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Questions about trimming (Read 6022 times)
Reply #2 - Dec 26th, 2015 at 9:05am

Widdog   Offline
Full Member
I Love YaBB 2.5 AE!
USA

Posts: 244
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Wow great post Terry and thanks much for posting. I was able to read your post before I went flying again. I really like the Guillow's 900 series kits. I think I was able to get the model close to trim. By which I mean get it to circle to the left.

I did get in a full power flight. I think it might have been a good flight if it didn't hit the tree's. Also right after launching the wind picked up and sort of carried the model. https://youtu.be/v6r-ymHyTzE

BTW i think i can fix the model with the ole hot glue gun.

Lastly I just wanted to mention that i used 1/16 inch thread rubber on these flights. I'm not sure but it seemed to help
 
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Reply #1 - Dec 25th, 2015 at 11:14pm

terryman   Offline
Senior Member
I Love YaBB 2.5 AE!
Los Gatos, CA

Posts: 865
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Widdog,

One can go on at length about what might be wrong, what's needed and how to accomplish it.  I'm quite interested to read what others suggest, where the discussion goes and the models progress.  It is already showing a lot of promise with both altitude and duration. 

For now I'm guessing what you are describing and showing just after launch is a power stall and may be improved by increasing down thrust.  As more turns are added the amount of down thrust may need to be increased. 

Try right thrust too if the initial left turn is too tight.

The inconsistent flight pattern from there may be helped by securing the nose piece and/or thrust button.  They must not be loose and free to rattle around or change angle. This is also required for the down thrust to be effective. 

This is assuming you have already done a number of things approximately correctly:

Built in adequate dihedral,
Built in some wash out,
Set the balance point OK,
Trimmed for a good glide.

If built to scale it's possible the tail flight surface areas are marginal, would benefit from being larger.  But the amount of work needed to change those makes it worth spending more time with trimming what you've got for now. 

The flight pattern I most often achieve on low wing WWII models is left turn during the initial power burst and cruise transitioning to right turn during glide (if it gets that far).  This is not cast in stone and you sort of have to work out an agreement with each model what flight pattern works best.  Smiley.  All my opinion of course

Terry
 
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Dec 25th, 2015 at 8:10pm

Widdog   Offline
Full Member
I Love YaBB 2.5 AE!
USA

Posts: 244
***
 
I posted a couple of builds on this forum. I received a lot of good advice. I feel my building skills has me at a strong D leaguer.  I build both kits and scratch building. I read a lot about others builds and learn a lot from that. However, I still seem to always struggle with trimming.

Not only do I have problems trimming. I also have problems getting my models to fly in any kind of a pattern. I get flights where the model flies strait up, stalls, circles and than flies straight.  .
https://youtu.be/Tqsh2Hn0aIA

I think on this case I may have overpowered the model's rubber motor. I ran out and re ordered 3/16 inch thick rubber. I used 4 strands of 1/8 inch rubber. Well that's what I think my be wrong. I'm  not really so sure


 
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