HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Apr 03, 2013, 03:25 AM
Registered User
Australia, NSW, Swansea Heads
Joined Mar 2013
57 Posts
Build Log
BBCC2 - Frog Vespa - Deanoseadog

Ok, I'm in!

http://www.rcgroups.com/forums/showthread.php?t=1842080

Right, I cut my teeth on RC planes with a 2m slope glider back in the mid 90's. Taught myself to fly on the dunes and loved it. Been into RC planes on and off since.... probably more off than on until recently. Well, since I'm getting old and all nostalgic these days I dusted off my old 2ch glider that I learned with (yes it still flies) and went back to the exact same spot where I first chucked it off all those years ago. In short, I loved it all over again and decided I needed a bigger quiver of gliders. Something to work in light lift would be nice....like the look of those new-fangled DLG's, but the price! Decided that the DL would probably just make me dizzy and fall over anyway, and really there are less embarassing ways of getting a glider up there, in fact I remember as a young kid towing them up on a towline. Ok, maybe they weren't RC, and maybe it wasn't really as successful as I remember... but surely with modern micro RC gear, and my ummm new found experience and patience (both were seriously lacking as a child) I rekon I could make one of those old FF balsa models fly really nice! I mean they were sooo much lighter than the current fad of flying esky's, and they had plenty of space for all the RC gear, and they looked cool! (to me?)

What could possibly go wrong?

This is the thread to find out...
Deanoseadog is offline Find More Posts by Deanoseadog
Reply With Quote
Sign up now
to remove ads between posts
Old Apr 03, 2013, 03:44 AM
Registered User
Australia, NSW, Swansea Heads
Joined Mar 2013
57 Posts
So here's the Plan.

Got this from "Outerzone". I'm sure you're all familiar with that site it's...AMAZING!
Can't believe the effort people have gone to so that all the info is there for others to build from.

Chose it because it's light, fairly small, looks easy to build, seems to be well documented (plans, printwood etc.) and looks nice.

I want something that is a real slow floater and very basic. I'm even thinking of building it rudder only, not sure yet, that's where you guys come in. To be honest this plan pre-dates me, and my FF experience is limited so all advice is welcome...just don't be offended if I don't take it. I still weild supreme executive power on my build, for better or worse.

So...anyone built one?
Deanoseadog is offline Find More Posts by Deanoseadog
Reply With Quote
Old Apr 03, 2013, 05:11 AM
Registered User
United States, IN, Hammond
Joined Jan 2013
541 Posts
Hi Deano
Ken USA is offline Find More Posts by Ken USA
Reply With Quote
Old Apr 03, 2013, 06:07 AM
Registered User
Norfolk, England
Joined Sep 2001
7,602 Posts
Such a classic look that it just has to fly well. The very similar (but smaller) Keil Kraft Cadet was a nice flyer.

I wish I could say the same for the Minimoa - ripped the wings off first time I towed it up. Too much childish enthusiasm I suppose - it was almost 50 years ago.

Pete
PETERRAKE is online now Find More Posts by PETERRAKE
Reply With Quote
Old Apr 03, 2013, 02:16 PM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
2,802 Posts
I do like it, too! Charlie "Old_Pilot" has me examining gliders for the first time.

I support the use of an elevator based on experience with my Ultra Micro Champ. I've learned to enjoy it's glide performance and have even experimented with a wing of the same area but increased aspect ratio. When I use rudder to turn the plane, there is a good amount of adverse yaw that raises the outboard wing in the turn and the aircraft falls into a diving turn. Given the undercambered airfoil, the plane swoops back to a stable, but lower, flight regime.

I've learned to use a bit of up elevator to counteract the drop, and keep the nose up in the turn.

I'm also pondering that it has a lifting tail, with the GC aft of the "usual" location, I'm used to. I have no experience there.

But I was thinking, for a moment, about making the tips of the tailplane/stab into independently-driven full-flying "ailevators" (a'la modern jet fighters) by duplicating rib T8, parting the stab at T8, putting it of a pivot about the rim and putting two of the little 2-gram UM servos on the underside of the stab to drive it. Then you could have roll and pitch mixed in by the radio. If you handled the fin in the same manner, you'd have a true fly by wire glider. No pushrods, just the little servos at the site. Look to the underside of the wings of the UMX Carbon Cub and UMX Mig 15 to see the sort of installation I'm thinking.

OK, I'll go back into my hole.
davidterrell80 is offline Find More Posts by davidterrell80
RCG Plus Member
Old Apr 03, 2013, 06:56 PM
Registered User
Norfolk, England
Joined Sep 2001
7,602 Posts
David,
That arrangement of lifting tail and rearward balance point works well. It worried me on my Veron Deacon, until the first time I flew it. A very gentle and forgiving model, but weighty with a geared 540 and Ni-Cad pack. Handled wind well with all that weight on board.

Elevators on something like this are easy. Just cut down the ribs, add a false trailing edge and make what would be trailing edge wider, acting as elevators and a fixed centre portion.

Pete
PETERRAKE is online now Find More Posts by PETERRAKE
Reply With Quote
Old Apr 05, 2013, 07:49 PM
Registered User
Australia, NSW, Swansea Heads
Joined Mar 2013
57 Posts
Wow, good to see some quick activity on these forums!
I think you might be right about the elevator David. It certainly will increase the versatility/practicality of the model.

After studying the plans a bit I have noticed that the wingspan is quite small for the fuselage length, so I may stretch the wings a little which will help offset the added weight of RC i.e. keep the wing loading down. And I noticed that the AR of the wings is quite low (maybe 7.5:1?). So, If I keep the same chord but stretch the wings to say 34" I get an AR of about 8.5:1 and and extra dm^2 or so of wing area...I imagine this to be a good thing for it's sink rate. I know (hope?) it's going to fly very slowly and I think that is why the original had such a low AR so I don't want to stray too far from that but what I am aiming for is maximum flying time on really calm days. If it turns out a brick, it just becomes a sloper!

As was pointed out, the CG is waaay back there from what I would have guessed. And I'm also a little baffled by the flat bottom foil on the H-stab. I might just build up a totally flat one or if I get fancy, a symmetrical one. All a long way down the track yet.....I still have to finish my ugly stick....

Anyway, while the planning is going on I have been shopping and bought some little 4.3g servos. I got three 'cause at the price they are I expected at least 1 dud. Turns out they all work....
They may be a little heavy for this project? I have zero experience with building planes this small, so this is all new and quite exciting to me.
Deanoseadog is offline Find More Posts by Deanoseadog
Reply With Quote
Old Apr 05, 2013, 10:14 PM
Registered User
conrad907's Avatar
China, Guangdong, Shenzhen
Joined Feb 2012
402 Posts
Well, I do not have any experience with gliders, but that is a darn lite servo. I would be more concerned about overworking it. I do not know these things. But others here do. Yer hangin with smart folks here. They will give you the right advice. Nice plan you are building from, Outerzone does the model building community a great service!

Conrad
conrad907 is offline Find More Posts by conrad907
Reply With Quote
Old Apr 06, 2013, 08:06 PM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
2,802 Posts
The Horizontal stab has a lifting airfoil. Because the wing and the stab both lift, the CG moves back. Most planes use a downward force on the stab.

Having both be lifting effectively increases the wing area... and will make it more of a floater. Making the stab non-lifting will eliminate that advantage.

Changing the wing area will increase the lift at that "Station" (location from front to rear). Perhaps you can safely change the stab to non-lifting and move the CG forward.

Regardless, the more I think of it, the greater the confidence that you will need an elevator.
davidterrell80 is offline Find More Posts by davidterrell80
RCG Plus Member
Old Apr 08, 2013, 04:15 AM
Registered User
Australia, NSW, Swansea Heads
Joined Mar 2013
57 Posts
Yeah, I rekon you're spot on David. The lift from the H stab moves the centre of lift rearward slightly, and hence the CG needs to come back a little also. Maybe this helps with FF models? Peter might be able to give a little more insight into this? I'm not sure if I should keep this arrangment when using an elevator (since you have all talked me into 2 CH) or convert it to something I'm more familiar with i.e. flat/sym H-stab and slightly more forward CG? Food for thought.

I got some more trinkets for it yesterday.
Got a ridiculously small ESC (just for the BEC), an even more ridiculously small 180maH 1S battery, and an ordinarily tiny reciever. All the RC gear combined (with 2 servos) weighs 21g. If I remove the Rx case I save another 1-2 grams. I have a RTF target weight of around 100g (+/- 10g) so we're on target there.

I got the reciever to bind (this whole 2.4GHz thing with no Xtals is a bit spooky) but since it is just a 3ch thing for cars etc. I'm not sure how the range will be. The plane might just return to its FF roots! Obviously I'll test it first.....if I remember.

Pic of approximate location below.
Deanoseadog is offline Find More Posts by Deanoseadog
Reply With Quote
Old Apr 08, 2013, 07:19 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,471 Posts
Quote:
Originally Posted by conrad907 View Post
Well, I do not have any experience with gliders, but that is a darn lite servo. I would be more concerned about overworking it......
Shouldn't do - I'm using similar sized servos in my 30" KK Ajax, which being powered I would think would require far greater forces. The tiny servos handle it no problem! In fact, Harry D's 21" KK Dandy used these 1.9g (true weight) servos:http://www.hobbyking.com/hobbyking/s...dProduct=17540.

As others have said, a rearward CG with a lifting tailplane is quite normal on Vintage FF designs.

If you are going R/E and may want a bit more than 'RC assist', it may be worth reducing decalage slightly - My KK Ajax & (to a lesser extent) KK Gypsy were built with the FF rigging, and are somewhat 'overstable' - to the tune that I have even launched the Ajax, and made a 1 minute flight with only a single control input - shutting the throttle at the top of the climb - and it still landed on it's wheels! Can't get a loop out of it though!
Colonel Blink is offline Find More Posts by Colonel Blink
Last edited by Colonel Blink; Apr 08, 2013 at 07:30 AM.
Reply With Quote
Old Apr 08, 2013, 08:29 AM
Registered User
Norfolk, England
Joined Sep 2001
7,602 Posts
CB,
Oh shame on you, the very thought of looping an Ajax.

I'd keep things pretty much as per the plan as regards tail section. The model is set up for that arrangement and you can't really change one major factor without altering other things too.
The one thing you might need to watch is those servos on a 1S set-up. The receiver too, come to that. Especially since it is already likely to have suspect range (being a 'ground' set). Servo speed shouldn't be an issue on a model like this but it would be awfully nice if everything worked when you need it to.
Just thinking about it, if you don't have a motor, and your receiver and servos are fine on the voltage from a single cell, why do you need an ESC? It won't actually be doing anything other than adding weight. If I were building a model like this I'd probably go for an Orange 410 receiver and a couple of 2.5 gram servos with a 2S pack - or 1S if I could get away with it (Orange 415 and 1.8 gram servos). It'll probably need at least the weight of a 2S pack as ballast though so you might as well make that weight earn its' keep.

Pete
PETERRAKE is online now Find More Posts by PETERRAKE
Last edited by PETERRAKE; Apr 08, 2013 at 09:15 AM.
Reply With Quote
Old Apr 08, 2013, 09:04 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,471 Posts
Quote:
Originally Posted by PETERRAKE View Post
CB, Oh shame on you, the very thought of looping an Ajax.
I am contrite........
Colonel Blink is offline Find More Posts by Colonel Blink
Reply With Quote
Old Apr 09, 2013, 04:35 AM
Registered User
Australia, NSW, Swansea Heads
Joined Mar 2013
57 Posts
The ESC is just there because it gives me a 5.5V 0.5A output to power the Rx. It weighs 2g. I don't think the Rx would run on 1S.....I haven't tried it though. And I'm using that Rx because I have a HK transmitter (yeah I'm cheap) and I'm not sure what other Rx's will bind with it.

As for the level of control.....RC assist will probably be fine. I just want to be able to keep it in sight, avoid any obstacles, and correct glide angle for wind gusts etc.

I was thinking that if I changed the tail size/shape I would probably have to change the wing incidence too? It all starts getting a bit complicated so I think I may just build it as per the plan.....maybe I should make 2? One original and one mod.
Deanoseadog is offline Find More Posts by Deanoseadog
Reply With Quote
Old Apr 09, 2013, 04:53 AM
Registered User
United States, IN, Hammond
Joined Jan 2013
541 Posts
"maybe I should make 2? One original and one mod."
Now you're talkin'. There's a bitcharger thread in the micro planes forum that may help increase the range substantially.
http://www.rcgroups.com/forums/showt...threadid=74227
Ken USA is offline Find More Posts by Ken USA
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Alert BBCC3 - Easy Built Models Ryan ST 20" - KnifeEdge51 KnifeEdge51 Balsa Builders 26 Nov 21, 2013 11:32 PM
Discussion BBCC2 - Another Knight PETERRAKE Balsa Builders 150 Jul 17, 2013 11:29 AM
Discussion Anyone ever hear from Frog Chief? LVsoaring Other Websites 39 Feb 24, 2013 07:25 AM
Discussion OT: Mad as a box of frogs. Jonathan Bradbury Motorcycles 0 Jan 25, 2013 10:46 AM