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Pitch Stability

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Old 11-10-2010, 11:23 PM
  #1
dale691
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Default Pitch Stability

Hi guys, this may not be the right place for this post but I thought I'd start here. I have had several 50cc size airframes all different brands and different styles (Yak Extra etc). Running a DLE55. I don't like flying 3D but seems to me that all the aircraft these days are designed for 3D. I set my aircraft up well towards the forward CofG limit most of the time this requires a lot of weight in the nose which I hate doing. Even at these CofG settings the aircraft seems to be unstable in pitch. Also I like to have a little bit of down elevator when inverted which I have not had at the forward CofG limit.

I realize that all the characteristics that I'm looking for requires a further forward CofG. I just hate adding so much lead!

Are you guys just adding the weight and not worrying about the penalty that comes with it?

Not sure why the designers are making these planes to suit DA/DLE 50/55 engines but then having to add a car battery to the front to make it balance.

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Old 11-11-2010, 08:44 AM
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Default RE: Pitch Stability

Some specifics would be helpful. My experience is that most of the 50CC class ARFs are built to balance with the DA50 or DLA55.
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Old 11-11-2010, 09:52 AM
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Default RE: Pitch Stability


Quote:
ORIGINAL: dale691

Hi guys, this may not be the right place for this post but I thought I'd start here. I have had several 50cc size airframes all different brands and different styles (Yak Extra etc). Running a DLE55. I don't like flying 3D but seems to me that all the aircraft these days are designed for 3D. I set my aircraft up well towards the forward CofG limit most of the time this requires a lot of weight in the nose which I hate doing. Even at these CofG settings the aircraft seems to be unstable in pitch. Also I like to have a little bit of down elevator when inverted which I have not had at the forward CofG limit.

I realize that all the characteristics that I'm looking for requires a further forward CofG. I just hate adding so much lead!

Are you guys just adding the weight and not worrying about the penalty that comes with it?

Not sure why the designers are making these planes to suit DA/DLE 50/55 engines but then having to add a car battery to the front to make it balance.

Most planes are set to do both. Are you putting all your batteries up near the engine? You could move the engine forward slightly which will help. A heavier prop would certainly help, how about the spinner? What kind are you using. How about just using a heavier engine. If you are using rudder servos in the tail, how about converting it to pull pull.


One thing to remember, if the ratio is 3 to 1 on the CG(three times more plane behind the CG than in front), then for every 1 ounce at the back, you need three ounces at the very front to offset it.

I have not ever had to add lead to any plane, I just plan the layout using the proper equipment. Remember, when you move into 50cc and larger, you have to change your way of thinking.

Now, biplanes are the exception in some cases. Especially smaller ones, Pitts especially are short coupled so you will be stuffing everything as far forward as you can
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Old 11-11-2010, 04:47 PM
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Default RE: Pitch Stability

Thanks guys, specifics are EG raven, gold wing yak x2 54 and 55. The 55 belongs to a friend and he is running a DA 50. All have aluminum spinners, mate has carbon prop and I have wood. Rx batteries on wing tube, ignition and battery on engine box. Both running canister muffler setup. One point I'm making is I don't want a heavier engine. These planes are made with these engines in mind, so much so they have drilling templates for them. Is it just poor engineering? We both have pull pull systems carbon tube for the tail spar.
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Old 11-11-2010, 04:54 PM
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Default RE: Pitch Stability

One thing to remember is with any YAK, or round cowl plane, you want the back of the spinner at least one inch away from the front of the cowl, this improves prop efficiency and will certainly help with tail heavy

For yours, I would move the batteries up to the engine box, move the engine out as I described above, maybe consider a heavy prop. No sense adding unusable weight in the form of lead when a few relatively minor changes will make a big difference
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