It comes from my aerobatics days ... we were all looking for more precise control. Remember in those days we didn't have the diddy seervos we have now for in wing aileron etc.
But some of us experimented with the new generation that JR brought out the 1000 series ... half the size of the 101, 501 etc.
One thought was whether we could bury the servo into the hinge line itself.
Imagine a rudder. You have the vertical hinge line.
Now take a servo and imagine a line passing through the centre of the drive shaft / control arm.
If you could embed that servo into the fixed surface such that the servo arm can now be fixed in the control surface - the rudder, the hinge line being perfectly aligned with that output shaft ... you'd have absolute direct control without need for clevis or rod.
I've never had the courage or model suitable to try it ... but the Lanc having twin rudders brought it to mind and especially that nowadays we have such tiny servos.
Wheels .... I think aesthetically - slightly smaller than scale might look better. Even looking at full size - they look a bit weird.
I also have to think about tucking them away in the nacelle underwing.... 3" is a lot !!
At least though if I make sure the wheels can freewheel while stowed - it will literally give me wheels just proud of the model !
It would be a permanent mount with need to cut out if any changes needed.
Originally as I say - it was about precision .. we were looking for that state of absolute and removal of every possible bit of slop. We were all looking to beat Hanno Prettner !!
The build will be started later when I get back .. at moment - I'm throwing the ball out into court to bring in ideas and solutions ... so that when I do start - we have a system that should work. Tweaks here and there of course ... but hopefully with the fantastic brains and experience here - we should arrive at overall goal.
Put it another way - how many people had thought of laminated foam spars spanwise to create an aerofoil shape in two sheets of foam ?
I'm sure I'm not first to use or think about it ... but I have never seen it in print ..
You remember my rebuild of the wood biplane with foam blocks ? same again.
If you Y together both right and both left motors you can use differential thrust. i.e. slave the motors to the rudder channel. Very useful for taxiing, especially on grass (or water). Some models use diff thrust all the time instead of rudder. Easy to do on the 9x with ER9x or Open9x firmware. You can even use conditional switches to define when it's active; say only when the gear is down and throttle below 30% for example.
Hi ... yes I had seen the thread ... he has an extra in the wing of the partial ribs ... mine only has the spar.
With the Lanc - and 4 motors - may add a wood spar as it will need strength to avoid twist.
The coupling of motors .......... both ways have their advantages ... at present I am leaning towards the inner paired, and outers paired. But point is on the table and valid ...
In terms of er9x ... sorry but I have avoided that as I want the solutions to be suitable for all radios .... the OEM 9x should be able to mix anyway.
Might not be a bad idea to build spare servo extensions in place in case you need them to try different motor control options once the plane has been maidened and trimmed.
I have a bag of 100 leads - so plenty of extensions to play with. I buy a bag like that as I make my own Y leads etc. Cheaper and better than buying proprietary .. can make them to length required etc.
The ESC's will most likely be fuselage mounted - so changing pairing will not be too hard. I need to leave space in the nacelles for the retracts. It also means I keep battery leads to proper lengths and not risk problems.
B****y assignment I'm on in Singapore is dragging on longer than expected ... delaying my getting home and start on this project !
If I get time - I may try and find a Hobby Shop here .. see if I can pick up a few bits ...
You definitely should. You never know what strange and exotic things they might have.
I can say this ... I first came to Singapore in 1974 .... most of what I remembered and enjoyed has vanished under concrete and steel ...... it's no longer a place I enjoy as much. It's also a lot more expensive now.
Hi Nigel, Just a couple of thoughts from my limited twin experiences so far if it's any help to you.
I've built three scratch built twins up to the present time, the Beaufighter, Hampden and Wellington.
I decided to standardize on a motor/ESC and lipo setup and placed them into the cowl/nacelle in each wing.
This placed the equipment well forward of the balance point, reduced cooling and wiring issues and made a complete power system swap out a five minute job.
I had heard about the dreaded dead motor issue with twins but I still preferred to go with a dedicated lipo for each motor as it kept the cost down in terms of being able to use smaller cheaper lipos.
The "running one lipo to cut off" issue was to be solved by careful flight timing and by including a UBEC for receiver and control power supply.
I saw an article about using a cheap V-tail mixer to link throttle and rudder outputs to the left and right motors to provide differential throttle control and thought this would be good insurance as well. In fact it works a treat and has proved to be totally reliable. To see a Wellington do a wide flat turn on throttle alone is great fun and of course if one motor does play up I can balance it out using the differential control.
Well worth a thought!
You mean a foam wing built like this?
For a very simple cheap foam trainer. It a true foam monocoque structure and has no reinforcing at all.
For a Hawker P1121 ducted prop. It has one hardwood caped spar the rest are just foam.
or even this.
For a F4D Skyray. Again one spar is wood reinforced.
These were designed for minimum weight rather than ultimate strength although all are capable of full aerobatic manoeuvres.
With "X" billion on this planet you can be pretty sure someone, somewhere has already done it.
So that's 4 cheap motors rated at about 200gr per 7x5 prop .... said to be under 10A ... but I play safe with ESC's 25A+ ....
2" diam wheels
Collets to fit shafts .. will have nuts fitted instead of the cones .. spinners will sort later once I know the real nacelle diameter to match.
Hi Nigel ,i have been building my wings like his for a while now ,i learned this way in the ultron 3-D thread . I use a piece of 1/2 inch tall by 3/16 piece of balsa for the main spar but if i realy dont trust it i use a flat piece of carbon fiber glued to the top and bottom of the spar (STRONG LIKE BULL) lol I learned this because i hate flat wings . Here is where i learned how to fold them over without snapping them in half. http://www.rcgroups.com/forums/showt...ghlight=ultron Looking foward to the rest of your build . joe
Not only that but the tileíng of plans didn't go too well. It seemed the tiles had a section missing horizontally on each join line ... So I've been messing about gett8ing portrait and landscape tiled sets to get full plan. Would you believe that despite setting same scale - the two sets are different sizes !!
Anyway - I've finally got a set that I can use ... at 70% of the 74" plans ... 52" / 131cms wingspan ...
That's big when laid out and is about as big as I dare go ... It will also take some stiffening in the wings to be safe. I have a 12mm square MDF spar I bought in local shop ... to test for suitability as a wing spar ... Yes MDF ! When flexed / stressed - it seemed to hold well enough. I reckon with foam added it may suffice. If not then it's 6mm pine rods ...
Will start to stitch plan tmrw and get on with templates.
Please note that fuselage will be a square'ish form to make easier instead of the curves. I may use my pink block foam to create turtle deck curves .. maybe ! canopy / Gun turrets etc. will be from beer botttles where suitable and carved foam where not.
I want this to be a simple build that anyone could tackle without too much hassle.
Decisions that need to be made :
Wing ? two halves ? or fixed centre and plugged in outers ?
Radio gear ? 2 Rx's ? split the servo load and each Rx is powered by separate LiPo ? As intend to carry 2 x 2200 3S packs on board ... there will be 4 motors each with ESC which are then paired ... giving me control separately of paired OUTERS and paired INNERS .... I decided against differential controlled motors ...
Ailerons = 2 to Ylead
Flaps = 2 separate
Retracts = 2 to Ylead
Elevators = 1
Rudders = 1
ESC's = 4 into 2 pairs with Yleads
How would you split the servo load to the Rx's ? My idea is :
At 52" I'd keep it as simple as possible. I know this often starts a debate, but I build planes that size with 5-9gm servos. Unless you're flying an aerobat with massive control surfaces, the load is within reason. An ESC with a 3A switching BEC will run 8 servos that size, with the retracts being only an intermittent load. I believe the servo power supply terminal on the receiver is bus terminal, making the receiver load irrelevant as the S-connector pins are also ample for the few amps required. Separate batteries could be useful in shortening supply cable length, but again a bit of a hassle. I'm sure some folks have used one nacelle per side as a battery bay, which would substantially shorten the battery lead.
The plan tiling is a pain. You're making me feel better about using my thick, grainy enlarged MS Paint drawings. I've devised a method where I set the page size to the desired wingspan, which is then used to determine the enlargement percentage with a bit of trial and error. Once determined, I enlarge the entire plan and print the 1 million pages. I've had some issues there however, where the size changes when I reopen the plan. I've learned to do the entire process including printing, all in one session.
One of the reasons I want to split the servos across the battery supplies - I'm trying to avoid high drain on one pack. Plus having 4 motors - I think it wise to split the power drain there.
Motor to ESC leads are no problem - heavy duty copper cable is abundant here at my house with the rebuild !
One question that runs through my mind - is where to mount the ESC's etc. I know that many use nacelles, but I want to keep transverse weight as central as possible. I know from previous that putting weight out in the wing lessens aileron effect and a model like this is already sluggish there. Plus I would keep batttery to ESC leads normal length.
Its another reason I considered the outer wing panels as detachable.
Has anyone a simple DIY plug-in wing system I can make ?
As to the tiling ... its a problem of Adobe Reader XI .... the online site I use is fine, but the online doesn't scale down / up as I needed. The original plan is 74" .... too much for my use. Even 52" is at my limits but smaller than that and a Lancaster would be daft in the air ! IMHO It's also still big enough to have 'presence' ....
Nigel, I've looked at four engined planes for ages deciding which would fit my build style and motor set up best and at last decided on the Lanc as well, due to the length of the nacelles which will hopefully make motor/battery set up easier.
I searched all the available free drawings and plans and decided on a really compact plan which was easily up scaled and printed to 84" to match the scale of my Hampden and Wellington without destroying a forest in the process.
In checking the front of your thread I realised that it's the same plan that you are using. It should be easy to build a solid foam model from the plan details.( famous last words)
I'm starting with the nacelles and motor / ESC / battery build as that's the determining part of the build for me.
Luckily the Skystreak nacelle mould is almost perfect for the Lanc and only requires minor re profiling in fact it's drying right now so I'll be able to shrink a test cowl very soon and get going on a nacelle test set up.
I would split the wing outside the nacelles and make the center section in one piece. It simplifies wiring and may allow transport with the wing center section still attached to the fuselage. Adding the wing tips and connecting just the aileron servos at the field.
The forces at those joints will be much less than at the center joint. You could use carbon tubes in a sleeve or a blade spar that slides into a box. It depends on how much dihedral vs wing thickness you have. There are several ways to retain the wings.