Shop our Airplanes Products Drone Products Sales
Thread Tools
Jan 10, 2015, 12:02 PM
less is more
Knoll53's Avatar
Just reading back over this thread, there has been some discussion about control surface layout. Have you decided what your final scheme will be?........so many options, so few planes.
Sign up now
to remove ads between posts
Jan 12, 2015, 05:59 AM
Registered User
miniphase's Avatar
Quote:
Originally Posted by Knoll53
Just reading back over this thread, there has been some discussion about control surface layout. Have you decided what your final scheme will be?........so many options, so few planes.
I'm following your lead with pitch positive flaps Kent. The model is ready to go, but with elevons only at this stage. If the weather doesn't choose to play ball any time soon than I'll cut the flaps in before the maiden.

I'll post some photos at some point in next few days....
Feb 02, 2015, 10:48 AM
less is more
Knoll53's Avatar
Quote:
Originally Posted by miniphase
I'll post some photos at some point in next few days....
Yes.......... will be inspecting the control surface layout with interest.
Feb 09, 2015, 09:57 AM
Registered User
miniphase's Avatar
Still waiting for the wind here. Plan is to test the wing off the slope and then work from there on propulsion.

Flaps are cut in, they run as far inboard as possible and will be pitch positive. Hopefully this will cure the nosing in traits I've experienced in the past.

Also shown in these photos is a little 'pack away' wing i built back in October. This is just over 52" span and breaks down into a small package for hiking. It uses the EH 3/12 section and is a little quicker than I expected! The finish on the smaller wing is a lot better than the 2 metre job (but hey, they're all prototypes atm anyway!), but I used some slightly out of date hardener on one wing and it'a taken on a brownish tint.....there's always something to trip you up isn't there!

Here's the maiden of the smaller wing...

wing test 01 (1 min 36 sec)


....still watching the forecast in readiness for the 2 metre maiden.
Feb 09, 2015, 10:29 AM
less is more
Knoll53's Avatar
Quote:
Originally Posted by miniphase
Flaps are cut in, they run as far inboard as possible and will be pitch positive. Hopefully this will cure the nosing in traits I've experienced in the past..............
....still watching the forecast in readiness for the 2 metre maiden.
The 2 metre job is looking good. The flaps look nicely balanced. Only slightly pitch positive is my guess. Of course that assumes a slow deployment. It should carry a motor well. FWIW, I too think that the flaps extending all the way to the root will solve the elusive nose-inish behavior. If it doesn't, then it's probably time to look at the airfoil.......just thinking out loud.

I too have been checking your weather for maiden. Holy Moly it gets cold in your neighborhood.
Feb 16, 2015, 04:10 PM
Registered User
EdSoars's Avatar
Looks good, Miniphase! I've built only two flapped wings this far, both 6" constant chord, pitch neutral 1.5m, and haven't yet experienced the nose dive. This will be interesting!

I HAVE, on the other hand, built mostly powered wings, and HAVE experienced plenty of flutter issues, usually because of not building enough torsional rigidity into the skins to handle the higher speeds caused by weight of the motor system.

I try to avoid FG less than 2 oz, as they usually have looser weaves than 2 oz, which means less strength to weight. There are two excellent pre-RCGroups articles on building wings, one by Neil Pollock, a good 12 years ago, and one by Stephane Duponsel in one of the 2004 RC Soaring Digest issues. Neil used multiple layers of FG, both spanwise and on 45 deg bias, to achieve torsional rigidity. Pierre used biased layups of unidirectional CF on a high aspect ratio, constant chord, F3B wing, which was VERY interesting. Neither wing used spar webs, only the skins to maintain the bending loads... and on the F3B wing, bending loads would be substantial.

If you're interested, I can send copies of both articles, but it will be a few weeks, as I am on holiday, away from home and files.

ed
Last edited by EdSoars; Feb 07, 2016 at 11:31 PM. Reason: poor english
Feb 17, 2015, 08:35 AM
Registered User
miniphase's Avatar
Thanks Ed...it could be that tomorrow is the day for the maiden. I shall have to check that my camera woman is available.

I think that Kent solved the nose dive issue. I'll be chopping around a couple of my other wings if this one shows no similar trait.

I think there's very little chance of flutter with this wing. With the 12% section I even feel that the spar was not needed. Thanks for the offer of the articles, I have seen them in the past, at the moment I'm more interested in increasing torsional rigidity in traditional built up swept wings....
Feb 17, 2015, 09:59 AM
less is more
Knoll53's Avatar
Quote:
Originally Posted by miniphase
I think there's very little chance of flutter with this wing. With the 12% section I even feel that the spar was not needed. Thanks for the offer of the articles, I have seen them in the past, at the moment I'm more interested in increasing torsional rigidity in traditional built up swept wings....
I've always thought that the conventional balsa skinned D tube provided a good result......kinda of light, rigid to a point, unaffected by heat and moisture, as monokote is. Maybe there is some hope in threading some carbon fiber thru the framework to create a space frame. I tried this on a long Bird of Time fuse with good, yet heavy, results.
Feb 17, 2015, 12:21 PM
You know nothing....
Stuart A's Avatar
Quote:
Originally Posted by miniphase
Thanks Ed...it could be that tomorrow is the day for the maiden. I shall have to check that my camera woman is available.

I think that Kent solved the nose dive issue. I'll be chopping around a couple of my other wings if this one shows no similar trait.

I think there's very little chance of flutter with this wing. With the 12% section I even feel that the spar was not needed. Thanks for the offer of the articles, I have seen them in the past, at the moment I'm more interested in increasing torsional rigidity in traditional built up swept wings....
Question from the back of the class
Would it not make for a stiffer wing if the shear web was continuous as shown here -
http://www.recreationalflying.com/tu...der/beams.html
and the ribs sectioned between the spars?
Feb 17, 2015, 12:40 PM
Registered User
miniphase's Avatar
I'm guessing at the scale we work at, it probably doesn't make much difference. I've used 1/16th balsa with a grain running vertically, each 5" strip of shear web is cyanoed to the adjacent ribs (as well as the spar) so it's as good as continuous for our purposes and makes the build a lot simpler.

I think at a bigger scale the continuity would be of far greater importance, as would be the make-up of the shear webs. In your link Stupot, it shows them laid down with the grain 45 deg....I think this gives a massive strength increase over my 90 deg approach. Bear in mind I'm just following my nose here....I'm no expert!

This built up wing is the same as the 2m foam jobbie, but scaled by 200%. My inner voice is telling me I need 4 metres to fully enjoy the spring thermals!
Feb 17, 2015, 12:41 PM
Herk
HerkS's Avatar
Quote:
Originally Posted by Stupot46
Question from the back of the class
Would it not make for a stiffer wing if the shear web was continuous as shown here -
http://www.recreationalflying.com/tu...der/beams.html
and the ribs sectioned between the spars?
Stu - to a large degree the spar and web are primarily resistant to bending.

To increase torsional stiffness it's best to move the main spar aft on the chord. That does several things. Mainly it moves the wing's center of twist aft aft as well.

We are in the habit of putting the spar at the point of maximum airfoil thickness - which does maximize its resistance to bending by giving it the maximum depth possible. Moving it aft does compromise bending a bit, but it has a fairly big effect on resistance to twist and particularly to flutter.

Also, if there is to be a D-tube it increases the chordwise depth of that tube. That also helps to stiffen the wing in resistance to twisting.

All of that is magnified on a swept wing.
Feb 17, 2015, 02:29 PM
Registered User
miniphase's Avatar
The D-tube sheeting is on and has added a great deal of stiffness. I think that along with a doped covering, this will be a very rigid wing. However, as I'm at at stage where I can put in a few struts for very little effort or weight penalty, which of these options will add most twist resistance just as a little insurance? Or would a continuous diagonal from corner to corner be better?
Feb 17, 2015, 02:35 PM
less is more
Knoll53's Avatar
Quote:
Originally Posted by miniphase
This built up wing is the same as the 2m foam jobbie, but scaled by 200%. My inner voice is telling me I need 4 metres to fully enjoy the spring thermals!
Yes, at least 4 metres. Although the California Condors suffer through with a 3 m wingspan they DO have a 24" chord, so I say why suffer....go big.

Any chance you could throw some more pics at us of the 4m job? you know, in your free time.
Last edited by Knoll53; Feb 17, 2015 at 03:04 PM.
Feb 17, 2015, 02:42 PM
less is more
Knoll53's Avatar
Quote:
Originally Posted by miniphase
The D-tube sheeting is on and has added a great deal of stiffness. I think that along with a doped covering, this will be a very rigid wing. However, as I'm at at stage where I can put in a few struts for very little effort or weight penalty, which of these options will add most twist resistance just as a little insurance? Or would a continuous diagonal from corner to corner be better?
For starters, I'd suggest that added shear only occur at the root, inasmuch as shear loads drop off in a more or less linear fashion. If a 2m wing does not need added shear, then the outer 1m of a 4m wing does not need it either.

Regarding diagonal strut layout, you might consider the strut design first. Will it be equally strong in compression as well as tension? Typically not. So cross bracing with tension ties only is an alternate to assure symmetry.
Feb 17, 2015, 02:53 PM
less is more
Knoll53's Avatar
the torsion strut will be more rigid if it's start point at the root (panel point) is at the TE rather than at the spar. So photo #02 is out. A steeper angle for the strut will be more rigid, so steeper nearer the root to match the increase loads there.


Thread Tools