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FeiJi's blog
Posted by FeiJi | Nov 01, 2013 @ 08:13 AM | 4,366 Views
Just doing some flying around. Finally resolved why takeoffs and slow flying would stall. I had rounded the leading edge of the forward half of the wing with wooden dowls but left the rear halfs flat - this is a 9mm epp flatplate. On takeoff the delta would roll left then right terribly until I got some speed up. So I rounded the rear half leading edges with dowls and problem went away. Now this is a really fun and easy to fly flatplate.
Also I cut the elevons down in an attempt to solve the problem but it wasn't due to too large elevons and now wish I hadn't cut them down.
I plan to make a slightly larger X45 like this but with an airfoil.

X45 EPP Scratchbuilt Delta Wing flight (3 min 29 sec)

Posted by FeiJi | Oct 19, 2013 @ 10:49 PM | 6,498 Views
AUW 22.9 ounces, Wing Area 511 square inches. WCL 3.4 and is pretty much a glider.


Ugly Plank (3 min 2 sec)

Posted by FeiJi | Oct 15, 2013 @ 07:47 PM | 4,703 Views
Decided to build another x45 type delta. Laminated 9mm epp foam flat plate with a few barbecue spits to reinforce - very stiff wing. Using a small brushed motor because I accidentally ordered a few brushed ESCs. AUW 270grams with 500 3s lipo. Wingspan is 680 mm. WCL is about 3.4 so hopefully the little motor will push it around a bit. Later I will install 2208 2600kv motor and see how fast I can go. Just have to install control rods- ran out of spokes. Took about two hours to build

Update Oct 18: little brushed motor barely pushed it around. So have mounted 1800kv motor w 7x5 prop. AUW 320grams 284 sq inches, WCL 4.3, 1100mah 3s lipo. Waiting for football field to clear from soldier trainees to fly.

Flew it, a little fast and difficult to launch as wings are warped down a bit.
Have reshaped wings so will see if it curse stall on slow landing.
Update Oct 27: Still twitchy especially on takeoff. These elevons are huge so trimmed some off and will move to lower hole on servo arm. Fun to fly though but this is my last flat plate - something just seems different about flying a real airfoil and the flatplate just doesnt seem like an airfoil.
Posted by FeiJi | Oct 11, 2013 @ 04:25 AM | 4,875 Views
Added these plug in wing extensions to my 1 meter plank to make it 1.5 meters. They plug inside the ends of the 1 meter wing and then are held on by tape. Feel very sturdy and little flex. Haven't tried flying yet. Made from 9 mm epp, then laminated then added couple barbeque spit spars. Each extension weights 50 grams.
Wanted to get more soaring time but still be able to fly 1 meter wing aerobatically without them. Also will allow me to test out different wing tips
AUW is 640 grams now with little 2208 1800kv motor - should still fly.
Update Oct 12: It flies. I was afraid it would be too heavy for the motor but in fact I had to back off the throttle to keep it under control. Tons of lift and in poor conditions, in the lee of a building, on a tennis court and in gusty wind. It also still banks sharply, I was afraid the now inboard elevons wouldn't work so well but they do. Just wanted to know if it would lift off. Sunday is supposed to be fair weather.
Update Oct 13: Took it out today and floated it around way up high to take some video of the school. Real floater and can be flown very slow.
Update Oct 18: Trimmed extensions a little to be more aerodynamic. Wing area = 511 sq. in., AUW 22.2 ounces for WCL 3.3. It really qualifies as a glider.
Posted by FeiJi | Oct 01, 2013 @ 07:48 PM | 4,771 Views
Replaced tail with a bit bigger and more aerodynamic one. Rolls are a bit better after I fiddled with elevons. Flew this morning for 10.5 minutes on 1100 mah battery. Just floating around with the birds at about 30% throttle. This wing is my favorite to fly now as it is so bird like. The only real weak point is my motor mount. Just a bit of plywood hotglued to epp. Tends to break on landing because the prop is still windmilling. I have some prop savers ordered but still need to build stronger mount. New Hobbit installment is due in Dec - looking forward to it.

Added piece to top of fuselage and it is stronger and looks better I think.
Added tail piece so have a few more square centimeters of wing area.

Am going to build a new plank similar to this one but use rectangular fuselage construction, thicker wing and bring top wing section all the way to the trailing edge so will be smoother airfoil without any trimming necessary. Also thought about building some wing tip extensions that plug into the end of the current wing tips to get some more soaring capability.

Update: I messed up putting a flat surface on the top of the fuselage that slopes up to the top of the wing - it is acting as a control surface and making the plane fly strangely and seemingly with more drag. Will take it back off and mount two panels at 90% angle to each other and see if that works.

Update Oct 5: rounded the flat panel on the fuselage and flew 3 flights. One was for 12 minutes on an 1100mah lipo. Flies beautifully now. Absolute joy to fly this wing.
The hollow wings are open at the ends so need to tape them up but they make a cool sound when they are open. The diagonal stripe on the tail makes it easier to see orientation of wing when it is far away.

EPP Foam Ugly Plank Wing (3 min 50 sec)

Posted by FeiJi | Sep 28, 2013 @ 04:31 AM | 4,416 Views
First flight of my 9mm laminated EPP foam plank. Great carves (banks I guess), nice loops, not very good rolls (that could just be me though).. Great fun to fly. Seems pretty stall proof. Have to make a better motor mount though.
Going to make a better tail.
Sound on video breaks up a bit - I am using a cheap usb mic adapter and the driver doesn't play well with my video editing software.

Update: found out it rolls to right great but not left. Right elevon doesn't have as much throw as left so increased it a bit. Will see how it goes now.
Fixed the problem, not enough up elevon. Rolls great - fast and axial.
Ugly Plank Maiden (2 min 35 sec)

Posted by FeiJi | Sep 27, 2013 @ 03:31 AM | 4,127 Views
1 meter 9mm epp laminated foam. Wing has fiberglass fishing pole spars and is unbendable. AUW with lipo is 520 grams. Could have saved another ounce if I skipped the spars which I really didn't need. 1800kv motor with 1100mah lipo. This one is a half pound lighter than my first plank which flies really well. Will maiden in day or two. Wing is really ugly as I trimmed with knife but didn't have any sandpaper. Wing held on to fuselage with couple of zip ties. About 5 hours to build.
Did I mention that it is ugly.
Posted by FeiJi | Sep 17, 2013 @ 04:56 PM | 4,262 Views
I pulled out my Plank wing, replaced 1800kv motor with 2217 2700kv motor and 1100mah battery with 1800mah. Flew right out of my hand, very fast and smooth then started doing loops and rolls, went into death spiral and boom. Surprisingly, the wings just separated from the fuse, the motor shaft got pushed back a bit and the casing of the rx came apart but it all fits back together. Couldn't find prop or prop adapter. Crashed not far from an automobile so am thinking I need to test this out on the island where there is nothing to hit. Wow, flying it felt so smooth and effortless - and it looks cool in the air. I thought as I was walking to pick up the pieces that there wouldn't be anything left but epp just bounces. Have to rebuild this one.

Figured out why I spiraled in, left screw out of servo arm and right elevon jammed all the way up when I was slamming it around. - so my theory goes. Bent motor shaft a bit, motor probably wont last long as I will fly it anyway. Don't have any straight shafts.

Took about an hour to get plank back together. Ready to fly tomorrow.
Posted by FeiJi | Sep 05, 2013 @ 06:01 PM | 4,242 Views
My one trick pony solution.
RC Foam WIng with Elevating Motor Mount (0 min 57 sec)


Since my first flights I have had a few more and now takeoff is smoother and when I transition the motor mount to normal position and add down elevons it goes nicely into level flight. If I transition the mount without down elevon the plane will nose up and harrier until I add down elevon. The original flights were tail heavy so added more nose weight. Landings are a breeze as the wing is pretty stall proof.
Posted by FeiJi | Aug 06, 2013 @ 08:08 AM | 4,625 Views
Here is a short video of my epp finless wing prop clawing its way into the wind.
The takeoff was abysmal. The final pass is what I guess drag sounds like.
Update: I woke up this morning and just realized what is probably making the whirring noise as the wing passes downwind: I have an exposed carbon spar holding the back of the wing together - except that it is broken on one end and free to vibrate, and the wing is hollow to boot so it is probably acting like a stringed instrument. Maybe.
That might be an interesting sound effect to pursue. Like throwing a guitar out of a 20 story window.

40 inch EPP Wing in the Wind (1 min 23 sec)

Posted by FeiJi | Jul 08, 2013 @ 06:34 PM | 3,934 Views
Here is a little trainer I made for someone who has never touched a transmitter. Kind of fun.
Scratchbuilt RC Flight Trainer for Copter or Airplane (10 min 40 sec)

Posted by FeiJi | Jul 05, 2013 @ 05:20 PM | 3,579 Views
Flew at 5:00am with slight breeze - 1800mah 3s lipo and got 15.5 minute flight on my 40" scratchbuilt epp wing. Guess that is my limit as my arm is sore from holding the radio and just tired of looking up that long but happy - longest flight to date.

From 12 sheets of epp foam I now have a fast wing, a putzing about aerobatic delta wing, a 40" wing, a P51, a couple of "normal flying" 30 inch wings, a forward swept wing, a plank wing, and a few failure wings.

Sitting at about 44 hours total air time now for about two years flying. 6 more hours and I could qualify for my private pilot certificate.
Posted by FeiJi | Jun 22, 2013 @ 08:09 AM | 3,451 Views
Finally got my 40" wing flying well. A pretty good glider at around 5 WCL. Got 12 minute flight in a little wind on 1800mah 3s lipo, 1800kv motor and 7*5 prop. Moves pretty fast full throttle and floats around on 30%. Want to try 2700kv motor next.
Boneyard #5. Laminated 9mm epp foam. Had to move motor forward and still has 2 ounces of weight in nose. Should just move up to 2200mah battery.
Shouldn't have made the weird prop cutouts though, should have rounded them. Put a fiber rod to tie back ends together.
Posted by FeiJi | Jun 15, 2013 @ 09:10 PM | 4,001 Views
Here is a video showing some of my experiments with using two propellers on a single motor. My simple thrust meter uses a single prop to get about 750 grams of thrust, dual props at 0 degrees angle from each other resulted in 850 grams and dual props at 90 degrees from each other resulted in 900 grams of thrust.

Of course, using dual props results in greater current draw. But just throttled back and bit and got same flight times as single prop at full power, better flying stability in calm and windy conditions and more thrust on tap if I wanted it.

Could use a bigger prop or multiblade prop but was just interested in seeing how two propellers would play out. Now when I fly my P51 foamy I just leave both props on as there seems to be no downside.

I would like to try this on my wings but my current 3mm prop adapters are too short for two props - my P51 having a 4mm extra long adapter which had enough room for two props.

Since my P51 is a belly lander, I had to go with 0 degrees separation of the props (I tried 10 degrees separation and it broke the props on landing). I plan to get my P51 that has landing gear flying again and will try the 90 degrees separation.

RC Dual Propeller Experiment (3 min 13 sec)

Posted by FeiJi | Jun 05, 2013 @ 04:51 PM | 3,867 Views
Was flying my p51 this morning (at 4:00am) when caught video picture of mosquito and my p51. The mosquitos are really big here.

Got to change the date on my camera.
Posted by FeiJi | Jun 04, 2013 @ 08:11 PM | 3,061 Views
Flying around with the pigeons a bit. Wing flies very stable, this is now my favorite plane cause it's pretty much indestructible, won't stall, you can hand catch it, and the superman logo looks good against a blue sky.

Got my P51 flying again, new horizontal stabilizer with balsa elevator makes a lot of difference.

Just past 40 hours total air time since I started flying.

X47A Foam Delta (0 min 0 sec)

Posted by FeiJi | May 29, 2013 @ 12:49 AM | 4,690 Views
Decided to resurrect my x47a delta, and move the motor forward yet again. Flies fun now. Video just shows low level putzing around but will loop and roll nicely. Will try a little faster motor but it is nice to have a nice slow wing to play around with and not be afraid of hitting anyone. I guess this is my first real parkflyer.

Laminated 9mm epp with copyshop laminate. AUW about 450 grams. 750mm ws,
1500kv motor, 1100mAh 3s lipo, 7*6 prop, bicycle spoke control rods - heavy but never bend.
Getting 8 to 9 minute flights.

Stallproof - as video shows at end, just cut power, pull up elevator and it just floats down. Added tail because flying without it sometimes results in flat spin from rolling.

Should name it Manta as it looks more like one than an x47a - but I like the x47a shape. Would be nice to add superman logo to bottom.

X47A EPP Delta (0 min 0 sec)

Posted by FeiJi | May 17, 2013 @ 04:07 AM | 5,840 Views
Finally got my P51 flying again - it was just getting so heavy I had to move up to a 2217 950kv motor w 9" prop. Now lots of power and still get 7+ minute flights on 1800mAh battery. The motor mount is held on with hair bungees so when I have a hard landing the motor just gets pushed out of the way - less damage - as I hit stuff frequently, trees, goal posts and nets and the ground occasionally. The wing is also held on with chopstick/acrylic/bungee and is pretty damage proof. I use a chopstick through the fuselage, acrylic standoffs and hair bungees. Not pretty, but effective.
The plane is getting ridiculously heavy for a foam plane, AUW 750 grams, but it flies nicely and looks great in the air.
I am just going to have to sling it faster for takeoff.

P51 Scratchbuilt EPP with bungee motor mount (6 min 28 sec)

Posted by FeiJi | May 10, 2013 @ 02:46 AM | 2,885 Views
Just another flight of my plank, this is becoming my favorite wing as it flies so smoothly and gracefully but has nice sharp turns. Loops and rolls are nothing to brag about. Running about 80 watts per pound.

Motor is mounted with hair bungees around a chop stick embedded through the side of the fuselage. Holds motor surprisingly well and a hard landing just pushes the motor mount up but doesn't break anything.


BoneYard Plank Flight 2 (4 min 45 sec)

Posted by FeiJi | May 04, 2013 @ 09:01 AM | 2,936 Views
At least I know which one is mine.