How to Mark Center Lines?  
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All Forums >> RC Airplanes >> Giant Scale Aircraft - 3D & Aerobatic >> Carden Aircraft >> How to Mark Center Lines?
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How to Mark Center Lines? - 8/17/2006 5:21:58 PM   
Bobby Folsom


 

Posts: 701
Joined: 3/11/2005
From: Vicksburg, MS, USA
Status: offline 		Guys, when the control surface is wider than the Robart hinge point drill guide will fit, how or what do you use to mark the center line? I've had mixed (bad) results trying to "eyeball" the line and subsequentky drilling the hinge holes off the center line.

I appreciate your suggestions and help.

Bobby
       Post #: 1

RE: How to Mark Center Lines? - 8/17/2006 7:09:37 PM   
swk550



Posts: 278
Joined: 4/18/2003
From: houston, TX, USA
Status: online 		I use a ruler and a fine point pen to mark the centerlines. I generally mark the centerlines before I make the final bevels. Then I install stick pins to center a straight edge ruler. Finally I mark the centerline down the entire cap strip. After that I make a drilling template from hard ply with the hole locations. This way I can match the control surface with the lifting surface cap strips.

I am sure there are simpler ways.

Steve

(in reply to Bobby Folsom)
       Post #: 2

RE: How to Mark Center Lines? - 8/17/2006 10:38:00 PM   
ibow24


 

Posts: 263
Joined: 10/27/2003
From: Mohnton, PA, USA
Status: offline 		the problem with straight edge rulers is I have yet to find one that is perfectly straight.. They all have a bow in them.
there may be some out there...I just haven't found one. Take your ruler and lay it down on big sheet of paper and draw a line down the edge.
Flip the ruler over, make sure the ends of the ruler are right on the ends of the line you drew, now draw another line down the same edge.
Most likely you drew a really elongated ellipse.
Anyway. I purchased an 8' piece of aluminum channel from Home Depot and did the same test...it was perfect. I may have gotten lucky too. I did not expect it to be perfectly straight.

I mark and exact center line at both ends of the leading / trailing edge I want to hinge. Place a pin at that mark and then run a piece of dental floss from pin to pin. I usually tie off one end and ask someone to pull the other end tight on the center mark. Then I just mark the location of each hinge along the floss line.

Lots of different ways but no so substituted for careful measurements.

good luck
steve

(in reply to swk550)
       Post #: 3

RE: How to Mark Center Lines? - 8/18/2006 1:14:09 AM   
Bobby Folsom


 

Posts: 701
Joined: 3/11/2005
From: Vicksburg, MS, USA
Status: offline 		Thanks to both Steves for your input. Sounds similar to what I've done in the past.

Bobby

(in reply to Bobby Folsom)
       Post #: 4

RE: How to Mark Center Lines? - 8/26/2006 4:14:34 AM   
OnTheEdge



Posts: 1166
Joined: 1/14/2002
From: Drums, PA, USA
Status: offline 		I do the measurement thing as well. As swk50 mentioned, it's better to do this before beveling. Once I have a line marked on the wing and mark the hinge location, I take small pins with the round colored ends on them (looks like a little ball on the end) and push them into the wing at the hinge marks. Then carefully set the aileron in place being carefull to line it up really well (don't forget the gap needed on the root end for clearence.). Then I push down on the aileron and the small ball ends of the pins will give you an indent exactly where the hinge should now go on that surface. Don't forget at this time to use the small indents to scribe your line on the aileron as the line will be nessesary for the later beveling. Also, drill your hinges before beveling as well.

Hope this helps.......Mark

_____________________________

Avoid zen aerobatics...when the ground........and the plane.......become as one.

(in reply to Bobby Folsom)
       Post #: 5

RE: How to Mark Center Lines? - 8/26/2006 2:06:46 PM   
BBW Walt



Posts: 929
Joined: 1/13/2002
From: NWest, IN, USA
Status: offline 		If you flip the parallel arms around on the robart centering fixture it will open up to 2-3/16ths. It will work just fine this way. I've use this method on all the 40% planes I have hinged and have yet to see a control surface or trailing edge thicker than this amount of opening. I also think Mark's idea is a clever one also. I may have to try that....

(in reply to OnTheEdge)
       Post #: 6

RE: How to Mark Center Lines? - 8/26/2006 3:13:33 PM   
OnTheEdge



Posts: 1166
Joined: 1/14/2002
From: Drums, PA, USA
Status: offline 		I was never happy with the Robart centering jig as it really only gives you a true center if the wing is not tappered (i.e. the parallel arms aren't really parallel). All my GS planes so far have had the taper so I didn't use it in it's stock form. What I did was removed the parallel arms and then screw the jig into two pieces of aluminum 3/4" square tubing. the tubing keeps the bit perfectly square in both axis on the trailing/leading edge.....again, this must be done before tapering. I then situate the modified jig over the line I scribed and then drill out the holes. (I can take a picture of the jig if the description doesn't make sense....lemme know....) My Robart jig came with two sets of inserts for the differnt size hinges. I always start with the smallest one and then drill to final size with the second insert.

.......Mark

_____________________________

Avoid zen aerobatics...when the ground........and the plane.......become as one.

(in reply to BBW Walt)
       Post #: 7

RE: How to Mark Center Lines? - 8/26/2006 5:04:26 PM   
zzw26n



Posts: 714
Joined: 5/18/2004
From: Shelby Twp., MI, USA
Status: offline

Mark,

Would like to see the robart hinge jig modifications you did, I know, it's another picture, sorry.

regards, Ward

(in reply to OnTheEdge)
       Post #: 8

RE: How to Mark Center Lines? - 8/26/2006 5:45:53 PM   
Bobby Folsom


 

Posts: 701
Joined: 3/11/2005
From: Vicksburg, MS, USA
Status: offline 		I too would like to see the pictures you descirbe. Boy, you guys have given me several excellent ideas to make the lines and hinge points! I'm inspired to start building again at the point (no pun) I stopped last fall!!

Thanks again to all of you for your excellent ideas.

Bobby

(in reply to zzw26n)
       Post #: 9

RE: How to Mark Center Lines? - 8/26/2006 5:50:05 PM   
OnTheEdge



Posts: 1166
Joined: 1/14/2002
From: Drums, PA, USA
Status: offline 		Here ya go. One thing to note. When I need to drill the hinge close to an air balance or the like, I simply take off one aluminum square end and then fold the jig as close to the other square as possible, then hold it tight so it keeps the bit square to the surface.

Hope this helps.........Mark






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_____________________________

Avoid zen aerobatics...when the ground........and the plane.......become as one.

(in reply to Bobby Folsom)
       Post #: 10

RE: How to Mark Center Lines? - 8/26/2006 6:09:14 PM   
OnTheEdge



Posts: 1166
Joined: 1/14/2002
From: Drums, PA, USA
Status: offline 		Oh one more thing. When I start the first hole I always run the bit backwards for a couple rotations. I find this helpful when drilling into balsa. It starts a nice indented cone shape that prevents the drill bit from walking and chewing up the outer edge when the bit takes it's first bite. I also use a barrel type cordless screwdriver that has quite slow rotational speed for this task. A barrel type kinda keeps it's own balance and helps me keep the hole going in straight. Todays 18V drill/ drivers are to hard (i.e. heavy) to keep centered on something like this in my opinion.

Perhaps a bit anal but nothing but the best for our Cardens .

_____________________________

Avoid zen aerobatics...when the ground........and the plane.......become as one.

(in reply to OnTheEdge)
       Post #: 11

RE: How to Mark Center Lines? - 8/26/2006 8:40:00 PM   
zzw26n



Posts: 714
Joined: 5/18/2004
From: Shelby Twp., MI, USA
Status: offline

thanks for the picture Mark .............

(in reply to OnTheEdge)
       Post #: 12

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