PAU (BME) Mini Yak

[Oilsands]

Not sure if this build was posted already, I did do a search and nothing came up.
I bought a Mini Yak 54 from PAU in November 2008 to fly over the winter and possible a few times in the summer.

Here is what I used:
E-flite Park 480 BL Outrunner 1020 Kv
Castle creations Thunderbird 36A Brushless ESC
Flight power 2170mAh 11.1v Li-Po battery
Futaba R617FS 2.4GHz FAAST
Hitec HS-55S servo's all around
APC 12x6 electric prop

It looks pretty strong and built well. I added some more CA to the area around the main landing gear and changed the stock wheels to 2" due to flying off a grass runway in the summer, this was due to suggestions in posts from another site.

It came packaged very well and everything was in great shape. Part of the balsa warped in the hatch but was easlier repaired with a little CA and held in place. The covering was pretty good but did need a little bit of heat to smooth out. The decals were not bad, but were starting to get a little stiff around the edges (still useable though). It came with a great manual that was easy to follow. The CG that I came out with was a little forward of the suggested (no more than 1/4").

[Oilsands]

Well the maiden went well (first electric other than a foamie). Hand lanch due to lots of snow on the ground and a harrier landing. The CG is too forward at 3.25" (recomended is 3.5"). Ended up pulling the landing gear out from a hard harrier landing (more of an oops), but continued to fly and land in the deep snow (got to get the harrier landings down). Due to the deep freeze temps, had time to repair the landing gear mount and make some improvements to the color scheme (had a hard time keeping orientation when flying below the tree line (spruce). I ened up cutting the front part of the engine mount off and mounted to the back one (still had the thrusts built in), this brought the CG to the recommend measurement of 3.5". Enjoying flying this plane. The battery is a little big as well, could go with a 1500 mAh which will cut down on the weight as well (with the 2170 it has lots of flying time). Right now it comes in at 31 oz with everything installed including the battery.
One picture shows the motor mounted on the front mount and the second after the modification (mounted on the rear). Just a quick note, when I moved the motor back, I also moved the cowl back.
Waiting for some warmer weather to get it out again. It should be better when inverted due to the adjustment of the CG.

[sweetpea]

I've got one of these also. I'm thinking of going with the Gearbox for the motor. I'll post the info when I find it in my bookmarks.

[Flyfalcons]

Looks nice, Anthony! I have one of these to build after I finish the 50cc Sukhoi. This should be a fun "in-between" plane at the field between my foamies and my gassers. I was planning on putting a Hyperion 3019/10 outrunner motor on this plane but I think that may be bigger and heavier than necessary. If I do go with a different motor I'll definitely be getting an outrunner. How was the performance on the Park 480? I was thinking about trying a Hacker A20-20L with 1200 3S pack to keep weight down to a bare minimum. That motor has a ton of power on a 15 ounce foamy so it may work on this Yak and help keep the weight down.

[Oilsands]

It had tons of power with the 480. I would not go any bigger or heavier. If I recall correctly, it should hover under 1/2 throttle (I can't hover yet but when lightly holding it pulls up at a little under 1/2 throttle) but will double check tomorrow. I would also go with a lighter battery maybe around a 1500 or 1800 mAh (which should cut the weight down by at least 1 oz) and it will still provide lots of flying time.

[Oilsands]

Thanks for the complement Ryan!
I double checked the amount of throttle needed to take up the weight of the plane (hover) and it was 6 clicks above 1/2. Also have some numbers from the Watt meter. At 0 throttle it had 12.42 volts, 0.18 A, 2W, 0.02 WH. At full it went to 10.5 V, 26.5 A, 277 W, 6.77 WH, .700 AH.
So far I have enjoyed the 5 or 6 flights with it. Would have like to fly it more, but the cold weather set in and has not let up yet. It has been -30 to -45 degree C (-22 to -49 degree F) for over a month and that is not including the wind chill. I have 2 other new planes to work on anyways (PAU's 37% Ultimate and 36% Edge 540).

[sweetpea]

Here's the package I was talking about for the PAU Yak

http://e-flightline.com/

Himax 2025-5300
Castle Creation Phoenix 25
Cobri 20
Color -Red
Pinion size 9T
Spur Gear Size: 68T

$143.99

Here's a video

http://e-flightline.com/movies/BME%20mini%20YAK%20... Right click here to save the video " title="http://e-flightline.com/movies/BME%20mini%20YAK%20..." target="_blank">http://e-flightline.com/movies/BME%20mini%20YAK%20...

://e-flightline.com/movies/BME%20mini%20YAK%203-20.wmv

[Oilsands]

Any idea on what size battery they used?

[sweetpea]

3s Tanic 1760 20C

I plan to use my Rhino 3S 1500 20c packs.

[Oilsands]

I too am looking at switching to a lighter pack (from the Flight Power 2170 11.1V to the Flight Power 1500 11.1 V), cheaper too. I don't need 25 min flight times. Never flew till the pack were low, but after a 15 min flight still had way over half power left on the batteries (probally enough for another 15 min flight).

[Flyfalcons]

Anthony, because climb rate is based on excess power above what's needed to keep the plane flying, I'm willing to bet a drop of just one ounce would make for a significant improvement in climb. I need to hook up my A20-20L to the wattmeter again to see how many watts it's pulling. Looks like 250 or so should give this plane unlimited vertical?

[3D1]

I think the perfect motor would be the hacker A30- 28S. I can only get 205 watts out of my 20-20l.

[Oilsands]

I too think that less weight would mean a quicker climb, not that it has any problem now. I would like to reduce the weight to have it float better when flying (not that it is a rock). Just think it would fly better if it was a little lighter than what I have it at now. If I go to a 1500 mAh battery that should drop the weight down by about 2 oz, I think that will make a better flying plane.

[Oilsands]

Just checked out the W and Amp required to hover (over come the weight of the plane) and it came out to 140 W and 14.3 A, at least with the set up I have.
Let me know if I am correct to think that if I drop 2 oz off in weight, then it should take less W and A to over come the weight of the plane. Thus I would be drawing less Ah than I am now.

[Flyfalcons]

It would definitely take less power (watts) to hover if the plane weighs less. If you can draw the same watts (same amps without any voltage drop) by going to a smaller battery then the plane would benefit both in wing loading and power loading. Total flight time would suffer with a smaller capacity pack but if you're already flying 15 minutes with plenty of reserve then I see no disadvantage to trying a smaller pack.