Motor attitude angles

[DavidS]

Hi guys I am DavidS,

I have just assembled a Wot 4 woody electric. There is no mention in the instructions of any down or right set on the motor. I have mounted it onto the ply mount and it appears to be dead in line with the fuselage in both plans. I have a Wot4 foamie and a Funcub both of which have down angle and some right ofset on the motor. can anyone advise me on any adjustments I should make before the maiden flight.

[Richard Wood]

Hi David,

My advice would be to fly it initially as it is - with no down or side thrust
& see how it goes.
If the model climbs too much on power add a touch of down.
Ideally down thrust should be set so the model flies straight &
level at your comfortable flight cruising speed.
Dave B wrote a very useful article in a recent RCME on trimming.
(can't remember the issue month!)

If it veers off to the left, particularly on take off, add a touch of right
side thrust.
The trad Wot 4 doesn't seem to require down or side thrust so you may
need neither.

[Biggles' Elder Brother - Moderator]

I'd agree with Richard - I'd "suck it and see" - its very unlikely to proove to be really problematically as is, provided the CoG is right. You can then decide wether to engage in a bit of "fine tuning" once you've seen how it goes. I had a WOT4 (original kit build) and that had no additional right or downthrust in it and it flew fine.

BEB

[Peter Miller]

Very few of my own designs need any side or down thrust. Only those with a centre of drag a long way from the the centre of thrust such as the Slingsby and Sandow need down thrust.

The swing on take off is a torque reation and can be held with a touch of rudder. Read up on full size aircraft and you will often get a reference to it "needed a bootfull of rudder to hold it straight on take off"

A few aircraft actually had an off set fin to cope with this. Note, not side thrust but an offset fin but no one ever suggests that for a model.

[Paul Adams]

Its fairly close to where it needs to be. However what I always do with all my model is to gain altitude and throttle down to tick over and trim the model for a nice glide (This is one manuver your model will always have to do at the end of each flight when you are bringing it in for landing). Once trimmed for a nice glide, without touching the elevator, throttle up to maximum and see what the model does. It it flies level and just accelerates - no need to adjust the down thrust, it it climbs add down thrust, if it noses down reduce the down thrust.

To adjust side thrust, go into a vertical climb at full throttle and see if it drift right of left. Note: Unless your model is well over powered the model will slow during the climb and what you are looking for is a generally straight climb during the time it is climbing at a good rate.

Note: If you change the CofG during the trimming phase, you may need to repeat the above.

Paul

[Biggles' Elder Brother - Moderator]

A correctly trimmed model will always climb at full throttle - if it doesn't then either the cruise is set too fast or its underpowered.

What it shouldn't do is go "nose upward" when you open the throttle to max. Simply gaining height is normal and expected - a major pitch change isn't!

BEB

[Paul Adams]

Agreed, steady climb ok,(ie you should not need to re-trim elevator between high trottle and idle).

It made sence to me when I wrote it but can see the confusion.

Paul

[DavidS]

many thanks guys for the helpful comments and advice. I will post the results when I fly the maiden but in better weather than we have at this moment.

[DavidS]

Once again thanks for all the advise and tips. My Wot 4 woody is now flying well with minimal down and side adjustment on the motor. A nice model to fly with the extra weight being a big plus in windy conditions.