[NSRCA-discussion] Elevator trim change

Tue May 9 16:49:34 AKDT 2006

 I've been using the Kevlar thread from Mcmaster  Carr .038" 130 lb tensile strenght 66 yards for $13.51 Part # 8800K43  I think I readjusted oncebut it's been 3 years so I can't remember. 

Steven Maxwell

----- Original Message ----- 
From: Nat Penton 
To: NSRCA Mailing List
Sent: 5/9/2006 8:38:40 PM 
Subject: Re: [NSRCA-discussion] Elevator trim change

I think the "settling in" is due to the coating. I never experienced this with the bare unidirectional kevlar.

----- Original Message ----- 
From: rcmaster199 at aol.com 
To: nsrca-discussion at lists.nsrca.org 
Sent: Tuesday, May 09, 2006 5:40 PM
Subject: Re: [NSRCA-discussion] Elevator trim change

Nat, et al, 

Kevlar actually has a negative COE, which, in theory at least, means it expands as it gets cooler. I saw a little of that in the stuff I used to make (the teflon coated type). Georgie is right that it took a couple weeks of settling in before adjustments held well over time. The negative COE still showed up when temps dropped, however, in a pull-pull set-up, it generally means nothing.

As far as very low COE of carbon tow, yup that's correct. Carbon in a plastic matrix isn't quite as clear. Fiberglass in a plastic matrix has similar issues. It's the delta between the two material types that important. In my experience they move enough to require a click of trim change as temp varies, fairly normal this time of year in the NE. 

Matt

-----Original Message-----
From: Nat Penton <natpenton at centurytel.net>
To: NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>
Sent: Tue, 9 May 2006 13:08:26 -0500
Subject: Re: [NSRCA-discussion] Elevator trim change

George I agree with your comments with one exception. The Sullivan controll line kevlar is the best of all worlds for our hookups. There is no stretch, no weight, no electromagnetic problems. It is unidirectional with, probably, a low COE like carbon.
----- Original Message ----- 
From: george w. kennie 
To: NSRCA Mailing List 
Sent: Tuesday, May 09, 2006 12:50 PM
Subject: Re: [NSRCA-discussion] Elevator trim change

Sorry Guys, I have some thoughts and opinions on this that are based upon my own logic, however flawed,and which may or may not coincide with someone else's logic.

Anytime you have a control system that is based on a system that incorporates an oscillatory motion (fore/aft up/dn) the ultimate result of this motion will generate wear somewhere within the system and wear translates to slop.

I think my contention would be that Lance had it right in the first place and was ill-advised by some well intentioned souls who may have had what they assumed to be good results, but failed to base their conclusions on really long-term experience(who really knows for sure?)

I have long felt that pull-pull cables (vinyl-coated steel) present the most reliable connection for the elevator and rudder inputs.They do not require that the horns be expensive ball-bearing units, they are the lightest by far and due to the fact that they are always under tension the generated wear manifests itself against only one wear surface instead of the two in the push-pull set-up. If the installation can be modified in such a way that the servo can be mounted just ahead of the stab the COE of the fuse can be rendered virtually inaffective. 

With time, you may experience some slight lessening in cable tension (very slight) which can quickly be rectified by disconnecting the clevis and spinning the eye a half turn at each connection.

I have used Kevlar thread and continue to do so, but not on two-meter projects.Kevlar stretches for quite a period of time before settling to it's final length.

Just my $.02
G. 

----- Original Message ----- 
From: Lance Van Nostrand 
To: NSRCA Mailing List 
Sent: Monday, May 08, 2006 8:55 PM
Subject: Re: [NSRCA-discussion] Elevator trim change

This rots.  I've used pull pull forever and switched to the deps system due to heavy promotion by Mike Harrison and Bryan Hebert.  They say it will be more precise.  Can anyone corroborate this?  I'd hate to switch to a system that has more downside than upside.
--Lance
----- Original Message ----- 
From: Gray E Fowler 
To: NSRCA Mailing List 
Sent: Monday, May 08, 2006 10:51 AM
Subject: Re: [NSRCA-discussion] Elevator trim change

Fiberglass laminate CTE = 6 X10 -6/in/in/F 

CF pushrod CTE = 1 X 10 -6 /in/in/F  ....could actually be 0 if fiber vloume is > 58% an all uni fibers 

Gray Fowler
Principal Chemical Engineer
Composites Engineering 

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