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Old Mar 08, 2012, 09:55 AM
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Joined Dec 2011
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My first scratch built..

Fellas..

Built and flew my first scratch built 3d foamy this past week.. Flies really nice and am quite happy with the end result... One issue i've noticed... When i go into a full aileron roll (axial roll) the plane kinda wobbles and doesnt hold a nice concentric roll... Some of the factory planes ive bought and own seem to have less of this.. Any idea what causes this?? Stiffness issues possibly? Started my second one and would like to make some adjustemnts to see if i can improve upon it.. Any insight appreciated...
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Last edited by tsilvers; Mar 08, 2012 at 10:14 AM.
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Old Mar 08, 2012, 01:39 PM
Pushin' the Limits
Olias's Avatar
Bellingham,WA.
Joined Jan 2008
2,849 Posts
Very nice! Sorry I don't have an answer for you but I am right in the middle of my 1st ever Scratch Built Foamie as well and couldn't resist poppin' in when I saw the thread title. Which plane is that exactly and what size is it? A Yak? Slick Extra? Edge? And where did you get your plans from?

I'm building a 32" Edge 540T from plans provided from LeadFeather (found on this thread: http://www.rcgroups.com/forums/showthread.php?t=1119161 ) . So far very simple and easy to follow/do. Hope to finish up this weekend, but actually flying it is questionable with the lousy weather forecast. Anyway, good luck to you on your next build and hope you get an answer to your question as I would like to know as well in case I run into the same problem.

-B
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Old Mar 08, 2012, 01:58 PM
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Joined Dec 2011
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thx Olias..
I designed the plane myself... Based off the TH yak... slightly diferrent lines but pretty close... I wanted a good template to work with and I love the TH YAK I have so what better to model off... Now that i got my first one done I will start deviating even further in my designs as I go and learn... Making some small tweeks to the second build which is now underway... I will eventually post some plans... This plane rocks... and hopefully will only get better... Stiil lots to learn and experiment with...

Here's a CAD pic...
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Old Mar 08, 2012, 03:04 PM
Pushin' the Limits
Olias's Avatar
Bellingham,WA.
Joined Jan 2008
2,849 Posts
Very cool stuff! I never got the hang of CAD although I do dink around from time to time on my buddy's CPU in Light Wave 3D, Rhino, etc.But even that is small baby steps. Looking forward to you putting out some plans on the new improved version. Good luck with everything!

-B
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Last edited by Olias; Mar 08, 2012 at 05:26 PM.
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Old Mar 08, 2012, 03:07 PM
Build straight - Fly twisty
Whiskers's Avatar
Australia, QLD, Little Mountain
Joined Feb 2010
4,293 Posts
It's probably got a case of Floppy Fuselage Syndrome.
Glue in a full length strip of foam to brace the structure as shown in the pic.
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Old Mar 09, 2012, 12:02 AM
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timatworksg's Avatar
Singapore, Singapore
Joined Oct 2011
506 Posts
As Whisker's has mentioned, you could be having the floppy twisty fuse mushing an axial roll. Give us more details such as EPP thickness and types of stiffening you have used in the build as is.

I can see you seem to have a small angle piece below the middle fuse between the cockpit and tail end....a stiffener? You could try as whisker's has said and run a strip angled down the side from stab to cockpit. Or if weight allows go all the way to the motor!

I found in my builds that 5mm EPP used needs bracing or stiffening somewhere. On a wing with a CF rod embedded in the wing, you'd still need some stiffening on the LE at least especially when flying outdoors. Indoors, windless, no issues.

Any CF Rods running down your fuse? You could try like Leadfeather's Yak profile 3d build where 2 pcs of carbon flats are glued to the fuse mid sides to provide the stiffening preventing the back end from twisting.
Also a suggestion is to have a the wing rod all the way of the wingspan so the tips won't flex. If your using 9mm/10mm epp, it'll make one very stiff wing when outdoors!!
If there is wobble between the rudder and stab then you could use some bamboo/CF rods (2mm-ish) and do some bracing to stiffen and keep the rudder straight!

Hope that helps! Fill us in on more details on the build! That looks like a nice 3D shape. I love the paint job with the voodoo mask!! awesome!
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Old Mar 09, 2012, 05:24 AM
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This is built from 9mm EPP...I have experimenetd with a bunch of stiffening methods particulalrly along fuse from the wing back to tail... Mt wing itself is fine.. I ripped some thin (3/32") strips of aspen on my table saw and embedded in wing.. the rear fuse has been the issue... My original design included some 45 degree triangle braces cut from foam and glued between vertical and horizontal fuse on the underside.. Although light and really strong they only reinforced locally at the joints.. twist was still pretty bad... I then added some carbon rod glued in at 45 between the foam braces... still not satisfied... I have not run a brace the lenghth of the fuse as suggested.. This is my next step for build 2.. I cut some full length strips and angle ripped them last night... Will update when I get them glued up on plane 2... Also considering the brace method WMPF or 3dhs planes.. Plane 3 will probably get this... Time permitting I plan to run some different concepts in my CAE/CAD program and analyze torsional stifness in this design.. At some point i'll oprimize it...

As for the paint job.. Inspired by my kids... I sketched up and cut a few quick paper templates to see how the rattle cans would do.. Turned out pretty cool.. We cut some new templates for plane two and painted last night... A little cleaner and more symetrical.... here's a pic...
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