Thread Tools
Dec 03, 2018, 09:14 PM
I Hate Orange Props
MicroPlane6's Avatar
Question

Do I need ailerons?


Hello, I am in the early stages of building a 3.5m balsa+hardwood glider with an electric motor (https://outerzone.co.uk/plan_details.asp?ID=3883). I am wondering if I need ailerons.
I see other large gliders, such as the Bird of Time, sometimes don't have ailerons. Would the plane work better with or without ailerons? About how big should they be, and with what servo size? I have already build the wing root and spar, so the dihedral is fixed at the quantity shown in the plans.
Build log: https://www.rcgroups.com/forums/show...onatnari-OZnoP
Sign up now
to remove ads between posts
Dec 03, 2018, 11:13 PM
Registered User
GliderJim's Avatar
You don't need ailerons to turn if you have enough dihedral. There are many successful sailplane designs that don't use ailerons.
Dec 03, 2018, 11:44 PM
Intermediate Multi
Trisquire's Avatar
The sailplane you’re modeling was free flight, hence it got by without ailerons, or rudder, or elevator, etc.
Dec 04, 2018, 12:34 AM
Registered User
I think you will find that response to the rudder is quite slow. However, years ago, there were many RC designs that used a small amount of dihedral.

If you add ailerons, you should use rudder along with them, at least when initiating turns, or adverse yaw will make the model actually turn the other way when flying slowly.

This is just a SWAG, but if I was adding ailerons I might consider starting them at 20 or 25 percent forward of the trailing edge, halfway out on the wing. I wouldn't bother continuing them around the curve of the wing tip. That's probably worth exactly what you paid for it. It would probably be better for you to look at successful designs to get an idea of what's normal.

If you were to add dihedral, you might or might not need a larger vertical stab to prevent dutch roll. Depends on the vertical tail volume and on the moment of inertia of the wing Actually, more like the radius of gyration, but they're related. The radius of gyration takes the total mass into account as well as the moment of inertia. More mass and same moment of inertia means a smaller radius of gyration. And the other way around too.

Are you sure you want to cover your model in slimy oil? Seems like it's just begging for an electric motor with some kind of offset gearbox.
http://www.maxxprod.com/mpi/mpi-10a.html or the Astro Cobalt pictured, which you can sometimes find on eBay. There are probably brushless inrunner equivalents, but I don't know what they are. The other thing it's begging for is a clean nose and a tow hook, of course.

I admire the ambition of your project. It's going to be a beauty.
Dec 04, 2018, 01:03 AM
Everything's A Compromise
Larrikin's Avatar
Quote:
Originally Posted by lincoln
Are you sure you want to cover your model in slimy oil? Seems like it's just begging for an electric motor with some kind of offset gearbox.
Quote:
Originally Posted by MicroPlane6
Hello, I am in the early stages of building a 3.5m balsa+hardwood glider with an electric motor ...
Just sayin'
Dec 04, 2018, 01:54 AM
I Hate Orange Props
MicroPlane6's Avatar
^ The plans show a .35-sized glow engine. I’ll need to find something equivalently powerful. The airplane has enough clearance for a fixed prop to not strike the ground on landing.

I think I’ll do something like the ailerons outlined in red. I’m not certain though, I might make them longer.
Dec 04, 2018, 02:34 AM
Brett
bjaffee's Avatar
I once converted a free flight glider (a Super Soarer) to rudder/elevator R/C, and found it it did not have enough nearly enough dihedral to turn on rudder alone. I ended up adding ailerons. Yours does seem to have a decent amount of dihedral, however.
Dec 04, 2018, 03:26 AM
Everything's A Compromise
Larrikin's Avatar
Quote:
Originally Posted by MicroPlane6
^ The plans show a .35-sized glow engine. Iíll need to find something equivalently powerful.
Quality is remembered long after the price is forgotten.
This Motor?
The number on this line of motors implies the IC engine equivalent.
Dec 04, 2018, 03:36 AM
B for Bruce
BMatthews's Avatar
Do you have some idea of what the final weight will come out to be yet? Or don't buy the motor until you're far enough along that you can have a decent idea.

For a good solid 45 degree climb angle on a lower Kv motor with a 10 to 12 inch prop you want to aim for about 65 to 70 watts per lb of flying weight. And franky I tend to think that would be a good match for a vintage style glider.

For a model of this size even with care a final weight of 6 to 7 lbs would not be at all out of the question. So using 7 lbs as a "worst case" if we go with 70 watts/lb that's 490 watts. So call it an even 500.

Going with the E-Flite line of motors as a comparison their Power 25 motor on a 4S pack and running a prop that is pulling around 30 amps will provide the 500'ish watts you need. Going with something less of a name the Suppo line of motors from Grayson Hobbies (and others) has a GH2820-06 that is good for 500 continuous as well. And on a 4S pack will let you run a 12 inch prop which I hope will fit with the landing wheel clearance.

And of course if it comes in at under 7 lbs then you've got a bit of extra power. You can either throttle back a hair to a climb angle that you feel is more in keeping or you can run a smaller or finer pitch prop to reduce the current draw and cut the power provided down that way.

Ailerons would not be a bad idea. I don't normally say that for vintage model. But the model you're doing does not have a lot of dihedral angle. And as a result I'd expect the rudder to roll response to be a touch "soft". It would be fine if you stay with calmer conditions. But with some wind and the turbulence that goes with it often ailerons would be nice.

Ailerons are best when they are out on the wings as far as possible or practical. So I vote for the green line you showed with the ailerons ending on the fourth rib in from the tip. And since the force from them is better the further out you don't really need to run the inner end in any further than the rib at the green line or at most the rib for the red line. The size you show or slightly smaller for the width would be fine. I wouldn't bother with going wider than shown. It won't be a stunter with those size of ailerons but then it's not that sort of design either. And if it is a touch "trainer like" with the ailerons then you can coordinate the rudder with the ailerons and that will really speed up the roll response to be easily twice as fast as either by itself.
Latest blog entry: Garden Gliders
Dec 04, 2018, 01:23 PM
I Hate Orange Props
MicroPlane6's Avatar
The plans say "with engine, total weight 3200 grams." So yeah, 7 lbs. I'll draw out the ailerons on my full-size wing plans and see what looks right.
Dec 04, 2018, 03:47 PM
B for Bruce
BMatthews's Avatar
If you have a good stock of low density wood to work with I would not hold myself a slave to that 7 lb weight. There's no reason at all why this model could not come out the other end at 6lbs or even a hair less... It's a lot of model so I'd still be very happy at a bit over 6 and call it a major victory. But the point is that with the motors and radio gear of today and with care in what you use for wood and covering a 6'ish lb weight is possible. And it would float in a most magnificient manner at that size and for any amount less than 7'ish that you can manage.
Latest blog entry: Garden Gliders
Dec 04, 2018, 06:31 PM
Registered User
Quote:
Originally Posted by Larrikin
Just sayin'
In the build log, he said he was going to use a McCoy 35.

------------
BTW, I suggested a motor with offset gears just because I thought it would fit the nose better. I'm sure it would fly just fine with an appropriately sized brushless, possibly for less weight.
Dec 05, 2018, 03:17 AM
I Hate Orange Props
MicroPlane6's Avatar
^I intend to go brushless, because it’s what I’m used to. I don’t want to add too many variables all at once.
I’m going electric, although I was originally considering a glow engine. I don’t really have much experience with fuel aircraft, and my local field is electric only. Not fuelproofing might allow for weight savings, and engines tend to have heavier firewalls to withstand the stress of starting.
Quote:
Originally Posted by BMatthews
If you have a good stock of low density wood to work with I would not hold myself a slave to that 7 lb weight.
I don’t know what counts as “low density.” There is a lot of hardwood, and I have very little experience with it. I’ll be cutting the formers with perhaps bigger central holes than in the plans, particularly aft of the wings, and shaving down weight in other areas as well. The landing skid/wheel thing looks a bit beefy in particular... I might be going with a bent wooden skid, like on full scale gliders, rather than the plywood keel/wheel well assembly (4mm thick!) shown on the plans. Mightn’t even need a wheel...
Last edited by MicroPlane6; Dec 05, 2018 at 03:34 AM.
Dec 05, 2018, 12:08 PM
B for Bruce
BMatthews's Avatar
I was thinking of the balsa you use. But looking at the plan a second time while still not trying to do any translation of the writing I can see where it looks like much of this model is done in plywood and likely spruce for the longerons and stringers of the fuselage. So that does stack the deck against you slightly. But I'm liking your ideas for those modifications.
Latest blog entry: Garden Gliders
Dec 05, 2018, 04:48 PM
The King Moonracer of balsa.
Windependence's Avatar

EDA calculator


If I run your wing through the EDA tool I come up with an EDA of 5.3. If you build it per the plans you may find you need ailerons to get it to turn well. Enjoy your build.

Wayne


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion What do I need to do to put my batteries in "storage mode" and when do I need to? SpeedJunkee Batteries and Chargers 25 May 01, 2017 08:31 PM
Discussion xt60 snapped off what do i do now please help do i need to put the qav 280 in spares Johnboy8569 Multirotor Drone Talk 7 Mar 30, 2017 12:25 AM
Help! What do I have and what do I need to get these two 2m sailplanes in th air pval3 Electric Sailplanes 18 Mar 13, 2017 02:26 PM
Discussion Where do I get these and do I need em jtroutt19 Power Systems 16 Dec 16, 2016 07:21 PM
Do I need to fly Both Ailerons & Rudder to do 3D? mrebman 3D Flying 9 Nov 24, 2003 09:23 PM