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Stormbird 2m

Doc James Hammond

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Update:

Henning Schmidt (Germany) just got an easy 320 Kmh (197Mph) out of a standard Stormbird - though a much newer one than the one Bruce was flying.

No flutter and the speed was only held back by a not so good flying site.
 

Konrad

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Who is the "Bruce"? And what is the design speed (flutter point) for the Stormbird? Not that I or any mortal can reach it!
 

Doc James Hammond

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HI Konrad,
the "Bruce" is Bruce Tebo - apparently a lovely guy - and is also Aloft's test pilot and de facto Ambassador.

A reportedly highly competent flier, Bruce is one of only a very few people on the planet who have gone over 500MPH with a DS model.

For the lowly Stormbird, I honestly have no idea what the theoretical flutter point would be because it depends on the entire control train, plus the control surface construction plus a lot of x and alpha. Obviously a carbon reinforced surface with a thicker hinge would be less susceptible to the dreaded shake rattle and roll.

The Stormbird that Bruce took to 174 MPH before flutter set in was an old and apparently well used example. Since then both the construction and materials used have been improved and so I guess it would be less likely to flutter.

Hopefully in the not too distant future, Bruce will be rearmed with a more robust example and then we will probably discover what the physical limits of the model may be. The aerodynamics will "Take it" but not being an expert on models at such speeds I'm not sure how far the materials and construction will go.

Cheers,

Le Bonne Docteur.
 

Konrad

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I've flown with that "Bruce" and I can report he is all that you mention!
Yep, design speed limits and actual speed limits are rarely the same for the reasons you mention.

What improvements have been made in the materials? Have you changed the epoxy, changed the fiber weave, gone with structural foam? Is it a process change like the fiber lay up changed, post cure heat treatment schedule modified?

I have a few RCRCM ships that show vastly different material performances, even between the wings on the same model! Quality pays it does not cost. Both you and Wayne warned me about the quality from RCRCM!

All the best,
Konrad
 

purview

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yes I had the luck to prove it:
be because it depends on the entire control train, plus the control surface construction plus a lot of x and alpha
...the control horn of the servo on the aileron broke and then the aileron began to flutter. The surface control horn was a allready glued in. The servo horn was too weak and lost its confidence. I then lost my beloved SB, I was not able to manage a save Landing (the good point of the story: the plane didn't look down somewhere into the valley to hide himself, it crashed after a nearly full circle just behind me)

I first checked the servo horn and found out that it was too much of less material to use it here, although the 2 year old SB had seen bigger storms, so it must be somehow of materials loser or bad air
The possibilities of the airframe are a way more higher. The limit was in this case set by the linkage and lead to aileron flutter. But planes can also flutter with very tight linkages because of physical properties

cheers
chris
 
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Wayne

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We are always seeking to improve our products. If we see room for improvement, we will always share this information with our suppliers. This goes for anything we sell. We try and take a very active roll with our manufacturers to offer better and better products for our customers.

With that said, we are currently working with Doc to offer a new version of the Stormbird that is a bit beyond his comfort level. I am excited about the prospects, and he seems to be also. Normally you would never see Doc talking about such speeds on his airframes. So why the Stormbird? Well, I love how it flies, and it has that massive wing joiner. I doubt you will find a 2 meter plane with a larger wing joiner. The convenience of a 2 piece wing, but the strength of a 1 piece wing. Win win.
 

purview

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sounds nice, but here we guess that there must be more than 25g's to kill the wing joiner? only DS with high speeds can deliver such demands
 

Wayne

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Yes. Exactly. :)

Intended use is DS Acro where speeds tend to be below 250 mph. The plane has no issues on front side, these are DS speeds we are talking about, and the plane was never intended for, thus a few tweaks and plenty of testing. The tweaks will add weight, mostly tail weight, so not something one would want for a front side only plane. If testing goes well, this will be a special version for this special task.
 

Doc James Hammond

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Stormbird aeros in Oz.

BTW the end looks a little "Iffy" but Darrin assures me that the plane simply plonked gently down behind them.

Doc

 

jvaliensi

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Hi all,
I am about to start building my Stormbird. I am thinking MKS 6100HV all around. I have bearing frames.
These should be good?
 

Konrad

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Might be a bit small for the performance potential of the Stormbird. For sure I'd want a larger servo for the flaps. If for nothing else these have larger more robust gears. The KST X10 mini would be my preferred servo for the wings.
And as the tail functions are NOT shared as with a V tail I'd go with something like these for X tails MS 325.

Now most 2meters don't need this much servo. But the Stormbird has the performance potential to take advantage of the stronger servo.

All the best,
Konrad
 

purview

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previous owner of a stormbird 2M...
the machine was in use with (all@6Vstall-torque servos) 2xAIL 3,5kg, 2xFLP 4,7kg, ELV 5,8kg and RUD 3,8kg
it worked well up to 30m/sec and more on gusts and with full of ballast (flying weight 2,5kg)
the wings are ultra slim and u have to find the correct placement for a 10mm servo on flap position. I also had to file the servo case. On aileron it is not possible to get 10mm inside the wing. Be careful on the decision of the right servo horn and the linkages. If u want to use clevises and/or z-bend plier u have to bend the rod to get it smooth around the edge of the hinge line. This was (in my case) due to a ultra tight rod position on the servo horn. Space is the most limiting factor on this build up.

I haven't used the "in the tail" elevator servo position. But it is the better solution for correct alignment I think

cheers chris
 

Konrad

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So the KST X08 plus would make a better aileron servo?
 

jvaliensi

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I can put KST 08+ w/ bushing mounts for the ailerons. And KST X10 mini for the flaps. It might be easier to directly epoxy the X10's to the wing skins, because the bearing frame is so wide.
The MKS 6110's fit it the best. They seem to lack the torque numbers of the KST's. I wonder how accurate the numbers are?
Spenser L told me he tested a bunch of servos and the MKS numbers tended to be realistic and that is why he recommends them for the K2DS. I've heard that Futaba is conservititve with their published numbers for servos.
KST may be optimistic.
 

Konrad

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I've been able to slide most servo frames under and into the servo opening even when the frame is bigger than the opening. This is in fact normal for most of the servo frames I've used.

While Futaba seems to have a good reputation. They are the brand of servo I've had the worst experience with. Now this was 30 to 40 years ago. OK, Blue Arrow were worse.

Today as everybody sources the same electronics I think servo performance comes down to gear trains and software. As to spec's I hope you aren't spec'ing the servo so close as to not have head room for marketing hype, over speed and under voltage.

I love my MKS servos and my KST servos.

I also like my KS servo and Power HD servos it all depends on the application. But it is true no KS servo can compare to a KST servo on their own merits. The KS servo has too much backlash. But for the price of one KST I can supply a whole ship set of KS servos. This is why I use 100% to 120% of the servo motion, resolution and backlash issues are minimized.

I shake my head in disbelief when I see radio programs with the servo limited to 70% motion!
 
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jvaliensi

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"I shake my head in disbelief when I see radio programs with the servo limited to 70% motion!"
I totally get this, but it seems I always have too much travel on the ailerons and not enough for the flaps. I have a few setups with the servo travel set less than 70%, there was no getting around it. The servos still work better than my thumbs-
 
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