HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Aug 30, 2014, 05:51 AM
KNS
Registered User
Switzerland, SO, Olten
Joined Dec 2012
399 Posts
Build Log
BBCC5 - Mara - RC conversion

I really like the Mara design and will try to keep a buildlog here. This will be slow progress. Your suggestions will be very welcome, and I am making a great effort to listen to any advice given

Now linking to BBCC5.
http://www.rcgroups.com/forums/showthread.php?t=2218067
KNS is offline Find More Posts by KNS
RCG Plus Member
Last edited by KNS; Sep 09, 2014 at 12:31 PM.
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 30, 2014, 05:53 AM
KNS
Registered User
Switzerland, SO, Olten
Joined Dec 2012
399 Posts
This thread follows up on a very illuminating discussion upon my initial question here:
Quote:
Originally Posted by KNS View Post
I wondered if it is possible to give RC (elevon or rudder/elevator) capability to free-flight flying wings by just adding control surfaces to the wing itself. A particularly beautiful and maybe also difficult example is quoted below. By "adding control surfaces" I mean without changing planform or wing section. If so - where would you place them, and what size? Would you prefer elevons over rudder/elevator - Does it make a difference? If it is not that easy, what would you do?
The initial thread is here:
http://www.rcgroups.com/forums/showthread.php?t=2231521
KNS is offline Find More Posts by KNS
RCG Plus Member
Latest blog entry: Latest concluded projects
Reply With Quote
Old Aug 30, 2014, 06:00 AM
KNS
Registered User
Switzerland, SO, Olten
Joined Dec 2012
399 Posts
The Mara is a freeflight design, and I want to convert her to RC. So I think I need to take a few decisions, and I hope these will make sense. I am trying to combine all the advice I was getting earlier - but don't hesitate to tell me where I am overlooking something. With the images here I hope everything will become clearer. "Mara" in Finnish means "mare" (as in: nightmare), andI hope now we can avoid some of that in advance.
I will enlarge the rudder in the simplest possible way. I will use the rudder outline as per plans to shape a piece of pink foam as a positive form to laminate the new rudder, thus enlarging the current rudder radius by 10% roughly (I will do the proper area calculations later). I plan on enlarging the tailboom by a bit (10-15cm) and will make the tail as close as possible to all moving.
I think I am happier with trying to fit elevons rather than spoilerons. That's just personal preference. I will have to modify the semi-monocoque structure of the wing to accommodate the loads of gentle RC and this will affect the wing joiners and wing root structure as well. So your input will remain very welcome and very much appreciated indeed. I understand I am deviating somewhat from the initial plans, but it is my idea to stick as close as possible to the planform. I will have to increase the width of the fuselage to accommodate RC gear - probably a 1S setup, voltage booster, micro-receiver and 3 servos. There is just too much work in a project like this to send it to the thermals without at least some hope of controlling the thing for my taste. Hope that doesn't put you off. From the get-go I am clear I might have to make a number of changes and/or build some-/everything over again. I think the design deserves it.
Lastly, I realized that there is a wealth of things to be learned from the free flighters, so I just got me used copies from Don Ross'es books on rubber models, and I much enjoy the read.
KNS is offline Find More Posts by KNS
RCG Plus Member
Last edited by KNS; Aug 30, 2014 at 06:36 AM.
Reply With Quote
Old Aug 30, 2014, 06:04 AM
KNS
Registered User
Switzerland, SO, Olten
Joined Dec 2012
399 Posts
The designer's name is Markku Thkp, a reknown Finnish veteran modeler. This is my attempt at trying to build one of his more complicated birds. I have access to a copy of his plans, and I am waiting to hear from him if/how I can make the plans available to others. Given I am a researcher I much respect authorship and copyrights. I think some might be interested in his plans, but I want this to be sorted first.
KNS is offline Find More Posts by KNS
RCG Plus Member
Latest blog entry: Latest concluded projects
Reply With Quote
Old Aug 30, 2014, 06:12 AM
KNS
Registered User
Switzerland, SO, Olten
Joined Dec 2012
399 Posts
The wing structure is highly complex - "compound curvature" at its best. I thus have to build a jig on which I can build the wing. I have started on that using 6mm lightply (poplar=aspen). Footprint of my building jig will be enlarged to 60*~120cm - the standard size of two sheets of lightply. I am trying to do a decent job on this jig as I want to use it for building an elliptical dihedral DLG wing as well. Jig will be made as a torsion box with 4 longitudinal and 4 cross-uprights stabilized by gussets. The elliptical shape will be covered by flexply or 4mm lightply. All in all I estimate 4-6 sheets of lightply go into this.
KNS is offline Find More Posts by KNS
RCG Plus Member
Latest blog entry: Latest concluded projects
Reply With Quote
Old Aug 30, 2014, 06:17 AM
KNS
Registered User
Switzerland, SO, Olten
Joined Dec 2012
399 Posts
I have also started to laminate the enlarged rudder and am using 3mm hard balsa for this (not bits of pine as called for on the plans).
edit: my current 3mm balsa batch is way to hard to bend with heat and even after being watered for half a day. I don't want to try with glass cleaner or other chemical treatments. So I start again, this time using 1.5mm sheet....
KNS is offline Find More Posts by KNS
RCG Plus Member
Last edited by KNS; Aug 30, 2014 at 06:39 AM.
Reply With Quote
Old Aug 30, 2014, 11:13 AM
KNS
Registered User
Switzerland, SO, Olten
Joined Dec 2012
399 Posts
Last post for the day - bending the wood for the rudder. The outmost 2 or three layers will not be glued in - they just take the dents from the rubber bands. In the picture on the left is the first, original sized rudder lamination. Center: the enlarged rudder outline. On the new laminations I will use the PVA iron-on trick. Thinner wood is definitely easier to handle. These are my first two attempts I ever made at bending balsa, but I am quite happy with how the second attempt looks like.
KNS is offline Find More Posts by KNS
RCG Plus Member
Last edited by KNS; Aug 30, 2014 at 11:18 AM.
Reply With Quote
Old Aug 30, 2014, 12:03 PM
David
dmarusa's Avatar
United States, TX, Houston
Joined Mar 2012
330 Posts
Very interesting. Subscribed.
dmarusa is offline Find More Posts by dmarusa
Reply With Quote
Old Sep 01, 2014, 10:14 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
14,248 Posts
I notice the middle picture of the plan, post #6, show the fin construction as though there is a rudder intended ?
eflightray is offline Find More Posts by eflightray
Reply With Quote
Old Sep 02, 2014, 01:47 AM
KNS
Registered User
Switzerland, SO, Olten
Joined Dec 2012
399 Posts
Correct, looks like it. I have no idea if this is a trim-rudder and/or the determalizer surface. I also don't know about the degree of deflection it will go to. I looks way too small for an RC surface for my taste.
KNS is offline Find More Posts by KNS
RCG Plus Member
Latest blog entry: Latest concluded projects
Reply With Quote
Old Sep 02, 2014, 01:27 PM
KNS
Registered User
Switzerland, SO, Olten
Joined Dec 2012
399 Posts
Build is continuing with the laminations. Realized it is better to glue the parts together with PVA directly - without applying heat. Rubber bands are back on and that's drying now. Continued to cut parts for the building jig. Halfway there. Loads of pieces in this one (80+) but I know the effort will be well worth it...
KNS is offline Find More Posts by KNS
RCG Plus Member
Latest blog entry: Latest concluded projects
Reply With Quote
Old Sep 02, 2014, 03:43 PM
Registered User
builderdude's Avatar
United States, TX
Joined Jun 2011
3,296 Posts
Why don't you join the BBCC5 contest?
That's what we all are doing. Converting a non-RC plane to RC control. It does not need to be powered.

This is a really pretty and unusual flying wing.
I'm definitely subscribed, but if I can talk you into joining BBCC5, that would be cool too...that is if you think 6 months is enough time to get through the build. If not, you can roll it over to BBCC6. Check into it and let me know what you think.
builderdude is online now Find More Posts by builderdude
Reply With Quote
Old Sep 05, 2014, 01:43 AM
KNS
Registered User
Switzerland, SO, Olten
Joined Dec 2012
399 Posts
This is how I will modify the wing, following this excellent suggestion from miniphase in the Nurflgel Forum:
"My favoured approach would be elevons.

You'll need to position them away from the curved tips to get a straight hinge line, another spar will probably be needed as well. I'd also be inclined to locate the fin further back.

No reason why you shouldn't end up with a perfectly flyable model! Good luck!! "


Building-wise the laminated blank for the enlarged rudder outline turned out good (but not quite perfect yet). Can start sanding soon... For future laminated outlines I will water the wood over night, and glue while still wet with a 50:50 mixture of white glue (PVA) and water. The pink foam shapes are easily made and ok for a few laminations, but I am thinking of using a jig made by setting nails around the outline on a piece of thick plywood.
KNS is offline Find More Posts by KNS
RCG Plus Member
Last edited by KNS; Sep 05, 2014 at 01:59 AM.
Reply With Quote
Old Sep 05, 2014, 10:07 AM
Registered User
builderdude's Avatar
United States, TX
Joined Jun 2011
3,296 Posts
You don't need to post them away from the tips to get a straight hinge line, by the way. Your hinge line can be made straight no matter where you put the elevons.
But the location you chose should work fine.
builderdude is online now Find More Posts by builderdude
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Sold Convering - 12 rolls unopened edbu1 Aircraft - General - Miscellaneous (FS/W) 1 Apr 06, 2014 11:27 AM
Discussion Mara Villa Flyer, update nemoskull Scratchbuilt Indoor and Micro Models 4 Aug 22, 2010 10:53 PM
Convering for beginners khaoz Beginner Training Area (Aircraft-Electric) 8 Oct 03, 2005 05:25 PM
RC MARAS Plans For Sale Endeavour105 Aircraft - Electric - Airplanes (FS/W) 0 Mar 01, 2005 06:46 AM
Cool RC MARAS Plans For Sale Endeavour105 Aircraft - Fuel - Airplanes (FS/W) 0 Feb 28, 2005 01:28 PM