AdrianM

I like reading build threads so I thought I'd give it a shot.

I did a lot of research on the Great Planes Extra 300 .60 size here and at other sites. Everyone loved their planes and everyone had ideas as to how to improve them. The goal of this thread is to provide a single reference source bringing together the info about engines, radio setups, and mods from all of the previous threads.

Here's a pic of my proposed scheme:


FYI, I build fast so this shouldn't be long and drawn out like other build threads.

Lets make some balsa dust!

AdrianM

Lots of guys have have added to the length of the Rudder and Stab so I wanted to do the same...with a twist.

Instead of adding 1' to the elevators I move the hinge line forward 1/2" and added counter balances a'la the Extra 330/300XL.

For strength and to have an easy point to determine where the counter balance should go I extended the front basswood spar to the tips.

AdrianM

Since the balsa around the hinge line is 1/2" wide moving the hinge line was easy.

AdrianM

I drew a few reference lines on the plan in pencil to rough out the counterbalanced elevators. I used existing rib locations to determine how wide to make the counter balances.

To make things line up prettier I moved the ribs in the elevators out a bit to line up with the innermost part of the counter balance.

Over all I am pleased with the result.

AdrianM

Moving the elevators forward 1/2" make the elevators ~50% of the stab area. The counter balances make the elevators a bit more than 50%.

So...The scale outline is still there, there will be less load on the servos and I will have more pitch authority.

Thats it for today. Vertical stab and rudder tomorrow.

barto

One question: what are counterbalances?

THX

AdrianM

They are 2 kinds, Mass and Aerodynamic Counter Balances.

Mass counter balances put a weight in front of the hinge line so some or all of the weight of the flying surface is balanced. Usually this is done to reduce flutter.

Aerodynamic counter balances put a portion of the flying surface in front of the hinge line. When an elevator deflects the air stream tries to push it back to the neutral position. This force increases with speed and added deflection. Aerodynamic counter balances reduce this load by entering the air stream on the opposite side of the surface. Because its ahead of the hinge line the air stream tries to deflect the surface more thereby reducing the load on the servo or reducing stick pressure on a real plane.

MinnFlyer

My Feedback: (4)

I'm liking it so far Adrian! I have a stock GP 60 Extra 300, but I made the same elevator mod to my 27% Extra.

AdrianM

The Rudder Is done. As per suggestions in previous threads I lengthened the rudder 1" at the bottom and tapered to a 1/2" addition at the top. I also brought down the counterbalance so it is ~1/2 the vertical stab span. Once again this is how the tail of an Extra 330/300xl is set up.

The rudder is quite stiff for how light and open it is. The covering will certainly add to the stiffness of the rudder.

AdrianM

Here is a detail shot of the rudder counter balance. The solid portion at the tip was the stock counter balance. The counter balance looks big but it is nothing compared to the one on my buddies Fiberclassics Extra 330 40%!

AdrianM

Complete Vertical Stab.

I did no structural changes other than shorten the vertical stab to account for the larger counter balance. The stick lying on the stab represents where the turtle deck sheeting will meet the stab.

Tomorrow I will start the left wing panel. So far the quality of the wood has been better than the last GP kit I built. All of the sheeting is nice and light. I need to inspect the rib material. If it is too heavy I will cut out all new ribs from lighter balsa (medium density).

nav8tor

Looking good so far Adrian. I'm just finishing up the same kit and first flight should be this weekend.

Having just been through the building process, I'm enjoying your posts. You had some good ideas for tail mods. I also increased the rudder 1" at the bottom, but I went with the standard elevator. I like how you modified yours.

What engine are you planning on using?

Lee

AdrianM

Lee - Thanks, i'm glad you like the thread! If you can offer any insight or things you ran into that you wish you had done differently let me know. Did you weigh your plane yet? How did your CG come out?

Engine: I have a new Saito 100 waiting to go in this plane. I'll start off with a 15x6 APC prop.

Radio: I use an Airtronics Stylus.

Elevators: I'll use one JR 3421 Digital Mini Servo (65in/oz, .18 sec at 4.8v) for each Elevator half. I run them on 6v and they are faster with even more torque.

Ailerons: I'll use one JR 3421 Digital Mini Servo for each Aileron

Rudder: An Airtronics 94358 (200in/oz, .10 sec @ 6v) on pull pull for the rudder.

Throttle: An Airtronics 94141 mini.

Battery: 720 Mah 5 cell pack.

AdrianM

My ribs look like they were cut from oak planks! The are very hard and brittle. I'm going to use them because I don't feel like cutting out a bunch or ribs with all of the lightening holes they have!

Wing Construction begins tomorrow.

nav8tor

I haven't weighed the airplane yet but I will shortly.

I'm also using a Saito 100. I ended up moving the elevator servos (Futaba 3003) to the tail because the airplane was nose heavy with that engine. Plus I'll have a lot less slop in the linkage. I'm going with a Futaba 9202 servo set up as pull-pull for the rudder.

Here's a link to a thread with a few photos of the plane in progress.

http://www.********.net/forums/showt...&threadid=4092

AdrianM

Great looking plane!

There are so many opinions about whether this planes ends up nose or tail heavy. I want to put my servos in the rear for the tighter linkages. Thanks for the heads up on your experience.

nav8tor

Thanks. I'll post pix of it when it's done.

I did a preliminary balance check (without covering) before I moved the servos to the tail. With them in the stock location it was nose heavy. With them in the tail it was pretty close to balanced. With covering it might be slightly tail heavy. I'll let you know how it comes out.

AdrianM

Here is the 80% complete left wing panel.

AdrianM

I had not planned to do any wing changes but this is so simple to do I have to do it.

The pic below is an image of the stock trailing edge with the stock aileron cut out. I am going to extend the aileron one more bay inboard from stock. This will give the ailerons more area and put them in the more of the prop wash for better control at low speeds.

Build-n-flyer-RCU

My Feedback: (4)

I just balanced and weighed my GP Extra 300. Built bone stock with a Saito 100, Performance Specialties muffler, alum spinner, JR 1100 mah battery and five 537 servos, fiberglass cowl and wheel pants, covered in ultracoat. Including 1 oz in the tail to balance, total wt is 8.4 lbs. Heavier than I would have liked, but we'll see how it flies. I'm curious to hear how everyone else's planes weigh in.

The only added wt is the "pilot" and some added bracing around the landing gear mount. The battery is mounted just forward of the servos.

I still need to clear-coat the cowl and wheel pants. I will do this tomorrow and given good weather for curing the paint this week, I should be up and flying next weekend. I'll post a pic later on this week after I finish dressing it out with decals and trim.

Miloh

Hay guys:

I just bought an extra 300s from the LHS used and ready to fly, heres the question. The LHS owner said it was an ARF but...... when I got home and looked for it on the internet I could not find an ARF in a .60 size only the .40 and the 1.20. the only .60 I can find is a kit so I was wondering if anyone could tell me how to figure this out for sure. the wingspan is 64 inches and the fust is 54 inches. is this a kit or an ARF????
Check the pict.

Miloh.

Build-n-flyer-RCU

My Feedback: (4)

Looks like a kit-built GP 60 Extra 300 to me. And I don't think that GP has ever sold it as an ARF.

Miloh

Kewl!!! thanks man

Miloh.

AdrianM

Flying and testing a new motor for a buddy put a stop on building this weekend. The left wing panel is as complete as possible. I habe to build the right side and join them before sheeting the top surfaces.

AdrianM

Flying and testing a new motor for a buddy put a stop on building this weekend. The left wing panel is as complete as possible. I habe to build the right side and join them before sheeting the top surfaces.