer looking model in my opinion.

[Jonathan W]

David has based the wing and tail shapes on the still popular Peacemaker control line model, designed many moons ago by George Aldrich. Those of us familiar with the Peacemaker will instantly appreciate the design of the Mediator.

[perttime]

Posted by David Ramsden on 18/01/2021 22:06:36:

Thanks for the compliments Jonathan and Robin. She's not been test flown yet so thought's of future plans are a bit on the premature side. Not sure my drawing skills are up to it either!

You have a plan that was used for your prototype. Hand drawn? Turning that into something that would fit inside a magazine would take some work. A little help might be needed if you cannot do it on a computer yourself.

[David Ramsden]

Hello perttime.
I do have my hand drawn plan but I have no experience of using computer aided design software. I'd imagine the Adobe version is probably the best (and probably expensive!) and that replicating non-standard curves would be too great a challenge for someone new to CAD.

[MattyB]

Looks nice, but whilst it is aesthetically pleasing that swept back fin and rudder is highly likely to give you roll coupling when you apply rudder, especially in knife edge. Try it by all means, but I suspect it will fly more accurately with a vertical hinge line and more rudder area near to the fuselage centreline.

[David Ramsden]

Posted by MattyB on 20/01/2021 15:28:53:

Looks nice, but whilst it is aesthetically pleasing that swept back fin and rudder is highly likely to give you roll coupling when you apply rudder, especially in knife edge. Try it by all means, but I suspect it will fly more accurately with a vertical hinge line and more rudder area near to the fuselage centreline.

Hi MattyB,
Yes I did consider that when I was drawing the fuselage/fin/rudder but I was so fixed on the idea of basing it on the Peacemaker fin-rudder shape that I decided to live with it. [Bearing in mind, 1) I'm not an experienced aerobatic flier and 2) I've watch plenty of vids of good aerobatic models with top-only rudders].

To compensate, (unlike the Peacemaker), I extended the rudder to the bottom of the fuse and I swept the fuse bottom-line downwards a lot to give the rudder more area below wing level.

As luck would have it, to get the cg right I had to put the battery pack in the top of the fuse. This means that the vertical cg is now above the wing section (she's top-heavy). Perhaps this will work well with having more than half the rudder area above wing level?

Thanks for your interest,

david

[Geoff S]

It does look a very pretty model and beautifully built.

I noted Matty's comments re the rudder hinge's being sloped back. I know little about aerodynamic design so I may be right off the beam here but I had a similar experience with the first 1 metre model racing yacht I had. It was a very nicely built own design I acquired s/h from the builder. I had an awful lot of trouble with direction control down wind in heavy weather and that had a sloping rudder hinge, too. It made the rudder very heavy because of the forces behind the hinge. I redesigned it with a vertical pivot about 1/3 of the way back from the rudder l/e and it was very much better.

I'm probably wrong but it struck a memory chord.

Geoff

[David Ramsden]

Thanks Matty and Geoff,
I'm sure you're right. Thanks.

If I ever get good enough that I'm having a problem perfecting my knife-edge flying then I'll try modifying the rudder design (add more below and straighten-up the hinge line). I think I have a very long way to go before I get to that point. In the meantime I'm happy just doing my own thing as a 'sport' flyer.

Just in case anyone is interested here's where you can read about my flying background. **LINK**

Edited By David Ramsden on 20/01/2021 19:28:31

[Piers Bowlan]

Posted by Geoff S on 20/01/2021 16:49:18:

It does look a very pretty model and beautifully built.

I noted Matty's comments re the rudder hinge's being sloped back. I know little about aerodynamic design so I may be right off the beam here but I had a similar experience with the first 1 metre model racing yacht I had. It was a very nicely built own design I acquired s/h from the builder. I had an awful lot of trouble with direction control down wind in heavy weather and that had a sloping rudder hinge, too. It made the rudder very heavy because of the forces behind the hinge. I redesigned it with a vertical pivot about 1/3 of the way back from the rudder l/e and it was very much better.

I'm probably wrong but it struck a memory chord.

Geoff

I don’t know anything about sand yacht design but a swept rudder on an aeroplane will produce a positive pitching moment when deflected apparently. Could make knife-edge interesting but it looks very stylish on your Mediator David. I like it. 👍

[David Ramsden]

Thanks Piers. I'm glad you like it!

To be honest, I've never tried knife-edge flying before and I might never progress beyond a fairly slow roll. However I do want a model that handles nicely and doesn't give me any nasty surprises.

Once I've got past her maiden and got used to her I'll try full rudder in straight and level and see if the nose pitches up noticeably. If it does I guess I could always programme in a bit of down elevator compensation. If I ever do get to knife-edge then maybe the elevator compensation will help there too.

That still doesn't get over the issue that most of the rudder is above the wing airfoil center-line, but, I guess that is true of most low and mid-wing designs.

On the subject of CAD, I've just been watching a QCAD tutorial on YouTube. It looks quite suitable and it's free.

[MattyB]

Posted by David Ramsden on 21/01/2021 01:08:08:

Thanks Piers. I'm glad you like it!

To be honest, I've never tried knife-edge flying before and I might never progress beyond a fairly slow roll. However I do want a model that handles nicely and doesn't give me any nasty surprises.

Once I've got past her maiden and got used to her I'll try full rudder in straight and level and see if the nose pitches up noticeably. If it does I guess I could always programme in a bit of down elevator compensation. If I ever do get to knife-edge then maybe the elevator compensation will help there too.

Very few gliders are capable of sustained knife edge, but the reason it still matters is that the manoeuvre you aspire to (a slow axial roll; this also applies to point rolls) requires extensive use of the rudder in different orientations. What you may find is that as introduce rudder in knife edge the model will tend to pitch up, bringing it off axis. That will require down elevator compensation in real time which is hard to do (a mix might help, but the speed dependency will make it difficult to dial in) and of course causes drag at a moment you are trying to preserve energy to get through the figure. Try it and see, but for absolute best aerobatic performance I suspect it will need a tweak.

[David Ramsden]

Thanks MattyB.

I find this very interesting and value your comments and everyone's.
I remember you [and others] helped me with my DR420 too which does now fly very nicely.

If I was a capable aerobatic flyer I could put her through her paces and quickly discover her faults (or limitations). But the fact is I'm not. Loops, stall turns, quick rolls, cuban 8s, and shorts periods of inverted flying are about my limit. Don't get me wrong, I'd quite like to be able to fly difficult maneuvers precisely but I don't need to.

What I most enjoy about the hobby is imagining a model, drawing it, watching my vision gradually turn into reality during the build, and then flying it just for fun.

I also really enjoy these forum conversations so thank you once again.

David

[Jonathan M]

Very impressive David.

 

You've successfully created a lovely proper model that is just a little bigger and only slightly heavier than the mass-produced foam (and not very robust) Ahi, but which seems more useful for typical UK conditions... and for people like me who are in middle-age only just easing themselves into more challenging aerobatic sloping.

The Ahi's wing-section and loading of 6oz/sqft is amazing for geniuses who are highly skilled at VTPR off the side of a porta-cabin in their sleep and can stop or flip on a sixpence etc, but for me it lacks momentum - there's very little 'running'.  Whereas I imagine your Mediator at 9.5oz/sqft would be a happier but still very capable aerobatic model.  (If you compare their Wing Cubic Loadings, then the difference in loading is in fact much less: 4.0 for the foam versus 5.3 for your built-up model.)

 

Re producing a drawing, either for publication or for upload to Outerzone, there's no reason why it has to be done on CAD.  RCM&E frequently contains older hand-drawn plans, and components don't have to be laser-cut as you've easily proved in your prototype.  Your original drawing can be fairly quickly re-done according to usual 'model plan' conventions... if you're inclined.

 

Jon

 

 

[leccyflyer]

I thought that David's model bore a resemblance to the Ahi too.  My pal has one of those and really didn't like it on the early flights, but once he had it dialled in it flew much better and is very aerobatic.