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OMP Yak build

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Old 02-09-2004, 08:19 PM
  #26
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Default RE: OMP Yak build

i dont understand that 89.5 degrees thing either. I dont see how 1/2 a degree is going to make any difference in rib alignment. as a matter as fact id be willing to bet that if you tried to get the all at perfect 90 degrees most of them would be off at least half a degree
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Old 02-10-2004, 09:09 AM
  #27
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Default RE: OMP Yak build

The ribs will always tip toward the tip in a quad tapered wing. Think about it: both the top and bottom surface of the wings taper toward the tip rib which is shorter than the root; so if you lay the wing flat on your board, the wing actually leans towards the tip. Many kits that have wings built this way will include a rib angle guide. I built a Great Planes kit one time that included a paper rib guide you had to cut out of paper and then glue to a piece of scrap wood. Not very accurate.

As far as the 89.5 degrees, that's the exact amount of angle if you go through the geometry of figuring it out. It may not seem like a lot but unless you do this, the root ribs will not fit flush against the fuselage when assembled. If we did not include this correct engineering into this kit, then we would have most likely the majority of experienced builders picking up on this error and posting corrections. So there you go, the 89.5 degrees is the "correct engineering" design for this wing sytle.

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Old 02-10-2004, 09:15 AM
  #28
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Default RE: OMP Yak build

All this thinking is making my head hurt
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Old 02-10-2004, 11:09 AM
  #29
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Default RE: OMP Yak build

Mike - are you saying that the taper on the top of the wing is less than the taper on the bottom of the wing? In other words a tiny bit of dihedral?

Also, if your fuse is set at 90 degrees, then all the ribs should be at 90 degrees..... All of them... This doesn't make a lot of sense to me. Can you try to explain your logic again?
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Old 02-10-2004, 11:24 AM
  #30
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Default RE: OMP Yak build

Not to spaek for him but I assume what he is saying is that because the wing tapers on the top and bottom, and your building it flat on a board, you actually have to tilt back the rib a bit to achieve a true 90 degree angle. The wing is actually not at 90 dgrees relative to the flat surface while your buliding it
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Old 02-10-2004, 11:28 AM
  #31
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Default RE: OMP Yak build

Ahh.... That make sense.... I thought the wing was build on tabs.....

"I see said the blind man as he spit into the wind.... It all comes back to me now...."
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Old 02-10-2004, 02:00 PM
  #32
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Default RE: OMP Yak build

Bingo young grasshoppers! There is no dihedral on the wings at all. They fit 90 degrees flush to the fuselage and are on a straight line from center of tip to center of tip. BUT.....since the top of the wing and the bottom both taper down and upwards respectively toward the tip, you have what's called a quad tapered wing. Top, bottom, leading, and trailing edges all taper toward the tip. So withthe wings mounted to the fuselage, yes the ribs are at 90 degrees, parallel to the fuselage side. BUT.....picture taking one wing panel off and laying it flat on your board with the main spar flat on your board. Now all the ribs are tilted toward the tip. There is still of course a tapered wing jig for the trailing edges of the ribs while building but that's lesson number 201.......next week!



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Old 02-10-2004, 03:11 PM
  #33
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Default RE: OMP Yak build

I gotta hear all of this. This plane is on a short wish list.

I think the 89.5 degree angle is to offset the fact that building the wing with this taper would otherwise require the tip to be supported somehow, perhaps on raised jig tabs. With the tip down on the board, with the root, all ribs must be canted to keep them vertical once the wing is squarely mounted to the fuselage. If you don't do this, when you mount the wings to the fuselage, the ribs will cant 0.5 degrees towards the fuselage, and not have the proper geometry.

smallfly, I'm with you, my head hurts...
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Old 02-12-2004, 09:44 AM
  #34
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Default RE: OMP Yak build

Ok I am in on this too I guess I better get my SUKHOI done so I can sell it to fund this YAK... when is lesson 201 ? I dont want to miss it
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Old 02-12-2004, 05:12 PM
  #35
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Default RE: OMP Yak build

Lesson 201 is next week on prop cavititaion factors versus pitch and rpm! ha ha ....don't get me started guys, I love this stuff.

Mike Pilkenton
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Old 02-13-2004, 09:07 AM
  #36
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Default RE: OMP Yak build

Make lesson 201 "Pitch and roll coupling, and how to eliminate it" I'll sign up
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Old 02-13-2004, 09:19 AM
  #37
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Default RE: RE: OMP Yak build

Again, I'm with smallfly. Pitch and roll issues are frustraiting.
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Old 02-17-2004, 08:14 AM
  #38
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Default RE: OMP Yak build

Well Im done with my build portion and as carefull as I was I still have gaps at the trailing edge of the wing to the fuselage fit of 1/8"to 3/16". I was extremely careful being I had this same problem with my ecstacy wing I built. Guess I'll shim it out and taper sand to fit, but just letting you all know to be ultra accurate on wing rib root placement. I thought I was and it still came out a little off[:@]
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Old 02-18-2004, 05:15 PM
  #39
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Default RE: RE: OMP Yak build

Wait a minute......You guys are building the wing flat on the board? I had a cheezy wing jig in my kit. Are you just not using it or what?
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Old 02-18-2004, 05:41 PM
  #40
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Default RE: OMP Yak build

Have you considered filling the gap(s) between the root rib and the fuselage using micro-balloons?
I just did this last night on my GS540 (Same basic design) and it worked out really well.
Basically same technique as fitting a wing saddle on a fuselage plane, just requires a little more glue.
Here is a link where you can get the basic idea - [link=http://airfieldmodels.com/information_source/how_to/construction/wing_saddles/index.htm]Airfield Models[/link]
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Old 02-18-2004, 06:16 PM
  #41
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Default RE: RE: OMP Yak build

the spar part of the wing is flat on the board, the trailing edge is held up by a nice jig that varies in height to keep the wing proper. I thought the jig system they provide works very well
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Old 02-19-2004, 08:15 AM
  #42
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Default RE: OMP Yak build

I had to add 1/8" and taper sand back to the tube but it turned out quite nice. I just glued my stab in and all up weight of the balsa model alone including the wing bolts was 3 pounds on the nose on a digital scale, seems a bit heavy to me but then again I dont think the rest of the stuff will add much more than 4 to 4.25 pounds so that still should put it in around 7 or so pounds. Time to start covering.... Yuk
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Old 02-19-2004, 08:42 AM
  #43
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Default RE: RE: OMP Yak build

Any pics of the bones, smallfly?
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Old 02-19-2004, 09:28 PM
  #44
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Default RE: RE: OMP Yak build

bare naked lady
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Old 02-19-2004, 11:11 PM
  #45
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Righteous![8D]
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Old 02-20-2004, 08:29 AM
  #46
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Default RE: RE: OMP Yak build

Uh Smallfly, you know you have your wings on upside down or reversed should I say. Servo bays normally go on the bottom but since the wings are completely symetrical I'm sure you just slid the left wing on the right side and vice versa.

Mike
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Old 02-20-2004, 08:43 AM
  #47
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Default RE: RE: OMP Yak build

Uh.. The servo bays are on the bottom, maybe the low resolution pic is fooling you. Now the aierons are just taped on and I didnt check which one goes to which for this photo, but I doubt that would matter. And the wing is bolted on in these pics, If theres a boo boo it's permanent. But Im sure there is'nt
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Old 02-20-2004, 09:34 AM
  #48
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Default RE: RE: OMP Yak build

here is a drawing to possible help everybody come up with a covering scheme. I started doing this on all my planes before covering. Its makes it a lot easier for me.
Its for the OMP 65" YAK

I think every kit should have something like this in their plans.

Let me know what you think.
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Old 02-20-2004, 09:37 AM
  #49
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Default RE: RE: OMP Yak build

UH, it's uhhhh invisible?
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Old 02-20-2004, 09:41 AM
  #50
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Default RE: RE: OMP Yak build

Sorry about the little delay in posting the drawings. Every now and then when i try to post RCU shoots me some error message saying that I my firewall won't allow RCU to verify something.
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