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GP Extra 300 build question

Old 02-17-2012, 10:02 AM
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abbott915
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Default GP Extra 300 build question

There are a lot of builds up here for the Extra 300, and what I'm not seeing in them is much if any talk about areas in the build that should be strengthened or reinforced.<o></o>

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I built a CG Ultimate 10-300 (RIP) and there were a number of places that got some reinforcement.<o></o>

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I’m currently building a Royal Corsair, and my build skills are such that it is going to take a while to make sure it comes out the way I want it to, so I’m going to pick up a kit today from the local hobby store and get started on it so I have a plane to fly this summer.<o></o>

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I won’t do a build thread on it, but I will be lurking in all the other threads to pick up some tips.<o></o>

<o></o>

Thanks!!

Old 02-17-2012, 11:52 AM
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SeamusG
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Default RE: GP Extra 300 build question

Firewall to tank box reinforced with tri-stock. Before assembling this area you need to determine if the engine that you are using will allow for the correct engine-thrust-plate-to-firewall-dimension. A YS 1.10 puts the thrust plate out an additional 1/2". Make sure that the cowl can accommodate the difference or cut the tank box back 1/2".

Landing gear plates (2 of em - 1/4" ply about 1" wide) are parallel and are notched into the former at the "wing bay", skipping a former, and terminates at a former of the tank box. Tri-stock was used to reinforce the formers - fore-n-aft at the notches. There is no "meat" to reinforce the ply to the sides. Guess you could load up balsa block around the plates. Perhaps you double the 1/4" ply plates with 1/8" ply. I chose to use the stock approach with a bit of tri-stock at the formers.

The wing's belly pan is pretty flimsy as the 4 rails are made of thin lite ply. Some have sheeted it. Mine were pretty wavy out of the box. Felt good just to get the darn things close.
Old 02-17-2012, 03:09 PM
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abbott915
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Default RE: GP Extra 300 build question

Thanks for the comments. I'll watch for those improvements.

I'm planning on using my ST G90 that came off the CG Ultimate.
Old 02-17-2012, 03:39 PM
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Default RE: GP Extra 300 build question

Ilied. Iused square stock rather than tri-stock for the firewall support.

I think that you can see why reinforcing the landing gear braces is tough.

In retrospect Imight lay down a piece of 1/8 x 1/8 stock on the inside of the wing's belly pan side rails to keep them straight. Gives you a side rail to glue them to rather than depending on thin CAto tack the contact points to thin sheeting and keeping them in a straight line and keep them formed to the curve of the wing bottom.

If you want any other specific picture of a structure let me know and I'll see if I have it.

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Old 02-17-2012, 03:56 PM
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Default RE: GP Extra 300 build question

BTW- with a YS1.10 my plane was very nose heavy. Ihad the elevator &rudder servos mounted in the wing bay per instructions. Iended leaving the pull-pull rudder servo in the wing bay and added a second elevator servo and moved both of them to the back, offset, on under the stab. The mounts would have been much easier if I had made that decision before the fuse assembly process.
Old 02-18-2012, 06:58 AM
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Default RE: GP Extra 300 build question

I discuss land gear in my thread:
http://www.rcuniverse.com/forum/m_93..._2/key_/tm.htm

But after one hard landing those ply rails were still torn out. I have had to fix about 10 times. I have to keep epoxy in blind nuts onto ply but is weak and fails on hard landings. I do believe putting the doubler on the F-4 (or F-5?) part helped but those rails suck. I do not know how I would do it next time to avoid this terrible design issue.
Old 02-18-2012, 07:33 AM
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Default RE: GP Extra 300 build question


ORIGINAL: SeamusG

BTW- with a YS1.10 my plane was very nose heavy. Ihad the elevator &rudder servos mounted in the wing bay per instructions. Iended leaving the pull-pull rudder servo in the wing bay and added a second elevator servo and moved both of them to the back, offset, on under the stab. The mounts would have been much easier if I had made that decision before the fuse assembly process.
Thanks! Pretty sure I've read some of your posts and noted how you had some weight issues. I see that the ST G90 is at the upper end of the engine range. I'll check out the weight differences between the two and make sure I know what I'm doing before Iget to far.

I've seen others do the servo's in the tail, and because of my limited build experience, always wondered why. I guess that is one good reason.
Old 02-18-2012, 07:35 AM
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Default RE: GP Extra 300 build question


ORIGINAL: chemie

I discuss land gear in my thread:
http://www.rcuniverse.com/forum/m_93..._2/key_/tm.htm

But after one hard landing those ply rails were still torn out. I have had to fix about 10 times. I have to keep epoxy in blind nuts onto ply but is weak and fails on hard landings. I do believe putting the doubler on the F-4 (or F-5?) part helped but those rails suck. I do not know how I would do it next time to avoid this terrible design issue.
Thanks chemie. Landing gear always seem to be a problem. I guess those that are designing these planes and providing the build material are all much better fliers!! I'll plan on looking at that part and get it beefed up and if Ido bend or break them, I'll make sure they are easily repaired in the field.
Old 02-18-2012, 08:44 AM
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Default RE: GP Extra 300 build question

Chemie - can you explain how the landing gear rails break out?
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Old 06-24-2013, 08:59 PM
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Default RE: GP Extra 300 build question

It's been a while since I posted, but wanted to thank everyone for their comments and help building this Extra 300.

It's flown a few times, and thought I'd better post a picture before something bad happens.

Here's how it turned out.

The checkers were done using the windex method and cutting the pattern on a glass sheet, then using the "press and seal" to lift it from the glass and onto the plane.
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Old 06-25-2013, 02:18 PM
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Default RE: GP Extra 300 build question

I built mine with a larger rudder (1") and added 1/8" aircraft ply (not light ply) on top of the stock landing gear blocks for added strength. I use a Magnum .91 FS, and had to add 1+1/4 oz of tail weight to balance. I like the performance, but it could use more power on up lines. I think a .90 2-stroke would be a great combination, but flight times might be short due to limit of tank size. Nice building plane, nice easy sport plane to fly.

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