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Feb 06, 2008, 08:46 AM
Confused? Who, me?
Roger Lombard's Avatar
Thread OP
Discussion

1.8-2.5m Minimoa


I'm trying to persuade Green Air Designs/Replikit (to be fair I feel I'm pushing an already open door) to bring out the old Keil Kraft Minimoa kit at either 150 or 200% scale, so either 75" or 100" wingspan. Obviously, since the original was a freeflight bird, anyone buying the kit would face some re-engineering to convert it to r/c but I'd expect it would be a full laser cut kit, because that's what they can do these days, and I'd expect it would be in a significantly different price range to the Minimoa kits that are already on the market. The laser-cut short kit for the stock 50" bird is 25/$50 so even at twice the size and with the stripwood included it's not going to be open heart surgery on the wallet is it?

Would anyone else feel as enthusiastic as I do?
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Feb 06, 2008, 09:37 AM
"To Fly is Everything"
britchris's Avatar
yea id be up for one,be nice to have a mini of 100"
Feb 07, 2008, 01:33 PM
Veni, Vidi, Napi
catrancher's Avatar
Sounds like a good idea to me!

Tom
Feb 07, 2008, 04:32 PM
Confused? Who, me?
Roger Lombard's Avatar
Thread OP
It's obviously not going to be one for the real scale purists but for myself I'm happy to live with stand-off scale - especially if the price is very user-friendly.

I used to free-fly one of the original KK ones nearly 40 years ago so maybe there's a bit of sentiment in there too. Aw shucks
Feb 07, 2008, 05:03 PM
daveosoar
I'll go along with that - just the size for my backyard 30M cliff!
Daveosoar.
Feb 11, 2008, 01:03 AM
Registered User
tinkrerpilot's Avatar
A 2.5 Mini? Count me in one this one. My other half is interested in the hobby to and this would really tickle her fancy. Of course I do all the building and such, and she gets all the benefits. One of her favorite models. Just can't afford some of the bigger ones. This would hit a real good market place for the sizes you guys are talking.
Apr 04, 2008, 06:19 AM
Confused? Who, me?
Roger Lombard's Avatar
Thread OP
Well I've now received a prototype kit from those lovely people at GreenAirDesigns/Replikit. We eventually went with 200% scale so it's going to come in around 100" - 2.5m.

It's a long time since I used to build wooden gliders so this is going to be fun. First impressions in the box are there's a lot of wood and the laser cutting is excellent.

It hasn't simply been doubled in size - there's a lot of ply and spruce where it all used to be balsa and replikit have re-engineered the wing mounting to suit the greater weight. But at the moment its a 2.5m freeflighter - if you ever built the KeilKraft 50" original you'll have no problem recognising the plan! - so I'm going to have to do the control surface mods myself. No worries but I'm neither proud nor very experienced at this - if anyone wants to kick in with suggestions or constructive (please!) feedback you're welcome. Conversely, if I can do it then anyone can!

It isn't going to be the most sophisticated Minimoa kit you could buy but I think retail is going to be around 80 and so it's in a different ball park from other 2.5m upwards versions. If I didn't have it already I'd buy one!

I should say I don't have any business connections with GAD/Replikit!
Apr 08, 2008, 04:34 AM
Registered Slopeaphile
awmeade's Avatar
Hi Roger,
Nothing on the GAD site yet - any ideas when they are going to be RTM?
Cheers,
Andy
Apr 08, 2008, 02:31 PM
Confused? Who, me?
Roger Lombard's Avatar
Thread OP
Don't have an answer to that Andy - I sent an e-mail to them yesterday but no reply yet. Hopefully I'll post a progress pic of the fuz tomorrow. Discovered this afternoon that in fitting the wing box, discovering it didn't fit and after chuffing about to make it fit I had made a mistake so mind bendingly and obviously stupid that I don't even want to think about it, let alone describe it . Suffice to say that had I asked my dog to fit the wing box she wouldn't have made the mistake I did . And she's been dead about six weeks

I suffer badly from AAADS and it's a terrible thing.

Age Affected Attention Deficit Syndrome
Apr 10, 2008, 08:59 AM
Registered User
vintage1's Avatar
Quote:
Originally Posted by awmeade
Hi Roger,
Nothing on the GAD site yet - any ideas when they are going to be RTM?
Cheers,
Andy
The GAD site is lagging behind reality, and I am supposed to be writing the new one, so blame a combination of Mike and I for letting the Minimoa fall between two stools.

There is a 'in development' site at www.blackandwhite-models.com/Replikit and largely stuff that shows up there is for sale or damn nearly for sale. But prices are not always correct, as once the kits have been cut and timings developed, the price changes a bit: also when we discover there are bits that should be in the box that we didn't cost for etc.

I haven't been involved in the Minimoa project - so I can't comment, but if any issues arise, post em up here and I will try and liase with Terry to get them sorted out. He doesn't have time to stay in touch here.
Apr 10, 2008, 04:07 PM
Registered User
vintage1's Avatar
OK it seems that I am on the case now batting from the Replikit/GAD corner as it were. Mike's dumped it all in my lap

Basically to take what was a halfway decent design and turn it into whatever you glider guiders feel is the best we can do with this model.

As long as its made of wood and doesn't get completely uneconomic, the target is a practical 'full house' R/C glider. And pretty near scale. And a pretty complete kit. Not just a few formers/ribs and a bag of sticks. We are trying to get away from that - amny custmers cannot easily get to a model shop if they suddenly find they are short of snakes, screws, bits of glass cloth etc etc. So the theory is to try and put everything in the box. And make sure its decent quality too.

This will not be an instant process though. I have to get up to speed on what has been done, and do some work to convert to my style of CAD.

So far Roger has asked for ailerons, amd Mike says as drawn there aren't any control surfaces at all - is that right, Roger?

So there are decisions to be made for routing snakes, or cables, or whatever, integrating the surfaces and where and how to hinge..

Then the canopy is apparently not scale. As long aas that doesn't have implications for the wing mounting, I can't see any reason not to extend the canopy back further.

Once I have the drawings converted I'll try and post them up at reduced scale so everyone who wants to get involved can see what's happening and make comments. Not tried a 'design by comittee' before, but it should be interesting. I get the casting vote tho

What do you expect out of a modern scale sailplane?
Apr 11, 2008, 01:08 AM
Confused? Who, me?
Roger Lombard's Avatar
Thread OP
Good news that you're at the party vintage1.

You are correct that the kit doesn't presently have control surfaces. So far as the rudder is concerned that's scarcely true because since its a full flying rudder it doesn't require any change except a hinge to the fuselage. The elevators aren't going to be difficult to do either. It's the ailerons that need a bit more creative thinking because the structure itself is completely different. Without the need for ailerons in the original 50" free-flight bird KeilKraft were free to put the spars in the positions that made most economic sense while delivering the necessary strength.

I plan to come up with my own short-cut solution but in so far as any part of the kit would benefit from a bit of a re-think I guess this is it. Another thing is that if the drawing below (of the full size Goppingen Go3 Minimoa, not the kit!) is representative then the dihedral on the model is too much. It's set at 3.5" at the elbow increasing to 6" at the tip. The drawing suggests that the outer wing has very little, if any, extra dihedral. Maybe KK put the extra in for stability in a FF model?

Input from Those Who Know would be welcome here!

Edit: I think I have established that the elbow position and tip dihedral on the bulk of production were varied from the early ones and another 3 view I found does show clear dihedral in the outer panels but not a huge amount. I'm back to "Input from Those Who Know would be welcome here!"
Last edited by Roger Lombard; Apr 11, 2008 at 01:28 AM.
Apr 11, 2008, 03:19 AM
Registered User
vintage1's Avatar
Yeah..I think a brand new wing is called for. FF dihedral not required for R/C.

I wonder if washout would be a good thing..there's a LOT of span there for quite a short fuselage. Looks like it would spin easily and drop a wing smartly if stalled in a slow turn.

Those ailerons are HUGE. The designer definitely wanted to have slow speed control authority!

Do you have any detail on how the rudder was moved? I see no sign of external cables..?

And was the tailplane strutted? The elevators look easy enough: central horn inide the fuselage and a pushrod or snake.
Apr 11, 2008, 07:04 AM
Registered Slopeaphile
awmeade's Avatar
I'd give Mr Williams a nudge if I were you gents - he's designed two of these monsters (1:3.5 and 1:4 iirc) which are superb flying machines in every respect.
Apr 11, 2008, 08:27 AM
Registered User
chris williams's Avatar
Design by committee eh? Let's hope we don't end up with a Brabazon...

Brief history: the earliest surviving Minimoa, HB 282 (The red and white one with the Swiss markings) has a smaller rudder, slightly less dihedral and a non-typical modern canopy. The difference in dihedral is that on HB 282 the undersides of the outer wing panels are parallel, and on the later models the upper surface of the outer wing panels are parallel. HB 282 has a non-shrouded rudder with quite a big gap, the later ones are shrouded with hinged plates either side. HB 282 has modern scissor style brakes, whilst the more common production model had spoilers on the top surface.

There's good and bad news in the smaller sizes: The Krick Minimoa always seemd to me to fly like a grand piano with the lid open, but the 1st RC version I built from the old Radio Modeller plan (RM 208) flew extremely well on 3 channels (No ailerons) at 3m span.

The key to the whole thing lies in two factors it seems to me:

Pick a good wing section (Selig 3021 works well in the smaller sizes)

Keep it light, then you shouldn't need any washout

If you can CAD it up to 3m all the better, because larger is always better.

Vintage ailerons always tend to be large, for the Minimoa it's essential to use lots of differential, at least 2 to 1

PM me your address Vintage 1 and I'll send you a copy of my Construction & Documentation CD: most of the info you need will be on there...

cw
Last edited by chris williams; Apr 11, 2008 at 08:48 AM.


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