WOT4 zoom climb / pitch up

[jpreou]

Hi Guys, I've got about five flights on my Wot4 Mk3 now. Two things I have noticed. One is that it screws out of a loop if I have too much elevator, so I can handle that by just dialling things down a bit.

Of more annoyance is that when airspeed gets high enough (like the bottom of a loop if I haven't slowed up) the model pitches up to the vertical violently and climbs hard. I can get this from straight and level with just a slight nudge of elevator; obviously the elevator is more effective at higher speeds, but the pitch up is really quite sudden and very quick / hard. Ideas on this one would be appreciated.

Cheers

-- JEFF, NZ

[Richard Wood]

Hi Jeff,
If the model is screwing out of a loop check the lateral balance & add
weight to a wing tip if necessary.
Regarding the pitching up - does it do this when power is applied or
just when elevator is pulled up?
Some things to check:
Make sure the CG point is correct - if its too far back the elevator response
will be very sensitive. Also check there isn't excessive elevator travel.
Check the wing is seated & held securely & that the incidence is correct.
If it pitches up when power is applied there could be upthrust so
check the thrustline is ok.
Hope this is of use.

[Alan Wood]

I second everything above. Sounds like a CG issue to me.

[jpreou]

Thanks Guys, will check the CG again, but pretty sure it is ok. I checked it in the shop when empty, so with fuel I would expect a more forward CG for most of the flight. I could get 24 mins from full to empty and dead stick, but I'm usually landing after 15 mins or so with plenty of juice left (other than that one fuel check flight). It flies well at all speeds and all throttle settings except when going very fast. That is, generally after a downward moanoeuver; full throttle straight and level is ok. I do have a fair bit of elevator travel so will dial that back. Lateral balance is ok; it already has a whopping great screw embedded into the left wing tip! I think I'll check the wing incidence, if I can, but I can't remember seeing anything in the manual about that; its a cut kit, so it is what it is.

[Richard Wood]

Jeff also try some elevator exponential as well if you don't already have it.
Try 40% - 50% for a start. This can make quite a difference.
There's a tip in section 14 on page 5 of the manual on checking the wing
datum.

[Martin Harris - Moderator]

A very unlikely possibility - but that sounds like the behaviour of an insufficiently banded on wing lifting at the leading edge. You haven't modified it to use bands, I suppose?

[jpreou]

I think (haven't looked) that I am using 25% - 30% expo. Will need to check.

Yes, I use wing bands. I band it on with four bands in total, crossed over. The leading edge fits under a little 'lip' which I would hope might prevent that. How on earth would I check anyway! I guess I'll try to lift the wing by hand and see if there is any give. The bands are quite tight though.

Back from a business trip now, so after flying tomorrow morning (full size) I'll check some of these things out. Thanks.

[David Davis]

I thought it might be wing bands! Try using six or eight bands both diagonally and from front to back then grab the wing tips and shake the model up and down to see whether there is any movement. If there is try using smaller bands. I've modified my WOT 4 to bolt on wings.

Finally, which engine are you using? If using a 61 or larger engine the model will be capable of flying at higher speeds and therefore any stresses on the flying surfaces, and the wing bands, will be increased.