D/T

[Anonymous]

I have been trimming my Prima F1B.All was going well with a reasonable right glide circle, but when the tail dethermalised it spun a bit to the right and landed breaking the right wing.What can I do to get a straight d/t other than setting the rudder centrally, which of course gives a long glide in a straight line.Can I angle the tail? If so, which way.

[REYNOLD MAZZOCCO]

SInce no one with more experience has chimed in, I’ll get it started.

Don’t change the rudder setting. It won’t effect the DT. I’ve had similar problems occur in the past, so I’ll give you the most common cures:

1. The stab isn’t “straight” when DT’ed. Sometimes you can’t tell this is happening because it pops into place when it hits the ground. Do several dry runs on the ground and see if this is the problem.

2. The stab DT angle is too shallow causing the model to go into a stall/spin instead of flat DT.

3. The stab doesn’t “pop” right up, but comes up slow enough to allow the model to stall/spin before fully deployed. Once the model enters the spin, it usually won’t recover, even when the stab comes up fully. Look for friction or sticking points in the system to cause this.

I built a Prima many years ago and didn’t have this problem, so I don’t think it is a design issue.

Rey

[Anonymous]

Many thanks. I realise now its not the rudder.I have improved the seat for the leading edge of the stabilizer and adjusted the tension for a good positive d/t.Its been too windy to fly since but I am confident that the problem is now solved. I was going to play with the rudder which would not have got me very far. Jim

[gos]

Like previous post said, get the stab at a higher angle—I always use about 45 to 50%.

Also as stated, make sure the stab stays ‘straight’ on decent.

[Author]

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