TT2

My Feedback: (13)

I bought the GSP Katana to fill the gap for a somewhat large, somewhat scale, 'every day' 3D-capable aerobat. After considering many engine choices I ended up using a used OS 1.60fx with a Bisson Pitts muffler, Perry VP30 pump, Mezjlik 18x6 prop. After assembly and test flying I'm convinced that this is a near-perfect combination. The first two flights of this plane were nothing short of amazing...I have never seen a plane of this size that flew so well.

During assembly I changed some things around:

1. I replaced the aluminum anti-rotation pins in the tail with a CF tube that extends from one stab half, through the fuse, then into the other stab half. A bit lighter and stronger.

2. I pinned the firewall and ran thin CA around every joint I could get to from the engine box to the wing tube.

3. Instead of adding washers to achieve the proper thrust angles, I mounted the OS 160fx squarely in the mount then using a belt sander I sanded the rear beams of the engine mounts until the proper angles were achieved. The cowl will completely clear the OS 160fx...only holes for the glow ignitor and needles are required.

4. I enlarged the servo hole in the side of the engine box so I could stuff a micro servo behind the firewall for the throttle. This provides a 'straight-shot' to the throttle with no bends in the pushrod. What more could you ask for? I covered the hole with clear Ultracote.

5. That heavy (8.9 oz) fiberglass landing gear had to go so I made some carbon fiber gear (around 5 oz) for this plane (available soon at www.fiber-lite.com). I have never used fiberglass gear, but I recently witnessed a flying buddy's Creek Staudacher shatter it's fiberglass gear on the second landing...not much of an impact either...I don't think that the GSP Katana's gear would hold up any better.

6. This plane leaves alot to the imagination when it comes to installing the fuel tank, receiver and receiver pack. I wanted my tank near the CG and didn't feel like using the supplied tank so I used a Hayes (my favorite) 16 oz. For the fuel tank I glued a couple 1/8" x 3/4" ply beams across the inner-most topside wing tube brackets, then padded and wrapped the tank (using vet-wrap), and zip-tied the tank firmly around the wing tube. Seems to be VERY solid. The receiver was padded and secured to the back of the wing tube bracket with velcro. The battery pack was padded and secured to the front of the wing tube bracket, but after test-flying I will move it to the back to shift the CG further aft.

7. I didn't feel like fooling around with the stock linkage and horns so I used #332 Robart 1" ball link horns for the ailerons and elevators, 'home brew' carbon fiber 4-40 pushrods and dubro 4-40 ball links attached to dubro HD servo arms (I'm NOT a big fan of these, but I wanted to check the geometry before ordering aluminum ones from SWB). On the rudder I used the same types of pushrods. I made a much larger (3 5/16" hole to hole) carbon fiber servo horn to enable full travel of the rudder while maintaining the 'parallelogram' linkage geometry. At the rudder I used parts from the #886 Dubro HD control horn system and some 8-32 threaded rod going all the way through. If you look closely at the pictures you may notice that the screw plates for the aileron and elevator horns aren't visible on the tops of the surfaces...that's because they aren't there! I drilled 1/8" holes at the screw locations, soaked the wood with thin CA, redrilled, installed lengths of inner nyrod and CAd them in place. I find that this is easier to do than trying to get the screws to match up to the screw plate on the opposite side of the horn, plus it looks a helluva lot cleaner and is super rigid and strong. Anyway, the horns and linkage are probably overoverkill but to me it's worth the added expense (around $25-$30) for the amount of peace-of-mind it provides.

8. I used a 10-22 lb Sullivan tailwheel bracket...the stock tailwheel looks like someone's idea of a practical joke.

9. I added 18g of lead to the left wingtip to correct the lateral imbalance.

10. I added a homemade fiberglass tube down the bottom of the fuselage interior to route the elevator and rudder servo leads through. I routed the antenna wire along the top interior of the fuselage (far away from the servo leads) all the way back to under the rudder servo.

Still reading this? Good. For radio gear I used (2) Hitec HS-5925 digitals for the ailerons, (3) Futaba S9402 for the elevators and rudder, and a Hitec HS-81 micro for the throttle. Currently installed is an old Hitec Supreme 8 ch (50.800Mhz) and a Nimh 1650mah 5-cell pack. Yes, I have more money in the servos than the airframe and engine (bought used) combined...but man, do those surfaces MOVE! If you want to know my radio setup just let me know...I use a JR 10x and can email you my setup file if you want it.

I didn't have a chance to weight the plane but it feels very light for it's size. My CG with everything installed ended up being about 1/2" behind the recommended CG range. Since I find that most aft-CG recommendations are typically on the VERY conservative side, I decided to leave it where it was for initial flights. The engine fired up without hesitation and I taxied it out onto the runway. I took off at about 3/4 throttle when WHAM! I hit a light pole. Just kidding...the plane flew off very nicely. I circled around, added maybe two beeps of right aileron and one beep of up elevator. I gained a bit of altitude and then pointed her straight up to check how it was tracking. The rudder and engine thrust looked correct. I kicked up the low rates to middle rates and did some loops and rolls. Nice. A few more loops and rolls then I slowed down to see what landings would be like. No wing wobble or stall at very slow speeds. Great. Next tried some knife edge with my 'approximate' elevator and aileron compensation mixing turned on. Pretty close on the mixes and the plane tracked BEAUTIFULLY in knife edge. Tried some high-alpha knife edge but found that my mixes were getting kinda wacky toward the ends of the rudder travel...I've got the elevator and aileron mixes setup as point-curve types so that very fine-tuning of KE mixes is possible. I'll get it nailed with more flights. OK, now time to land her. Setup on approach, cut the throttle to 1/4 and basically watched it land. Too easy.

At this time I'm thinking to myself 'Wow...what a great flying plane!', but I hadn't seen anything yet. The second flight I decided to get a bit more aggresive and fly like I normally do. I pegged the throttle on take-off and the plane was in the air and climbing in maybe twenty feet. Pointed it straight up and did some axial rolls while watching the Katana get smaller and smaller. Hammerhead, cuban eight, then set up for a hover. Held the hover for about two seconds then the plane began to torque roll like a top! WOW! I was so shocked at how axial the TR was that I froze and fell out of it. At this time I was still on middle rates so I kicked it up to high rates...FULL surface travel. I went on a shallow upline and added quite a bit of elevator to see at what point the plane would snap...it didn't...it did a PERFECT 'wall'. I was so freakin' happy that I yelled at a flying buddy and said 'Man, you have GOT to see this!'. I was flying dead level at about 1/4 throttle setting up for another 'wall'. I pulled the elevator, the plane pitched up perfectly then we heard a loud 'POP'. Oh crap. I brought the Katana in as fast as I could. We immediately noticed that some sheeting had split near the end of the (very short) wing tube. I disassembled the plane and we were looking over the wings. One guy looked down the inside of the wing and said 'well...there's the problem'. I took a peek and noticed (for the first time) that the grain of the shear webbing was running parallel with the top and bottom spar caps. The shear webbing had split from the leveraging force being applied by the wing tube. When it all let go it split some of the ribs while the top and bottom surfaces of the wing were trying to get away from each other. I was bummed! Not because of the fact that the plane had broken, but because I couldn't fly it any more that day! I really wanted to see how elevators and harriers were with this plane. Judging from the 'wall' they should be excellent.

I called GiantScalePlanes and told them how great the plane flew and how the wing had popped at the shear webbing. Irwin promised to send me a new set of wings and asked that I took pics of the damage and sent it to him...which I did. Maybe I got a bad set of wings and the rest have the shear webbing grain in the right direction...so look down YOUR wing and post your findings.

The fix: I removed the covering from the three bays where the damage occurred. Using 3/16" medium balsa I made and installed shear webs in the three bays between the end of the wing tube and the wing servo. Then I used popsickle sticks and glued one to the top and bottom spar and to the rib in front of the wing tube. The other was glued to the same rib behind the wing tube (see the pics). I hope that this fix will do the trick. I'm dying to fly this plane again and don't want the wings pulling off during one of my very violent blenders.

Even though there is a serious issue with the wings I still think that this is an incredible airplane. Sure, the covering leaves a little to be desired but I bought this plane to FLY not to stare at. The workmanship is better than most others ARFs I've seen...all the parts are nicely laser cut and the fit of the parts is near perfect. The covering scheme is very visible in the air and greatly contrasting top from bottom. You certainly don't have to think too long about which side is 'up'. For the price it can't be beat IMO. I'm going to buy another one of these just so I can have a backup...

-Tom

TT2

My Feedback: (13)

Here's some pics so you can see what I'm talking about:

(Click on pics for full size)







Have fun,
-Tom

TT2

My Feedback: (13)

More pics:

(Click on pics for full size)



The Damage:


The Fix:


-Tom

SeaDog-RCU

Awesome wright up, except for that " 3/4 throttle when WHAM! I hit a light pole " comment, darn near spit coffee all over my monitor. Way to early for that kind of shock.

Dangerous Dan

My Feedback: (1)

I love the write up, great Job. I have been planning for sometime on making the GSP Katana my next plane. I have a couple of questions for you:

1. did you have to add nose weight, most posts on this plane recommends moving the elevator servos forward to prevent having to add nose weight with an OS 1.60?

2. have you considered CF wing tube? If so where could you fing one?

3. Can you give more details on the CF tail support?

4. How did you attach the wings I have heard a lot of negative comments on the factory way of getting to the weak springs?

5. Is it hard to remove the wings through the small opening? I was considering cutting out the canopy area and making a hatch/removable canopy?

6. Was your covering transparent as so many were?

7. Servos-servos-servos, I have been contemplating hard on my servo selection. Cost vs. weight vs. torque vs. speed. It is driving me crazy. I would love to go with hitec digitals and get the programmer and eliveate the need for a reversiny y harnace, but that is really costly. What torque would you recommend on each surface?


I know this is a lot of questions, but from your AWSOME write up it seems like you dont mind typing.....LOL


Thanks for the write up

Watch out for the light poles......LOL

TT2

My Feedback: (13)

Thanks. I know the post is long...I'm sure it's my longest yet. Perhaps it should have been titled 'Too much coffee'.

Now to answer your questions:

1. No extra nose weight was required to get it to balance near the aft recommended CG. IMHO, people who are adding nose weight or moving the servos amidships to get the CG in the recommended range are doing the airframe a great injustice...my CG is still too far forward for my liking. I consider any CG recommendation to be just that...it's not a 'limit'. You gotta fly the plane to find the sweet spot. I spend the first ten or so flights of any plane working on setup (CG, mixing, thrust line, etc.). If you spend the time on the planes it will show...if you don't it will show. Too many people think the work is done after the first successful flight. To me it's just beginning...

2. The wing tube is 30mm. Finding an off the shelf CF tube might be tough. I considered making one but don't think it would be worth the trouble. Maybe later...

3. The CF tube I used is roughly the same diameter as the anti rotation pins. The CF tube extends all the way through the fuselage whereas the pins only penetrate part way. When you build it you'll know what I'm talking about.

4. You can make a tool from music wire to hook the springs. The tool should be long enough to go all the way through the fuselage, hook onto the spring, then you can pull the spring tight. After I pull one spring through the fuselage I use 1/8" bamboo skewers to temporarily hold it in place while I'm stretching the other spring through the fuselage. I stick another skewer through the other spring, slide the wing on, then stretch the springs over the eyebolts. Works OK but I think I'm going to opt for another set of bolts to hold the wing to the fuse and do away with the springs altogether. I could save a few ounces this way and I'm sure that it would be strong enough...plus the springs are a pain.

5. A top-access hatch would be nice but I didn't feel like putting the effort in. The small hatch provides enough room to get to the servo leads and wing bolts.

6. I'm sure the covering on mine is just as good (or bad) as everyone elses. I'm very picky on the things I BUILD but not very picky about the things I ASSEMBLE.

7. I hate to say this but if you have to 'Y' the servos together it sounds like you could benefit from a better transmitter...like a JR 8103DT. It's tough to recommend servos. Use the best ones that you can afford. I'm sure that you could get away with HS605s all the way around, but they don't center well and aren't nearly as powerful or fast as the HS5925s or S9402s even though the specs will tell you that they are. Feed the servos with 6V for extra punch.

My fingertips are bruised...

-Tom

Dangerous Dan

My Feedback: (1)

thanks tom good looking plane, anyway you could get a dry weight?

TT2

My Feedback: (13)

The digital bathroom scale says 10.5 lbs, but I think that's probably only accurate to within 1/2 lb. My epoxy scale only goes up to four pounds. I'll try to get the Katana on some better scales soon.

-Tom

Dangerous Dan

My Feedback: (1)

I use an Hitec Eclipse 7 channel computer radio. I have the abilitity to run the elevator servos on seperate channels, but the drawback is that I have to do it on a switch with a P-mix. I lost my hanger 9 Pizzaz(dual HS 85mg) because I forgot to turn this switch on and the plane would roll left when elevator was applied, once i realized my mistake it was too late.
I desided that on the next plane I build, with dual elevator servos, I would use a miracle reversing Y to get rid of this problem. The reversing y has a pot. that you can adjust to match the center, but you loose the abilitity to match the endpoints individually. I am on a tight budget, but am willing to wait until there is enough funds to build this plane correctly. If I buy Hitec Digital servos (expensive) and a Hitec Digital servo programmer(expensive) I can reverse the servos, adjust the endpoints, and adjust the centers on a standard y. Or I could use standard HT servos on seperate channels and tie a string around my finger to reming me to check the switch, or go with the miracle Y.

One question: Why did you use HS 5925MG on the ailerons(Digital 130 or so torque extremly fast) and use three Futuba S9402 on the evevator and rudder(not digital, slower, and less torque than the HS5925MG). Why not use HS5925 all the way around($10 more each, and the same weight with better specks).

HS 5925MG $89
Futuba S9402 $79
HS81 $17
Hitec programer $159

Wow do the math

rc-sport

My Feedback: (12)

Gonna test fly mine this weekend, my hands are shaking already.

TT2

My Feedback: (13)

There's alot of people cussing the Eclipse and Prism radios due to the lack of decent dual elevator functionality. The reason I suggested the 8103 is because I've used them for years and KNOW that they would provide adequate functionality for a plane like the Katana (and nearly anything else)...plus they're super easy to program...not quite as easy as the 10x but pretty easy.

The reason I used the S9402s is because I had them sitting on the shelf. They're among the best non-digital servos I've seen. I would have used the HS5925s all the way around otherwise. Another reason is that I wanted to give the HS5925s a good test before flying another new plane I have which has (4) HS5925 and (4) HS5945...and two HS225 for throttle and choke. So far the servos seem to be solid. I reprogrammed them using a borrowed programmer so I know the firmware loads are current.

If you could borrow a Hitec programmer you'd be set. If you can't, rather than buying the Hitec programmer, you might be better off using some of the less-expensive JR digital servos and a 'matchbox'. This would enable you to fine-tune the centers AND the endpoints. The drawback here is the added weight, complexity and expense of the matchbox.

Where can you get the S9402 for $79 NIB?

-Tom

Dangerous Dan

My Feedback: (1)

you can get them here:

http://www2.towerhobbies.com/cgi-bin...?&I=LXH305&P=7

Geoffbob

My Feedback: (12)

Dntmn- I have an Eclipse also, didn't want to use the mix for elevator servos so I used one of the Y's. Worked great for 26 flights; on the next I got a wicked snap (one elevator half went to full deflection), then another, then no elevator at all. When I got to the plane the Y was shrieking like a digital servo. Lost the plane utterly (WM Extra 80") and the gas engine attached to it. I don't know why the Y failed but for sure I would never put one in an airplane again.

Dangerous Dan

My Feedback: (1)

Was it a miracle Y?, I am thinking about saving up for digital servos at least for the elevator halves. I can borrow/buy a programmer, reverse one of them electronically, match the centers, match the endpoints, then put them on a standard heavy duty Y. Otherwise I will use seperate channels and always! check the p-mix switch before flying. I have 5 planes on this radio, what I was in a fun fly and switching between planes when I forgot the switch and lost my plane. This plane is getting expensive, but on the brigt side If I save up and go with 5 HS-5928 (1-rud, 2 ale, 2 elv) I can re-use them in a 33%-40% plane in the future.

You can get your eclipse updated to PCM cheap

http://www.hitecrcd.com

click on Eclipse QPCM update

$99 +$5 s/h
update firmware and hardware to PCM, with added functiona and get a 9 channel PCM receiver

$25 + $5 s/h

update transmitter no receiver

grnd0

My Feedback: (4)

I have an Eclipse also, and on my Fun World I had
one of my servos reversed when I purchased them.
I heard some bad stories about those reversing
Y's and had to go another route. I deal a lot with
Servo City and they charge about $5. to reverse
a servo. That's for standards, not sure about digitals.

Larry

Swat Cop

My Feedback: (11)

I have an MPI reversing Y and an MPI Miracle Switch on my GSP Katana, I have about 80 flights on it with no problems. I also have the stock landing gear which is very durable, I have had several less than perfect landings and the gear has been torn off twice on two very hard deadsticks. The top hatch looks like a lot of work and the stock bottom hatch is a real pain. I enlarged mine, it was very simple to do and makes life a lot easier. Click on my gallery to see pics of the larger hatch. And no the covering on mine is not stock.

TT2

My Feedback: (13)

Bike, it looks like your hatch mod would provide access to the front spring holes. I'm thinking about filling the front and rear spring holes with balsa, backing them up with 1/8" lite ply and drilling through this so I could use 1/4" x 20 nylon wing bolts at the spring locations. If I did this I wouldn't need the springs at all nor the 'stock' wing bolt. Whaddaya think?

Regarding flying, have you been flying snaps, blenders, walls and other high-G maneuvers? GSP tells me that out of a thousand or so Katanas out there, I'm the only one reporting deficiencies in the wing spar design. Maybe I just got a dud.

TO ALL GSP / CHIEF KATANA OWNERS: Do me a huge favor...look down the inside of the wing halves and tell me which way the grain of your shear webbing is running. I'm very curious...

-Tom

Swat Cop

My Feedback: (11)

TT2, I just got home from flying my GSP Katana. I flew about five flights today (about 80 flights total) and was taking the plane apart cleaning up when I remembered reading your post in reference to the grain on the webbing running the wrong direction. Guess what, its running length wise and both wings are cracked down the center of the webbing. Thanks for bringing that to my attention it probably saved me from folding the wings. Yes, I do a lot of high G manuvers and my plane weighs a lot more than yours but you're right that webbing needs to be going the other direction.

Your about installing wing bolts sounds great. I have no trouble getting at the springs with my enlarged hatch. I think the stock bolts and are fine, I don't think there is a whole lot of force pulling the wings away fuse. One thing I do recommend if you are using the bolts is to install larger washers. I use the small stock washers on top of some big ones (about the same diameter as a quarter but still has the small hole) I got from Home Depot. The larger washers have a lot more holding surface.

rc-sport

My Feedback: (12)

I flew my Katana today, 3 flights, I think I'm in love. I have the Creek Hobbies Staudacher and this plane blows it away. After the 2nd flight I was on high rates and tearing up the sky. It floats in on landings, my first one was a dead stick. The plane flies on rails. I couldn't believe the slow speed stability. I have a Saito 180 in it and it was going veritical at half throttle. I wish I could fly it tomorrow but I have to take my daughter back to school, dang it!

Swat Cop

My Feedback: (11)

RC Sport, what prop are you using on your Saito 180?

rc-sport

My Feedback: (12)

I'm using a Zinger Pro 18X6. Tomorrow I'm going to the hobby shop to upgrade all my servos and linkages.

MustangFan

TT2 and Bike466:
I received my KATANA from GiantScalePlanes ... checked the grain direction of the wing webbing ... mine runs the wrong way also.

Thanks for the heads up.

I think I am going to bond some carbon fiber at least around the wing tube installation.

Someone should educate the Chinese and the kit designer.

Planeclothes

My Feedback: (1)

Hey guys, I also received my Katana from GSP today. Unfortunately, the left wing panel is crushed on top, repairable but not acceptable. I called GSP, they're sending me a new panel. I'm very impressed with the general quality of this arf, the see-through covering is not that bad. Now what about those funny round CA hinges? I've used CA hinges before but never seen them round shaped. Now I understand what you guys were trying to say about the access hatch, how can a normal person get his/her hand in there? One of the first things I did was check the wing webbing. It looks just like yours, so as much as I hate having to cut the wing covering, this time I have no choice.

wyldman

My Feedback: (1)

I've been flying my Katana for several months and have not had a shear webb problem yet ,but I will besure to check mine tonight my saving grace maybe the bolt on wings two of us built the GSP katana at the same time and we came up with several mods, one being bolt wings using studs and wing nut on the inside and we installed a top hatch and sealed the bottom hatch. some reinfocement was add to the engine box as well as some added to the counter balance s on the elevators , I have cracked both of them .
mine is over powered if that's possible ,brison 2.4 swinging a zinger pro 20X8 prop. Even with the engine and ignition battery still had to add 1.5 oz of lead to the nose to balance in the rear of the CG range.
total weight is 12lb 10oz ,a buddy is finishing one now and he is under 12lbs with brison 2.4.
I have really pushed this plane to the limit and the only thing I dislike is at high speed and full up elevator (60 degree's) it will tip stall and drop the right wing ,this is also why I have cracked the elevator counter balances. this is a great flying plane .I like it so much I'm thinking of buying another just to have it in my personal stock ,you know for the one time I take off and hit a light pole or something.

WYLDMAN

Dangerous Dan

My Feedback: (1)

wyldman,
Do you have pictures of the removable hatch?

I would likemore detail on this, I will be ordering my Jet Hobbies Katana(same one as GSP, but cheaper with free shipping and scale pilot) soon, and wanted to try and make a removable hatch.

How long did it take you?

Do you have pics of the wing bolts?

Where is your CG?


Thanks


PS: I dont worry about light poles but PICNIC TABLES thats another story...LOL