My first Gasser/Giant Scale Project - Page 2 - RC Groups
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Nov 14, 2010, 07:53 PM
Registered User
You might want to reconsider the use of the 485HB's on the elevators. Pretty sure Hitec advises against it as well. While the Karbonite gears are strong, they are also brittle which is not good when dealing with the vibes of a big single gasser. I would use some 645MG's, at least.
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Nov 14, 2010, 08:47 PM
Registered User
Originally Posted by StrangeGager
You might want to reconsider the use of the 485HB's on the elevators. Pretty sure Hitec advises against it as well. While the Karbonite gears are strong, they are also brittle which is not good when dealing with the vibes of a big single gasser. I would use some 645MG's, at least.
Good advice, especially if flying 3D.
HS-485HB specs include:
"*See Karbonite Guidelines Below
FeaturesApplications: Heli's and Aircraft up to 72 or up to 12lbs when using just one servo per control surface.
Note: Be aware that high vibration gas (not glow) engines combined with large contol surfaces and large thows (3D models) can put undue strain on the gears. Metal geared servos are recommended for these applications even if under 12lbs.
Warning: Do not use thread lockers on Karbonite geared servo as it will cause the output shaft to fail.

Alan T.
Nov 15, 2010, 05:34 AM
Trees are our enemy
I am well aware of the guidelines. And thanks for looking out. However, the vibration alone being so strong that it would shatter the gears of servos riding in the tail?!?!?!?! Highly unlikely...

Being that I'm a plastics engineer for a decent sized, and well known molding house, I have a considerable amount of experience with plastics, especially polycarbonate. PC is actually pretty tough stuff, has good wear resistance, tensile strength, compressive stength, and impact resistance.

The bigger issue is the load on the control surfaces as large as they are and as heavy as the plane is. For this reason, and due to fit problems I switched out the aleron servos for HS-645MG's. At some point a will do the same to the elevator servos, but the fact is; I dont plan on jumping strait into 3D flight with this plane and I actually prefer the high speed, smooth areobatics. The beauty of the katana is ita capable of both styles of flying.

Later down the road I will defintely upgrade the servos, but for now I think I'm ok. I'm trying to build this thing on somewhat of a bugdet and there are still other areas to be addressed at the moment. Besides, i do have two elevator servos. Roughly half the load, and If one goes I still have one to get me on the runway.
Nov 15, 2010, 12:22 PM
Registered User
So you are willing to risk your plane and potentially other peoples property over 30 bucks or so?
I'm about as cheap as they come, but damn.
Hows that saying go again? Penny wise and pound...
Nov 15, 2010, 06:02 PM
Trees are our enemy
1.Dont come on here calling me cheap or foolish, it's uncalled for and rude.

2. I dont fly over or near other peoples property or other people, to do so with something more than a small foamy would be "foolish"

3.I do plan on upgrading the servos. I dont think the ones I have are going to fail in the manner that you say, but I do really like the HS-645MG's I bought for the alerons, and would like to keep those all around. However, as I mentioned in my last reply, I have other areas of the build that require attention right now so I'm not going back into the tail until the rest is handled.

4.FYI, the HS-485's are a much tougher servo than you're giving them credit for. I use one on a 1m sailboat as the sail servo on both the main sail and ~125% genoa. I used to sail that thing in 15-20mph winds all the time. Switching tack in a 20mph headwind can create some serious strain and vibration on the boom which goes strait to the servo. If a single HS-485HB can handle that, I think two would be pretty safe on the elevator.

You know, come to think of it...I've never had a Karbonite geared servo fail on me...I've had a ton of HS-55 copies (..kyosho comes to mind..) and other nylon geared servos fail and even a metal geared micro servo go bad...but never a karbonite. Actually all together I've only lost one hitec made servo, and it was due to a burnt motor..
Nov 15, 2010, 07:53 PM
Registered User
Try asking over on Flying Giants if you should 485HB's and see what kind of replies you get
Bottom line, it's both cheap and foolish to go against manufacturers recommendations and use a karbonite on the elevator of a 50cc aerobat.

Here's a little proof that I know what I'm talking about. But then again, I'm not an engineer either...
Last edited by StrangeGager; Nov 15, 2010 at 08:06 PM.
Nov 16, 2010, 12:10 PM
Trees are our enemy
Fitted a 4" Magnum Spinner, and Fitted the cowl around the new pitts style muffler. Also had to make some modifications to the engine box to fit the pitts muffler in.

Still have to go back in and beef up the engine box where I had to remove some material. I'm also starting like like the idea of glassing the entire engine box and Firewall.

I also have to make some thottle linkage/servo installation decisions. The servo cut outs for the throttle and choke servos are inside the engine box which I dont like at all. I know the servo is supposed to be atleast 12" away from both the engine and CDI. I considered shielding the engine box to reduce the EMI/EFI problems but with the position/location of the throttle arm as opposed to the servo cut outs, I think life is just gonna be so much easier to move the throttle servo back by the rudder servo. I also need to start moving weight behind the CG/CL cuz this thing is headed towards being a little too nose heavy.
Jan 26, 2011, 12:34 PM
Registered User
Any updates?
Jan 27, 2011, 04:03 PM
Trees are our enemy
Got caught up in another build and have been busy with work but I have made a little progress. I'm the middle of installing the smoke system and fuel system. I talked to a few Giant scale guys at the AMA expo about the servo issue and they said I should be ok for sport flying but if I plan to fly hard core 3D then I should defintely use MG servos. It does much matter anymore since I need the HB's on my cub.( im going from the flaperons to true flaps), so I'm going with the 645MG's on the tail anyways. I guess it doesn't make much sense to run them on the alerons but not the elevator.

The other issue I have is that my original idea of 24oz fuel tank and 16oz smoke tank isnt gonna pan out. They fit side by side perfectly but I cant quite get to the front wing bolts with them both in there. so I have to run a smaller tank that I can fit down by the wing tube. Looks like I'll have to go with a 10oz..very curious to how much smoke I'll get outta a 10oz tank.
Aug 31, 2011, 07:00 PM
Trees are our enemy
After about a 7 month break from this project due one event after another, I'm finially back into build mode. I have been squeezing a little build time in here and there for the last couple weeks, and well, things are headed into a little different direction than before, and most of the pending decisions have been made and executed. I am definitely seeing positive motion...
Last edited by FBodyexpert; Aug 31, 2011 at 07:19 PM. Reason: typos
Aug 31, 2011, 07:18 PM
Trees are our enemy
Status/Decision Updates:

For the switches and fuel/smoke dots I have decide to go with miracle switch/dot combos. Both switches are mounted under the canopy split just behined the leading edge of the wing. On the left size I have a dual switch for the radio and iginition packs with a fuel dot in center for the gas. On the right side I have a single switch for the smoke pump pack and a fuel dot for the smoke.

Servos- the HBs are out of the Katana and have found a new home in my .40 cub. Now have HS-645MG's all around

Batteries-Decided to stick with the single 6.0v 2200mah NiMH for the radio gear, a single 6.0v 2000mah NiMH for the ignition, and a 6.0v 2000mah NiMH for the smoke pump.
Aug 31, 2011, 07:24 PM
Trees are our enemy
Smoke Muffler Installed
Aug 31, 2011, 07:43 PM
Trees are our enemy

The Next Major Issue and Decision

As i mentioned in the first post of this thread, I got a good deal on the airframe buying NIB off craigslist from the claimed son of the designer.

Although I felt I got a great deal, there were some things I definitely disliked about the kit. The first being the hardware. The included hardware was the worst I've ever seen and was quickly scrapped and replaced with Dubro's best.

The second issue was the covering. I thought it was ugly, and I'm sure many others would agree. But, at that time I figured build it, fly it, and if it survives eventually one day recover it. Well, as time progressed I found another major issue with the covering: IT SUCKS!!!

The covering seems to be merely clear film literally painted the choice color on the inside and then coated with an adhesive as cheap and crappy as possible. The result, if you lightly touch the covering anywhere not supported from behind the paint flakes off leaving a clear window. Also, all the seams were pealling away.

Well, 7 months ago, shortly after my last post before the drama, I completely finished building the plane, fully ready to go. When I went to started the engine for the first time, which runs like a champ, the covering started peeling away everywhere.

Then I saw this:

<iframe width="420" height="345" src="" frameborder="0" allowfullscreen></iframe>

Thus I decided to recover the plane completely
Aug 31, 2011, 07:44 PM
Trees are our enemy
Since the video wont embed, heres the link to the video that scared me into recovering before the maiden:

Paul Kelly flies his RC Katana airplane model with hole in wing (2 min 3 sec)
Aug 31, 2011, 07:51 PM
Trees are our enemy
Before I could start the recovering process, I had to come up with the new design scheme. After sketching about 20 different designs, this is what I decided on:

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