H9 Cap CG Question
 

My Cap balances at 6 3/8". OS 1.6FX moved as far ahead as possible, 2700mAh battery mounted in forward compartment, left side, throttle servo mounted in forward compartment, right side...Servos in standard location. I really don't want to add weight, but I've got everything (except the receiver which weighs very little) as far forward as it can go. The engine is at the end of it's rails.
I have read that the factory recommended CG (5 5/8") is quite conservative. But is it 3/4" conservative? I would love to hear from anyone who flies their CAP in this range...


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h9 cap
 

timber i have a few flights on this same combo 5 3/4 c.g. was where i was comfy. i have battery next to fuel tank left side. after about 4 flights the big os didn't transition from low speed very good. even had two dead sticks. i leaned down the low speed needle a full turn {what a difference} if i was you i would add a little WEIGHT to the motor mount and fly it first you can always remove a little at a time . these planes seem to vary a bit so your kind a on your own . better safe than sorry. { it flys very easy just keep the throws on the LOW side at first .this plane is very sensitive to imput}

Shifted it to 6
 

Well, I added 6 oz of lead (Doh!) to the left part of the firewall, and now it balances at 6". I think I can live with that...I will heed the advice of others and decrease the elevator throws for the first flights.

HP 1/4 scale Cap 232 CG
 

Timber,

Take a look at the other threads on this very subject through the RCU search engine. One thread that is good is on CAPs snapping.

The answer to your question about balance point is between 6.0 inches and 6.5 inches. The factory guys fly them at 6.5 inches per the VP R & D at Horizon. I also spoke with one of their flight demo people and he also flys the plane at 6.5 inches.

At our club we have had at least 6 to 8 of these ships. I have two of them now and have recently put one to sleep. Our experience is that they will snap at most any balance point if you use too much elevator throw.

What is interesting is that when you move the balance point back towards the center of lift the elevator becomes more sensitive and will cause the aircraft to snap more. When you move the balance point back you must reduce the low rate elevator throw. This reduces the snapping considerably.

The book calls for 5-5/8 inch CG and 1-1/8 elevator throws on low rate. My best CAP is currently at 6.5 inches and 3/4 throw on the elevators on low rate. The snaps are almost gone and the airplane is really responsive without "feeling" or acting tail heavy. There is no lead on the plane and this one has a YS 140L on it for power.

So, if you are at 6.0 inches now, try it. Watch the elevator rate and use expo. As you find your comfort level with the plane, move the balance point back more, remembering to watch the elevator throws. Again, the factory people state that the 5-5/6 inch balance point is very conservative.

I am interested at what balance point others are flying this plane. If you fly one, weigh in with your balance point.

Tim Adams

H9 Cap CG Question
 

Hey Tim

Good reading! Your experience with the H9 CAP232 seems pretty extensive. What is the weight of your YS-140 powered "best" of your CAPs?

Brad

H9 Cap CG Question
 

Timbersnake, on my H9 Cap, I have the battery mounted on top of fuel tank right behind the firewall, and it balances dead nuts with the 1.60 all the way forward in mount. Daz...

H9 Cap CG Question
 

Hey Snake. I would offer a word of caution. It is not uncommon for the elevator servo to be mounted to one side. If you don't keep the push rods super straight,(NO BENDS) they can colapse to one side with the high forces on those big elevators. That lets one elevator deflect more than the other one. Boy is that exciting! I'm runing an MDS 148. It seems to balance the plane at 6.25. Elevator throws at 1" on low rate. No snap problems. I moved the elevator servo so the arm hole is dead center at the back of the cockpit right over the pull pull cables to get a straight shot at the pushrod fork. It's really stiff that way.

I have gone to metal gear servos since I have stripped the plastic gears on three of the surface servos in flight. Each time I managed to get back down, but not gracefully. When you lose a gear tooth or two you have no particular neutral on the servo. It's like flying an old galloping ghost system. (Whoops, now you know I'm an old guy.)

wieght of H9 CAP 232 1/4
 

Brad,

The weight of the "best" of the birds is just over 13#. The excess here is caused by hanging a Hatori pipe/header and hardware under the belly of the plane off the YS 140L and carrying a redundant JR 1750 battery pack and switch.

I spoke to Dave Patrick about this plane (original designer) and he suggested that Horizon beefed up the plane and made it heavier than what he originally penned. Having one of the first releases of this plane, we discovered that the firewall mounting and the landing gear area needed additional structure. We did this on the early ones and the factory did this on later models.

Bottom line, even at 13#, if you move the balance point back between 6.25 and 6.50 and reduce the elevator throw, you will have a great performing aircraft---and it lands nose up and slow without being tipsy. You have to love these planes.

What about others and their experience with flight performance and balance?

Tim Adams

H9 Cap CG Question
 

Brokenprop...I'm having trouble imagining how you have your elevator set up. Any chance you have a picture you could post? I too am running metal gear hi torque servos. Did you have to build another mount for the elevator servo?

Everyone else...thanks for the great posts...I think I might just try flying it at 6". I will lower the elevator throw to 3/4 up/down, and give it a shot.
TM

H9 Cap CG Question
 

Tim:
My CAP has been flown at 5-3/4 (too many snaps at low speeds) and 6" where it did much better at landings and inverted flat spins. It is powered by a Saito 1.50 FS. It weighs in at about 12.7 lbs. I do have an onboard glowliter with a 2800 mah nicad tucked in along side the tank. The 4.8 v 800 mah system battery is on the other side of the tank. I will go to 6.25" being careful to to keep my elevator throw on low dual rate at a more modest 3/4".

I will be commissioning my 2nd CAP soon (I hope) and will eliminate the onboard glow and use a Saito 1.80 FS up front. Needless to say I will incorporate a lot of what I learned on this thread. I hope to come in at 12.7 lbs, +or- a few tenths.

I seem to be the only one flying the H9 CAP in the two clubs (small) that I belong to.

Thanks for your response ....... Brad

H9 Cap CG Question
 

I'm not sure how to put a picture on here. I tried to drag and drop one here last night and it just opens another brouser screen. I put another set of servo bearers across the fuse positioned closer to the top of the fuse. You can then slide the servo anywhere from left to right and the arm is higher in the fuse than the pull pull cables by about 1/2". Looking down into the inverted fuse the way you work on it, the servo and arm are below the cables. Then I positioned the hole on the arm I intended to use right in the center of the fuse and anchored the servo there.

I'll try to email you a picture, I know how to do that.