hi,
i have a new GP Super Skybolt that is simply amazing. the first flight was uneventful in that it only needed about an 1/8" (total deflection) of up trim.
the plane would not do a spin. second and third flight i have removed some nose wieght, and thus have reduced the up trim that was initially needed, but the plane still will not spin. the elevator is not sensitive at this point, should i continue to remove nose wieght?

It usually takes four things to spin - CG, elevator throw, rudder throw, and slow entry speed. I would check the GP web site to see if they made a mistake in the instuctions and have updated the CG first. Also, while it may not want to spin at the beginning of the tank, it might towards the end (which shows it to be a CG problem). But more rudder and elevator will almost always force a spin when the airplane slows down.

I'll bet it's warm there and your going flying.

no it's not warm here, unless 34* is warm by your standards.
went flying yesterday all day and today is the wife's day, every year this time i make here an outrageous Turkey dinner.

i can't wait to get the bolt back in the air though.
GP instructions give you the low rate and high rate settings to use. i had the high rates on when attempting to spin, in fact i ended up staying on high rate.
from reading the Skybolt thread here on RCU, aparently GP is way conservative on their CG location as it starts out at 4.625" back from the upper wing LE, and specifies that going back another .375" is better for aerobatics, but most of the current flyers of the bolt who posted here have gone further back and found the plane to be even better.

i'm at 4.875" and high rates, but still get a lazy spin and at high speed i get a somewhat lazy snap.

The CG and the surface throws are best found out from how the airplane flies. What the mfg suggests is nothing more than a very safe starting point. The mfg almost always considers a couple of things when publishing the numbers on an airplane. The manufacturing process is very apt to create as many tail heavy models as it creates nose heavy ones. So the throws need to take that into consideration. And then, the mfg almost always opts for very, very conservative CG locations. It's safer for him and safer for the percentage of modelers who really bought too much model this time around.

You always want to consider the written word for the model's maiden flight, but from then on, let the airplane tell you what it wants. It's actually very safe and easy to do.

You know right now how the airplane flies. And it's telling you that the CG is more than safe. On models that size, moving the CG can cover a couple of inches sometimes and still have a model that is perfectly stable. About all that happens is that the elevator gets more and more effective as you move the CG back. So you remember that and watch out for it. In your case, you want more effect, so you're going to win in two ways.

One other suggestion. Forget about measuring to the thousands of an inch. You've got the wrong idea about CGs. They aren't that critical. Nor is that accuracy of any value at all.

If your model is safe to fly and you're comfortable with it's response the way you've got it trimmed, moving the CG a half inch won't suddenly make it dangerously sensitive. Matter of fact, most inexperienced flyers wouldn't notice the difference.

If you're not flying with exponential on your elevator, dial some in.

Then move the CG back a half inch at least.

And see if snap rolls happen easier. They should. And you should get used to the increased effectiviness of the elevator in a flight or two, if that.

You have to work a couple of things against each other. The farther aft the CG, the more effective the elevator. That gives the elevator enough effect to stall the wing. Stalling the wing is what makes a snap roll more than just a fast roll. But having a more effective elevator can make some flyers uncomfortable on landing. The pitch control at landing speeds is somewhat more sensitive. To deal with that, use more expo. It's perfect for making small pitch corrections easier to do without hurting full deflection power. You're going to get more full deflection power with the CG move so...................

Good thing about this is that you wind up being a better flyer, and a smarter one too.

Lots of modelers consider CGs as being very, very critical deals. They're not.

I just ran the numbers the other day on my 60size Sukhoi's CG locations. The classical equations suggest that my model should fly perfectly safely with the CG from around 3.25" back to 4.5". And that's just the range that will give good performance without starting to degrade it. I know of the same ARF with a gasoline engine in it that probably has the CG up around 2.5". I'm guessing about that simply because it's such a slug. And he's got more elevator throw than mine by a mile. He needs it. Mine will snap in a blur and I don't need nor want the deflection he needs just to fly level.

This may not come as a bolt of lightning - but slightly nose heavy models snap and spin far better than tailheavy setups .
Either competitition or sporty setups .
What is often overlooked tho -is ENOUGH elevator deflection under load.
My so called 3D setups are at 30+% CGs -and further aft than that makes for sloppy recovery from any type maneuver -also leads to wanderitus during stuff like a nice precise 8 of any type
back when-flying pattern competively -I always went for nose heavy setups - overall-- best compromise. and they did excellent predictable spins and spin exits.
FWIW

Dick has pointed you in the right direction, in order for any airplane to spin, it must first stall. To stall any airplane the wing must exceed its stalling angle. To do that the control surface that controls the wing angle to the relative airflow must have enough `power' (lift) to pivot the wing about the cg's lateral axis to achieve that angle at whatever speed the airplane is flying at. If you have a `standard' setup then you will be using a tailplane/elevator setup. With the cg in a `normal' position(25~33%) this amount of elevator movement will be found by experiment, ie, you have to fly the thing. If you think that the model is too elevator sensitive with all that movement then might I point out that we use proportional radios now, and you must learn to be more gentle with the elevator stick. It is not a switch, we stopped flying them sorts of radios, oh, years ago. If you feel that some sort of assistance is needed then a bit (30%) of expo will help. Properly done you can now land the thing properly too, as you will be able to control the models' airspeed all the way to the stall, which is a real help when trying to land at the minimum speed to prevent bouncing.
Evan, WB #12.

In other words, if you can't stall the wing it's because the elevator isn't effective enough to stall the wing, and to get it effective enough you can increase it's movement. Sometimes just moving the CG does the same thing, make the elevator more effective. Sometimes the CG way forward is why it's not effective enough. Sometimes it's because it isn't deflecting enough. Sometimes it's both.

The suggested elevator throw for today's ARF Skybolt spins the two that fly around here and they both have the CG aft the suggested location.

thx for all the input, it is well taken and gives me some insight as to trimming the model out.
i have just a tad more throw in the elevator at low rate than what was called for.
today while cleaning things, i removed the 1.75 oz of lead/mounting plate combo i had on the nose. rechecked the CG and it's now 1/4" back from the 4 5/8" mark that is suggested.
this is going to be a fun airplane as well, it flies like it's on rails, lands like a trainer, and so far just urges you to fly it again and again.

OK, you have flown that airplane with the weight you just removed and have a feel for it's elevator response with the CG where it was with that weight. And removing it only moved the CG 1/4". Expect to feel a bit more response from the elevator with the CG moved 1/4" back, but don't worry that it'll suddenly become lots more sensitive and dangerous. Because it won't. If the airplane was comfortable to fly before, it'll be perfectly safe, but maybe a bit quicker now with just that 1/4" change.

The low rate elevator throw being more or less the mfg's recommendations isn't really a big deal. And low rate is usually setup on most non-3D airplanes to be the setting you fly most of the gentler flight with. It's very often that the high rate is expected to drive the airplane into snaps etc where the wing has to stall into the maneuver, and low rate is what's used to just fly around the sky.

Lots of experienced flyers adjust their elevator throws so that the high rate will be just enough to stall the wing at however slowly you intend to do it. Then they check to make sure the low rate deflection won't snap the wing out of their faster, round maneuvers. That gives them a setting they can use on the more violent manuevers, like snap rolls, and another setting that won't surprise them when they're not doing violent stuff.

One nice thing about our hobby is that we can edge up on things. Moving the CG a bit like you're doing is a very safe way to do things. Good thing about the CG is that it doesn't go over the edge suddenly on you. When you start getting it back into the twitchy zone, you will have felt it getting twitchy without doubt if you're only moving it 1/4" at a time.

thx again Rock,
funny thing is, the ARF version calss for 5/8" deflection of the ele. at low rate, while the kit version calls for 7/8".
i have a feeling this bird is gonna be a very fun plane to play around with.
heck just 2 flights in and i was doing manuevers i use to do back in the early 70's with pattern stuff.
i never really fooled with much other than setting things up the way the designers laid it out, and we didn't have dual rate switches at that time.

i never really expected much out of the Skybolt, but boy is it proving me wrong.

And it's pretty while doing all that stuff, ain't it.

The ARF comes out at a flying weight around 7.5 pounds. The kit version says it comes out around 9 pounds. Close to 20% heavier. That MAY be the reason for the different deflections.

Mine does well on a 60 with a 3-blade. And is pretty doing it.

pretty it is..........i see you didn't put the stickers on either. i like this bird without the stickers as well, but i have been asked by everyone so far "what is it?".
i may have to put the "skybolt" stickers on just so people will know what it is. i thought everyone knew the Skybolt.

mine came in at 7lbs 8oz before i removed the last bit of lead, so needless to say i was exstatic. i built the kit version years ago and lost interest as i saw how heavy it was going to be.
light airplanes just fly better, i don't care what anyone says.
this bird lands so sweet, you just don't mind landings at all as i did with a couple heavy pigs i once had.

Don't over analyze. I have my Skybolt balanced at the recommended position and it flat spins like there's no tomorrow both inverted and right-side-up. It also does beautiful blenders and snap-rolls. The secret is max throw in rudder and elevator. I use max rates for extreme aerobatics and recommended high rates for general flying. Recommended low rates are too docile for anything except gentle loops and rolls and flying the pattern. The plane is very tough. My Skybolt has about a year and a half of violent snaps and rolls with absolutely no signs of stress on the airframe.

So the recommended low rates remain on your model and you recommend to ignore them. And choose to "max rate" the surface throws for high rate.

The other beauty of our hobby is there are very often a number of "right" ways to do things.

Setting the max throws over recommended works and only flying them really isn't a way that'll work for everyone, especially people who haven't gotten into 3D. Those people often don't want an airplane that takes very fine, very slight stick movements for lots of the flight envelope. Moving the CG works. It often brings both the recommended low rate throws and the recommended high rate throws into effective use and doesn't make one rate "useless" and the other harder to fly.

Different ways to do things are good.

I agree moving the CG aft would allow the plane to spin at with lower rates. No, I said nothing about ignoring low rates. I stated recommended low rates are too docile for anything except gentle loops and rolls and flying the pattern. This thread is about spinning a specific aircraft. If a CG needs to be moved to make a plane fly better, I'm all for it. The fact of the matter is this plane flys great with the CG at the recommended position and spins great if you use more than the recommended throws as your high rates. If you can go from higher to lower rates with a simple flick of a switch and still preserve the great flight characteristics of an aircraft, why wouldn't you. Why do I think the CG is in the best position at the recommended point? It flys inverted with very little down elevator, it does beautiful harrier rolls with virtually equal imputs on the control surfaces, it holds an inverted 45 degree upline at 3/4 throttle with no elevator imput (IMAC balancing) and it lands like a trainer. This is why I choose not to move the CG just to make it spin at lower rates.

i have to agree with Rock on all accounts here.......i just flew my Skybolt 2 weeks ago and once i set my CG back to almost 5", the controls (set at default) came alive. it felt sluggish at first at the suggested CG. now it flies, and lands like it's a trainer with attitude.
i don't think 2 planes alike will ever perform the same at the set CG unless all things are equal such as stab wieght, rudder wieght, etc, and incidence and thrust are identical.
CG's are a critical final adjustment.
experiment with it, but just don't get carried away, especially when moving aft of the starting point.
my spins were also sluggish at the orignal setting, but now it spins with ease.

You're right. No two planes fly alike. Glad you are happy with how it flys[8D]

i think we all fly differently as well and that also makes things different.
one thing i went through once though with a model was a Lanier Citron (a Jim Kirkland design) which i had a Super Tigre 60 mounted. the weight came in at 6.75 lbs.
it flew perfectly right out of the box until i got to be a real smart a## with low inverted passes and forgot about the yaw effect and tagged the rudder to the ground when pushing too much down elevator to gain altitude....ouch
so plane number 2 was given life from the box. same weight, same engine, but the CG ended up being 1/2 forward of the first one to get the same flight characteristics.
i mainly flew upside down back in the 70's as a typical showoff and my CG's were usually based on inverted flight.