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Old Sep 10, 2012, 01:37 PM
I don't like your altitude
Stupot46's Avatar
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This must be an iPad thing,go advanced on a long post to add a smiley and the last few lines are hidden;edit does the same.
Any way,here's a great big grin for Mark
Regards to both Stuart
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Old Sep 11, 2012, 03:43 AM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
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Meanwhile back at the bench---
3mm ply plates over the existing balsa,drilled from topside and nuts refitted.
The damaged wing felt a bit "soft" at the root,so some tape applied chord wise at that area and some half span carbon rod "drilled in"at the l/e and near the pivot.Tape applied span wise,the result feels stiffer,we shall see.The undamaged wing got exactly the same treatment.
Weight is now 253g/8.9oz
Stuart
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Old Sep 11, 2012, 04:27 AM
I don't like your altitude
Stupot46's Avatar
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The resulting graph.Allowing for measuring discrepancies and that I rounded the decimals,there would appear to be a slight curve developing.
Stuart

I'm going to recheck those last few measurements,no logical reason why it should rise like that.
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Last edited by Stupot46; Sep 11, 2012 at 06:21 AM. Reason: Put brain in gear
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Old Sep 11, 2012, 10:26 AM
Herk
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Quote:
Originally Posted by Stupot46 View Post
The resulting graph.Allowing for measuring discrepancies and that I rounded the decimals,there would appear to be a slight curve developing.
Stuart

I'm going to recheck those last few measurements,no logical reason why it should rise like that.
Hi Stuart,

Your construction is looking more and more flight capable.

I'm still having a bit of a problem grasping exactly what your CofG concern is, and what you are doing about getting a grasp on it.

That said, I have another little offering that you can play with if you wish. To use the spread sheet you will need Excel or Open Office. I included a picture of the result just in case those programs aren't available to you.

The fundamental (simple) assumptions are that you have a constant chord wing layout like Gulliver. Each panel is ten inches wide and fifty inches long. The weight of each panel is ten ounces. The spanwise CG of each panel is half way out. The chordwise CG of each panel is at the 25% point. (just to simplify things) As the panels sweep, the CG of the panels moves aft and the effective chords of the panels increase. Likewise so does the length of the nose moment increase. So the question this attempts to answer ---

Ready for this!! --- In order to keep a longitudinal static stability margin of ten percent, how much weight must be placed at the nose point centerline to balance the model to that criteria at each station as the wing sweep changes in increments from 0 degrees to 60 degrees?????

Disclaimer. I have not done a lot of error checking. If there are errors I will apologize in advance. I wanted to check more by head is beginning to hurt.
EDIT
I did some error checking and found some small ones. If you want the spreadsheet, I'll make it available but here is the corrected result. Not greatly different.
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Last edited by HerkS; Sep 12, 2012 at 03:24 PM. Reason: Did some error checking - found some errors
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Old Sep 11, 2012, 12:05 PM
I don't like your altitude
Stupot46's Avatar
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Herks--YOUR head hurts(you made a career out of this stuff)
I couldn't open the zip,went straight to my printer app,so I'll have wait for that one.
The graph in the PDF is interesting,am I right in thinking it implies that any balance weight movement needed will be non linear as Mark suggested early on?
The cog thing was done to satisfy my curiosity,seems to me what you have shown above is a lot more relevant.


Now seems a good opportunity to send out my sincere thanks to yourself and the rest of guys for all the help and advice you have offered to me on the forum,particularly on this project.Whatever the outcome I have learned a hell of a lot thus far.The time you have taken out from your own projects and the patience shown is greatly appreciated.
Regards Stuart.
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Old Sep 11, 2012, 02:15 PM
I don't like your altitude
Stupot46's Avatar
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I've been giving some thought to the wing roots and a way to make them.I like Marks thrust race idea and home making them is feasible.A sheet of 6mm nylon6 sufficient for 8 races@125mm is less than £20.If milling them myself doesn't work out I can get them made locally.
To mount them I have thought of cutting the root shape out of foam and inserting rods or tubes around the area of the race circumference-as per the revised drawing.
A sleeve for the central pivot and the wing joiner tubes plus a wiring harness way also inserted.
The whole thing glassed on it's three sides.
This is the lightest way I can think of to mount the races and keep them rigid in the structure.
As always thoughts and comments welcome.
Regards Stuart.
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Old Sep 13, 2012, 02:37 AM
I don't like your altitude
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Would this ,glassed both sides be suitable for the top and bottom(dark blue)plates in the drawing?If so what weight of cloth to use.
Careful placement should allow more spacers/connection points between the plates,maybe two each side of the centre line.
Regards Stuart

Carbon tow,laid similar to Marks plank fin?
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Old Sep 13, 2012, 03:50 AM
Deniable plausibility
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Joined Aug 2008
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Stuart,
To be sure, I'd need to see the entire drawings. Though just a guess is 5-6mm would be needed and probably a couple of layers of 200g glass (carbon better, though). Don't forget - set hard points (for bearings, attachment points etc.) into the foam before you laminate the skins on. Pierced foam may be better as resin can form bridges between the skins to resist them peeling off.
Richard
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Old Sep 13, 2012, 04:38 AM
I don't like your altitude
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Thanks Richard.I'll put up a provisional drawing tonight,point taken about hard points.If carbon cloth is deemed necessary I'll have to stretch the budget to suit.I'll have to refine things so that these prototypes are usable in a final version.
Regards Stuart
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Old Sep 13, 2012, 06:33 AM
I don't like your altitude
Stupot46's Avatar
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Quote:
Originally Posted by Shedofdread View Post
Stuart,
To be sure, I'd need to see the entire drawings. Though just a guess is 5-6mm would be needed and probably a couple of layers of 200g glass (carbon better, though). Don't forget - set hard points (for bearings, attachment points etc.) into the foam before you laminate the skins on. Pierced foam may be better as resin can form bridges between the skins to resist them peeling off.
Richard
Richard,a google of pierced foam got me a lot of info on cleaning my Prince Albert& a link back to here!
Do you have a link to a supplier?
Regards Stuart
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Old Sep 13, 2012, 10:08 AM
less is more
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United States, CA, Marina
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Quote:
Originally Posted by HerkS View Post
Ready for this!! --- In order to keep a longitudinal static stability margin of ten percent, how much weight must be placed at the nose point centerline to balance the model to that criteria at each station as the wing sweep changes in increments from 0 degrees to 60 degrees?????
Oh boy !....related rates. This is a problem for the Calculus. Where's that old text book???

Kent
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Old Sep 13, 2012, 10:22 AM
less is more
Knoll53's Avatar
United States, CA, Marina
Joined Sep 2006
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Originally Posted by Stupot46 View Post
The whole thing glassed on it's three sides.
This is the lightest way I can think of to mount the races and keep them rigid in the structure.
As always thoughts and comments welcome.
Regards Stuart.
In regards to the whole wing hinge area, this such a complex problem that I'd take the easiest approach just to get some thing working first, then reinforce it as needed. You can try to make it light later, if it works.

For me this would be to build everything out of 1/32" plywood. Use epoxy for glue. Should be quick. Plywood cuts with scissors and can be drilled. Then if it works, you can lay on as many layers of glass cloth and epoxy as needed to be strong enough for flight.

But I'm a fast and dirty builder.....have you seen my camera pod? A little over a day from concept to creation.


Kent
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Old Sep 13, 2012, 10:31 AM
I don't like your altitude
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Originally Posted by Knoll53 View Post
Oh boy !....related rates. This is a problem for the Calculus. Where's that old text book???

Kent
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Old Sep 13, 2012, 10:48 AM
I don't like your altitude
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Joined Sep 2011
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Quote:
Originally Posted by Knoll53 View Post
In regards to the whole wing hinge area, this such a complex problem that I'd take the easiest approach just to get some thing working first, then reinforce it as needed. You can try to make it light later, if it works.

For me this would be to build everything out of 1/32" plywood. Use epoxy for glue. Should be quick. Plywood cuts with scissors and can be drilled. Then if it works, you can lay on as many layers of glass cloth and epoxy as needed to be strong enough for flight.

But I'm a fast and dirty builder.....have you seen my camera pod? A little over a day from concept to creation.


Kent
Thanks Kent.The current plan is to cut the wing root shape from pink foam(got the templates made) bore the holes for the spacer tubes,central pivot and radial slot-I've tried some test holes with a couple of cutters on the stand drill and made a good job of a 6mm and 12mm hole.
For the slot I think drill the ends and hot wire.
I'm just going to use some plastic tube for this trial,and a thickness of 20mm
Regards Stuart.
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Old Sep 13, 2012, 11:11 AM
I don't like your altitude
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Joined Sep 2011
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Revised again drawing to show the area of the top and bottom plates(outlined in blue)
The positions circled in red are spacing tubes/connection points between the two plates.
The distance between the two wing root discs is 60mm at present,this will be reduced to the minimum in the final design.Present dimensions are 345mm x 145mm.
Stuart
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