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Twin Otter 125inch wingspan

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Twin Otter 125inch wingspan

Old 06-29-2009, 07:00 PM
  #101  
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Default RE: Twin Otter 125inch wingspan

Well, I just finally asked John to do me up a 130" kit! Guess I'll have yet another project this winter!!!!

Edit: So keep the the build pics coming!
Old 07-25-2009, 07:41 PM
  #102  
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Default RE: Twin Otter 125inch wingspan

As of ten minutes ago, I officially ordered a kit!
Old 07-26-2009, 01:27 AM
  #103  
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Default RE: Twin Otter 125inch wingspan

GoNavy, what size tires are you running? I would like to run scale 'Tundra tires' for mine.
Old 07-26-2009, 01:44 PM
  #104  
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Default RE: Twin Otter 125inch wingspan

Lins:

We went per plans, 5 1/2 inch mains, 4 1/2 inch nose; Dubro "Big Wheels"; They are big donuts, and inflatable. I fly off grass and my landings have occasionally been, well, er, let's say less than stellar.

These come pre-drilled for 3/16 inch axles. The plans show two landing gear rods, one 3/16" and one 1/4". The plans show the axles on the 1/4", but we put them on the 3/16" to avoid the risk of off-center drilling on the wheels which are expensive.
Old 07-27-2009, 11:27 PM
  #105  
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Default RE: Twin Otter 125inch wingspan

Any luck cutting the strut down to size as mentioned on your thread?
Old 07-28-2009, 06:11 AM
  #106  
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Default RE: Twin Otter 125inch wingspan


ORIGINAL: Lins

Any luck cutting the strut down to size as mentioned on your thread?
Sorry, but I don't think I understand the question. Could you clarify?
Old 07-28-2009, 09:02 AM
  #107  
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Default RE: Twin Otter 125inch wingspan

You have another post about your front strut. You could not figure out how to take it apart, and I'm wondering how it turned it.
Old 07-28-2009, 09:41 AM
  #108  
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Default RE: Twin Otter 125inch wingspan

Lins: I found out how to disassemble the robo strut, but decided to leave it alone. The length was only about 1 inch longer than desired. There were other factors I considered, if they are of interest to you.
Old 07-28-2009, 10:56 AM
  #109  
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Default RE: Twin Otter 125inch wingspan

I'll keep that in mind, thanks. I won't be at that stage for a LONG time.
Old 07-28-2009, 06:33 PM
  #110  
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Default RE: Twin Otter 125inch wingspan

Here is your Twin Otter "Landing of the day": http://www.youtube.com/watch?v=JwMlgc1saHs

That long wing on the Otter can really fly slow, so on a windy day, landings can be very short on the full size ship or model.
Old 07-28-2009, 06:38 PM
  #111  
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Default RE: Twin Otter 125inch wingspan

I might have been in that plane, actually. That video was in Mary River, I was coming from a camp back into Rankin Inlet. I don't think Kenn Borek has too many twins in that area usually.
Old 07-28-2009, 08:54 PM
  #112  
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Default RE: Twin Otter 125inch wingspan


ORIGINAL: thailazer

Here is your Twin Otter ''Landing of the day'': http://www.youtube.com/watch?v=JwMlgc1saHs

That long wing on the Otter can really fly slow, so on a windy day, landings can be very short on the full size ship or model.
Oh my goodness!
Old 07-29-2009, 07:36 PM
  #113  
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Default RE: Twin Otter 125inch wingspan

Lins, small world!

Here is a better landing, and one which looks perfect in every way to me. The Twin Otter can come in very steep, and still flare for a nice nose-high landing.

http://www.youtube.com/watch?v=2pk2y...eature=related

By the way, go-arounds in the DHC-6 with 15 degrees of flaps end up being nose down. (The nose points down as you climb with power, so you have a view of the runway getting smaller. Very different.) For you guys building, slow flying the mode will be a blast as that is what it is really good at. Too many flyers just keep it powered-up and flying full tilt and it doesn't look very scale that way. Slowing it down is where the fun starts!
Old 07-29-2009, 08:40 PM
  #114  
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Default RE: Twin Otter 125inch wingspan


I agree, slower flight looks much more realistic.

On this tangent; John has faithfully reproduced the stabilizer rib profile, greater curve on the bottom than on the top. Does anyone know the reason for that airfoil?
Old 07-29-2009, 09:53 PM
  #115  
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Default RE: Twin Otter 125inch wingspan

All I can think of is to stop the plane from wanting to nose dive at high speed?
Old 07-30-2009, 01:31 AM
  #116  
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Default RE: Twin Otter 125inch wingspan

Whereas the main wing is producing positive lift, the tail plane actually is creating a negative moment, or giving negative lift. Hence, the airfoil is curved more on the bottom. Working with the center of gravity (CG), if the tail plane stalls, the nose drops and this provides the stability needed for a normal configuration aircraft. Does that make sense? Sounds like John is doing it up right.
Old 08-01-2009, 06:58 AM
  #117  
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Default RE: Twin Otter 125inch wingspan

A couple years ago I asked why they were using an inverted airfoil on The stab. I was given a complex answer most of which is way over my head but the simple parts I understood were the it is to add stability, and is used mainly because the thrust line is high and above the "Z" axis center of gravity which causes the nose to push down when thrust is applied and the extra propwash over the tail keeps the nose from pushing down. They have the airfoil figured out to provide a very pitch stable plane . it also apparently helps with the flaps being behind the center of lift and also aids tail stall recovery and other things beyond my understanding . I used the airfoils angles etc off the full size plane and so far the prototypes are extremly pitch stable. cheers John
Old 08-01-2009, 10:23 AM
  #118  
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Default RE: Twin Otter 125inch wingspan

It's hard to tell from the pictures but are you using the Double-slotted flaps and the Flaperons??

Any consideration of doing scale floats??

Old 08-01-2009, 11:16 AM
  #119  
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Default RE: Twin Otter 125inch wingspan

the wing on the ist prototype had scale double flaps and ailerons but was way too delicate and complicated for reliable use and building by anyone except expert builders so I made the controls look scale but work simply , strong and reliable as does normal Rc models, The full size version is extremly complex and not suited for scaling down in models. anyone capable of making the replica controls certainly can add that system to their plane John
Old 08-01-2009, 11:50 AM
  #120  
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Default RE: Twin Otter 125inch wingspan

Is it something that you've included on the plans though?
Old 08-01-2009, 03:25 PM
  #121  
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Default RE: Twin Otter 125inch wingspan

no because any model built with the split ailerons etc is almost certain to be doomed to failure it is far to complex and delicate when reduced to model size. , if they were on the plans it would be assumed that I believe it sensible to use on the model and I do not think it practical . There is no real reason to split the ailerons etc as the flaps and ailerons are extremly effective as drawn and the hinge outline looks and is scale in shape, but feel free to take the chance if you desire. I know from the prototypes it is a real challange and very risky as any bind up will probably result in a crash if only on one side John
Old 08-01-2009, 03:32 PM
  #122  
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Default RE: Twin Otter 125inch wingspan

Fair enough.....

What part was fragile? The flaperon or the hinges? I would think 1/8" aircraft ply or even aluminum would be strong enough for the hinges and if it is the flaperon maybe going to a foam wing would be an idea.

I think you're Twin Otter is outstanding and have wanted one for some time now but without the flaperons & Double slotted flaps I would feel that it would be missing something.......

Any idea on floats?
Old 08-01-2009, 06:07 PM
  #123  
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Default RE: Twin Otter 125inch wingspan

There is no problem making the double slotted flaps and they are no problem to mass produce. That is what i was suppose to release my model of the Twotter with.. Either you go 100% scale or nothing was the whole idea of producing a twin otter. Here are the prototypes of the hinges. They would be produced in aluminum once the project was started.
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Old 08-01-2009, 06:45 PM
  #124  
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Default RE: Twin Otter 125inch wingspan

I agree with turbo-prop that there is no problem making th eparts for the controls . the problem came when I tried using the flaps under load especially with the engines propwash creating uneven force inboard and outboard this causes the flaps to try to move inboard and outboard and binding them at no predictable time or conditions. The only soultion is to have the extended parts and their pivot points strong enough to overcome the side loads. I agree this can be done by extremly talanted builders or with costly machined provided parts. if there is enough interest in this costly accessory I will entertain the idea of producing the system but it would be costly and complex mainly because of the side loads to be dealt with John
Old 08-06-2009, 01:51 AM
  #125  
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Default RE: Twin Otter 125inch wingspan

More inspiration to you guys building!

http://www.youtube.com/watch?v=rQMQA...c-HM-fresh+div

Note how flat the A/C fuselage is as it climbs out..... A very high lift wing with flaperons and a 10-to-1 aspect ratio. I didn't think my 13.5 lb 100 inch span Twin Otter would fly on the two .28 OS Max engines, but it flew very scale thanks to that high lift wing.

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