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Old Nov 05, 2012, 01:55 PM
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2m vs 3m decisions decisions

Hello all.

I recently posted a short thread on comparing the chrysalis and the spectra/spirit. I like the ability with both to use the same wing, and switch between electric and pure glider.

I was talking to a guy at my club this weekend, and he threw another option into the mix. He recommended the bird of time and converting itto electric.

Wouldn't have any problems with the build, and this option is really starting to appeal to me. I like also the full flying tail on the bot. It seems that the kit benefits from swapping out some of the wood as it seems very heavy. Just an observation from other build threads.

Any opinions?
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Old Nov 05, 2012, 03:34 PM
Dragons, WindMills, all Same
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United States, IN, Indianapolis
Joined May 2002
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3m usually flies better then 2m.
If you are looking at the BOT, there are other options verses the dynocrunch ironwood replacement process.
Some old Marks Models BOT kits come up now n then for around $125.00.
Or you can by plans and scratch build.
Also, almost any plane can have it's fixed stab converted to full flying.
Just thoughts to consider.

Jared
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Old Nov 05, 2012, 04:07 PM
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dynocrunch ironwood?
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Old Nov 05, 2012, 05:46 PM
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The wood quality and "die crushing" quality on those kits is reported by many to be disappointing.

Be careful about switching to an all-flying tail. Since the primary structure is now a moving part, the structure tends to be heavier, and more difficult to make slop-free than a 2-element tail.

The so-called "trim drag" of a slightly deflected elevator is not that much different from that of an all-flying stabilator set to make the same amount of tail lift.

If the size of the tail is dictated by control authority requirements, an all-flying tail needs to be bigger than the equivalent stabilizer+elevator. When you deflect a stabilator, all you change is its angle of attack. When you deflect an elevator, you change the tail's angle of attack AND its camber, so it can make the same tail force from a smaller area.
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Old Nov 05, 2012, 07:51 PM
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Quote:
Originally Posted by Don Stackhouse View Post
If the size of the tail is dictated by control authority requirements, an all-flying tail needs to be bigger than the equivalent stabilizer+elevator. When you deflect a stabilator, all you change is its angle of attack. When you deflect an elevator, you change the tail's angle of attack AND its camber, so it can make the same tail force from a smaller area.
I guess I always assumed the opposite all these years. Your explanation is much appreciated. Iím going to be thinking about this for a while.

Piper J3
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Old Nov 05, 2012, 09:32 PM
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2M tends to be more maneuverable. 3M tends to have more performance, as the Reynolds numbers are better, although you can trade in some of the Reynolds number advantage to get a higher aspect ratio.

If you're thinking of this larger size, there are lots of other models to consider, depending on what you're going after. For instance, there are several versions and sizes of the Olympic from Skybench, as well as a series of gliders similar to the BOT, though I forget the exact names. And the 3 meter Scooter. And the Paragon....

Then there's the Mirage from Isthmus models, the Scepter 100 (100 inch, ie. a bit more than 2.5 meters) from Mountain Models, the Marauder and the Oculus from MM Glider Tech, and on and on.

I suspect the most fun for the least effort would be the Chrysalis, but I don't know that. And it depends on what you like.
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Old Nov 05, 2012, 09:50 PM
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I thought this post would be appropriate here as it is from a World Champion and something I had never thought of before, it was thinking out of the box.

http://www.rcgroups.com/forums/showp...9&postcount=15

Curtis
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Old Nov 09, 2012, 12:23 AM
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I have come across the skybench aerotech big bird. has the same cool looking wing as the BOT, but more modern by the looks of it. it might be in the future, but atm, ive decided on an electric chrysalis. I am looking forward to being able to compare the difference between a 2m and a 3m bird in the future, but for now it will be a 2m.

itll also be easier to build, transport, and store the wing in 1 piece being only 2m long =P
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Old Nov 09, 2012, 08:02 AM
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Friends don't let friends fly Two Meters ...
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Old Nov 11, 2012, 01:50 AM
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whats wrong with 2 meters?
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Old Nov 11, 2012, 02:02 AM
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2m vs 3m

Quote:
Originally Posted by Forced_Inducti View Post
whats wrong with 2 meters?
Nothing is really wrong - just some leg pulling.
That said see post #2 above, first line.
3m will thermal easier,faster,blah,blah compared to a 2m most of the time flying in the same circumstances.
Even the difference between 2.5m vs. 2m is noticable.
As so many advertisements say, size matters

Just make the best choice you can and enjoy what you got, there is always another model lurking in your future

js
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Old Nov 11, 2012, 02:08 AM
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2 meter planes are the best ever...until you've tried sumpin bigger.
You can get a 100" (or bigger) higher and still see it well. This allows hunting at an altitude where the thermals are (sometimes) stronger. Also, up to the point where you have to buy better servos etc, the gear for a 2 meter can go into the bigger plane. This allows for possible lower wing loading. Then there is the "mines bigger than yours " factor. ;-)
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Old Nov 11, 2012, 11:32 AM
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Except that the Chrysalis 2-meter has a bigger chord than many open class ships. Chord is more important than span when it comes to visibility.

We can make an excellent-performing sailplane with a high aspect ratio and higher-lift airfoil (such as our Spectre series), or from a low aspect ratio and a "racing" airfoil.

In the case of the Chrysalis series, beginners (and others) often need some help in the visibility department, so we used that second approach.
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Old Nov 11, 2012, 07:16 PM
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I've got a whole gaggle of 2 meter planes. I like 'em!
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Old Nov 11, 2012, 08:15 PM
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I figured it was just a bit of ribbing =). I have placed an order for a Chrysalis 2m electric. Its getting shipped to canada, and technically its my fiances christmas gift to me, so shes not letting me open it until christmas. so i wont get started on it until the new year, but Im looking forward to building it very much. as far as servos, my plan was to use hitec 5065MGs. im assembling an arf for a buddy and he wanted them, i have to say, they center EXTREMELY well in my opinion. i think those might be on the small side for a 3m tho.
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