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Author Topic: trim  (Read 341 times)
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Copper Member

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Argentina Argentina

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« on: April 17, 2017, 06:28:18 PM »

Hello everyone.
What trim and CG would you give an F1B for wind conditions?
Greetings and good flights !!
Thank you
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United States United States

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« Reply #1 on: April 23, 2017, 03:53:37 PM »

Hi Claudio,

One common practice is to trim the model in calm air, where it is easier to see what adjustments to climb and glide trim are needed. For wind, the model's center of gravity is moved forward a few percent (i.e. Igor Vivchar showed the CG at 58% for "small wind" and 56% for "strong wind" on his 1997 F1B model.

A simple way to move the CG forward is to add extra weight to the nose. One way is to strap a spare wing wire on the top of the motor tube just behind the nose ring. (An F1B wing wire weighs about 4 grams.)

On my models with Vivchar front ends I add an aluminum ring that fits around the rear bearing housing and is held in place with a set screw. The aluminum piece weighs about 4 grams; I've also turned one out of brass that weighs about 8 grams for very windy conditions.

The other method of dealing with windy conditions is to lower the trailing edge of the stabilizer slightly. This requires careful measurement and note-keeping so you can re-set stabilizer for calm weather. Using a nose weight has the advantage of showing that the model is set up for wind or for calm without having to measure stabilizer setting.

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Canada Canada

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Me with F1B - epic retrieval (flew 10km after DT)

« Reply #2 on: April 24, 2017, 12:12:57 PM »

The Canadians do as Louis described below. We trim for optimum performance in the calm and then add weight as wind and turbulence increases. On a nice dat with good thermals we would typically start the first round with no weight. By 2nd or 3rd round we have 2g on the front end (Vivchar, same as Louis) and by the middle of the day we are up to 5-7g.

In very windy conditions we would fly with more (10g).

If you use AA front ends you will have to devise a different method for adding nose weight (a piece of motor tube that is split so it can open up with weight glued in place could be a good solution). Or you can do like the other AA guys and use stab adjustments. But, as Lois says, this means being very careful with your vernier to measure everything correctly and also means that you have changed the flight surface setting for the climb. I prefer the simpler CG shift approach.


F1B guy but its not my fault, Tony made me do it.
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