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GP Extra 300S 60 Build 2013

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GP Extra 300S 60 Build 2013

Old 01-06-2013, 08:34 PM
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ChinookRC
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Default GP Extra 300S 60 Build 2013

I graduated from a trainer (Nexstar EP) to an E-Flite Carbon-Z Yak 54 foamie (48") this past season and had such a great time with the Yak that I bought a .60-size Great Planes Extra 300s kit from Tower Hobbies for $120. A reasonable price for a nice kit, great reviews and plenty of build threads to reference made this an easy choice. I'm pretty sure there isn't a need for yet another build thread for this plan, and I'm certainly not experienced enough to be able to contribute anything new to the build but I'll go ahead anyway - documenting the build forces me to slow down and get help before making mistakes.

I'm a couple days in with the tail almost complete following the mods suggested on this 2004 thread.
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Old 01-07-2013, 08:45 AM
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prgonzalez
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Default RE: GP Extra 300S 60 Build 2013

Very nice, welcome to building!!!

Please post your progress and questions here. Everyone will be happy to help you.
Old 01-07-2013, 06:55 PM
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LargeScale88
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Default RE: GP Extra 300S 60 Build 2013

Will be following for sure!

Had one of these on my bench at one point maybe I'll get back to it.


Jason
Old 01-07-2013, 08:25 PM
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ChinookRC
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Default RE: GP Extra 300S 60 Build 2013

I'm wondering how to handle the elevator halves which I've left joined for now, but in the plans are separated, with two 2-56 control rods coming from a single fuse-mounted servo. My previous builds (TFCorsair, TFBearcat, DP T-28) all had a single control rod with elevators joined by a u-shaped 1/8" wire with a soldered on control rod connector in the middle of the wire.. I know some people were concerned about balance (and to a lesser degree slop) and put the servo in the tail but I don't think I'll need that with the DLE 20 I'm planning to buy (if anyone ever gets them in stock). I remember some people regretted the tail servo but it does seem standard for modern aerobatic models.

Also to note is that I've kept the overall shape of the stab + elevators but I made the elevators themselves 1" longer than the plans. So there's the potential for more force than the designers originally considered.

So Iguess the options are:
  1. split elevators, two rods, one fuse-mounted servo (the plan)
  2. joined elevators, one rod, one fuse-mounted servo
  3. joined elevators, one rod, one tail-mounted servo
  4. split elevators, two rods, two fuse-mounted servos
  5. split elevators, two rods, two tail-mounted servos
I'm afraid Idon't have enough experience to know of any other options. Any opinions on what the best solution might be? The pic is from the manual (#1 above). I think the main consideration for me would be the ability to make adjustments to the elevator alignment after the plane is covered since I did have issues with that on previous builds, particularly getting good alignment of the two holes drilled to accommodate the u-shaped joiner wire. So perhaps #1 is the simplest solution?
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Old 01-07-2013, 08:59 PM
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Gray Beard
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Default RE: GP Extra 300S 60 Build 2013

All the methods work. It's a tough choice. When using only one servo I like to make up a single rod from a carbon fiber arrow shaft with a single wire going to the servo and two rods that come out the back end of the shaft and out each side of the plane to the two control horns on both rudder halves. It's just called a Y. I can take a photo of one tomorrow and post it for you if you need. It's just another way to do the same thing.
These days I try to run a servo for each half. I have broken the clevis and the control horn on an elevator half a couple times and still been able to bring the plane in without problems. It just acts sluggish on elevator. The same thing would work with a Y I guess? A lot depends on your radio and receiver too.
A lot of ways to do the same thing. None are right or wrong, just different.
Old 01-08-2013, 05:27 AM
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ChinookRC
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Default RE: GP Extra 300S 60 Build 2013

Thanks for the suggestion, it reminds me of the late 70's Dave Platt T-28 that I set aside to build this Extra that had pretty fat balsa sticks running through the fuse instead of carbon fibre arrows. Ijust had an image of the Extra plowing in, impaling itself on the arrow and left quivering, tail up). It's a good modern twist but I do like your idea of two elevator servos operating each half independently as a failsafe mechanism. I'm using a DX8 so I have channels to spare.

For the rudder I'm leaning towards trying a pull-pull system which is probably overkill for this size plane. The rudder size is the same as the plan but I've enlarged the counterbalance by 60-70% which Iassume will take some load off the servo. Still, I'd like to give pull-pull a try now before I move on to larger planes - unless there's a good reason not to?

Anyway, these linkages are some way off - next step is to build the wing.
Old 01-08-2013, 07:12 AM
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OldScaleGuy
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Default RE: GP Extra 300S 60 Build 2013

The two Goldberg Extras that i have built used the method as shown in your instruction manual. There has been no issue with that set up. I did not use the plastic retainer at the servo, i don't trust that arrangment, plus i soldered the two pushrod between the servo and the tubing. Nice plane, i will be following along.
Old 01-08-2013, 02:55 PM
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LargeScale88
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Default RE: GP Extra 300S 60 Build 2013



On my sport planes, I have the elevator halves seperate, and I have 2 setups in 2 different airplanes. I have one setup with 2 servos hooked up, and the manuals method of 2 control rods held together with 1 servo. Either one I think will work, I just always liked having 2 servos.


Jason

Old 01-08-2013, 05:27 PM
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Gray Beard
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Default RE: GP Extra 300S 60 Build 2013

I even make up pull/pull systems in my little electrics. I use it most everything I build. I make up my own systems using braided stainless steel plastic coated fishing leader I buy at Bass Pro. I can get it in different weights/thickness. I'm installing it right now in a very light weight three channel electric powered plane I am building for a friend. I just find Pull/pull an easy way to set up a ruder.
It's really the same reason I use two elevator servos too, I like easy and they are really easy to set up and adjust.
Only plane I have broken the clevises or horns on is my little 60 size hots. It's nothing like my Extra at all. The Hots gets thrown around doing things that would kill most planes. I also stuck a YS 1.10 in it just for grins. There is a reason things have broken on that plane! Redundant is a good thing on the Hots!
Old 01-09-2013, 05:55 AM
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prgonzalez
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Default RE: GP Extra 300S 60 Build 2013

In my experience, pull-pull for rudder is the way to go. In regards to elevator halves using two separate channels (one master and one slave), I have found that it works best with a radio with adjustable delay in the channels. If not, the master servo will be moving faster that the slave that possibly cause some roll torque. For that reason, I have changed my models to D.E.P.S (Dual Elevator Pushrod System) as used by pattern models.

my 0.02.

Pedro
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Old 01-11-2013, 12:28 PM
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bgfireman
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Default RE: GP Extra 300S 60 Build 2013

This is a great plane. Pardon the pun, but you will enjoy it! Mine had a Saito 120S on it with a 16 X 6 Vess Prop. I wish I still had it. The only problem I ever had was with the landing gear. I pulled them out several times.
Have fun,
Alan
Old 01-12-2013, 07:10 AM
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OldScaleGuy
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Default RE: GP Extra 300S 60 Build 2013

Can this one be fitted with a TnT landing gear? Would that improve the landing gear issue?
Old 01-12-2013, 11:00 AM
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Default RE: GP Extra 300S 60 Build 2013

The stock gear looks very strong. Fireman, was it the screws mounting the gear that stripped out of the wood, or did the plywood break out? I recall reading about a fellow that re-designed the ply mount for the gear, but can't recall the details. You said you had a 1.20 on yours, was it nose heavy with that much engine?
Old 01-12-2013, 12:32 PM
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ChinookRC
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Default RE: GP Extra 300S 60 Build 2013

Here's a full-size scan of both the plans and the die-cut parts. Working on the wing and will return to earlier comments on the linkages soon.

The 2003 and 2010 threads have a lot of discussion on the landing gear mounting bolts and hardwood mounts failing. Maybe looking at the plans will spark some ideas for improvement.
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Old 01-13-2013, 07:12 PM
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Default RE: GP Extra 300S 60 Build 2013

I'll return to the elevator linkage topic later but thanks for the advice earlier. In the meantime I worked on the wing which is taking longer than I expected - a lot more parts than the typical 60-size warbird sheeted wings that I've made. Nothing too unusual but it's not entirely clear to me yet what to do with the TE sheeting at the root so I've left it uncut for now. Ialso miss building the aileron while it is still attached to the TE - that seems to be a more accurate method of construction. I'm building on glass per the Dave Platt videos and am thankful for the aluminum/lead weights I made over the summer.

Rather than follow the servo installation shown in the plans with the entire top portion of the servo sticking out the bottom of the wing I'm going with a typical side-hatch-mounted servo. I haven't done this method before and am wondering if I need to add support to the hardwood posts that I just CA'd to the 1/16" ply hatch. The hatch is a lot bigger than I'd like but I'm not too worried.

I'm using Hextron HX5010 plastic dual bearing 96 oz-in .16sec/60deg servos that I got super cheap from HK.
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Old 01-14-2013, 10:46 AM
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Default RE: GP Extra 300S 60 Build 2013

Sorry to jump in with criticism, but I really don't like the control surfaces mods...
I've been flying my Extra for 1.5 years now, built to plans.
The plane has enough control authority, even for snaps and tumbles:
http://youtu.be/Vy4IXccsMv4
I'm using the suggested control throws and medium range CG, nothing extreme.

It is a smooth flyer, an old design for sport scale aerobatics and not all-out 3D.
The wing profile is sharp, and knife-edge flight requires some speed.

Build it light and it will reward you with nice smooth flight and land very well. Don't go out on reinforcing everything. I've seen some "lead sleds" built at my club, good for some scary landings!
The gear is stiff, and it is NOT designed for rough landings. I haven't ripped mine appart (yet), but I make an effort to land smoothly everytime.

I'm using dual elevator servos on the tail. Here's a pic of my setup:
http://www.rcuniverse.com/forum/m_10...9/key_/tm.htm#
Post 209
You'll probably need them for balance, I'm using a Saito 125 and had to add 0 lead for CG.

I added fiberglass parts, even so they cracked a little. The abs plastic would have been shattered with the Saito!
Elevator and rudder throws in the manual are good, low rate aileron was a little low for my taste...

Good luck on your project, keep building them!

And sorry for the criticism...


Saludos,
Jean Paul
Old 01-14-2013, 12:46 PM
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Default RE: GP Extra 300S 60 Build 2013

J.Paul, thanks for the input. I just started one a few days ago, and I did opt to extend the rudder an inch at bottom, 1/2" at top, but plan no other control surface mods. I think I'll do some minor reinforcement to ply landing gear mounts, and run a Magnum .91 four stroke. I built a .40 Extra about 15 years ago, and it was a fantastic build and flew just as well. Always liked the way 300s fly.

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