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Old Aug 29, 2009, 02:15 AM
nolebotic is offline
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How Do I Add Dihedral to My Bird of Time?


I am currently building a modified BOT kit. I'm using the suggestions from this site and the step by step instructions I found at this link http://isoar.ca/~andrewm/rc/bot/bot.html for building a stronger wing. The plans call for 1.5" (3" when only one panel is propped up) of center dihedral. The designer, Dave Thornburg recommends 2.5". (5" one panel) for better turning. Here's my issue that I need all of your help with: I am dry fitting the brass joiner tubes and find that I'm not getting the dihedral I need. I cut the (mock) steel rod down by about 2" already. (It's supposed to be 10" according to plan). That helped a little, but I still need more dihedral angle. I also shortened the brass tubes as well and filed the ends to the proper angle. I also angled the root ribs appropriately using the gauge from the plans. All pieces right now are mock ups while I dry-fit thankfully, so I haven't wrecked the real steel joiner rod and brass tubes....yet. What can I do to get the 5" of dihedral?

Thanks guys!

N.
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Old Aug 29, 2009, 02:58 AM
TOSSPilot is offline
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Instead of trying to glue in angled brass tubes, would it be easier to find a carbon fiber angled blade joiner and then just build square boxes between the spars? I thought I saw some on the NSP website and I am sure other members can provide sources for this type of joiner. Just a thought on another way to approach the problem.

Also, I have seen some planes with angled steel rods but I am not sure if this would have other issues (alignment, strength, etc).

Craig
Old Aug 29, 2009, 10:38 AM
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Thanks Craig- I've never thought of that option. I might have to do something like that if I cant get the current setup where it needs to be.

N.
Old Aug 30, 2009, 10:29 AM
Zeitweise is offline
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Double dihedral


Quote:
Originally Posted by nolebotic
I am currently building a modified BOT kit. I'm using the suggestions from this site and the step by step instructions I found at this link http://isoar.ca/~andrewm/rc/bot/bot.html for building a stronger wing. The plans call for 1.5" (3" when only one panel is propped up) of center dihedral. The designer, Dave Thornburg recommends 2.5". (5" one panel) for better turning. What can I do to get the 5" of dihedral?

Thanks guys!

N.
Hi,

you do not need more than 1,5" which is more than 3,5 degreeon the inner panel.

The outer panel has additional 5" which is another 8 degrees. Build the outer panel light than you can turn in small circles.

Regards
Alexander
Old Aug 31, 2009, 01:18 AM
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If you build the joiner box right, the stress on the very inboard end of the top spar cap is fairly low. You could chamfer it some. If you're really using the .060" spar cap, this is where most of the strength is and you can chamfer more. Take a look at the joiners shown at the URL's below.

http://charlesriverrc.org/articles/b.../joiner_V2.pdf
http://charlesriverrc.org/articles/s...PDFs/bends.pdf
Old Aug 31, 2009, 10:34 PM
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Quote:
Originally Posted by nolebotic
I am currently building a modified BOT kit. I'm using the suggestions from this site and the step by step instructions I found at this link http://isoar.ca/~andrewm/rc/bot/bot.html for building a stronger wing. The plans call for 1.5" (3" when only one panel is propped up) of center dihedral. The designer, Dave Thornburg recommends 2.5". (5" one panel) for better turning. Here's my issue that I need all of your help with: I am dry fitting the brass joiner tubes and find that I'm not getting the dihedral I need. I cut the (mock) steel rod down by about 2" already. (It's supposed to be 10" according to plan). That helped a little, but I still need more dihedral angle. I also shortened the brass tubes as well and filed the ends to the proper angle. I also angled the root ribs appropriately using the gauge from the plans. All pieces right now are mock ups while I dry-fit thankfully, so I haven't wrecked the real steel joiner rod and brass tubes....yet. What can I do to get the 5" of dihedral?

Thanks guys!

N.
When I rebuilt the wing on my Bird of Time, I used a 7-in.-long joiner rod that fits in a 3/8-in/-OD brass tube. I had no problem getting the dihedral that is specified in the plans I have (from an old BOT kit). A shorter larger-diameter-wing rod provides more strength than a longer narrower wing rod.

The web site you cited suggests using 0.060-in. carbon fiber on top of the spar. I used tapered carbon fiber with the 0.060-in. thickness at the center.
Old Sep 04, 2009, 06:36 PM
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Thanks guys for the tips. I think I might just add an inch of dihedral to the tips to accommodate or maybe just bend the joiner rod a touch.

N.


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