elevator unresponsive

[og]

i have a skipper XL but the elevator will not pull her out of a dive, I am thinking that the COG will need to move back - is this correct - I have the throws on max

Edited By og on 09/05/2017 12:04:07

[Martyn K]

It could be that the elevator is being blown flat - dont underestimate the load on the elevator.

Is the aircraft responsive in normal flight?

[Jon H]

Im with Martyn. A bendy foam elevator connected to a wimpy 9g servo could easily be blown flat at high speed.

[og]

will check it out once its glued back together

[TIM Shaw]

As Martyn said - does it fly ok at normal speed?

Is your horn secure and not floating in the foam?

I don't know the model, but is the servo pulling the elevator up from a top mounted horn, or pushing it up using a horn mounted on the underside. If the latter, a bendy pushrod may be to blame, again allowing blow back at high speed.

Typically, a nose heavy plane will be sluggish on elevator - but failure to pull out of a dive could actually indicate a rearward CG - there is a well-known trimming check for CG, known as the "dive test" Trim for straight and level flight at mid throttle,take it up high, then push the nose down to about 45 degrees and watch what happens.

If the CG is correct, the model should slowly recover to straight and level.

If it's too far forward, it will snap out of the dive rapidly, while if it too far back the nose will tuck under and the dive will steepen. I know this sounds counter - intuitive, but trust me, it's correct, and is to do with where you have your elevator trimmed for straight and level flight.

[og]

normal speed - not really thats why i have it on max throw

[Martyn K]

That would indicate a CG slightly too far forward but would also suggest that it should recover naturally from a dive.

Do you have to hold up elevator for straight and level or will it fly hands off?

[og]

it seems to fly level hands off

[Martyn K]

That suggests the CG is correct for the wing incidence. Moving the CG back will make it over elevated. I suspect the problem is the elevator is too flexible or problems with the linkage. Can you post some photos?

[GONZO]

The HK Skipper XL is the same as the Eachine Ripple XL from Banggood. Some links that may prove useful:

**LINK**

**LINK**

**LINK**

**LINK**

YouTube is useful as well.

[Mike T]

I rearranged my elevator linkage to pull for up:

It's always pulled out (so far...)  A side benefit is that this arrangement helps to stiffen and support the rod.

Edited By Mike T on 09/05/2017 18:09:43

[og]

mike you might be on to something here - if i have the servo arm upwards and reverse the elevator control horn with the push rod above the tail plane then the up elevator will pull

[Don Fry]

I used to have one of these. I recall the stated CG was way forward. Using 4s 2200 batteries, the CG was ok ish, with them as far back as they would go in the supplied box. But I would sugggest it ain't designed for power dives.

[Simon Chaddock]

"ain't designed for power dives"

That would be my take on a foamy. At high speed it only takes the tail plane to flex under the load of the deflected elevator and the net result is no 'elevator' effect at all or even control reversal.

Edited By Simon Chaddock on 09/05/2017 20:15:05

[Denis Watkins]

The foam under the horn would compress at Mach.5

[og]

it only went into a dive cause i coudnt get it to pull up !!!!!

[Piers Bowlan]

Nothing like the HK Skipper I know but I had a HK Fox. It was a big for a foamy at 2.3m and although the elevator worked, to my mind the supplied servo didn't have the strength to pull the skin off a rice pudding. I changes it anyway for something more fit for purpose in my view as I felt that it was only a matter of time before it let me down. Probably at the bottom of a dive!

Edited By Piers Bowlan on 10/05/2017 06:52:41

Edited By Piers Bowlan on 10/05/2017 06:57:03

[Trevor Crook]

I've got the smaller Skipper, which flies on 3s 1300s. Even with this small battery, it's well nose heavy but flies well enough with plenty of up trim, and has never entered an uncontrollable dive.

However, the elevator is in two halves for shipping, and you join them using self-adhesive pieces of stiff plastic sheet top and bottom. After a few outings, I noticed mine were starting to peel off, which would have led to only one elevator working. I let in a small elevator joiner made from a length of piano wire bent into a U shape, secured with cyano. Worth checking.

A great little "chuck in the boot" all weather flier.

[MattyB]

Posted by Simon Chaddock on 09/05/2017 20:14:15:

"ain't designed for power dives"

That would be my take on a foamy. At high speed it only takes the tail plane to flex under the load of the deflected elevator and the net result is no 'elevator' effect at all or even control reversal.

That is somewhat of a sweeping statement - sure there are some floppy foamies, but models like the EFX, EFXtra, Roc Hobby pylon series and the Mpx Dogfighter are well reinforced and good to >100mph in stock form, more with a few mods. Horses for courses.

My gut feel is that the OPs issue in this instance is most likely to be CG related, but if worried about flex check the linkage run thoroughly, upgrade the servo ff needed, check the elevator horn is solid and reinforce the elevator itself with a few pieces of inset carbon strip and CA.

Edited By MattyB on 10/05/2017 11:32:35

[Piers Bowlan]

I agree Matty, MPX models are well designed and fit for purpose. I sometimes glue a thin square of ply under the control horn to reinforce it on my HK foamies, to stop the horn moving independently of the control surface!

[Ian Jones]

Erm, a bit obvious but have you tried some careful resistance testing? That is, when you put in up elevator and rest you finger on the elevator, does it give up trying, is there some unexpected happening like the horn moving it's mounting but not the whole elevator?

An over rearward CG doesn't give much trouble for long but the problems associated with a forward CG are often overlooked and are far more common. It could be the issue. There's lots of ways of checking, often by a certain amount of observation and guesswork as to how much to adjust it based on that observation. I have found online CG calculators useful for at least getting the model flying safely. If nothing else it's worth eliminating it for once and for all. You could try this CG Calculator for example.

[Mike T]

Using 'standard' 1300 3S LiPos, mine flies perfectly (elevator 'zeroed'.

Apart from the pushrod mod (and replacing the ridiculous foam spinner with a smart alloy one that actually fits), it's otherwise OOB.

If anybody's tried upgrading the motor, it would be good to know how it worked out, but I have to say, the whole package just works so well as it is!

[KiwiKid]

I have the Skipper (jnr) to which I think you are referring Mike T (Og has the Skipper XL) and love it to bits too. Really a fun flier and nice and quiet for park flying. As you have found, it flies great stock and is a very good bang for a buck.

Og, have you flown the XL again? Interested to see how you got on. The recommended CG is a bit far forward and, as others have alluded to, moving it back a bit helps, but it did sound like you were having some mechanical problems.

Both the XL and jnr do have a bit of a wobbly goblin problem if there is a bit of wind about. Two fixes are to extend the rudder or add additional verts on the horizontal stab. I have a Polaris Ultra (made from the same moulds as the XL - but that's another story) and it flies very well with the verts added.

[og]

hi

have done the pushrod mod but have not had it ouit yet - certainly has a better feel to it

[Don Fry]

Kiwi, greetings. Hope your lot are in training for the Lions. Any chance of dimensions for the verticals. I have just ordered a replacement airframe to replace the one I broke, and without the Dutch roll would be much nicer.