Switching to electric gliders from fixed wing large scale electrics

[Adrian Smith 1]

Thanks yes, Dick that's the one. I am going to have a go this afternoon and hopefully do a bit more to the build too.

[Adrian Smith 1]

Fitting the spinner turned out to be a straightforward affair. However, the 10x8 10x6 blades have an 8mm root while the original blades with the spinner have a 6mm root, therefore the spare blades won't fit the spinner slots. Really annoying as there are all JP kit !! Will have look for some other root sizes now.

 

[Adrian Smith 1]

Right next on to fitting the rudder servo. I had a spare standard Futaba 3010 servo which weighed 41g as per the manual's spec. At a 6kg+ torque it's a bit of overkill, but it might need it as I will relate.

[Adrian Smith 1]

I fitted the rudder rods and I must say I am not happy with them as despite vaselining them there are very stiff. The tubes needed shortening  slightly by the way. Furthermore they stick out the back at an acute angle which would require bending.

Edited October 15, 2021 by Adrian Smith 1

[Adrian Smith 1]

Plan B meant I dug out some thin rudder wire and couplers which I am considering fitting instead to improve the situation. Seems like a better idea. 

[Adrian Smith 1]

Next modification was to form the elevator servo mount and cut the opening to shape. Feeding the elevator servo wire through the L bend in the tail to the RX through the fuselage is going to be a challenge..... 

 

[Adrian Smith 1]

Time to bite the bullet and pull out the rudder push/pull rods and replace with wire. First job before that was to thread the elevator servo wire through the fuselage. Given the "corner" to be negotiated I used some thin string with the trusty bolt tied to the end and let gravity do the job. Next I threaded the rudder wires through the tubes using some very thin carbon fibre rod. Attached the couplers to the rudder servo horn. The rudder end to be done later. Much happier with the result.

[Adrian Smith 1]

the rudder fitting comes next. The kit provides fibre hinges to be cyano glued. Don't like them particularly because it stiffens the joint, but we will see. Cut the slots in the tail with a very thin blade for a tight fit.

[Adrian Smith 1]

Have test fitted the rudder it was plain to see that it is too long and would foul the ground on landing even allowing for the tail wheel. Looking at the manual the rudder base should follow the slant of the rear fuselage. I decided to trim the rudder and re-cover. Hopefully the slightly smaller rudder area won't the affect performance.  I did check that the top of the rudder was at the optimum height of course!!

[Adrian Smith 1]

Last job of the day was to fit my chosen rudder horns from way back when that I dug out from the draw. I didn't use the supplied horns that were to be glued as I wasn't too keen to chop around the rudder  as it's not that thick. Pleased with how that went.

[Adrian Smith 1]

Time to tidy up the rudder wires at the tail end. I thought I would test fit the tail which required some trimming of the covering.

[Adrian Smith 1]

Now I was a bit puzzled by the way it sits on the tail fin. The fin slopes downward while the thickness of the seating at the rear is quite pronounced. Nevertheless bolted on it appears the shaping is deliberate.

[Adrian Smith 1]

Next the job of cutting the aileron and flap slots with a sharp knife by first scribing a line on the working surface. Cutting the slot was done with care by first measuring the surfaces' depth and cutting horn to length. 5mm is the maximum depth.

[Adrian Smith 1]

lastly the horns were stuck in with Gorilla glue and put aside to dry. The other wing replicated. I did centre the servo arms while I was at it. I guess i should do the elevator horn but another arrangement might be necessary at the elevator is quite thin to be taking that type of horn.

 

[Adrian Smith 1]

On to the elevator now. Marked the alignment line for the horn. I used a bolt through horn on this working surface and then fitted the push rod using a standard coupler..

[Adrian Smith 1]

Connected all the other push rods and then screwed the servo housing panels to tidy it all up.

[Adrian Smith 1]

I now have a bit of a problem to solve. The manual sheet points out where the CoG should be (65mm) while the ailerons are 20 mm +/-, elevator 25mm +/- but unhelpfully there is no suggestion for the rudder throw. Additionally, I have no idea what I should dial in how much down flap to use. I will just use the flaps for lift so no up flap being considered unless any suggestions are forthcoming.

 

[GrumpyGnome]

I set all my rudders to as much as I can get, then tone down if necessary.

 

Not sure if you plan on any jiggery-pokery with the wing surfaces (like coupled flaps and ailerons), but the ability to use the flaps to 'dump' lift by moving up can be useful in getting efficient planes down.

[Adrian Smith 1]

Ah! Didn't think of that GG. I had a mental block which made me think just about keeping the glider up. I can see now in some conditions the reverse is true. I am sure I can set that up - I know my Futaba TX will do all of that, but I just need to find out how. Being a fixed wing aerobat Herbert such things are not usually required! Steep learning curve coming up.

[PatMc]

12 minutes ago, GrumpyGnome said:

I set all my rudders to as much as I can get, then tone down if necessary.

 

Not sure if you plan on any jiggery-pokery with the wing surfaces (like coupled flaps and ailerons), but the ability to use the flaps to 'dump' lift by moving up can be useful in getting efficient planes down.

IMO it's better to use up aileron combined with down flap - i.e. "crow brake". 

[Adrian Smith 1]

Might be easier to set up too, PatMc. Will have a look. ?

[PatMc]

It's a fairly standard arrangement. I have an old redundant Futaba FF8, IIRC it's referred to as "butterfly braking" in the manual. 

 

[Frank Skilbeck]

50 minutes ago, Adrian Smith 1 said:

I now have a bit of a problem to solve. The manual sheet points out where the CoG should be (65mm) while the ailerons are 20 mm +/-, elevator 25mm +/- but unhelpfully there is no suggestion for the rudder throw. Additionally, I have no idea what I should dial in how much down flap to use. I will just use the flaps for lift so no up flap being considered unless any suggestions are forthcoming.

 

Can be useful if you are using flight phases to mix flap to aileron for full span ailerons, I have this on my Multiplex Heron, but set up as per the manual the flap only moves up with the upgoing aileron and not down, i.e. roll right both right aileron and flap move up, left aileron moves down but left flap doesn't move. Also a bit surprised the manual has equal up and down aileron, on gliders it's quite common to dial in some differential to counteract adverse yaw, again flight phases are quite useful here so you can have different aileron differential for different flight modes, e.g. acro has reduced aileron differential (and flap mixing), but thermal mode would have more.

 

+1 for butterfly/crow braking, best on a proportional control, I always have it on the "throttle" stick so it's easily modulated but a lot of dyed in the wool power fliers find this hard to accommodate so put it on another control

Edited November 2, 2021 by Frank Skilbeck

[Adrian Smith 1]

Thanks for the input appreciate it, Frank. Speaking as a dyed in the wool power flier I have much to learn!

[MattyB]

Start with 2:1 aileron diff at minimum; flaps need to be able to go up a few mm for reflex (speed) flight mode and as far down as you can get (at least 45 degrees, ideally 60-70) for crow. This will normally require a horn position offset significantly towards one end of the throw (I.e not perpendicular to the wrong skin). Rudder throw is not too critical, but aim for at least 30 degrees for first flights, ideally 45 degrees.

Edited November 2, 2021 by MattyB