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-   -   HK Ask 21 spoilers installation (http://www.Wattflyer.com/forums/showthread.php?t=74423)

solentlife 09-02-2014 04:40 PM

HK Ask 21 spoilers installation
 
The HK Ask21 is a real floater and rel;uctant to land ... she just floats on by !!!

So
I decided it was time to install some HK Spoilers ... these are the scissor type with linear push / pull rod.

Servos 4.5gr Turnigy's..... slots cut for spoilers :

http://i6.photobucket.com/albums/y24...pse0d1db3a.jpg

http://i6.photobucket.com/albums/y24...ps66e0d08e.jpg

I did have to lift and move the decals back so I could install the spoilers immediately behind the main metal tubes in wings ... as near CoG as possible.

Simply hot glued in and taped up the 'cutouts' ...

http://i6.photobucket.com/albums/y24...ps34b1ab32.jpg

Rigged and closed :

http://i6.photobucket.com/albums/y24...psd60af451.jpg

http://i6.photobucket.com/albums/y24...psc93e424a.jpg

Popped up via the Gear switch ...

http://i6.photobucket.com/albums/y24...ps4ae242b2.jpg

http://i6.photobucket.com/albums/y24...psf7ed9ce7.jpg

They are adjustable to pop up a little .. medium as I set or a full 40mm ...

Just one niggle - all was fine then once finished - one servo just lags a touch in reaching set open position ...

If I was installing again - I would try to use LINEAR servo mechanism - not rotary.

Will report further on these ...

Nigel

kyleservicetech 09-02-2014 06:18 PM

Quote:

Originally Posted by solentlife (Post 956445)
The HK Ask21 is a real floater and rel;uctant to land ... she just floats on by !!!

So
I decided it was time to install some HK Spoilers ... these are the scissor type with linear push / pull rod.

Servos 4.5gr Turnigy's..... slots cut for spoilers :


Nigel

Hi Nigel

If this is your first run at spoilers, just a note. DO NOT hit the spoilers when the model is 10 feet off the ground! Your model might drop like a rock. (Don't ask)

What I did was, at about 50 or 100 feet high, hit the spoilers to set up a descent rate. Use the spoiler command like a "Reverse throttle" to modulate your descent rate as required.

JetPlaneFlyer 09-02-2014 08:13 PM

They can also effect the trim a fair bit so once you try them out you might want to mix some elevator in.


PS.. too late now but usually the spoilers are positioned more outboard on the wing so that the wake they create doesn't mask the horizontal stabilizer. I appreciate that wing thickness might have prevented them going further out.

Turbojoe 09-02-2014 08:37 PM

Watching with interest as I have a few powered planes that are very clean and hate to slow down. Been wanting to try spoilers mainly to have just one more gadget to play with. ;)

Joe

RV Winkle 09-02-2014 08:51 PM

Thanks Nigel
Will be putting spoilers in my Sailaire. The photos helped me see what folks are talking about

kyleservicetech 09-02-2014 09:38 PM

Quote:

Originally Posted by RV Winkle (Post 956457)
Thanks Nigel
Will be putting spoilers in my Sailaire. The photos helped me see what folks are talking about

Yikes
A giant scale Sailaire WITHOUT spoilers? That must be a real SOB to land anywhere close to the pit area :eek:

For the other wattflyer readers, you just can't yank a giant Sailaire around 10 feet off the ground for another approach to the landing area.

I installed spoilers on my two giant scale 10 foot wingspan Craftaire Viking sailplanes. Those spoilers made it easy to land within a few dozen feet of where I was standing. Without them, it was a :censor:. I had those Vikings in the mid 1980's, and sold them in the mid 1990's.

fhhuber 09-02-2014 10:37 PM

Power planes that hate to slow down... first thing that comes to mind it excess prop pitch.

Calculate pitch (inches) X rpm (max throttle holding the tail on the ground) / 1000 = ? (mph)
This gives a very good estimate of how fast the prop WANTS to pull the airplane. If its about 1.2 X actual level flight @ max throttle you have a good prop choice for most purposes. If its more than 1.5 X actual level flight max then you have the wrong prop. Pylon racers can approach calculated pitch speed = actual sustained level flight speed.

Second thing you can play with is reflexing the ailerons upward as "spoilerons" This often lets you hold a more nose-up attitude without dropping a wing, presenting the bottom of the wing as a big air brake.

Wagging the rudder helps bleed speed but you can cause a snap into a spin if you get too aggressive about it.

Lots of tricks to get rid of unwanted airspeed.

JetPlaneFlyer 09-02-2014 11:16 PM

Forward slip is a good one to bleed off airspeed... Again you need to be careful not to overdo it and cause a snap.

Here's an extreme example:
YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.

solentlife 09-15-2014 01:48 PM

Well I gained height ... flipped the switch and she bled height with a nose down pitch that was without any roll or nasty vices. The decision now is whether to mix in elevator with spoilers to reduce the nose down or do it by stick.

I didn't get chance to use for landing as I mistakenly fitted a 'used lipo' instead of a charged one ! Had an unexpected 'distant' landing !

I only set the blades to raise about 35% of full ... so amazed at the effect.

Recc'd ? Yes. But I would advise using linear servos to reduce installation height.

Once I'm back flying - I will try get a video of them in action.

Nigel

RV Winkle 09-15-2014 03:54 PM

looking forward to that video


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