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Old Jan 18, 2012, 08:39 AM
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I'm using servo covers. The frames for the flaps are really glued in. I don't think they'd need more.

I'd imagine the servo horn would break first.
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Old Jan 18, 2012, 11:32 AM
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USA, KY, Louisville
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Mounting Servos

Molded wings skins tend to 'oil can' under servo mounting, so we have learned to add some extra layers of carbon or glass around those areas to firm up the skins. With Bagged wings, the areas are already supported by the surrounding foam.

Dork landings don't affect aileron servos much since they are fairly light weight and the linkages fairly short.

Using shortest possible servo arm hole lessens the leverage of those kind of loads on the gear trains and the mounting areas.

Consider your application, this is a thermal wing. 98% of its job is to fly around with almost no loads of any kind. 1% is fiercely loaded during hard launches, and 1% is shock loads during landings.

Also consider how many of the 1% loads your particular model will be enduring in a season. If you don't fly very often...you don't need steel under the servo mountings :-).

IF you aren't 'dorking' often in a season, the same applies.

IF you intend to F3J task practice multiple times per week and fly aggressively at contests....buy a molded model with plenty of carbon in the wings.

A big contest in the USA was won by a model that was created as a test...to see how light that model could be made and still fly contests. It had micro servos on each surface! With plastic gears. The pilots main models were damaged early in the contest so all he had left was the test model. He knew he couldn't do anything extreme so he launched and flew it as though it were an old wooded model...and won. Now there's no way he'd ever suggest something like that, and the weight savings added nothing to the equation..but it did provide a excellent point of clarity about how it is possible to do the tasks without the airframe abuse of giant launch pings and landing pokes. Don't build to crash. Install to fly.

Too often I have seen installs where the builder was either lazy or uninformed about optimizing servos installs for best durability and operation. Instead of putting a foam base to raise the servo mount in order to have the servo flush with the linkage side of the skin they simply glued them in, then used a lonnnggg servo arm to 'reach' out of the abyss...then wondered why there was so much slop in the servo and linkage, as well as poor centering.

..and do you really want linkage sticking out of the top of your wing?

Gordy
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Old Jan 18, 2012, 01:14 PM
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Greensburg, PA
Joined Feb 2008
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Aileron Install

Everything is 90ed up, no offset.

I do run some differential, but that will take some flight testing.

I don't run expo or D/R. Can't flip a switch in full scale and change the control throws
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Old Jan 18, 2012, 04:56 PM
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Hi Gordy,

You raise some good points.

However, I fly F3J and do hard dork landings... it is what I do :-)
This plane is going to be installed for F3J competition use. I will be honest and say that it will be my light weather glider for mornings and evenings. I have a spread tow supra for the heavier work and windy flying.

I just noticed with the molded supra that the linkages run from bottom to top and this makes for a very clean install. All inside the wing apart from the top exit. I must say I agree with you it seems against my aerodynamic religion to have anything sticking out the top surface as a larger proportion of lift is generated there, however, considering the significantly reduced surface area of linkages this way it ends up with a net gain in my head.

Then there is the point you raise about percentages of the flight envelope these effects take part on. It is true that the higher reynolds numbers will only apply during the launch, which is one to 5 seconds of the 10 minute flight time, but affects the launch height. For all the rest of the flight it is low speed flight, with relatively low parasitic drag effects from the linkages.

Then there is the most important argument and something I feel constantly. I love optimising design, it suits my engineering minded head, but experience proves that 99% of winning a competition flight is flying in the good air, which is something I still get wrong :-D Perhaps I should move to New Zealand and beg Joe Wurts for some pointers as I have a lot to learn.

Now, for the install, the foam wing offers the stiffness solution by its own design, which is very helpful. Molded wings require mating the servo to both top and bottom surfaces to resist wing skin flex which can cause flutter. As you say, this flexing is unlikely to be a problem with foam core wings - bonus!

For impact loading, this is quite large during a good dork. Especially if I were be stupid enough to leave my flaps out, which is rare, but can happen. For this reason some pilots even install a '3rd bearing' to absorb 50% of the shock load and save the servo bearings / shaft. I am going for MKS6125Mini's on the flaps - as they are the nicest servo's I have ever owned. For the ailerons it is not such an issue as they are never deployed during landing and the hinge absorbs the impact mostly. I am going for ATX809's on the ailerons.

About linkage geometry. I agree that making the servo arm as short as possble and maximising servo travel is the way to go. However, this also bids in the favour of the linkage running from bottom to top surface, as it does not need to clear the bottom wing skin anymore.

About servo strength vs weight. Light is great, but nothing sucks more than doing a repair on a contest field fixing servo gears, linkages and messing about with epoxy in the sun with the grass and dust flying around... I've been there... So a little margin goes a long way.

About the plugs, I happen to have the same deans plugs for the wing servo's to the fuse (4 pin), which are nice. These will be compatible with the standard Molded Supra wiring harness, so I can switch wings / fuses. I dont have any 3 pin ones for the wings. What do you guys think about using normal gold plated servo plugs for the wing tips?


But like I said, Will is doing a very neat job and is making me doubt my own convictions. Unfortunately I am finishing off another glider install before I get started on this one, so I am letting my mind wonder - I hearby apologise for my overthinking... it is what I do best :-)

OK, my epoxy is geting tacky, so back to my wingtip... (I am installing some servo's in my Corado - the predecessor of the Zephyr with a SD7037 airfoil). It went down very hard after someone turned on their transmitter on my frequency during a F3J launch at a competition nearly 10 years ago. Thank God for 2.4GHz !!!!!

Keep up the good work!

Daan
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Old Jan 18, 2012, 08:29 PM
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Mounting servos like in a Supra...

Hi Daan,

The linkage on a Supra and on many molded ships do work off the top of the hinge line...originating from the bottom skin of the wing.

Its a neat install and works 'pretty well'. However its not a good idea for bagged wings..and really not so good for molded long term.

First a molded wing has stiffer skins....a bagged wing relies on the bond between the skin and the foam and its not much of a connection as the foam doesn't have that good of an abililty to avoid sheer.

The next thing about mounting servos like in a Supra moldy is the bagged wing hinge relies on the bond around it. Delamination is a problem even on the molded wings at the hingeline.

The molded linkage set up of the Supra and others puts a tremendous amount of load on the hinge area at certain points in its travel.

The standard linkage I mentioned, coming out the bottom of the skin to the longer surface horn puts almost no load on the hinge line area. The longer moment arm of the surface horn makes holding position that much better and easier on the servo and hinge materail.

Vibrations from micro flutter are resisted far easier than with the molded linkage mechanics (almost no lever arm advantage).

The "outy" system used on bagged ship provides the best over all mechanical advantage for F3J and TD task flying planes.

...and for task landing abuse. Almost all of the abuse loads are handled by the linkage and servo, instead of the hinge.

As far as aerodynamic drag enters the equation...find a thermal, keep your sailplane in it for the 10 minutes, then put the nose of your model on the spot before the horn blows. If you are relying on some mechanical advantage of an airframe, or balance or mix or weight to get the time and landing points for you... your chances for winning are unlikely at best.

Gordy
Yes I have flown F3J :-)
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Old Jan 18, 2012, 08:46 PM
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Greensburg, PA
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Good Stuff.

I might add... I've only done top drive once. What I didn't like is the non-linear way they deploy the flaps. Its a whole bunch in the begining and then less and less as they extend out-to push down.

RDS is an option if you want to take your servos out after every flight and enjoy lots of slop
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Old Jan 18, 2012, 08:48 PM
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4 Pin

The other side of the wing is almost complete. Notice one is red the other is black and the male, female ends are flipped.

I also like this setup because if a power or ground wire comes loose you still have the other side of the wing working. Along with the big flipper on the tail, you should make it back home.
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Old Jan 19, 2012, 03:38 AM
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Allrighty guys, I think you have pushed me over the edge, and will probably go bottom actuated. I think the delamination issue due to forces on the hingeline is an important one. However I can't see in my head which way round it works and whether top or bottom actuated is better for the bottom hinged flap, which is most important due to the forces, I agree.

One small benefit to top actuated flaps is that you can add the flap thickness to the lever arm and end up with a shorter flap horn.

Once I get started, I will post here and I will stop hogging your build bandwidth :-)
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Old Jan 19, 2012, 10:22 AM
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When everything is said and done...you fly F3J

And that means all the concern about top or bottom, hinge line defense etc is often voided on the first launch mishap, mid air or attempt to beat the clock to the landing spot.

As with over all weight, dif settings, cool cambers, super scientific airfoils, and tremendous launch height technique obsession....those are all distractions to the main...and that is to focus more of your study and attention on finding 10 minutes of air, developing the patience to stay in it and to make the spot before the bell.

Foam wings don't last all that long, but neither do molded, not so much because of their design but because of their use.

That being said, looking out for things like linkage abuse to hinge is a really good thing to consider when installing gear.

Molded ships focus mostly on looks, and drag for the most part, there are some that have really done their home work on linkage design, you can tell by just wiggling them whille the servos are off.

As far as top or bottom horns, I think that bottom takes more of the load off the hinge than a top linkage...because a lot of the force during landing is pull and up. the bottom link arm provides more of a lever arm against pull...pull that wants to delam the hinge from the surface leading edge.

You?
Gordy
PS keep hogging the bandwidth, its good brain food!
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Old Jan 19, 2012, 01:18 PM
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Greensburg, PA
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Switch and Voltage regulator.

I found this gem on a thread somewhere on here. Its a regulator, and magnetic failsafe switch.

Here are the instructions: http://www.hkm-models.com/images/Anl...ro_2009_EN.pdf

They can be found here:http://www.hkm-models.com/Emcotec%20Switches.html

I'm going to be using a 2100mah duralight Li-ion Battery.
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Old Jan 20, 2012, 06:25 AM
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ok, more brainfood:

Well, it is the winter and it is freezing out here, so that is my excuse to let my mind wonder. Well, we both agree that although this is a great exercise in logic and optimisation the key is finding that elusive thermal during hard conditions. During easy conditions anything will go up and it is all about launch and landing practice, during tricky conditions it is all about your strategy and flight choices and only during those flat dead-air conditions does your equipment truly matter, and still only second to your piloting skills.

It is for those difficult morning and evening rounds that I am putting together Will’s beautiful enlarged Supra wing; so I am keen to optimise, or at least have considered my options. This thing is HUGE and incredibly light, I simply love it. Having a glider that flies itself is paramount in these rounds (it reduces stick inputs).

About the loads on delamination, I did a quick sketch on a piece of paper looking at pivot points and the shear forces on both the hinge and the linkage. Both top and bottom driven flap setups actually have the same situation:
  • Aerodynamic loading (flap deployed during approach) wants to pull the hinge down, off the foam). In the bottom actuated setup this force looks like it will be lower.
  • Impact loading if the flaps are still out during a dork tries to pull the flap off the wing directly rearwards – pulling on the Kevlar, so no issues there at all for both setups.

So there’s not much in it, but your setup wins one point
So far during completion I have been able to avoid mid-air’s by staying out of the myriad of gliders. Also during approach I avoid circling and milling around. During launch, I setup my towhook a little bit conservative, as the last thing you want is breaking out and colliding. But… you can never control what the others do (touch wood) – and I have had to dodge the odd bullet.

Will, I love your servo and linkage setup. Simple, clean and will result in pain-free operation. Thanks for posting the pictures. So no Kevlar reinforcement on the servo wells? I guess that for the flaps the spar does most of the work and for the tips, you chose the location where the wing joiners still carry most of the loads, so reinforcement is probably not really necessary…

One thing I would add for bottom linkages is putting something over them to protect the horns from catching something whilst sliding on the ground. I have broken out a servo this way.
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Old Jan 21, 2012, 12:14 PM
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Greensburg, PA
Joined Feb 2008
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Polish them up!

New info posted above.

Your wing might need some more shine. Sometimes the Frekote wants to stay on the wing, looks almost milky. A paper towel will work just fine, you don't need a buffer
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Old Jan 21, 2012, 01:17 PM
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Funny you propose this solution.

I have been looking far and wide for regulators because they are a critical component. For now I have decided to stay with high discharge NiMh's. However, my conclusion was that the Emcotec regulators were the best. The failsafe switch is nice (just keep a spare magnet with you on the field). They can deliver high amps and have good cooling built in. Also it is a linear regultor, which is much more appropriate for 2s LeFE and have no noise generation. They are also designed using FMECA to reduce failure modes and have a double output cable to the receiver. All in all the perfect solution, good choice!



Quote:
Originally Posted by heliwill10 View Post
I found this gem on a thread somewhere on here. Its a regulator, and magnetic failsafe switch.

Here are the instructions: http://www.hkm-models.com/images/Anl...ro_2009_EN.pdf

They can be found here:http://www.hkm-models.com/Emcotec%20Switches.html

I'm going to be using a 2100mah duralight Li-ion Battery.
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Old Jan 22, 2012, 10:42 PM
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Greensburg, PA
Joined Feb 2008
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Finishing Touches.

Just the final bits!!

I still have to build myself some tailfeathers...

All kevlar rudder AND a Disser stab! It will be my first time stringing up the carbon, still working on the jig. The stab will also have a small strip of uni laminate for a spar and end grain for the mount. Should be light and strong with limited twist.

Here is where I got the lazer tape: http://www.northeastbandsupply.com/tapes.htm
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Old Jan 23, 2012, 02:52 PM
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Disser

On my way to making the stab! I wanted to post a picture of my first fabric attempt. Its a little uneven in places, next time will be better
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