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pelon_mx
09-11-2006, 09:38 AM
:confused: Hi, I`m new in this sailplane stuf, I have a Sprit 100 ailplane and want to convert to ep, What kind of motor and what size should I get to get this bird in the air, not to slow, not to fast something that`s reasonable whithout damaging my bird, what should be the highest motor range.
This bird has spoilers activated by a servo en two thin cods it wanna change this to servos, what servo could go just below the spoiler, I was thinking about a Hitec mg125, my radio is a Hitec eclipse 7

Sky Sharkster
09-11-2006, 04:08 PM
Hello Pelon, Welcome to Wattflyer! The Spirit is a fine glider, you'll be happy with it. As far as motors go, you'll be looking for (about) a glow .15 size, 250-400 watts. One of the least-expensive choices would be the E-Flite .15 http://www.toddsmodels.com/Brushless%20Motors/EFLITE/EFLM4015A.htm (http://www.toddsmodels.com/Brushless%20Motors/EFLITE/EFLM4015A.htm).
Other choices are the AXI 28/26/12, Hacker B40/10L w/4.4:1 Maxon G/B, Jeti Phasor 30/3 or Mega 22/30/3.
These are all brushless motors, most are "Outrunners" which don't require a geabox (except the Hacker) and cost around $100.00 or more.
If you want to try a brushed motor you'll be looking in the "Speed 700" size and I'd suggest a ball-bearing drive. The GR6317 Speed 700 BB (Ball Bearing) Turbo 12V from Hobby-Lobby.com is about $50.00. This won't have the all-out power of a brushless motor and will consume the amps faster (lower efficiency). Another drawback is the life expectancy, brushed motors have a generally short usable lifespan. This isn't as noticable on a glider where the motor runs are fairly short but it is running "full blast" so don't expect more than a couple hours or less, of run time. They don't conk out at the end, they just slowly lose power. If you buy 2 or three of these you'll spend as much or more than the price of a brushless, which will last (unless you crunch it!) forever.
The MG125 servo is plenty of power for the application, you might be able to use HS81's which are lighter.
Check out your Hitec transmitter user manual for Glider Mixes, you'll find a "Spoiler" mix for elevator/spoiler mix and usually a "Throttle/elevator" mix, this adds some "down" elevator to the power-on phase, to correct the pitching-up problem common to gliders under power.
I've posted a link to a site called Fatlion on this Forum a few times, check'em out, very good glider and E-Glider site.
Good Luck!
Ron

pelon_mx
09-12-2006, 05:31 PM
Thanks Ron, let me get investigate and try to understand all this electric powered stuff a bit more.
Thanks

tillmas
09-15-2006, 02:20 PM
I have seen folks use a much weaker motor than the E-Flite 15 and have excellent performance. That big of a motor will make a Spirit 100 climb like a hotliner. The thing to keep in mind here is that the big wing was not sized for any level of loading. This thing was designed to be a floater, with just a little penetrating capability. The center wing split can be weak, and shouldn't be flown aggressively. You should use a motor that will not encourage you to push the limits of the airframe.

Depending on how you build, you should be able to build that glider for an AUW of around 40-50 oz, most of the kits came out tailheavy, so the addition of the motor upfront should come with very little weight penalty.

Matt

pelon_mx
09-17-2006, 11:31 PM
Thans Matt for your feedback
The box says the sailplane weights between 4 and 4.5 lbs, it`s an ARF kit and yes it`s tail heavy, I like speed even as I`m a newcomer here. All opinions are welcome and the more the better.
What motors for this hobby concerns I really have no idea what to choose, for sure their must be a way to find out how much power I need and what kind of motor to select, what I`m sure of is that it will be a brushless motor or outrunner and sure their should be some good places on the net for motor selection but where?
Additional to all the comments here from the experienced people I wanna make the exercise how you come to the recommended type of motor to use because there are so meny makes and each one of them has different identification of their motors that`s the point where I get mixed up,
I`ll apreciate it very much to know how to clear up all my confusion about all this motor ID`s
The more info I receive the better, I hope not to get more confused than I`m, but nobody never know too much
All feedback I can get is very welcome and I know also that every head is a different world
Thanks guys
Chris

AEAJR
10-03-2006, 11:29 PM
Thanks Ron, let me get investigate and try to understand all this electric powered stuff a bit more.
Thanks

You probably want something in a brusless motor. Your glider is probably about 70 ounces as a pure glider. Add motor and battery adn you probably come in around 80 ounces, assuming you use lipos. That is 5 pounds. You probably want a brushless in the 250-300 watt range for a strong climb without adding too much weight.

SIZING POWER SYSTEMS FOR ELECTRIC AIRPLANES
by Ed Anderson
aeajr on the forums
Revised 8/25/06

This may get a little technical but I will try to keep it as simple as I
can. I will draw parallels to cars and bicycles in many places as most
people can relate to these and know at least a little about how they work.
I will use round numbers where I can and will use some high level examples.
If you are an engineer you will see that I am taking some liberties here for
the sake of simplicity. I will go through the parts of the power system,
then, toward the end, I will show you how we tie these all together to come
up with a complete power system.


POWER = WATTS

I will be using the terms Volts, Amps and Watts throughout this discussion.
Let me define them.

Volts = the pressure at which the electric energy is being delivered - like
pounds per square inch or PSI in a fuel system or water from a garden hose.
Volts is about pressure, it says nothing about flow. You will see volts
abbreviated as V.

Amps = the quantity or flow of electricity being delivered, like gallons per
minute in a fuel system or that same garden hose. Amps is about flow, it
says nothing about pressure. You will see amps abbreviated as A.

Watts = V X A. This is a measure of the energy or power being delivered.
This is how we measure the ability of that electricity to do work, in our
case the work of turning a propeller to move our airplane through the air.
Watts is about both pressure and flow. This serves the same purpose as
the horsepower rating of your car's engine. In fact 746 watts = 1
horsepower. So if you had an electric car, the strength of its motor could
be reported in either watts or horsepower. You will see watts abbreviated as
W.

If you want more depth on this, visit this thread.
http://www.wattflyer.com/forums/showthread.php?t=1933 (http://www.wattflyer.com/forums/showthread.php?t=1933)


MOTOR EFFICIENCY - Brushed vs. Brushless

Whether brushed or brushless, the motor's job is to convert electricity into
mechanical motion to turn the propeller to move air. Efficiency is how we
measure how much of the power, the watts, that our battery delivers to the
motor is actually turned into useful work and how much is wasted as heat.
A higher efficiency motor delivers more energy to the motor, and wastes
less.

A typical brushed motor, say a speed 400, is only about 40-50% efficient.
Only about half the watts delivered to the motor actually end up as useful
work turning the propeller. The rest is wasted. Motors that have a "speed"
designation, like speed 400, are brushed motors. There are other names for
brushed motors but the "speed" term is a common one. They are inexpensive
and they work. For example, you can buy a speed 400 motor and electronic
speed control, ESC, for $30. A comparable brushless motor/ESC combination
would
typically cost 2 to 4 times that much.

Brushless motors tend to be more efficient. They typically deliver 70-90%
of that input power to the propeller, Thus you get better performance per
watt with brushless motors. Seen a different way, if you use a brushless
motor, then, for the same flying performance you will use less energy which
means your battery will last longer. Or you can use a similar size and
weight brushless motor and get much higher performance because the motor
turns more of the watts from the battery into useful work of turning the
propeller.

As with many decisions we make, this is a cost benefit decision. Am I
willing to pay more to get more? That is up to you.


THE BATTERY IS MORE THAN JUST THE FUEL TANK

Think of the battery as the fuel tank plus the fuel pump and a supercharger
all rolled into one. It feeds/pushes energy to the motor. So you have to
look at the battery and the motor as one unit when you are sizing power
systems for electric planes. In many cases we start with the battery when
we size our systems because the motor can't deliver the power to the prop if
the battery can't deliver the power to the motor.

The higher the voltage rating of the battery, the higher the pressure, like
a supercharger on a car engine. More pressure delivers more air/fuel
mixture to the engine which allows the engine to produce more power to turn
the wheels of the car.

Higher voltage pushes more electricity into the motor to produce more power,
IF AND ONLY IF, the battery has the ability to deliver more electricty.
Again using the car analogy, if you put a big motor in a car and put a tiny
fuel line and a weak fuel pump, the motor will never develop full power. In
fact the motor might starve and stall once you got past idle. Such is the
same with batteries. We need voltage, we need capacity, but we also need to
know how many amps the battery is capable of delivering at peak.

If we compare an 8 cell AAA battery pack to an 8 cell C battery pack we get
9.6 V for both packs. However the AAA pack may only be able to deliver 6
amps. After that the cells will heat up and either be damaged or the
voltage will strart to drop fast. The C pack, also 9.6 V, might be able to
deliver 60 amps without damage. So we have to size not only by voltage, but
by the ability to deliver amps to the motor. Again, think of the fuel line
and the fuel pump as your image of what I am trying to explain. If the the
motor needs 12 ounces per minute to run but the fuel line can only deliver
8, the engine will starve and die.

Using our electric motors, a given motor may take 10 amps ( the quantity of
electricity flowing ) at 8.4 volts ( the pressure at which the electricity
is being delivered) to spin a certain propeller. We would say that the
battery is delivering, or that the motor is drawing 84 watts, ie: 8.4V x
10A. If you bump up the voltage to 9.6 volts, the battery can ram in more
amps into the motor, more energy to the motor, which will produce more power
to the propeller. In this example, if we move from an 8.4V battery pack to a
9.6V battery pack the motor may now take 12 amps. This will typically spin
the motor faster with any given propeller or allow it to turn a larger
propeller at the same speed.

However, if you bump up the pressure too much, you can break something.
Putting a big supercharger on an engine that is not designed for it will
break parts of the engine. Too much voltage can over power your electric
motor and damage it. So there is a balance that has to be struck.
Different motors can take different amounts of power, watts, volts X amps,
without damage. For example, a speed 400 motor might be fine taking 10 amps
at 9.6 volts or 96 watts. However bump it up to 12 volts and ram 15 amps
down its throat and you will likely burn it out.

Our goal is a balanced power system. If you match the right battery with
the right motor, you get good performance without damage to the motor. In
many cases airplane designers will design planes around a specific
motor/battery combination so that they match the size and weight of the
plane to the power system for good
performance.


PROPELLERS

Propellers are sized by diameter and pitch.

The diameter of the propeller determines the volume of air the propeller
will move, producing thrust, or pushing force. Roughly speaking the
diameter of the propeller will have the biggest impact on the size and
weight of the plane that we can fly. Larger, heavier planes will typically
fly better with larger diameter propellers.

Pitch refers to the angle of the propeller blade and refers to the distance
the propeller would move forward if there were no slippage in the air. So a
7 inch pitch propeller would move forward 7 inches per rotation, if there
were no slippage in the air. If we combine pitch with the rotational speed
of the propeller we can calculate the pitch "speed" of the propeller. So,
at 10000 revolutions per minute, that prop would move 7000 inches forward
70,000 inches per minute. If we do the math, that comes out to a little
over 66 miles per hour.

By changing the diameter and the pitch of the propeller we can have a
similar effect to changing the gears in your car or a bicycle. It will be
harder for your motor to turn a 9X7 propeller than an 8X7 propeller. And
it would be harder to turn a 9X7 propeller than a 9X6 propeller. The
larger or steeper pitched propellers will require more energy, more watts,
more horsepower, to turn them. Therefore we need to balance the diameter
and pitch with the power or wattage of the motor/battery system.
Fortunately we don't actually have to do this as motor manufacturers will
often publish suggested
propellers to use with a given motor/battery combination. We can use these
as our starting point. If we want we can try different propellers that are
near these specifications to see how they work with our airplane.


GEARBOXES

While unusual on glow or gas planes, gearboxes are common on electric
planes. Their primary function is similar to the transmission on a car. The
greater the gear ratio, the higher the numerical value, the slower the
propeller will turn but the larger the propeller we can turn. So you can
use a gearbox to help provide more thrust so you can fly larger planes with
a given motor. However you will be turning the propeller slower so the
plane will not go as fast.

With direct drive, that is when the propeller is directly attached to the
motor shaft, we are running in high gear ( no gear reduction). Like pulling
your car away from the light in high gear. Assuming the motor doesn't stall,
acceleration will be slow, but over time you will hit a high top end!
Typically direct drive propellers on a given motor will have a smaller
diameter.

With the geared motor, it would be like pulling away from the green light in
first gear - tons of low end power and lots of acceleration, but your top
speed is reduced.

So, by matching up the right gear ratios made up of the propeller and,
optionally, a gearbox we can adjust the kind of performance we can get out
of a given battery/motor combination. How this is done is beyond the scope
of this article.


NOW WE CAN START TO MATCH UP THE PIECES!

The simplest approach I have seen to figuring power systems in electrics is
input watts per pound of "all up" airplane weight. The following guidelines
were developed before brushless motors were common but it seems to hold
pretty well so we will use it regardless of what kind of motor is being
used.

50 watts per pound = Casual/scale flying

75 watts per pound = Sport flying and sport aerobatics

100 watts per pound = aggressive aerobatics and perhaps mild 3D

150 watts per pound = all out performance.

Remember that Watts = Volts X Amps. This is a power measurement.
In case you were wondering, 746 watts equals 1 horsepower, .

AEAJR
10-03-2006, 11:30 PM
Continued -

AN EXAMPLE!

This should be fun. Let's see where these formulas take us! We will use a
24 ounce, 1.5 pound plane as our example. If we want basic flight you will
need 50 watts per pound or about 75 watts input to your motor for this 1.5
pound plane. That is, 50 watts per pound X 1.5 pounds = 75 watts needed
for basic flying performance. If you want a little more spirited plane, we
could use 75 watts X 1.5 pounds which is about 112.5 watts.

Lets use 100 watts as the total target, just to be simple, shall we? I am
going to use a lot of round numbers here. I hope you can follow.

The Battery:

If we use an 8 cell NiMh battery pack at 9.6 V it will have to deliver 10.4
amps to hit our 100 watts input target ( 100/9.6 = 10.41amps) If my
battery pack cells are NiMh cells that are rated at 10C then I need an 8
cell pack rated at 1100 mah to be able to deliver 11 amps. Sounds about
right.

Now I select a motor that can handle 100 watts or about 10.4 amps at 9.6
Volts. From experience we know this could be a speed 400, a speed 480 or
some kind of a brushless motor.

We now need a propeller that will cause the motor to draw about 100 watts. I
don't know off the top of my head what that would be. I would go to some mfg
chart as a starting point. GWS has good charts!
http://www.gwsus.com/english/product/powersystem/edp400.htm (http://www.gwsus.com/english/product/powersystem/edp400.htm)

I see that if I use a direct drive speed 400 with a 5X4.3 prop at 9.6V then
the motor will draw about 12.4 amps or about 119 watts. This would be a
good candidate motor/prop for the plane using a 9.6V pack that can put out
12.4 or more amps. This would be a set-up for a fast plane as that motor
will spin that small prop very fast.

However maybe I don't want such a fast plane but one with a really good
climb and lots of low end pull to help out a new pilot who is in training or
to do more low speed aerobatics

I can also use a speed 400 with a 2.38 gearbox and run it at 9.6V spinning a
9X7 prop and run at about 12.8 amps for 120 watts.
http://www.gwsus.com/english/product/powersystem/eps400c.htm (http://www.gwsus.com/english/product/powersystem/eps400c.htm)
The larger prop will give this plane a strong climb, but since the prop
speed has been reduced by 2.38 times, it won't be as fast. Spinning a
bigger prop gives me more thrust but a lower top speed typically. This is a
common strategy for 3D planes.

Back to battery packs and motors

So if I shop for a 9.6V pack to be able to handle about 15-20 amps, I should
do just fine and not over stress the batteries. In NiMh that would probably
be a 2/3 or 4/5 A pack of about 1000 -1300 mah capacity.

We view the battery and motor as a linked unit with a target power profile,
in this case about 100 watts. We use the prop and gearbox, if any, to
produce the manner in which we want to deliver that power to the air to
pull/push the plane.

If this is a pusher, I may not have clearance to spin that big prop so I
may have to go for the smaller but faster prop combo.

If this is a puller, then I can choose my prop by ground clearance or some
other criteria and match a gear box to it.


See, that was easy, right? ( well sorta but ....)

But we are not done! Oh no!

I could try to do it with a 2 cell lithium pack rated 7.4V. To get 100 watts
I now need a pack that can deliver 13.5 amps and a motor/prop combination
that will draw that much. So if I have 10 C rated lithiums, then the pack
better be at least 1350 mah. Probably use a 1500 mah pack to be safe.

Well, when I look at the chart for the geared speed 400 I see that,
regardless of prop, at 7.4V I am not going to have enough voltage (
pressure) to push 13 amps into this motor. So the 2 cell lithium won't meet
my performance goal of 100 watts+ per pound using this gear box.

If I go back to the charts and look at a different gear boxes I can't hit my
power goals using 7.4V. Maybe we go back to direct drive.
http://www.gwsus.com/english/product...tem/edp400.htm (http://www.gwsus.com/english/product...tem/edp400.htm)

We see that the best I can get this speed 400 to do is a total of 70 watts
at 7.2V ( close enough ) so I can't hit my power goals using a speed 400 at
this voltage. but 70 watts would be about 48 watts per pound so I could have
a flyable plane, but not an aerobatic plane using this two cell pack.


REALITY CHECK!

Now, in fact that is NOT how I would do this. I would decide on the watt
target, go to the chart, find a combo that meets my goals, then select a
battery that will meet the demand and see if my weight comes up at the
target I set. A little tuning and I come up with a workable combo.

For those who like to be even more analytical about it, there are packages
like MotoCalc that will allow me to play with all sorts of combineations and
make suggestions on what I should use. There is a link for MotoCalc below.

Summary

So, in these few paragraphs have taken in a basic knowledge of how electric
power systems are sized, the factors that are considered an how to predict
the outcome. Simple, right?

Of course there is a lot more to know and time and experience will teach
you plenty, but with this basic understanding you are better prepared to
begin playing with the power systems you put in your planes.

Here are some additional resources that may be helpful.

Good luck e-pilot!

Clear Skies and Safe Flying!
Ed Anderson

Brushed Motors
http://www.hobby-lobby.com/elecmot.htm (http://www.hobby-lobby.com/elecmot.htm)

Brushless Motors
http://www.hobby-lobby.com/brushless-motors.htm (http://www.hobby-lobby.com/brushless-motors.htm)

Battery Packs - NIMH
http://www.cheapbatterypacks.com/main.asp?pgid=packs&pid=AIR&sid=445976&ctype (http://www.cheapbatterypacks.com/main.asp?pgid=packs&pid=AIR&sid=445976&ctype)=
http://www.hobby-lobby.com/hydride.htm (http://www.hobby-lobby.com/hydride.htm)

Battery Packs - LiPo
http://www.cheapbatterypacks.com/main.asp?sid=445976&pgid=tp&sort=PL (http://www.cheapbatterypacks.com/main.asp?sid=445976&pgid=tp&sort=PL)
http://www.hobby-lobby.com/lithium-polymer.htm (http://www.hobby-lobby.com/lithium-polymer.htm)

Gearboxes - Speed 400 & 480 examples
http://www.hobby-lobby.com/gear400.htm (http://www.hobby-lobby.com/gear400.htm)
http://www.hobby-lobby.com/gear480.htm (http://www.hobby-lobby.com/gear480.htm)

A series of posts on electric power system basics
http://www.wattflyer.com/forums/showthread.php?t=1933 (http://www.wattflyer.com/forums/showthread.php?t=1933)
http://www.rcgroups.com/forums/showthread.php?t=417868 (http://www.rcgroups.com/forums/showthread.php?t=417868)

Maxx Products has a pretty good tip sheet on coming up
with a glow to electric power comparison. You can find it here:
http://www.maxxprod.com/mpi/tips3.html (http://www.maxxprod.com/mpi/tips3.html)

This reader says Keith Shaw originated the watts per pound rule
http://www.rcgroups.com/forums/showpost.php?p=6156600&postcount=39 (http://www.rcgroups.com/forums/showpost.php?p=6156600&postcount=39)

MotoCalc
MotoCalc will tell you everything you need to know: Amps, Volts, Watts, RPM,
Thrust, Rate of Climb, and much more! It is a popular tool for predicting
the proper motor, prop, battery pack for electric planes.
http://www.motocalc.com/ (http://www.motocalc.com/)

TeslaWinger
10-04-2006, 02:18 AM
P-MX- I have a 10 ft Bird Of Time I converted that is larger and heavier than the Spirit and the E-Flite 10 works well with a 13x7 CAM folder and a 7 cell 1500 Nicad using a 30 amp ESC. If you go with a 3 cell lipo setup (of a size that can safely handle that amp load), expect to use a smaller prop so excessive amps don't burn things up!

It makes well over 200 watts and is light enough to still soar well. I tended to use overly large and heavy nicads in my early days with a Speed 600 direct drive ARF (don't even consider it!) and thought soaring was impossible since it would sink out of light lift all the time unless it was a Magic Day when even trash was soaring!

Adding a reduction drive to the Speed 600 improved climb to the point I could get way up in 1/3rd the time and still have enough battery to climb again- and again! The HL price for the heavy S600 w redrive is only $10 less than the E-Flite 10 I bought at the local hobby shop! Far lighter and much more efficient- with no gears to wear out or waste power!

If you don't have a WattMeter- which is mandatory for experimenting with your own setups- you have come to the right place to ask! Copying a known good setup is very good practice for a safe and reliable combination!

I have converted several pure sailplanes to E-Power and have enjoyed the way they fly so much I seldom fly much else these days! You're gonna love it!

The reason these guys take so much time and care answering your questions is because not one of us has forgotten how difficult it was to make things work when we were beginners- and only grim determination kept us going when more reasonable types quit!

Now the really hard part- cut the nose off that pretty bird and get started!

Enjoy,
TW

pelon_mx
10-04-2006, 05:58 AM
Thanks Ed and TW, I seems to that I have homework for more than a few days, Great work ED I appreciate this very much for spending so much time to help others out and also your feedback TW of your BOT. It will take a while before I come back because You put a lot of links for reference and information
Tnx to both of you

bert269
07-23-2007, 06:32 PM
TW

I am also in the process of converting my Spirit 100 to EP. As I am now at stage of assembling the fuse, I need some input/help/assistance of what mods I need to make the the nose to get the motor in. I'm planning in using the Axi2820/10 for this setup, but since it's outside dia. is 35mm, I need to make the nose a bit wider. Do you have any pictures you can share. I notice that the E-Flite 10BL is also 35mm outside dia. so you must have made some mods to the plans. Please advice.

Thanks a lot for your input so far.
Bert

pelon_mx
08-20-2007, 09:02 PM
Hi,sorry for the delay in answering but I did not make trhe conversion yet to electric for different reasons, I still don[t like to cut the nose of and the other eason is that I haven t had the time to think what should be the best way or method to wider the nose, so the ep conversion is still pending,now Im fixing up a hobby room completely separeted from the house to be able to work without any interruption and comments frommy wife
Have a nice day

bert269
08-20-2007, 09:15 PM
Hi,sorry for the delay in answering but I did not make trhe conversion yet to electric for different reasons, I still don[t like to cut the nose of and the other eason is that I haven t had the time to think what should be the best way or method to wider the nose, so the ep conversion is still pending,now Im fixing up a hobby room completely separeted from the house to be able to work without any interruption and comments frommy wife
Have a nice day

Great!...well it is sometimes better to get some work done....LOL. take care and keep me posted. as soon as I have a working solution, I'll let you know.
Bert

Bird
04-12-2008, 09:14 PM
I would like to build and convert a Spirit 100 to electric. I have done this to a Bird of Time with good success.
I am not sure what to do about getting an AXI 2820/12 in the nose. Is there room and if not has anyone found a good way of enlarging the nose section to contain the motor. I will us LiPo cells (Thunder Power 2200 2 cell).
I would appreciate any advice. Thanks????

mred
04-28-2008, 11:10 PM
Greetings;
I just bought Spirit 100 and am going to convert it to E power. I have the ARF version and I was going to put a nice 35mm motor in until I found out the fuse is not that wide and would have to make some extensive mods to make this kind of motor fit. There are several ways to do this as far as I can see.

1. Cut the daylights out of the fiberglass fuse and rebuild the nose section which I don't like, but I can make the 35mm motor fit this way. You would have to cut off most of the front leaving the area where the cockpit is and where the canopy fits to the fuse. Then you can build it up with either balsa or fiberglass and make the nose wider for the 35mm motor to fit.

2. Get a HIMAXX inrunner motor and install that. I found one that is 20mm in Dia. and puts out around 300 watts and it would be much easier to put that one in, but it cost $105.00 for the motor and greabox.

3. Build a whole fuse out of balsa to fit my 35mm motor and use the nice fiberglass fuse for Hi-Starts.

I am strongly leaning towards No. 3 as I would rather build a balsa fuse and make it fit the motor and overall it would look better then cutting up the fiberglass fuse and it would not be that hard to do. It should not take long to build a balsa fuse (I guess a week to finish) and I think in the end it would look better then the butcher job and I also think I can make it lighter then the fiberglass fuse. I can also stretch the fuse a little as to make it easier to get the CG right without adding all the extra weight. I think adding about 1 inch to the nose would make it about right for the CG and with the extra length I can fare in the nose to the spinner and make it look better. I can also move the equipment around to help with the CG instead of doing it the way the plans call for with the servos up front and having to add led to get the CG right.

Now, having said all that, is there anyone that has any ideas about doing this and anything I may have missed? Any input would be much appreciated.
Thanks for the help.
Ed

Bird
04-29-2008, 01:27 AM
Thanks mred., I appreciate seeing your ideas. I have thought I would get the balsa kit and build from there. I have had good luck with Bird of Time conversions. Does anyone have experience comparing the flight ability of Spirit 100 compared weth Bird of Time. Do the aileron and flaps really add that much to the performance and enjoyment?

mred
04-29-2008, 07:35 PM
I have flown the Spirit 100 a couple of times, but not the BT, although I have seen it fly. The BT is a real floater and flies nice, but really need spoilers on it to help it come down. The Spirit is great with flaps as you can add flaps both up and down and with the ailerons, you get crow for landing. You can also give it full span flaps for climbing which is great and also aids on thermaling. I guess it is just a toss up as to which is best. The BT is RES and the Spirit is full house. I bought the Spirit because I wanted a full house glider and I bought the ARF because I don't have the time to do all the building I want to do. I am going to build a new fuse out of balsa so I can fit my motor in there and then I can use the fiberglass fuse to fly on a Hi-Start when I want to. As to which one is better, I think the BT is probably a little more of a floater then the Spirit and will stay up longer in no lift conditions, but I can't say for sure. Take care.
Ed