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Question 260: "Karl, I have a Ziroli C-47. It weighs roughly 40 lbs. has a
114" wingspan and a 92" fuse. I have 2 Zenoah G-38's for
the power plants, swinging a 19X10 3W carbon fiber prop. Here's my
question, I get a maximum rpm of 5900(left) and 6000 (right) on a
32/1 fuel mixture (89) octane. Engines are just about broken in. Is
this sufficient to fly the plane? It feels like it has good thrust, I
have not flown it, just taxied it. I'm trying to figure out how to
maximize my set-up. Should I change props?Should I change fuel mixt.? The engines
run great, sound great, idle smoothly,
transition perfectly. This is my first large scale warbird, and my
first twin. I just want to make sure I cover all the bases. Please advise. Thanks Frank V. Puccio,
Jr. "
Karl: "Thanks for visiting our site, Frank.
Hope we can help you out here. I believe the G-38s will be plenty for
your plane. Regardless of the wingspan it IS only 40 lbs. so that
shouldn't be too much. One suggestion I have is to look into getting
a SoloProp for that. Not only would it look
cool but you can adjust the thrust with the pitch. The SoloProps are ground-adjustable which means you
either tether the plane to an anchor and test the thrust (in a twin
that may be one way to check the yaw-rate so you can make sure you're
flying true without having a boatload of rudder trim to keep it true..the tether will bias to one side or the
other to show which engine is pulling more--assuming you've adjusted
fuel/carb and props evenly), and they have the round-tipped blades
used on this transport. You can get them in many diameter ranges from
16" to 32" (they're at www.soloprops.com).
Now, I haven't seen the owner's manual for the
Zenoah line but I'm assuming that for break-in purposes they have
listed that fuel/oil mix for a reason. Normally they recommend 50:1
regular unleaded fuel so 32:1 would tend to make it smoke more. Make
sure you've read the differences between pre-and post-break-in
fuel/oil mixes to keep the thing from giving you grief early on. The
Zenoah line is just one of the best 2-stroke gassers out there and
the competition is strong so you've made a good choice. Of course,
being who I am and loving round-engines I would try to put radials on
that bad boy and wow the pants off anyone at the airfield. But that's
just me. Hope this helps. Karl"
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Question 261: "I
have a 1/4 scale P-51D, Quadra 100, and a lust for that big throbbing
4-blade propeller. OK that was a little weird. My question for you is
very simple. I have developed a conversion plate for Mick Reeves' Torque
Master that will fit on the front of my quadra
100 and allow me to swing a near scale propeller (
I think). I, like every other P-51 groovy, am looking for a 4
blade option with a happy medium between thrust and speed in order to
swing a 4 blade and not feel like I am on a six flags ride for 5 year
olds and under. I have seen how this engine can pull a 50lb. one quarter
scale P-51D with the correct two blade prop.
My question FINALLY is; at 40lbs.,112 inches, Quadra 100, 1 to 1:1.75
reduction ratio, 32" Solo prop, what pitch would give me 70-80
mph clean and flat, but enough thrust to climb out on takeoff confidently.
I know I may be dreaming. but remember this
is a huge engine. There are paraplanes
flying around with people hanging under them with 100cc reduction.
Could this be enough muscle to get up with a speed pitch? Your
thoughts and opinion are? greatly
appreciated."
Karl: "Hi Randy and
thanks for the question. I love these type
of questions because they force me to stay up on some of the developments
(not ALL of them of course) in the RC hobby, especially in what we
could call here the "accessories" category.
I
took the liberty of sharing some of the plane spec's with what I call
an "electronic friend" since I've never met the guy in
person. His name is Joe Boyd and owns an operation called Warbird PropDrives. He and the crew of
designers/engineers (all fellow RC plane hobbyists) have been
developing what is, in my opinion, the best full-functioning reduction
drive that also has true constant-speed prop adjustability. Just the
ticket for all you rabid P51 fans out there. Go to
www.warbirdpropdrives.com and look at the movie, the info and you
will be amazed. They even found an outfit in Oregon that can make the
fully- functional scale side exhaust stacks. Just go there and you'll
see what I mean.
For
a plane your size and spec's I believe the Q100 is a good choice. The
prop on a plane works the same in principal as the rear-end gears and
transmission does in a car. I have a couple other questions in these
posts that address that more in-depth. As far as the SoloProp you might have to change that since the
wide, square-tipped blades on the Mustang are unique I'm not sure if
Solo has that kind of profile in their product line. I might be wrong
so don't hold me to that.
Anyway,
it sounds like you're planning properly so have fun. It's good to
hear as well the passion in the hobbyists
voice like you shared. That sort of love of the sport is what keeps
it going--and going--and going....you get the picture. Hope this
helps. Karl
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Question
262: I
purchased and build a ESM ME-109. It looks
great and flies even better. The problem is I live in Mexico City
(2500 meters above SL), I have a DLA 32 on
the plane and are flying it at a grass polo field. Take offs are very
difficult, I let the plane roll very much and when it gets airborne
it is very sluggish. I know I need more airspeed. I am using a 18-10 prop, should I jump to a 18-12 to get more
"power" from the engine as I take off??
What
would you recommend?
Karl: First, I'd like to thank you, Manuel, for
visiting our site. It's good to be back on line for our world-wide
group of fans and fellow RC'ers.
First, work out any bugs you have with the engine. At that altitude
the air/ fuel mixture can be affected somewhat, so you want to make
sure it's as good as you can get it. Make adjustments to your idle
mixture and "cruise" mixture (the "high",
and "low" needles on the carb). I forgot about this engine
so if it's gas, make a couple flights with it and check the spark
plug. If it's running too lean--meaning too much air and not enough
fuel-- the spark plug will be almost new looking; If the plug is
black, it's in danger of carbon-fouling because the mix is too
rich--meaning too much fuel and not enough air. What you want to see
is light grey/ tan deposits on the spark plug. This usually is the
indicator that the engine is running well.
If it's a glow engine, the glow plug will have somewhat related
indicators, although if the engine is running too lean it likely will
burn up the glow plug pretty quick.
The best, most proven propeller on the market is one which started
life in Canada, but now is being manufactured in Florida, USA. The
name of the company is SoloProps and they
have ground-adjustable-pitch propellers ranging in diameters from
16" to 32". You set the pitch in between flights to
maximize your flight time and characteristics. The safety record is
excellent, and they are practically museum-quality. I started
building a 1/5-scale F4U Corsair a few years ago, and plan on using
their 3-blade, 32" prop on a radial for that. The cost for the
hub, three blades and adapter came in at just under $400, but they
sell two-bladed ones as well. I believe that a SoloProp
is the best bang for your buck to get you flying the way you want to.
Great question, and thanks again for visiting our site!
Karl
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Question 263: Hi Karl, I
am running an older style orange case 4.2 sachs
engine with ch ignition, Can you help me
with the battery to run on this engine
Karl:
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Question 264: Karl, I
like your little nook of the web. you give
good answers to folks so I wanted to know. I have an ASP 400R 5
cylinder radial. It totals out to be 65cc and it is a wonderful
engine. What I would like to know is whether you do not like these
or? I only see one place where you mention them in response to a
fella building a round cowl plane. (the only
real war bird lol). Anyway, there are many
times you recommend other radials of similar size but never the ASP.
I would like to know why? The one I have had always done very well.
Simply the easiest to start and it has never failed
me not one time. I think it is a wonderful machine and
normally it can be bought for 777 dollars. Nobody else comes close in
a five cyl radial. I have taken mine
apart (was curious on how they were made) and the internals were
perfect. If you have a moment please let me know any pros or cons
about it and why you recommend robart, saito and OS but not the lower priced ASP?
Karl:
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