Simple construction question - I hope. - RC Groups
Shop our Airplanes Products Drone Products Sales
Thread Tools
Oct 31, 2017, 04:24 AM
Registered User
Discussion

Simple construction question - I hope.


I've become used to using carbon fibre tubes as spars in wings, but I've never made a flying wing. I'd really like to , but I have a quick question: Would it be feasible to use the cabon tube spar through the centre of the ribs (say 45-50% chord), adding the LE/TE and then get the required wing twist by pivoting or twisting the ribs the required amount and then gluing in place. It seems such a simple idea, but I cannot find pictures of it online, yet I cannot think of the downside?
Sign up now
to remove ads between posts
Oct 31, 2017, 10:13 AM
less is more
Knoll53's Avatar
Yes of course. See my Plank 101 thread. I used epoxy at the joint between the big spar tube and the ribs. Dual spars are warranted for swept wings. See threads by Herks.
Oct 31, 2017, 02:31 PM
Red Merle ALES VI
Curtis Suter's Avatar
Is some sheeting required to help keep the wing from twisting in flight? I would assume that it depends if it's a 40 inch span or 140 inch span.

Curtis
Oct 31, 2017, 03:28 PM
less is more
Knoll53's Avatar
No sheeting is required. All torsional strength comes from spar. In the example of my Plank 101, an over sized carbon fiber tube provides torsionally rigidity.
Nov 01, 2017, 06:44 AM
Registered User
EdSoars's Avatar
If you are building a plank, then yes, the tube is enough. If it's a swept wing, probably not, unless the wing is going to be very lightweight and flown at low airspeeds.
Nov 01, 2017, 11:41 AM
less is more
Knoll53's Avatar
See Herks build threads. Dual carbon spars for swept wings at 2m wing span.
Nov 01, 2017, 11:43 AM
Herk
HerkS's Avatar
OK here is my story. I've built several wings using only CF tubes as spars. All have been successful.

For swept wings torsional stiffness is very important to prevent flutter. That means use a substantial tube - as much diameter as is practical for your wing. Even more important is to locate the spar farther aft than is usual for straight wings. Most people just don't seem to grasp the physics involved, but locating the tube back at 50 - 60 percent of the local chord is very important.

One of the weaknesses of many D-tube structures is that while they are stiff and strong, they locate the center of torsional stiffness rather far forward. The wing is strong and stiff, but it will flutter at a lower speed than if the spars and sheeting extend farther aft,

This wing is very successful with no problems even during the rather strong bungee launches. A flight video here:
https://www.youtube.com/watch?time_c...&v=1J0mBWmo-Tk

Photos show construction.
Nov 02, 2017, 04:25 AM
Registered User
Thank you all, the idea of a thermal wing seems more worthy of trying. Herk that is inspirational stuff.
Nov 02, 2017, 04:51 AM
Herk
HerkS's Avatar
Not sure how I got two copies of that photo in there, but ......

Anyway whatever you decide to do, put it up here so that we can enjoy your project along with you.
Nov 02, 2017, 05:09 AM
Registered User
I would really like to build one of these, but had better start smaller:
Segler UP 2 Date - FMT Bauplan - 4200mm - Startwagen - MSG Stiftland - Siegfried HD (2 min 1 sec)
Nov 02, 2017, 07:14 PM
Registered User
Herk I've watched your videos a couple more times, how do you find the vision when fllying your wings?
Nov 02, 2017, 08:36 PM
Herk
HerkS's Avatar
Quote:
Originally Posted by RaceMag
Herk I've watched your videos a couple more times, how do you find the vision when fllying your wings?
Same as everyone else that flys these things at any distance. Have to be very focused and just don't get too high or two far out. Fins do help some.
Nov 02, 2017, 08:38 PM
Registered User
I'd imagine some additional size might help a bit in some circumstances. I have to admit I lost your model a few times in the videos.


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Simple question(i hope) about Freewing SU 35 PARALYZER Electric Ducted Fan Jet Talk 3 Feb 04, 2016 02:11 PM
Discussion New to RC, simple (hopefully!) battery question twinflyers Batteries and Chargers 4 Jan 09, 2008 10:31 AM
Discussion Hopefully a simple Nimh question. gqllc Batteries and Chargers 10 Jan 01, 2007 02:11 PM
Discussion Another, hopefully simple, question... digikid Micro Helis 10 Nov 14, 2006 06:33 PM
hopefully a simple thrust Question HardDrive Beginner Training Area (Aircraft-Electric) 12 May 10, 2005 12:49 PM