[DO335]

I wonder who designed that plane - GP or the Chinese manufacturer? Was there ever any prototype testing? If so, the serious snags you and every other purchaser of the YAK 54 have encountered would definitely have shown up.

This is another case of a supplier putting out a crap product and being fully aware of that. GP knows that the LG, as designed and built, is a failure in waiting. Anyone with even a rudimentary knowledge of RC planes can see that from the pic of the plane as supplied. And even if the design was not tested, they now know it's flimsy because Second time around advised them of it.

What a joke - you pay that kind of money and then you need to totally re-engineer and rebuild the thing in critical areas before you can even think about the assembly.

Well, I suppose as long as people keep putting up with this nonsense and continue to be apologists for the suppliers (GP is not the manufacturer - some Chinese place is), this is the junk and required solutions that you'll keep getting.

Watch those landings, Grizak!

[grizak]

DO335,

I know what you mean about getting a product that is not designed well. It can be frustrating.

However, I wouldn't consider this plane "junk". I think that it is a nice design and is well built, it just has a couple of problems that need to be addressed. I find this to be case with many ARFs on the market.

I also like to build, so I have tendency to want to change and reinforce things.

That being said, I haven't flown this plane yet. If it flys well, then I would consider these modifications a minor investment for a nice plane. If this plane doesn't fly well, then I probably would not recommend this plane.

So far my research indicates that it will fly well (I wouldn't have bought the kit otherwise).

Back to building....

Grizak

[Second time around]

I was dazzeled when I saw the Yak 54 ,
So much so I bought instead of a Ptty Wag staff.
Am I sorry I hope not . Disapointed yes.
Still dazzeled yes but that might be because I fell off the ladder LOL.

Keep up the great pictures and information Grizak .

Sparky

[scott H]

i put the gp yak 54 together last winter ive got 20 flights onit and love it.it has a poulan pro 46 cc on ei bought the props xoar 21 .8 from jeff at thunderbolt rc.it will hover but not much pullout.i drilled each landing gear and run a 4 40 rod across under the fusefor strength.i put a 5955 hitec midship for rudder and 2 5645 in the back for the elevators and the gas tank in the stock location.the plane balanced perfect by the book. it weighs 15.3 pounds dry. for a 399 dollar arf i feel i got my moneys worth.and yes i did have to put three screwsin each side of the engine box plus i ca the whole frame work no rattle sounds wile running.all in all a easy plane to fly and land plus hardly any elevator on knife edge. keep up the good work jeff.

[grizak]

Scott,

Thanks for the feedback. I'm glad you have had success with your GP Yak.

Once I get everything going, and get some time on the plane and the MT50, I plan on switching to a newer Xoar PJE 20B or 21A "3D" prop on this plane. These props are variable pitch props designed for aerobatics and 3D flying. The produce significantly more pull than a standard prop.

Grizak

[grizak]

Back to the build....

I decided to reinforce the aluminum landing gear struts. They seemed a little soft to me, and I have always found that once you bend them with a hard landing, they get weaker and will continue to bend.

I use a set of landing gear reinforcement standoffs and some 3/16" music wire to make a reinforcement wire that goes under the landing gear struts.

The music wire will act as a shock absorber on landing and will add strength to the overall landing gear.

This reinforcement is another reason that I cut away a section of the bottom of the fuse.

Here is a pic of the bottom of the fuse before I added the reinforcment wire:



I then bent a section of 3/16" music wire that forms to the shape of the landing gear.

Holes are then drilled in the aluminum landing gear struts (2 on each side - one near the top and one near the bottom) and the music wire slides into the standoffs and screwed into aluminum struts.

Here is a pic:



And here is another picture of the landing gear strut with the standoffs mounted.

It should also be noted that I did add a small piece of hardwood underneath the music wire that is epoxied to the stock landing gear wood block. This additional piece of hardwood will provide some additional strength and stop the music wire from moving to far upward on a hard landing.

I now have these Landing Gear Reinforcement Standoffs in stock. They are available here:

http://www.thunderboltrc.com/index.p...roducts_id=550

Grizak

[rcpilot]

I flew one of these for the whole last season, I bought it crashed from a fellow club member and repaired it, it was my first gasser. I put a DL50 in it, it was an absolute blast to fly, although the landing gear is weak, I was able to survive almost to the end of season, At the nats last year, I hit the dirt and broke the landing gear off, So, although it is weak, if you are careful with it, it is fine, re-inforcement before hand of course is a great idea.
Other than the landing gear, couple of other things to watch for it are

It slows down almost instantly on landings, so better be on the throttle, you have to fly it in, I know it is the same with most scale birds, but this one tends to slow down too fast.

The other thing to watch for is that it sometimes tends to snap when pulled hard at some positions, test for it and get the feel at some altitude.

CG suggested was too conservative for me, I had to move it back further than suggested.

The tail wheel is a POS, better replace it with something decent.

Other than that, rock solid in hovers, rolling harriers, rolling circles etc.

Here are few pics.

[d_orgera]

I've got one of these birds also. I don't know if I agree with stiffening the gear using music wire and standoffs. The gear is flexy and will momentarily splay on a bouncy landing, effectively absorbing much of the bounce, but it springs right back...at least mine has never bent. I think if you stiffen the gear, you're only putting more stress on the gear mount.


Cheers,
Den

[grizak]

Maqsood,

Thanks for the info about this plane, it will come in handy on my first flights. Do you know what the CG was set at on your plane (The CG that you liked best?)

Thanks,

Grizak

[grizak]

Den,

Thanks for the feedback. I tried bending the landing gear struts that came with my plane and they do have some spring, except at the main bend. At the main bend they have very little spring. The music wire still allows the gear to spring, but it stops it from springing to far. The music wire also absorbs some of the force and spreads the force along the gear. I think with the modifications that I have made, the gear will be ok.

I've used these Landing Gear Reinforcement Standoffs and music wire on several planes with very good results.

Grizak