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Speed,Combat,Scale,Racing => Carrier => Topic started by: Dennis Saydak on September 07, 2009, 12:00:54 PM
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Has anyone built & flown this model? In reviewing the plan I noticed that there is a lot of positive incidence built into the the wing. I'm wondering why this is necessary since the model does have flaps for slow seed. The + wing incident seems at first glance to be unnecessary and could be detrimental to high speed flight but I certainly stand to be corrected on that observation.
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The Robert's Martin Mauler had too much positive incidence and would fly with a lot of down elevator at high speed. If this was taken out during the building prosses it flew much better. I would agree that positive incidence is a bad thing, make it zero. Mike
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The Robert's Martin Mauler had too much positive incidence and would fly with a lot of down elevator at high speed. If this was taken out during the building prosses it flew much better. I would agree that positive incidence is a bad thing, make it zero. Mike
thanks for the heads up on the Mauler.
Wayne
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I built my Robert's Mauler box stock with McCoy 60 and had no problems with the high speed. DOC Holliday
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It's been some time since I looked at the Wyvern plan so the airfoil shape doesn't pop into my memory. I do have a Mauler plan. A number of Carrier designs used something like a Clark Y section. One thing to remember, incidence isn't measured from the bottom surface of the wing. It is measured from the chord line. The chord line runs from the center of the LE to the center of the TE. So, when the lower rear surface of the Clark Y is parallel to the longitudinal datam the wing has positive incidence.
Without realizing it we probably trim in some down on most of our planes at high speed. It did seem that the Maulers I have seen looked like they flew tail high. But, no one ever said it caused any particular difficulty.
It wouldn't hurt to build the model with zero incidence.
Bob
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It's not that you can't control the climb it's how much easier it is to control with zero insidince.
Mike
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It's been some time since I looked at the Wyvern plan so the airfoil shape doesn't pop into my memory.
Bob, here's what the Wyvern plan looks like. Perhaps the + incidence was used to counteract the effect of the "drooped snoot"? I was hoping that someone who built the model could report on its flight performance at high speed. Apparently Marvin did well with it in competition.
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That rib looks small to be a center rib. Of course I know little about the design. I can see the tip being positive for low speed. DOC Holliday
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That rib looks small to be a center rib. Of course I know little about the design. I can see the tip being positive for low speed. DOC Holliday
DOC, that is definitely the center rib shown. The construction article states that when building the wing the centerline of the ribs should be parallel to each other. So, the entire wing would have + incidence as set by the lower fuselage keel. I think the model would tend to climb like a homesick angel at high speed unless lots of down elevator was used to compensate. The design has LARGE flaps for low speed flying.
Aklthough we chose to build Boss's Sea Furys this winter we are thinking ahead that the Wyvern could be next winters project. It's good to have as much information as possible beforehand and everyone's opinions and advice is greatly appreciated.
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With that much camber in the airfoil, you are going to fly with lots of down elevator anyway - as speed increases, so will the need for down elevator.
The positive incidence MIGHT be to partially counter any nose-down tendency when the flaps drop - given the low wing and the high camber I'm guessing that large flaps will cause a large 'negative pitch' response.
As for the tips being washed in (or out) probably none is the best, but if anything you would want the tips to be at a lower angle of attack then the center rib so that they stall after the center section.