Plastic noses and off set

[Seeker]

I'm building a 403 Spitfire at the moment, and I'm wondering about setting the propeller thrust line.

I understand that I'll probably need some down and right thrust, and that it's a good idea to make it adjustable in some measure to aid trimming.

Now, I'm a bit of a loss how to achieve this accurately with these plastic noses.

I've been following a couple of really nice build threads on this forum showing other Guillows plastic noses models, how do you guys set the thrust line?

At the moment, I've taken the vinyl motor fire wall mount, and sanded it down so that it just fits inside the nose cone. I've cut out the centre of the firewall to clear the rubber, and I'll glue it into the nose cone as a mounting plate.

I plan to glue magnets to the vinyl fire wall/nose former and the "face" of the two F1 formers and glue to pins onto the face to act as guides and positive locators.

This will give me a demountable nose cone so I can pack the nose with the appropriate weight of clay for balance.

I'm still a bit hazy how to measure the thrust line of the mounted propeller so as to make any necessary corrections

Or at least, that was the plan, but I notice most of you cover the platic nose cone. So how har you adjusting and setting the thrust line?


Any "best practise# guides out there?

[supercruiser]

You could do a search for: adjustable nose block. Somewhere on this forum is an example. I tried looking but several threads showed up and I didn't read them all.
My method is simple and crude but, it will work. I add different thickness
balsa shims under the thrust button. I have a semi-permanent glue called:
Walthers GOO. I can attach and remove my shims fairly easily with this glue.
Some adjustable nose blocks use small brass screws, that you can turn one way or another and change the angle of the thrust button.

The removable nose that you made with magnets and guide pins is a very good idea.

[Seeker]

This is what I'm trying to reproduce:

http://www.easybuiltmodels.com/Removabl ... %20peg.pdf

But I can't think of a reliable way to measure what angles I've actually got once the prop's in place.

What's the trimming symptoms?

What is it, in those first flights, that makes you guys think "hmm, that needs a bit less right thrust" instead of more up aileron on the left wing....

[supercruiser]

First, get it to glide properly. Some people say that it should turn right under power and glide in a left turn.

I get it to glide straight ahead, without that little dipsy-do thing.... climb a little-dive-climb-dive-climb.....

Crank in about 3 to 5 degrees downthrust. Wind it up and let it go.
There really is no need to know the exact angle of downthrust. It just needs to be easily adjustable and repeatable. Different rubber motors, number of winds,and other variables will change downthrust angle needed.
Left or right thrust angles is just "to taste". Get the best flight performance.

Got to go... I'll check back in later.

[supercruiser]

What I'm saying is that once you get the glide set correctly with rudder/aileron/elevator adjustments. You generally leave it alone.
During the powered portion of the flight you notice..."hmmm, always want to go in a left hand turn", then crank in a little right thrust.

You can add too much left/right thrust and get reduced flight performance.
It's a delicate balance. Thats why adjustable nose blocks are so useful to make those fine adjustments.

[Seeker]

Thanks, that makes sense.