HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Nov 15, 2012, 11:24 AM
Graham Dyer
pardus's Avatar
Johannesburg, South Africa
Joined Jul 2003
698 Posts
Quote:
Originally Posted by kcaldwel View Post
If changing the motor thrust line affected the power-off dive test results, it must have been out of trim in glide before the dive test. The dive test is only meaningful at all if the airplane is in trim near best L/D speed for a hands-off glide.

A better test for CG position is inverted flight. The amount of down elevator required inverted for level flight at the same speed as upright is a good indication of the stability margin - less down elevator, lower stability margin.

Thrust issues are easy to confuse with pitch trim and stability. The pattern guys have systematic trimming routines in a particular order to sort out which is which.

http://www.australianpatternassociat...tholdsmith.pdf
Yes I believe it was, having tried to get the pitch-up-on-power corrected, it seemingly was still trimmed nose down for the dive test which exacerbated the effect. Giving some up thrust I think has effectively given a bit of up force to the HS when adding power so negating a bit of the pitch up.

Anyway thanks for all the advice and info, hope this can also help someone else with a similar issue.
pardus is offline Find More Posts by pardus
Reply With Quote
Sign up now
to remove ads between posts
Old Nov 15, 2012, 03:11 PM
Registered User
Joined Nov 2007
1,764 Posts
Good suggestions, guys. Thanks!

I'll let you know what I choose...
Flyboy Steve is offline Find More Posts by Flyboy Steve
Reply With Quote
Old Nov 16, 2012, 11:12 AM
Registered User
Blacksburg, VA 24060 USA
Joined Feb 2000
3,178 Posts
"Thrust issues are easy to confuse with pitch trim and stability. The pattern guys have systematic trimming routines in a particular order to sort out which is which."

So what do you work on first? Pitch first, then thrust?

Jim R.
JRuggiero is offline Find More Posts by JRuggiero
Reply With Quote
Old Nov 17, 2012, 07:13 AM
Registered User
richard hanson's Avatar
United States, UT, Salt Lake City
Joined Oct 2007
6,720 Posts
Just use the logical approach

once you get it in the air , trim the flying surfaces for an easy to fly trim.
the speed for this stage of trim should be a nice easy to fly cruise speed .
Once you get this sorted out - try lower power and higher power
If you see big differences in climb or dive as power changes- - First see if cg is reasonably close to correct - make gradual cg changes - finally- play with the thrust setups .
The old pattern trim charts are a decent starting point but getting sensitivity .
Here is the good part - with more experience in trimming -it all gets easier -
If you just chase the plane around - -it never gets easier
It is a learning curve - I have taken "trimmed" models which are difficult to land,etc., and by going thru the very basics, retrimmed the model for good manners.
You can't do the trimming on paper - you have to fly it to do it.
beleive it or not - once you "get it", you will find you can figure out the trim of someone elses model - by just watching them fly it.
richard hanson is offline Find More Posts by richard hanson
Last edited by richard hanson; Nov 18, 2012 at 07:11 AM.
Reply With Quote
Old Jan 12, 2013, 03:32 AM
Registered User
Joined Nov 2012
2 Posts
Quote:
Originally Posted by pardus View Post
Looks familiar
Darkwingdean is offline Find More Posts by Darkwingdean
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Build Log yet another scratchbuilt twin boom pusher xatled99 FPV Talk 54 Aug 18, 2012 11:41 AM
Discussion Inv V-tail Twin Boom Pusher Ė Yet another one wingnutt FPV Talk 6 Apr 28, 2012 05:40 PM
Discussion 100" Pusher Glider with Twin Booms A-tail rclab1 The Builders Workshop 4 Mar 06, 2012 05:43 PM
Discussion Looking for pusher prop planes. Preferably twin boom tail. SFGuy Electric Plane Talk 8 Oct 31, 2009 06:06 AM
Discussion Another Twin Boom pusher AP plane Bob Chiang Aerial Photography 5 Nov 02, 2008 12:46 AM