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RE: Aviation Models 33% Yak Build Thread - 6/29/2008 11:53:11 PM   
diamondave



Posts: 1673
Joined: 9/2/2004
From: marana, AZ, USA
Status: offline 		well over all it went well, i need to move the cg back some more for sure, more importantly my rudder geometry is wacky, i thought it was going to be okay but its not, i think that aluminum arm has too much offset for what i need, if i snug the wires up at center, its way too tight at throw, i could riff out a slide solo if i were dicky betts , and if i snug them at throw then its slopy at neautral, i am going to get a different arm, i guess the offset one right? we dont use strait ones anymore on a set up like this do we? my horns at the rudder are close to the hinge line, maybe a little behind but no more than a 1/4, looks like less actually, anyway a guy at my field who has set up many big planes said my set up is way off, that arm i used with the kit is more than 3/4 offset from the servo screw, hopefully just replacing the arm and cables(mine may be too short now) should fix the problem, will call tbm tomorrow, other than that i was impressed, i only flew it 2 times cause of the loose rudder, but it was good, flat spun upright and inverted nice(even with the forward cg), lots of power, very stable in a hover and excellent pull out with the menz 26-8, i will try my vess 26b next time out too for the heck of it, this has the poetential to become my new favorite plane just need to do some adjustments, any ideas on the rudder?

(in reply to P-Diddy)
       Post #: 2151

RE: Aviation Models 33% Yak Build Thread - 6/30/2008 12:13:40 AM   
wind junkie



Posts: 981
Joined: 11/16/2002
From: N. Syracuse, NY, USA
Status: offline
quote:

ORIGINAL: diamondave

well over all it went well, i need to move the cg back some more for sure, more importantly my rudder geometry is wacky, i thought it was going to be okay but its not, i think that aluminum arm has too much offset for what i need, if i snug the wires up at center, its way too tight at throw, i could riff out a slide solo if i were dicky betts , and if i snug them at throw then its slopy at neautral, i am going to get a different arm, i guess the offset one right? we dont use strait ones anymore on a set up like this do we? my horns at the rudder are close to the hinge line, maybe a little behind but no more than a 1/4, looks like less actually, anyway a guy at my field who has set up many big planes said my set up is way off, that arm i used with the kit is more than 3/4 offset from the servo screw, hopefully just replacing the arm and cables(mine may be too short now) should fix the problem, will call tbm tomorrow, other than that i was impressed, i only flew it 2 times cause of the loose rudder, but it was good, flat spun upright and inverted nice(even with the forward cg), lots of power, very stable in a hover and excellent pull out with the menz 26-8, i will try my vess 26b next time out too for the heck of it, this has the poetential to become my new favorite plane just need to do some adjustments, any ideas on the rudder?


If you cross the cables, you need to mimic the geometry you have at one end exactly on the other end. If you want to keep that servo arm, then you need to figure out how to get the 3/4" offset at the rudder. Conversely, you could measure what you have at the rudder, and then mimic it at the servo. Of course, measure the distance between the pivot points too as they should be the same.

Just get a piece of sheet aluminum from K&S or use some G10 layered to give you strength to mount the ball link bolts in there and you'll be all set.

It pays to be precise. Even 1/8" makes a difference in the cable tension.

_____________________________

Arguing with an engineer is like wrestling a pig. Everyone gets dirty and the pig likes it.

(in reply to diamondave)
       Post #: 2152

RE: Aviation Models 33% Yak Build Thread - 6/30/2008 12:28:11 AM   
diamondave



Posts: 1673
Joined: 9/2/2004
From: marana, AZ, USA
Status: offline 		well i think my horns are off a bit between the 2 sides of rudder, not drilled strait i guess, one side appears almost on the hinge line, maybe 1/8 back, the other side is further back, less than 1/4 but further than the other, its hard to measure distance exaclty from the bottom of rudder, but appears to be 3&3/4 or so horn to horn, so ideally i should use 3&3/4 arm with maybe no offset or the 1/4 one that is commonly available, but mostly what i see searching is 4" arms, with that 1/4 offset, i think it will be way better than what i have...my cables are not crossed, strait back, should they be?

(in reply to wind junkie)
       Post #: 2153

RE: Aviation Models 33% Yak Build Thread - 6/30/2008 12:40:09 AM   
BROKE STAB


 

Posts: 156
Joined: 11/9/2003
From: somewhere, USA
Status: offline
quote:

ORIGINAL: wind junkie


quote:

ORIGINAL: diamondave

well over all it went well, i need to move the cg back some more for sure, more importantly my rudder geometry is wacky, i thought it was going to be okay but its not, i think that aluminum arm has too much offset for what i need, if i snug the wires up at center, its way too tight at throw, i could riff out a slide solo if i were dicky betts , and if i snug them at throw then its slopy at neautral, i am going to get a different arm, i guess the offset one right? we dont use strait ones anymore on a set up like this do we? my horns at the rudder are close to the hinge line, maybe a little behind but no more than a 1/4, looks like less actually, anyway a guy at my field who has set up many big planes said my set up is way off, that arm i used with the kit is more than 3/4 offset from the servo screw, hopefully just replacing the arm and cables(mine may be too short now) should fix the problem, will call tbm tomorrow, other than that i was impressed, i only flew it 2 times cause of the loose rudder, but it was good, flat spun upright and inverted nice(even with the forward cg), lots of power, very stable in a hover and excellent pull out with the menz 26-8, i will try my vess 26b next time out too for the heck of it, this has the poetential to become my new favorite plane just need to do some adjustments, any ideas on the rudder?


If you cross the cables, you need to mimic the geometry you have at one end exactly on the other end. If you want to keep that servo arm, then you need to figure out how to get the 3/4" offset at the rudder. Conversely, you could measure what you have at the rudder, and then mimic it at the servo. Of course, measure the distance between the pivot points too as they should be the same.

Just get a piece of sheet aluminum from K&S or use some G10 layered to give you strength to mount the ball link bolts in there and you'll be all set.

It pays to be precise. Even 1/8" makes a difference in the cable tension.



Just like WIND said.
If the servo arm has a 1/4 offset then the control horns at the rudder have to be 1/4 back from the hinge line or you will have this problem.I f you are even with the hinge line then you need a straight servo arm.
Another thing to consider is if you are using a 3 inch arm at the servo then at the rudder you need to be 1 1/2 inches from the center of the hinge to where the cable connects.

(in reply to wind junkie)
       Post #: 2154

RE: Aviation Models 33% Yak Build Thread - 6/30/2008 12:55:09 AM   
diamondave



Posts: 1673
Joined: 9/2/2004
From: marana, AZ, USA
Status: offline 		i think the hole problem is that i didnt get the clevises that are supposed to thread on to the "screw" that goes through the rudder, so i used some horns very similar to the ones used on other surfaces of this plane, but that changed everything, i looked at my arm on my other yak, its the 4" arm with the 1/4 offset, and it looks like i could use the holes one in from the end and then it wouldnt be on the offset part, and closer to my distance from the hing line to horn, maybe that might work, or i could try and find those swivel clevises that screw on to that threaded piece and remove my horns and star all over, and leave my servo arm on there, cause that threaded peice would sit further back on the rudder past the hing line right, anybody know what threads that is? ...i am not sure which would be the better of the two to try and set up, i think getting an arm to match would work the best at this point, seems like thats better than removing horns and drilling another hole into the rudder right?

(in reply to BROKE STAB)
       Post #: 2155

RE: Aviation Models 33% Yak Build Thread - 6/30/2008 1:14:08 AM   
diamondave



Posts: 1673
Joined: 9/2/2004
From: marana, AZ, USA
Status: offline 		well after looking one more time, maybe replacing my horns will be the best, it looks like i can enlarge the rear hole of my horn and that may be a perfect spot for the threaded rod to go through, looks like 4mm set up using a die i had, so tbm sells the hole set up with threaded rod and clevises, i may go that rought, leave my servo arm alone and try and get the back set up correctly, i will call them tomorrow and see whats up, thanks for the tips so far, once this is done, im ready to put that darn rudder to the test

(in reply to diamondave)
       Post #: 2156

RE: Aviation Models 33% Yak Build Thread - 6/30/2008 4:30:02 AM   
wind junkie



Posts: 981
Joined: 11/16/2002
From: N. Syracuse, NY, USA
Status: offline 		FYI, I believe the exit slots for the rudder cables in your plane are cut expecting the cables to be crossed. Every build thread I've seen on this plane crosses the cables.

If you dont' cross the cables, they will want to exit the fuse sides further forward than they are, so you are probably rubbing the cables on the front of the exits all the time and that's not good! IF that's the case they will not only have bad geometry but they will get looser every flight as the cables wear through the slots enlarging them!

_____________________________

Arguing with an engineer is like wrestling a pig. Everyone gets dirty and the pig likes it.

(in reply to diamondave)
       Post #: 2157

RE: Aviation Models 33% Yak Build Thread - 6/30/2008 7:48:50 AM   
P-Diddy


 

Posts: 670
Joined: 12/12/2005
From: Eugene, OR, USA
Status: offline 		Yep, agreed on crossing the cables. Mine are crossed, and once you cross them and see how they fit, you realize that it was meant to be that way. Also, attach one clevis to the top of the servo arm and the other to the bottom. This way, the cables won't rub together halfway back inside the fuse...

_____________________________

Currently:Aviation/SD Yak 54 33%(3W70),UltraRC GilesG202(BCMA 40cc),T-Rex600N(O.S. 50 Hyper), MSH Protos 500

(in reply to wind junkie)
       Post #: 2158

RE: Aviation Models 33% Yak Build Thread - 6/30/2008 9:07:55 PM   
diamondave



Posts: 1673
Joined: 9/2/2004
From: marana, AZ, USA
Status: offline 		i was going to ask about the crossing thing, the guy at a lhs said to cross them if it rubs at exit, otherwise you dont need to, mine was bad to start with so i didnt notice, but i will try and cross them now, i got all new stuff, here is the plan someone give me the okay before i mess up again , i am leaving the supplied arm on the servo, looks like 2" from servo screw to center of hole for ball link, 4" total span, and double checking with a strait edge looks like 7/8" offset to the rear from servo screw...so my rudder link(the clevis attach point) wants to be 7/8 behind the center of the hinge line correct?, and 2" from the hinge line or the surface of the rudder??

(in reply to P-Diddy)
       Post #: 2159

RE: Aviation Models 33% Yak Build Thread - 6/30/2008 11:26:44 PM   
wind junkie



Posts: 981
Joined: 11/16/2002
From: N. Syracuse, NY, USA
Status: offline
quote:

ORIGINAL: diamondave

i was going to ask about the crossing thing, the guy at a lhs said to cross them if it rubs at exit, otherwise you dont need to, mine was bad to start with so i didnt notice, but i will try and cross them now, i got all new stuff, here is the plan someone give me the okay before i mess up again , i am leaving the supplied arm on the servo, looks like 2" from servo screw to center of hole for ball link, 4" total span, and double checking with a strait edge looks like 7/8" offset to the rear from servo screw...so my rudder link(the clevis attach point) wants to be 7/8 behind the center of the hinge line correct?, and 2" from the hinge line or the surface of the rudder??


The 4" spans sound right be sure that you're 2" from the CENTER pivot points to the clevis/ball link attachments at both the servo and rudder.

However, I think we need to be clear on what you mean by "behind" the rudder center. I should have said "mirror" the dimensions before. Your 7/8" dimension is to the rear of the servo that is "behind". However, the pivot points at the rudder need to be 7/8" AHEAD of the rudder hinge point this "mirrors" the servo dimensions and will give you perfect geometry.

_____________________________

Arguing with an engineer is like wrestling a pig. Everyone gets dirty and the pig likes it.

(in reply to diamondave)
       Post #: 2160

RE: Aviation Models 33% Yak Build Thread - 7/1/2008 2:59:18 AM   
diamondave



Posts: 1673
Joined: 9/2/2004
From: marana, AZ, USA
Status: offline 		sure now you tell me , haha, i gave up on that arm now, i was trying to get my new rudder horn set up 7/8 behind cause i thought that is what i should do, but with the length of the clevises i would have had to drill my hole for the shaft behind the hard wood block, so instead of altering the rudder to add a hard point, i mounted my horn so that the clevis is on the hinge point, i will call tbm and get a straight 4" arm now, seemed like the thing to do so thats where im at, i was hoping to be able to get it going for this weekend again but now to get the arm i know my lhs doesnt have that, so depending on how much for next day air i may just wait and fly my ef yak this weekend and fix this later when i get the arm, i will find out tomorrow, if its only 5-8 bucks or so i may rush ship it.....geez, i never had this much problem with a set up before, guess its all a learning curve for me, all because i didnt have the included parts so i tried to make my own up, but i am sticking to it now, the horn is already mounted even with hinge line and that offset arm had been removed, we will get there again one of these days....just frustrated a bit at the moment, i know it will all be worth it in the long run

(in reply to wind junkie)
       Post #: 2161

RE: Aviation Models 33% Yak Build Thread - 7/1/2008 7:51:45 AM   
P-Diddy


 

Posts: 670
Joined: 12/12/2005
From: Eugene, OR, USA
Status: offline 		Dave,

One thing you are doing RIGHT is that you are trying to make everything PERFECT. Of course, this is near impossible, but when you aim for perfection, you get the best result possible. You certainly chose the right airframe if you're striving for perfection. Everyone that sees me fly my SD/Aviation/TOC Yak thinks that I'm a lot better pilot because of how well this plane flies... And mine is underpowered with a little 3W 70 in the nose... Keep your chin up, it sounds like you're almost there.

-Pat

_____________________________

Currently:Aviation/SD Yak 54 33%(3W70),UltraRC GilesG202(BCMA 40cc),T-Rex600N(O.S. 50 Hyper), MSH Protos 500

(in reply to diamondave)
       Post #: 2162

RE: Aviation Models 33% Yak Build Thread - 7/1/2008 9:10:33 PM