Notices
RC Gliders, Sailplanes and Slope Soaring Discuss rc gliders,rc sailplanes and slope soaring in this forum. Thermaling techniques, airfoils, tips, etc

Viking balance problem

Old 04-11-2006, 12:37 PM
  #1  
Alaska Reeves
Member
Thread Starter
My Feedback: (3)
 
Join Date: Nov 2002
Location: Wasilla, AK,
Posts: 30
Likes: 0
Received 0 Likes on 0 Posts
Default Viking balance problem

Hi, I am building an old Craft Air Viking kit which came with a fiberglass fuse. After mounting the tail group I find it will take at least 12 ounces of lead to balance and I have not covered the tail feathers with Ultra-coat yet. Any solutions to this problem? Should I shorten the fuse 2" or more? I will already be building a lighter fin assembly. Seems a shame to add that much lead up front to this sailplane. Anyone else actually built and flown one of these? Thanks, Reeves in Alaska.
Old 04-11-2006, 12:58 PM
  #2  
erich44
Junior Member
 
Join Date: Nov 2004
Location: Holden, MA
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Viking balance problem

This may be a silly question. But, did you check balance with receiver battery, placed as far forward as possible?

erich
Old 04-11-2006, 05:18 PM
  #3  
Alaska Reeves
Member
Thread Starter
My Feedback: (3)
 
Join Date: Nov 2002
Location: Wasilla, AK,
Posts: 30
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Viking balance problem

Hi erich, The 12 ounces does include the rx btry. In a plane of this size I normally would use a 2 ounce 720 mah NIMH battery. I was checking what would happen if I bob-tailed the tail by 3" and it still will require lots of weight up front. Too bad the designer Tom Williams is not here to ask how he did it.
Didn't you do those build threads on the OLY II, the Mirage and one other? They were very informative. How much lead did you need up front to balance those? I have both the Mirage and the Oly plus an SD100. Which was the qucker build? Have you flown them yet? Thanks, Reeves.
Old 04-13-2006, 09:03 AM
  #4  
jbrandon
Junior Member
 
Join Date: Jan 2006
Location: Kansas City, MO
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Viking balance problem

I built one a long time ago and as I remember it took quite a bit of lead up front, couldn’t now tell you how much. As I remember things I ended up making a larger battery, 4 sub C cells about 1100 mah to use up some of that weight. Now days I almost always use a 3000 mah battery for the same reason. Also as I remember the Viking you may want that extra time for flying, it flew well.

Personally I would not shorten the fuselage, but I like planes with long tails. Besides, does it really matter what the plane weighs (to a point).
Old 04-13-2006, 11:29 AM
  #5  
slopemeno
Senior Member
My Feedback: (2)
 
slopemeno's Avatar
 
Join Date: May 2003
Location: San Francisco, CA
Posts: 450
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Viking balance problem

Better to balance it per the plans. You may find that once youre comfortable with flying it, you can remove a small amount of the nose wight and move the CG back slightly, and see a small performance increase. Many models have the CG very far foreward of what is necessary.
Old 04-13-2006, 12:27 PM
  #6  
Rick K
Senior Member
My Feedback: (6)
 
Join Date: Nov 2003
Location: Fontana, CA
Posts: 259
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Viking balance problem

Just a test to see if my upload will work this time
Old 04-13-2006, 12:48 PM
  #7  
Rick K
Senior Member
My Feedback: (6)
 
Join Date: Nov 2003
Location: Fontana, CA
Posts: 259
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Viking balance problem

Sorry about the funny post, after writing a resonse to you (for a half hour) it wouldn't post!

Ok, here goes again. I'm building a Viking a being reproduced by Skybench aerotech and wanted to lighten it up a little so I called Ray (the owner of Skybench) and asked if there'd be any trouble subing a carbon rod for the rear steel one. He said there shouldn't be any problem as long as I didn't go for contest style max effort zoom launches off a winch.

Humm . . . I went out to the shop just now and weighed one of the rods. . . 5oz, okay now 5oz at 3.25" from the CG gives a effective (arm-moment weight) of 16.25 oz as to your CG. (handy formula: weight x distance from CG = balance arm moment weight) . . . Lets say you wanted to balance out that rod weight, in my plane the fwd nose compartment is 11" from the CG so take the 16.25oz and divide it by the 11" arm moment = 1.5oz in the nose would do it.

That's one way you could cut the nose weight down. If you're going to have to use extra weight it might as well not be 'dead' weight, use a bigger Rx pack then.

Rick K
LSF 6493
Old 04-13-2006, 09:24 PM
  #8  
slopemeno
Senior Member
My Feedback: (2)
 
slopemeno's Avatar
 
Join Date: May 2003
Location: San Francisco, CA
Posts: 450
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Viking balance problem

I dont think you need to worry so much. Most planes from that era flew fairly slow, and the extra weight wont hurt performance much (it might even help a little). Test fly it once you get it balanced and I think you'll be fine. Have you calculated the wing loading in ounces / sq. ft.? I bet its low.
Old 04-15-2006, 05:55 PM
  #9  
forrest adams
Senior Member
 
Join Date: Dec 2002
Location: benbrook, TX,
Posts: 119
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Viking balance problem

don't shorten the tail boom - flying characteristics will suffer - the extra weight will not be a problem - most of those splanes (floaters from that time period) needed some ballast anyway - tail volume coeff is important and unless you think you are a designer - go with the plans - if you shortened the boom, a larger tail would be required and even then the dynamic response would not be the same as before - good luck - it's a large plane and it should hardly feel the extra weight. my sailaire (a bit larger version of that splane) flies better with a little extra weight - regarding the carbon wing rod - that's not a bad place for extra weight anyway - the mass moment of inertia will hardly change at all.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2022 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.