Jerry_Hailey

I just flew a new Cap 232 ( 120 size with Fugi 32B)for the first time and it is very snappy. Even in a big slow turn it wants to snap out. I think the balance is OK, inverted needs just a small amount of down to fly level. I don't like the way the elevator pushrod is constructed. The first owner had the elevator servo up front with a 1/4 inch wood rod to the rear, then two metal rods, one to each elevator. Lots of flex between the elevators. I'm going to change this, but not sure what would be the best. Dual servos at the rear? carbon fiber pushrod? Will a stiff elevator help the snap?

Dr1Driver

You may be experiencing different elevator throws caused by that weak linkage setup. Move the servos to the rear, and use a short piece of 4-40 rod for the linkage. You can also use carbon fiber and a "Y"ed rod at the elevator end. Even the carbon fiber rod must be supported at one point, preferably two, somewhere along the length.

Reduce the elevator throw a little, and recheck the static balance.

Good luck with it.

Dr.1

DMcQuinn

My Feedback: (13)

Stiffening the linkage is always a good idea, but it is not likely the cause of the snapping tendency. I have flown a 35% CAP for 5 years and it is also quick to snap. I have learned to like this behavior, but you must be careful. I use exponential (about 50%). I have three rates on elevator. But even on low rate, it will snap if full elevator is applied. Can you lighten it at all? (batteries, landing gear, wheels, etc.). This may help.

Jerry_Hailey

This is a second hand plane that was crashed a few time and has lots of epoxy and glass holding it together. He crashed a few weeks ago and just gave up and gave me the plane. Not much chance of getting it light. This is my first large plane, but not my last. I plan on getting a new plane soon. This plane is a lot of fun, I just can't throw it around like my GP Cap 580 46 size.

Thanks for the replies,

Just makes me want to fly today, and get used to the big ship.

gnirwin

My Feedback: (25)

I owned a Cap that was snappy if I had too much elevator throw. Give it less throw and see if it helps.

Darrinc

My Feedback: (5)

I am a really big fan of Caps and have been flying them for years. They seem to be more sensitive to weight than your Extra's and such, especial since they are so short coupled. I would suggest switching out the engine for something lighter and get the dremel out and turn the plane into swiss cheese.

Elevator travel is also a very important factor with a Cap, I believe my 1/4 scale had about 1/8" up and 1/4" down on low rates, and still needed a lot of expo. (those measurements might be on the high side)

A Cap is very unforgiving with just a little of travel if you do not make your inputs very smoothly. There was a guy in our club who was getting it to bigger planes, but he still liked to grab a hand full of elevator, his Cap lasted 20 seconds, although he would of lost a Extra too flying like that. These are not rip around planes.

The up side is that a Cap will make you very disiplined and smooth flier, weither you want to or not.

Darrinc

My Feedback: (5)

After thinking about it, those measurments for elevator travel are too high in my post above. I would cut those in half, especially if you are tail heavy at all.

Thats how little travel these planes need.

T. Bob

My Feedback: (9)

I would try to reduce the weight.
A heavy Cap is a snappy Cap.

majortom-RCU

My Feedback: (40)

Snapping tendency is aggravated by too heavy, too much elevator throw, CG too far aft, too little airspeed, lateral imbalance, and using ailerons at low airspeed. Some of it is static problems, which need to be fixed in the shop; and some is dynamic problems, which need to be compensated by how you fly the model.

I have a 120 size (72" wing) Sukhoi ARF set up with dual CF elevator pushrods, +/-10Ëš elevator throw, lead on one wingtip for static lateral balance, wing loading just over 30 oz/sq ft. So far I've burned four gallons with it, and no snaps other than clumsy landing on one gusty day, and all that did was pop the landing gear. I've snapped a few planes to destruction, so now I know to keep speed up in banked turns, keep the nose pitched down or no worse than level on landing approach, take a two-wheel landing whenever I can get it.

This model has 2-56 size dual CF pushrods from DarrolCady.com, routed through outer nyrod which is fixed in place at two points between servo and exit slots. I had to open the bottom of the ARF to install the supporting points, which I've done on several ARFs, so it no longer bothers me to do that.

I've just started a 78" ws Edge ARF, and first operation is dual CF 4-40 pushrods on elevators. Pushrods will be supported at two intermediate points between servo and exit slots, one directly accessible at rear of radio compartment, the other will take some finagling but I think can be done without opening the fuselage, since I have a good internal mid-tail former to glue a brace to.

My elevator servo gets side-mounted, so servo arm swings through a vertical plane, centered laterally. To connect two pushrods I silver solder a 2-56 stud between two steel pushrod ends, which get JB Welded into the CF hollow rods. Darroll Cady says rubberized CA will work, but I had one of them come loose, so nothing but JB Weld for me.

I have tail-mounted servos on a 120 size Edge ARF, and they work great where the CG is manageable, but I don't think they're the best solution for the situation you describe. If your plane is reasonably close to good fore/aft balance now, tail-mounted servos will need more noseweight to maintain CG, and with a gasser up front I don't think you want to be adding any more weight.

Darrinc

My Feedback: (5)

I am suprized that with such a heavy engine that you do not have the elevator servo's in the tail. That will not help the snapping that much, but it might help for balance if there is any lead in the tail.


Be "one" with the elevator stick!

Jerry_Hailey

I have 1/2 up, 5/8 down. WOW 1/8 up? I'll try today.

Lose weight? have to wait till we have snow or rain or some reason not to fly for a few days. 60 deg clear skys no wind today.

Flyjets

My Feedback: (51)

Jerry


Too heavy, too much elevator throw and a CG too far aft.

The best thing to do is figure out a way to drop a few pounds this will lower the speed at which the model will snap.

Lower the control throw will get u max deflection without the snapping tendency at the new lower weight.

CG causes the moment to be to far rearward further aggravating a plane thats prone to being snappy.

If it's worth the trouble and price replace the stock wheels and wing tubes with much lighter parts then move the batteries around for the CG.
Control throws reduce and this should get you in the right range.

Ian

Darrinc

My Feedback: (5)

Ding, ding, ding! We have a winner! It will seem strange at first, but your flying will really smooth out.

I don't have 1/2 up, 5/8 down on my 35% Cap, that would be way too much!


"60 deg clear skys no wind today."

Grr, it is 20 degrees here and windy.

Jerry_Hailey

Now I feel Like a real bone-head. Just found a rookie mistake on my part. I went to move the elevators down and found I had one clevis in the upper-mid hole and one in the lower-mid hole. I moved them both down to the lower hole and still have 3/8 up and 1/2 down. I have an old JR F400 radio. I can get longer horns, but for today I'm just going to fly like this.

Reading some of the replies make me want to move some weight forward. My 580 is nose heavy, but does not snap near as bad as the 120 cap.

Thanks to all

Darrinc

My Feedback: (5)

We have all done that a few times. Just try one thing at a time, that way you know the feel of the change which will help you down the road when troubleshooting and you will really know what actually helped.



(I used to teach college, so sorry if thats sounded like I was lecturing, I do that sometimes)

v-snap

My Feedback: (18)

Wooha on the weight transition...Moving weight foward may make it snap at higher speeds...Make sure it is balanced correctly, a tail heavy airplane will stall at a slower airspeed then a nose heavy one, although it will be deeper in the stall. Caps have a tendency to stall at the wing tip not the root. This if uncoordinated will cause a wing to drop and the snap, so check you rudder and lateral balance also. If it is always dropping right or left add some modeling clay to opposite wing tip and make sure your rudder is straight.
With that gasser in it, it just may weigh to much to slow down period. I luv Caps also and prefer Cap 21's to all others for thier snapability when set up right. The key is setting it up right and you will luv it. So go easy on moving the weight around a little at a time will do it.

ICE_MAN

I'd drop that fuji...

Get a nice 1.60 sized 2-stoke glow... Or even one of the RCS gas engine, like the 180.

Jerry_Hailey

Little less elevator, and an equal elevator made all the difference in the world. This thing flew great. Still if I go too slow and yank on the stick, It will snap. I got it hover for about 15 seconds, record for me.

I like the gas. I used 24 gallons of glow fuel this year. At near 15 bucks a gallon it hits the wallet hard.

Tomorrow I will try some of the other tips, move the cg forward.

I love this Hobby, Thanks to a few tips from here, I had a great day of flying!!

Thanks

Darrinc

My Feedback: (5)

I would get used to it before I moved the CG. If you are not complaining that it balloons on landing, then your CG is not aft enough, but thats my opinion.

Have you flown it through all the standard trim checks? What did that tell you?

3DDino

hi guys im kinda lost here
if every cap is so snappy then how do u account for
the harrier monsters out of capx and ef cap
they are all close in specs with h9 cap 120
thx

bentgear

Because 45 degrees of elevator in 3D mode is a lot different on a Cap than pulling 15 degrees when just flying around.

Ed M.

3DDino

u meant 45* of elev. in 3d mode is more stable than pulling 15* when just flying around
sorry still dont get it
thx

Darrinc

My Feedback: (5)

At 45 degrees of throw, you have the tail stalled perfectly, thats why it harriers so well and low rate on a Cap is around 7 degrees.

Don't be in between, unless you like picking up pieces.

3DDino

so if we go straight to 45* elev. even the h9 cap120 can be a harrier monster
without snapping out
thx

Darrinc

My Feedback: (5)

Absolutely, flew one for years!!! I loved that plane!