Faltus 5m ASG-29

[ferincr]

ok, so I wasn't wrong...
Let's see what Scott says about his setup.
I resumed the finishing of this model and I'd like to know the throws (if any different then recommended by the manufacturer) and radio programing others use.
As far as I know everybody else posted being very happy with the CG @ 84mm.
Fernando

[Tom]

Yes, at 85 mm it should fly nice and stabel...... As you move CG back ie: take lead out of the nose the airplane will become more un-stabel and become more sensitive to control inputs. Go to far back and it will become un-flyable

[Marnochs]

Hi Fernando,

You want to strike a balance on the CG between stability and responsiveness. The further forward the balance is (nose heavy), the more stable the airplane will be flying.
The further rearward the balance is (tail heavy) the more unstable the airplane becomes. What I try and acheive is a neutrally stable aircraft. If you go too far back then the airplane becomes truely unstable.
If you have a neutrally stable ship, you will need very little elevator input in a typical thermal turn, where as a nose heavy ship will require a lot of up elevator in the turn and not be able to slow down. This is because of the required aerodynamic counterbalance of the up elevator and the air movement over the elevator to acheive that effect.

I was helping a friend trim out his ASG-29 because it looked like a rocketship while thermaling. We moved the CG back to about 100mm and found the ship was twitchy, apon inspection of the elevator throw we found about 15mm instead of 10mm. We reset the elevator travel to 10mm up and down and flew it again.....major differance, now its a well behaved, responsive sailplane for my friend.
We did a dive test and found a very slight tendancy to pull out of the dive

A quick way to check your airplanes stability is with the dive test. Nose the airplane over to a 45 degree dive and see how it responds. If you have up tirm in the airplane then it will pull out of the dive.
If it's neutral then it will continue on the dive until you pull it out. If it' tail heavy (down trim ) then the airplane will "tuck" or increase the dive as it Accelerates.

I have my ASW28 balanced so that it continues down on the 45 degree dive with no "tuck" or "pull out" as it keeps accelerating.

A neutrally stable sailplane with indicate lift better ( the nose will rise as your enter the thermal then the tail will rise as you exit the thermal) where as a "stable" sailplane will tend to plow through a thermal.


Scott

[ferincr]

Sorry you are right...
Brain fart

[Steve P]

And don't forget these forums are attached to a great website! Here's Don Stackhouse's article on the subject: http://www.rcaerotowing.com/2461-cen...ailplanes.html

[fnev]

If I may jump in here... Contrary to common belief, a nose heavy (forward CoG) glider is not necessary "more stable". In fact it can be the opposite. Any glider (aircraft) has a CoG range from the most forward to the most rearward. It is true that the vast majority of manufacturers have a tendency to recommend a range that is in the most "forward" part of the proper CoG range, if not sometimes pass the most forward CoG that should be used. The results are usually a nice dog to fly and to compensate outrageous control surfaces throw are used.

A "balanced" glider means a tuning (to each pilot taste) between CoG position, decalage and control surfaces throw (yes, all the primary control surfaces efficiency are affected by the CoG position even if it is not due to a direct effect as for the elevator). A nose heavy glider will not only perform poorly but as well not allow for a nice flare at landing and will have a tendency to "tuck in" when trying to thermal too steeply. It will have a tendency to balloon up all the time as speed increases and will go trough "good" air as if it was "bad" air... In an other hand, the too rearward CoG settings will (long before real instability comes in) give an overly sensitive machine to control. Unfortunately, most of the time, no adjustment to the control surfaces throw is done and the "instability" is in fact induced by an overly responsive set up.

To get a glider "dialed in" to the pilot taste (and flying skills) doesn't happen in a few flights. It is a somewhat long process and necessitates to fly the same machine in a lot of different situations in order to get the best COMPROMISE. Just one point of interest: I do fly at sea level and at 2000 meters altitude; for some specific gliders a CoG adjustment is required due to changes in air density (especially when it is "warm" at these higher altitude because the air density may be over 20% LESS).

These "subtle" setups are not to very one liking and some people never bother. This is absolutely fine and nothing is wrong about it. For the pilots that belong to this category, maybe just a little bit of experimenting will lead to a new dimension of flying large high performances model gliders and the "discovery" of a new facet of the hobby: to understand and analyze flight mechanics. This comes as well to a new level of performances...

[yyz]

This post should be made sticky or copied to a "guru" thread. Really informative.

Mike

Hi Fernando,

You want to strike a balance on the CG between stability and responsiveness. The further forward the balance is (nose heavy), the more stable the airplane will be flying.
The further rearward the balance is (tail heavy) the more unstable the airplane becomes. What I try and acheive is a neutrally stable aircraft. If you go too far back then the airplane becomes truely unstable.
If you have a neutrally stable ship, you will need very little elevator input in a typical thermal turn, where as a nose heavy ship will require a lot of up elevator in the turn and not be able to slow down. This is because of the required aerodynamic counterbalance of the up elevator and the air movement over the elevator to acheive that effect.

I was helping a friend trim out his ASG-29 because it looked like a rocketship while thermaling. We moved the CG back to about 100mm and found the ship was twitchy, apon inspection of the elevator throw we found about 15mm instead of 10mm. We reset the elevator travel to 10mm up and down and flew it again.....major differance, now its a well behaved, responsive sailplane for my friend.
We did a dive test and found a very slight tendancy to pull out of the dive

A quick way to check your airplanes stability is with the dive test. Nose the airplane over to a 45 degree dive and see how it responds. If you have up tirm in the airplane then it will pull out of the dive.
If it's neutral then it will continue on the dive until you pull it out. If it' tail heavy (down trim ) then the airplane will "tuck" or increase the dive as it Accelerates.

I have my ASW28 balanced so that it continues down on the 45 degree dive with no "tuck" or "pull out" as it keeps accelerating.

A neutrally stable sailplane with indicate lift better ( the nose will rise as your enter the thermal then the tail will rise as you exit the thermal) where as a "stable" sailplane will tend to plow through a thermal.


Scott

[ferincr]

On the winglets subject...
They have a little tab that fit on a slot on the wing tip, did you guys epoxied them there or used something not so critical (like silicon, hot melt glue or just plain tape)????
Thanks,

[Bob Morrow]

On my AGG-29 I found some very small countersink scews. Not sure what size they are, but they have a total length of about 3mm from the top of the screw head to the tip of the point. I used a drill and countersink on the winglet area of the wing tip and the I can insert the winglets and use the small screw. The friction of the screw being slightly tightened in the drilled hole is more than enough to keep the screw in place. Just be sure the screw length from the top of the head to the tip of the point is slightly shorter then the thickness of the wing tip where the tab slides in place.

I like having the winglets removable so they don't get broken in transport. Also it is easier to store the wing sections with the winglets removed.

I'll try to take a picture or two tomorrow or Saturday and post them with the screws next to a mm scale as well as the wingtip and winglets on my ASG.

Bob

[ferincr]

I like having the winglets removable so they don't get broken in transport. Also it is easier to store the wing sections with the winglets removed.Bob

Thanks Bob, that is exactly why I ask. I didn't see the screws but I'll look into it. Seems like a nice solution.

Edit:
No extra screws with the kit, just the tiny ones for the servo covers but I managed to scavenge a couple from an electric motor that I have lying around.