Carl Goldberg Eagle vs Eagle 2 Conversion - RC Groups
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Oct 14, 2017, 02:27 AM
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ninjasword71's Avatar
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Carl Goldberg Eagle vs Eagle 2 Conversion


I have the original plane mostly built before I bought it for $10. The wings are covered and fuse mostly built as well as the rear stabs. Still some small parts to do. There is still covering to finish it. I read a post of someone converting an eagle 2. Does anyone know the difference between first and second version? Pretty sure I can build the rest. This is by far the biggest and heaviest plane I have.
What size and type of servos to use and how and where do they hook up?
What motor size and kv is the best for a mild, relaxing flyer?
Everything will come from China so price will stay down.
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Oct 14, 2017, 10:01 PM
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Clive66's Avatar
Never heard of one named Eagle, just Eagle 2
They did make an ARF version of the Eagle 2 for a while.
63 inch wingspan plane.

Easy to convert to electric.
I did that on mine about 2 & 1/2 years ago.
Needs standard size servos & a 46 size brushless outrunner electric motor
I'm running a 4 cell 4200mah LIPO battery in mine.
If this helps any, here's a link to the kit build manual.
http://manuals.hobbico.com/gpm/gpma0955-manual.pdf

Here's some picks of mine
I built the plane in 1990
Oct 15, 2017, 01:33 AM
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ninjasword71's Avatar
Wow, thanks! Those are the instructions I'm missing. Looks pretty close to Eagle 1. To me, a standard size servo is 9g is all I use. Yours are much bigger. How long are your flights?
Oct 15, 2017, 06:26 AM
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Ken Myers's Avatar
I never heard of a Goldberg Eagle or Eagle 1, only the Eagle 2. There was a Goldberg Eaglet 50. It had a wingspan of about 50", if I remember correctly.
Oct 15, 2017, 11:05 AM
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Clive66's Avatar
Quote:
Originally Posted by ninjasword71
Wow, thanks! Those are the instructions I'm missing. Looks pretty close to Eagle 1. To me, a standard size servo is 9g is all I use. Yours are much bigger. How long are your flights?
There is no Eagle 1
If the wingspan on yours is 63 inches, you have an Eagle 2.
As Ken stated, the smaller one is the 50 inch Eaglet.

A 9g servo is a Sub-Micro servo (much too small for the Eagle 2)
As for the run times I get, that varies a lot, depending on how I fly the plane.
I usually use a fair amount of throttle with my planes, so I have the timer set to 7 minutes on my Eagle 2.
That usually leaves my battery around 3.8 volts per cell after the flight, which is storage charge voltage on a LIPO.
If I fly on the conservative side, 9 minute flights wouldn't be a problem.
Personally, I don't care for flights lasting longer than 6 minutes.
Very easy to land, put in another battery & go up again.
Last edited by Clive66; Oct 15, 2017 at 11:11 AM.
Oct 15, 2017, 12:43 PM
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ninjasword71's Avatar
From 1969 and does not say eagle 2 on the box. The eagle 2 is claimed to have better design. Thanks for the help. Seems pretty straight forward
Oct 15, 2017, 01:33 PM
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Clive66's Avatar
Quote:
Originally Posted by ninjasword71
From 1969 and does not say eagle 2 on the box. The eagle 2 is claimed to have better design. Thanks for the help. Seems pretty straight forward
Gotta eat my words here.
Learn something new every day.
That's definitely not the same box my Eagle 2 kit came in.
Does look like the same plane though & the wingspan is 63 inches.
Good luck with the conversion & post your results here when it's done.

All this posting about the Eagle, has renewed my interest enough to take mine flying in the morning.
Oct 22, 2017, 05:26 AM
I am a nice guy! Really!
Quote:
Originally Posted by ninjasword71
Wow, thanks! Those are the instructions I'm missing. Looks pretty close to Eagle 1. To me, a standard size servo is 9g is all I use. Yours are much bigger. How long are your flights?
I used the Futaba S3003 Servo in my Tower Trainer, which is about the same as the Eagle.

https://www.towerhobbies.com/cgi-bin...?&I=LXVW84&P=7

That is the bulk version of the servo, which does not include grommets, output arms or mounting screws. Tower does not seem to offer the non-bulk servo. At the time I ordered I accidently ordered the bulk servos instead of the individuals. They were both the same price but the individuals came with the hardware. I ended up having to buy several kits of hardware at about $3 each.

Anyway the S3004 will be an excellent replacement for the S3003

https://www.towerhobbies.com/cgi-bin...&I=LXVW07&P=ML

Of course you can use another brand. Just get a servo with at least the same torque spec. The 40+ inch pounds is what Tower spec'd for their Trainer.
Oct 22, 2017, 09:44 AM
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Cougar429's Avatar
I built two of these back in the 80's and at that time remember it was called the Eagle 63. Yes, there was a smaller Eaglet. Bolted my first sport 40, the OS FP onto the first.

Strong, reliable, easy to build and remarkably aerobatic with a few mods. Even had a piped 40FSR on the second, (till the tail fell off!). Could be assembled with different dihedral angles to control stability.

This was a 40 size aircraft and would fit any engine in that class. About a decade ago built the Eagle 2 as an engine test bed. Different engine plate measurements would allow for quick changes and I could have a new setup up and flying in less than 10 minutes. I have run all the way up to a 52 for testing, all using pretty much the same 10/6 prop.

That firewall, engine plate and mounting already has the correct amount of side and down thrust so converting this to electric is much easier. Just be cognizant the fuel tank bay and cabin has no airflow so opening that up would be critical.

While putting it together decided to make a few other mods along the way. The tail was replaced with one from a friends destroyed 3D plane for much more elevator authority. Doubled the wing bay and added two aileron servos. That allowed for Flaperons and it would allow for some astounding slow flying.

Only other structural mods were to make it a taildragger and strengthen the floor aft of the cabin for float attach points. All this added weight, but it still topped up under 7 lbs sans floats.

Back on the original we worked with the stock Futaba 128/148. The 3003 is their more modernized version and shares a lot of the same geartrain, so should be fine.

NOTE: Rule of thumb is 100 Watts for each pound aircraft weight, so you would be looking for anywhere from 550-700 Watts. However, your final weight and type of flying would determine how much you want or need.

I have the Eagle II manual in .pdf format and can send it to you. PM me your Email.
Oct 22, 2017, 10:30 AM
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Clive66's Avatar
About air flow when going electric with this plane.

I found that isn't a problem.
I don't have any heating issues at all, with either the LIPO or the ESC on mine.
The cabin area is large, so IMO, it would take a lot to heat it up enough to matter.
The hole in the firewall where the front of the tank came thru & the hole in the back of the plane where the elevator push rod exits, apparently allows enough air flow.

All up flying weight on mine, with a 16 ounce battery is 5.8 pounds, which is almost exactly what it weighed with fuel before the conversion.

Checked mine with a watt-meter (720 watts at full throttle)
Last edited by Clive66; Oct 22, 2017 at 10:37 AM.
Oct 23, 2017, 05:10 PM
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ninjasword71's Avatar
Quote:
Originally Posted by Cougar429
That firewall, engine plate and mounting already has the correct amount of side and down thrust so converting this to electric is much easier
So the first eagle is set up the same as the 2 in engine bay? And thanks but I've already downloaded the 2nd version PDF.
Oct 24, 2017, 10:55 AM
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Cougar429's Avatar
From what I remember both were close to the same setup.
Oct 24, 2017, 02:01 PM
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Quote:
Originally Posted by ninjasword71
So the first eagle is set up the same as the 2 in engine bay? And thanks but I've already downloaded the 2nd version PDF.
I have the plans and manual for Eagle 2 ( plans say Carl Goldberg kit #56, designed by Carl Goldberg, Mark II improved by Dave Patrick)
Just now I looked at the Eagle 63 plans downloaded from Outerzone (which have the RCMagazine logo).

The engine/motor side thrust appears to be the same between both plans, perhaps 1 or 2 degrees..... the Eagle 2 manual says the left fuselage is 5/16" longer than the right side.

What immediately struck as significantly different - just on an "eyeballing" level - was that the downthrust on the Eagle 2 plans was given (printed) as 8degrees (with the stab and bottom of the wing airfoil both given as 0 degrees.
I didn't go thru the hassle of printing out the Outerzone plans for the Eagle 63 but used by Tiltbox digital "inclinometer" - which I hold to be very accurate - to measure the screen image of the plan and on that reading the downthrust is around 4.5 degrees.

Interesting difference in downthrust.
My off the top of my head reaction is 8 degrees downthrust is a lot. I think the downthrust on similar/more recent planes such as the Sig LT-40 have about half that amount.

good luck

Michael in Ontario, Canada
Oct 24, 2017, 08:10 PM
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ninjasword71's Avatar
That's good news because whoever had this before me already glued the motor box in. Looks about right for angle. There is some odds and end parts which I will have to cross reference to see where they belong. Compared to a smaller foamie, this one will probably feel much different in the air with metal and wood parts. Not a whole lot of balsa on this one either.
Oct 25, 2017, 10:37 AM
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Cougar429's Avatar
I too would think than 8 degrees down would be excessive, but a lot depends on wing and tail incidence and that is something not sure if changes made between versions. No longer have the airframe so no way to check. Did have a boo at some other Goldberg designs I have built over the years and unfortunately nothing listed as to firewall specs I can find.

Good thing is that the engine plate and mounting design would tend to allow for easier adjustments with washers or spacers between the plate and beam.


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