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Warbird Flyers, highly tapered wings...

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Nigel R18/09/2019 09:41:26
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I have a hankering to build a 60 some inch span Yak or Mig in the future.

But I confess, I have been at this game for a few years and have not actually flown a warbird with a set of highly tapered wings. Models with a 50% sort of taper, yes, a few, some with lots of sweepback, and I've not found any to be particularly badly behaved when it comes to landing or spin or any sign of high speed stalls.

But the more extreme tapers, no, not flown one. I'm thinking airframes like the Yak 1 or 9, or Mosquito, where tip chord is around 25% of root.

To those who do or have flown these types, how do you find their behaviour?

How much do typical warbird flaps improve or reduce (or even make worse) any tip stall tendencies?

Will I find much difference between split flap or plain flap here? (yes, I know, split were de rigeur in WW2, but I'm looking at a stand off build)

Bob Cotsford18/09/2019 10:03:43
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De rigeur? Mais non!

Et ici

I have a Warbird Replicas La7 that I've yet to complete (where do the years go?) but reports were that handling is quite benign.  I suppose the Ta152 and Ki61 that I had weren't quite that tapered but they both handled well, perhaps the secret with those was high aspect ratio and low wing loading respectively.  I've had far worse handling models with less  tapered wings, my late unlamented Extra 300 and VQ Yak9 spring to mind.

My experiences have only been with club sized models (60-120 size) and I think size must matter as I don't find flaps really make or break a model at this size other than as gizmos to display.

Perhaps someone with larger model experience would care to comment?

 

Edited By Bob Cotsford on 18/09/2019 10:32:31

Nigel R18/09/2019 10:41:37
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Thanks Bob

Ok not entirely de rigour!

I'm looking at club size too. 90 four stroke.

I find slippery models very tight on our patch. It is a short strip and from some directions a long low approach isn't a good idea unless you have a hedge proof airframe! Drag of some sort and the stepper approach that goes with it just makes life easier.

Don Fry18/09/2019 10:57:36
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Am I missing something. Why does inboard flap deployment, effect tip stall characteristics?

Jon - Laser Engines18/09/2019 11:41:57
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Like Bob i have an La7. Its pretty infamous by now and its highly tapered wings did give me cause for concern when i originally bought it. Once trimmed out on the test flight the first thing i did was a stall test. I was pleasantly surprised, all was well and as i was just about to shrug my shoulders and forget it the darn thing flipped on its back and went into a 60 degree inverted dive. Recovery was no problem due to the height i had chosen to do my test, but yikes!

So, to summarise it was very tolerant to a point and after that it just threw itself at the ground. 9 years later its still flying and i dont even think about the stall. I know where it is and know how to fly around it so its really not a concern at all.

I dont see high speed stalls being a problem in warbirds as you dont tend to yank them around like a cap or extra. If flown smoothly its really not a problem. Again stalls on landing should never happen if the right approach is flown. For me stalling a warbird is the most likely on an aborted landing. Say you touch down, catch a bump and bounce. You are now 2ft in the air again you have a very small window to get the power on and go around. You cant float it down from there, warbirds are too heavy, you can just firewall it as it will torque roll/spin, and you cant be too gentle as you do need to accelerate. This is the real danger zone in my experience.

As for flaps, all of my current models have split flaps but a flap is a flap. Full flaps tend to be a little more effective but its not something to loose any sleep over. I do find them pretty vital but most of my warbirds are very big and heavy. On a smaller one i would fit them as you can always not use them if they give you nothing. Its easier to do that than add them after you find you need them.

Nigel R19/09/2019 11:15:06
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3047 forum posts
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Many thanks Jon, that's kind of confirmed what I thought. Essentially, just fly around the stall, you know it is there, these are airframes built for fast and smooth maneuvers anyway. I have flown airframes with some sharp stalls so I guess I would just expect more of the same.

I'm leaning toward the idea of a non scale plain flap and essentially using it as a landing brake for a final approach of "brakes on and 25% throttle".

Don with flaps down, the inboard section is at an effective higher AoA. I don't know that it has a very big effect as the stall (as I understand it) is mainly controlled by the shape at LE and the area of the wing immediately behind; the TE isn't in very clean air at this kind of airspeed.

Don Fry19/09/2019 12:11:46
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3910 forum posts
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Hank you Nigel. That makes some sense.

Simon Chaddock19/09/2019 12:19:05
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Nigel

Try building a scale modern scale airliner! The root and tip section of my Airbus A350..Root Tip

It is of course quite highly swept and fairly flexible which seems to "pacify" its characteristic somewhat although positively exploring the extreme parts of the flight envelope is not recommended. wink 2

I would suggest go ahead, build to scale and simply treat it with respect.

Edited By Simon Chaddock on 19/09/2019 12:20:35

Jon - Laser Engines19/09/2019 15:46:29
4789 forum posts
179 photos

Nigel, as food for thought i have the plans and laser cut parts for a 68'' span jerry bates yak3. It would be suitable for 150 4 strokes and would probably be about 14lbs.

As i have way too many unstarted models i was thinking of selling a few and this one is shortlisted. If you are interested let me know.

Nigel R19/09/2019 16:24:18
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3047 forum posts
475 photos

Looks very nice Jon and I appreciate the thought, but sadly above my pay grade (and I don't have a 150!) - 60 class (at most) are more realistic for me.

I keep looking at the (very) simplified 61" Yak on outerzone (**LINK**) with a view to re-engineering some of the design and material choices to keep it light; size wise, keep it as is with a 70 (?) or a few % larger to suit the 90.

Simon, yes, now that is some taper.

Edited By Nigel R on 19/09/2019 16:24:44

Jon - Laser Engines20/09/2019 09:43:27
4789 forum posts
179 photos

No problem Nigel, it was just a thought...although, it just occurred to me that i have another yak of about 55 inch that i might part with. I had forgotten all about it! I have the plans, canopy, cowl and all the laser cut/foam core parts.

There are a bunch of photos on this thread **LINK** showing the build the other guys did with this kit. i was going to join them, but never got round to it and as things have now moved on its unlikely i will ever put it together. A decent 50 or 60 4 stroke would pull it just fine.

Apologies if it seems like im just trying to flog stuff, its just that i have so much gear i need to thin it out a bit.

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