CofG

[freeble]

Hi,
i have flown nitro for quite a while now and have recently bought a Gentle Lady to try my hand at thermal/slope/slermal. i have set it up with micro Rx and Nano servos to save weight but while trying to get the CG within the recommended range (9 - 9.5cm from TE) i have had to put about 80g of lead right up against the firewall on top of the Rx battery and it now feels too nose heavy. with this extra weight it is now only 55g below the max flying weight, has anyone else had this issue or is it not an issue at all?? any help appreciated because i REALLY want to throw it off my hill soon!

[jkettu]

That's perfectly normal, just go and fly it. The recommended CG range is somewhat conservative (but safe), you can fine tune it after some test flights. Your total weight will not be a problem.

[aeajr]

Yes, don't worry about being a bit nose heavy to start.

Do your first flights as hand glides on fairly calm days with smooth air. Strong flat throw into the wind. Try to keep your hands off the sticks as much as possible.

The plane should glide out level and just drift down to a fairly flat landing. If it does that, and does not seem to have a tendency to turn in one direction, you are good to fly.

Over time you may find you wish to remove some of that weight and move the CG back. If the weight is hard to reach, just put a dime or a quarter on the tail and see if the plane flies better. Easier than digging out lead.

Most glider pilots will try to push the CG back back back till the plane becomes hard to handle. Then you move it back forward a bit and that becomes home. This is something you may adjust over a few flights or over a few flying sessions at the field.

If you huse a hi-start or a winch, remember that as you move the CG, the hook location will be changing in relation to the CG. As you move the CG back, the hook will be moving forward relative to the CG. Again, over time, you may end up wanting to move the hook back too.

One other note. The further forward you can get the weight, the less weight you need. I drilled out the nose block on my Spirit and was able to remove about 1/2 oz by moving the weight forward about 1 inch.

This is a gradual tuning process, so don't rush it. Enjoy it! :D

[freeble]

fantastic advice aeajr & jkettu, thank you both very much i will go throw her off a hill today!

[lincoln]

If you're under the recommended weight at all, that's just fine. It would probably fly ok 50 or 100 grams overweight, maybe even more. I wouldn't worry about it. If it was 100 grams overweight the first places I'd look would be at the wood density on elevator and rudder.

[freeble]

g'day lincoln,
yeah the tail does seem rather heavy considering there's nothing to it, anyway weather looks promising here tomorrow so i'll give it a crack.

[Blavatski]

Yes, don't worry about being a bit nose heavy to start.

Do your first flights as hand glides on fairly calm days with smooth air. Strong flat throw into the wind. Try to keep your hands off the sticks as much as possible.

The plane should glide out level and just drift down to a fairly flat landing. If it does that, and does not seem to have a tendency to turn in one direction, you are good to fly.

Over time you may find you wish to remove some of that weight and move the CG back. If the weight is hard to reach, just put a dime or a quarter on the tail and see if the plane flies better. Easier than digging out lead.

Most glider pilots will try to push the CG back back back till the plane becomes hard to handle. Then you move it back forward a bit and that becomes home. This is something you may adjust over a few flights or over a few flying sessions at the field.

If you huse a hi-start or a winch, remember that as you move the CG, the hook location will be changing in relation to the CG. As you move the CG back, the hook will be moving forward relative to the CG. Again, over time, you may end up wanting to move the hook back too.

One other note. The further forward you can get the weight, the less weight you need. I drilled out the nose block on my Spirit and was able to remove about 1/2 oz by moving the weight forward about 1 inch.

This is a gradual tuning process, so don't rush it. Enjoy it! :D
Again aeajr great information; however, there seems to be too much emphasis on sailplane weight. You are right that most pilots prematurely adjust CG, and end up fooling around unnecessarily. Overall weight because of trim ballast should not be a concern. ;)
Weight is the prime factor controlling airspeed, and is illustrated by "wing loading." 3 or 4 extra ounces of plumpness means little, since it is divided by the sq ft of surface area. [Unless you're stuffing it into the tail!] :eek:
Vehicular airspeed should not be determined by an engineer designing a model, but is an attribute controlled by a knowledgeable pilot through ballast ~ to appease the demands of nature. Using enough ballast to sate a 15 mph wind while forcing one's self to fly calm air with it. Makes for valuable "practice” experience. :D

[aeajr]

Again aeajr great information; however, there seems to be too much emphasis on sailplane weight. You are right that most pilots prematurely adjust CG, and end up fooling around unnecessarily. Overall weight because of trim ballast should not be a concern. ;)
Weight is the prime factor controlling airspeed, and is illustrated by "wing loading." 3 or 4 extra ounces of plumpness means little, since it is divided by the sq ft of surface area. [Unless you're stuffing it into the tail!] :eek:
Vehicular airspeed should not be determined by an engineer designing a model, but is an attribute controlled by a knowledgeable pilot through ballast ~ to appease the demands of nature. Using enough ballast to sate a 15 mph wind while forcing one's self to fly calm air with it. Makes for valuable "practice” experience. :D

I didn't say anything about overall sailplane weight so I presume you are speaking in general terms.

My opinion, which is based on wise council from others plus my own experience is that you can make a light plane heavier by adding ballast. But you can't make a heavy plane lighter when conditions would make it advantageous.

I am not obsessed with weight but I prefer my planes on the lighter side with a planned out ballast apparoach.

My first full house sailplane was an old Airtronics Legend purchased from a club member. It weighs in at 82 ounces on a 3M wing. ( maybe 2.9M, not sure.) It flies like a truck and I have had trouble getting it into lift where others have been skying out.

I moved to a Thermal Dancer at 59 ounces on a 3.1M wing. All of a sudden I can now fly the thermals that every one else finds and perhaps some that they can't find.

Same me, so it must be the plane. However when the wind is blowing hard, that Thermal Dancer can get tossed around where the Legend is just coming into its own. So I made up ballast for the TD to get it back up to about 80 ounces for windy conditions.

I now also fly a Supra on 3.4M wing at 64 ounces and an AVA with a 3.2 M wing at 44 ounces. I have spent a lot of time working on ballast for them so I understand how much helps and how much is too much for given conditions.

Light is good but heavy can be the ticket when the wind comes up.

[Blavatski]

I didn't say anything about overall sailplane weight so I presume you are speaking in general terms.

My opinion, which is based on wise council from others plus my own experience is that you can make a light plane heavier by adding ballast. But you can't make a heavy plane lighter when conditions would make it advantageous.

I am not obsessed with weight but I prefer my planes on the lighter side with a planned out ballast apparoach.

My first full house sailplane was an old Airtronics Legend purchased from a club member. It weighs in at 82 ounces on a 3M wing. ( maybe 2.9M, not sure.) It flies like a truck and I have had trouble getting it into lift where others have been skying out.

I moved to a Thermal Dancer at 59 ounces on a 3.1M wing. All of a sudden I can now fly the thermals that every one else finds and perhaps some that they can't find.

Same me, so it must be the plane. However when the wind is blowing hard, that Thermal Dancer can get tossed around where the Legend is just coming into its own. So I made up ballast for the TD to get it back up to about 80 ounces for windy conditions.

I now also fly a Supra on 3.4M wing at 64 ounces and an AVA with a 3.2 M wing at 44 ounces. I have spent a lot of time working on ballast for them so I understand how much helps and how much is too much for given conditions.

Light is good but heavy can be the ticket when the wind comes up.
Your education is excellent. My husband broke things down into simple numerical expressions. Airspeed is what nature demands, and the prime control is mass. His calc expresses that from the hundreds of experiments that I assisted; Profile is the secondary attribute that controls lift quantum thus: Cutting lift in half equals doubling the mass of a sailplane. That, has an LD improvement in either case - that favors thinner profiles because of more overall streamlining.

Don Chancey and my husband, proved that the aspect of loading an aircraft for thermal generation (intensity and frequency) is just as important as loading for wind. Best Goal and Returns were made in calm air, with moderate ballast. Practicing flying with ballast in calm air has proven to be effective training for competition, more so than standing in a field peering at a dot (that is too light) skimming under a cumuli.