Kris' GP Yak-54 buld thread

[KrisW]

Okay, I walked into the LHS, plunked down $437 hard earned dollars (list for 399.. plus TAX. . YUCK) and bought the Great Planes Yak 54 ARF siting on the shelf. I am our clubs "amabassador" to Hobby Town, off Harris Blvd here in Charlotte, and last week when I was making my initial visit to the place (checking out their stock of goodies, rubbing some elbows, swapping lies etc etc etc) I saw THE PLANE. Great Planes Yak 54, marked down from the list price of $549 to a paltry $399.

Well, I checked the plane out on the Tower Hobbies website, and liked what I saw. So, I opened the box at the LHS today, and liked what I saw. . so I bought it.

And HERE we go. . .time to build this puppy and get her flying.

Here's what I have planned. I have a LOT of digital servos on the shelves, from 8411's to 5945's, 5925's 5955's and 5995's .. . gee. . ya think I got some servos that can handle this 81" planes flight loads????. . Okay, whatever goes in, it's gonna be digital. Then there's radio gear .. I can use Airtronics (4 available receivers) or JR (again 4 available receivers) The plane takes 5 channels if I use HiTecs (because they are programmable) or 6 channels if I use some JR's. Either the Stylus, my 10X, 10sx or 8103 can handle the control duties, so there's a poll for everyone to pick and choose the equipment for the plane. It's ALL good stuff. .

Okay .. powerplant. Well. . I just happen to have a BME44 on the shelf, or a BME50 that I can take off another plane to use in this one. . OR I can gut it out with an OS-1.60. The belly of the plane is foam with sheeting, so no canisters are going to fit inside (oh darn. . . NOISE). The instructisn call for up to a 43cc engine . .sooo. .. MORE POWER. If I can get a carb for the BME44, and keep the weight under 13 lbs, that will be my engine of choice. Otherwise the BME50 is going to get the nod.

Batteries. . we got Nimh. . we got Li-Ions from Fromeco. . we got NiCads. . lessee. .Fromeco and a single 4800 pack will do the trick, with a 2100 ma NiMH 4-cell pack on ignition. Use a Pin-switch for the receiver (regulated reliaswitch) and be done with it I say.

The plane is going to be set up for dual purpose flying, depending on where the clevis is attached to the servo arms. by merely moving the clevis in and out I can adjust things so that the plane flies IMAC style pattern or 3D. I want to see how well this plane can fly IMAC. . since it is a logical first plane for pilots wanting to get into IMAC on an entry level basis. I figure if I can fly last years Advanced sequence adequately with this little 81" plane, then it ought to pass muster in Basic or even Sportsman in IMAC. A lot of guys are buying BIG planes, even in Basic. I think it's time we explored less expensive options for the entry level pilots.

So. . have a look at the poll, and punch some dots. We have a few days before I start installing radio gear, so you guys get to make up my mind for me.

[ShortBus]

We all know it was my beautiful picture that sold you

[Kiwi]

Chris,

First off want to thank you for doing what you are about to do. I certainly agree that today we seem to set very high expectations for the guys who are about to start in IMAC and of course despite all our best efforts we all tend to drift towards the state of the art top end equipment. That you $pell as expensive by the way.

I agree fully with you that a $399 airframe properly done and trimmed can and will take you to the top of the sportsmans or intermediate levels as the competitions are normally fought hard and are very much based on pilot skills. And for those not reading between the lines here I mean those that practice and practice and when they get sick of it, go practice some more. It should not required $100 plus servos, 10 channel radios etc etc. You can install it all but will it fly better?????

Mate to me the airtronics setup, the mid range HiTEC, single packs for rx and ign is the way to go. Do not over power it as that will bring along a lot of other vices with it. Weight being one of them.

I really would like to see one of these built by the book but with intelligence, not the check book.

Then lets see how it flies. You just might save a whole heap of budding IMAC flyers a lot of coin and get them interested much earlier.

GitR Done mate.

Kiwi

[3-d flyer]

Finally! A build thread on this beast.... I thought i was the only one building this thing....
5645MG's all around
1- 5955TG on rudder
Fromeco 2400 on R/X
Futaba PCM R/X
BME 55 on "the waiting list" for end of april
Or a D/A-50 in 2 or 3 weeks.... if i can't wait untill the end of april!

Hinged the Ailerons last night, as well as mounted my gear....
servos are on the way, so there is not a whole lot left to do without them.
This is going to be a S L O W build for me waiting for the servos and Motor.
Ohh well, weather sux here anyway!

I figure if they are mounting that Fugi on there as recommended a D/A-50 will do just fine.... The BME-55 even better as i believe we will shed a pound off the nose!

[KrisW]

Glad to have you aboard, 3-D. . .

I got home at 6:30 . .at 7 the stabilizer was installed and hinged with elevators in place, and the Gear and wheels and tail wheel were in place already. Rudder took another 10 minutes, and I just finished the ailerons on the wings by 9:30.

This thing builds FAST!!!!

Oh. . I haven't opened the instruction manual yet either. . .

I'll have pics and notes on the build tomorrow.

[3-d flyer]

Kris.... What did you wind up doing with the stab.... That's when i quit last night, I was not to crazy about just epoxying it to those sides only.... seemed kind of weak? Did you do anything to strengthen this area up? Yeah... it builds quick! If i had the rest of my gear, i could have this thing ready in a couple more days.... that is besides the wait on the powerplant!

[Dennis C]

How about some picture's guys

[KrisW]

Okay. . STab installation 101.

First off, I got the stab aligned and centered with the fuselage. I used the tried and true "pull a string" method to set the stabilizer square to the length of the fuselage, after centering the TE on the fuselage. It took a bit of work to get the silly thing square. The holes on each side of the fuselage are not perfect, so one side is just slightly off, and I had to play with things and do a touch of trimming to get the stab to line up properly.

Then I marked the covering on the stab along the sides of the fuselage. I then cut the covering using a model knife, and removed the covering on the middle part of the stabilizer. I then tacked the TE of the stab in place, on the marks for centering it, then again checked it for being square on the fuselage. Then I tacked the front on one side to hold it square, using medium CA, installed the wing tube, and checked the stab to make sure it was parallel to the wing tube. When it was parallel, I tacked the other side using medium CA. I then double checked EVERYTHING one more time. When I was satisfied, I ran a bead of Medium CA on each joining line, between the fuselage and stabilizer, making sure it flowed between the two surfaces. I then "flexed" it a bit to make sure the CA got well onto both pieces of wood, waited about a minute, then cured it with Kicker. I did this to all four joining areas, one at a time, also rechecking alignment at each step, until all 4 mating areas were fully glued with the Medium CA.

Then, I opened up the servo mount holes for the elevators, and VOILA!!!!! you can see the inside of the fuselage where the stabilizer mates with it. You can also see the bottom side of the stabilizer if you open one of the rudder servo mounting holes (if you are using tail mounted rudder servos). Simply use good aim, Medium or Thick CA (or 15-minute epoxy or ProBond) and let gravity do your work for you. Drip the CA onto the LE of the stabilizer on the inside of the fuselage, right where the two join, and allow it to flow back toward the tail, along the joint of the fuselage and stabilizer. When enough has been dripped into place that you cannot see it flowing back anymore (you only have 3" of stabilizer you can see through the elevator servo holes, the rudder servo holes give you a full view of the bottom of the joints) stop dripping the CA into place, grab the bottle of kicker, and kick the CA by spraying through the Servo holes. Repeat for the other side of the fuselage.

It's simple, Quick, no mess, muss or fuss, and if you ever break that joint, you have hit a very large tree or the ground.

[GremlinX]

Sure is a pretty Blue..!

[KrisW]

Okay, lets talk engines for a bit.

Great Planes lists two engine choices for the Yak. . the OS 160 and the Fuji BT-43 gasser w/electronic ignition. I have a BME-44 ont he shelf, which is what I'll be using. Lets compare the three.

OS 160. . Glo fuel, about 50 ounces total weight with muffler and mount.

Fuji BT-43. . Gas, About 64 ounces w/muff, 70 w/ignition and battery. . backplate mount is integral and bolts directly to the existing motor plate.

BME-44 . . Gas, about 57 ounces with JA Pitts muffler and mount, about 64 including Ignition and battery. It also requires a stand-off mount to be built, adding another 6-8 ounces, so figure 70-72 ounces total weight, plus you have to build the standoff.


Great Planes specifies a total firewall-spinner backplate length of 6.75-7.25". The Fuji is 6.73" long, the OS 160 on a Beam mount can be adjusted out to about 7.5" if desired, and the BME44 on the aluminum mount I had for it is 5". So, either of the choices GP lists will drop right onto the airframe with minimal work.

As they say. . "some assembly required". . this applies to anyone using engines not specified by Great Planes. If I wanted to buy an engine, I'd opt for the Fuji 43 in this case. Since I'm cheap, and have a bit of ability to adapt things, I'll stick with the BME44.

[tl3]

Kris,
Could this thing be modified (without major re-construction) to accept a tuned pipe? I have a 3m 170 and pipe I haven't found a buyer for - now looking for something to fit around it.
t

[KrisW]

NOW is when we start taking a HARD look at the plane, and determine if we are satisfied witht he built in strength of things. I'm hanging about 4 POUNDS of mass on the end of the firewall, vibrating the hell out of it, and yanking this plane all over the sky, pulling G as much as possible, and want this thing to hold together no matter what.

Great Planes says, in a tongue-in-cheek manner IMO, "built to withstand ALL flight loads". . . . . . . hmmmm. . okay, so during landings and takeoffs its okay to rip out the gear plate, right??

After I got the tail surfaces mounted and hinged, and did the same with the ailerons, I started examining, closely, the fuselage glue joints, especially in the motor box area. I tugged on a few things to see what would come loose. I got a little upset when the fuel tank mounting plate lifted up at one end and came out of the fuselage with a light tug.. i mean LIGHT tug. . one finger. Then a couple of the fuselage formers easily separated from the fuselage top plate. . again with a light tug.

OKAY Y Y Y Y Y . . . . .

I STRONGLY urge everyone to chase every glue joint with Medium or Thin CA, especially if you are going to install a gas engine. I took 10-15 minutes to do that, and now I'm satisfied that no glue joints are going to fail.

Then I moved on to the motor box. It's looks beefy enough for a 1.60 glo engine, but for a gasser I'd do a bit of "strength modification"

First order of business. . please note that the tri-stock gussetting on the motor box is hardwood. A nice consideration in the design. Secondly, the motor plate-box joints are tongue-in-groove, making them very strong. But, the corners of the box are not gussetted, which will allow the seams to separate over time. So, I cut out some 3/8 hardwood tri-stock and CA'd it in place using medium weight glue.

One thing to consider. . the entire motor area is "sealed", to prevent glo-fuel soaking into the wood .. again, a nice touch. But it makes it really hard to epoxy anything. CA, being a bit more aggressive, will stand a better chance of sticking to the sealer. I advise sanding any wood you are going to glue things to, if possible, to allow a better bond.

After I got the gussets in place, I got some #4x3/4" screws and sank them through the sides of the motorbox into the firewall, to keep the sides from ever separating. This effectively "dowel pins" the assembly, and goes a long way to ensuring that the motor box will not fail at a critical joint. It adds minimal weight, but sure gives you a warm fuzzy feeling about the box's integrity. I did the same to the top and bottom of the box. See the accompanying photos for details

THEN. .I had to make a standoff mount for the BME44. I needed 2" of depth. so I layered up some wood, marked out the shape of the motor mount on the front, matched it to the centering on the rear where it was going to mate to the planes stock firewall, and put it on my trusty bench belt sander to taper it to shape. I then drilled the holes for the 10-32 screws I'll be using to hold the engine in place.

Okay .. the thing weighed a LOT. .but you do not need all that wood in the center of the thing, so I got out a 3" hole saw and used my drill press to slice out a 3" diameter chunk of wood directly on center of the standoff piece. VOILA!!! a 50% weight reduction in one swell foop!!! I then tapered the hole slightly on the backside, where the block was wider, and smoothed things over a bit. (photo #3 shows how BIG the plug of wood is)

BUT, being that the front has a small footprint, I decided to strengthen it a bit using a piece of 1/4" aircraft ply, to keep things from flexing or splitting and spread the loads a bit more evenly. The block was then epoxied and screwed to the stock motor mounting plate, as shown in the pictures, and the 1/4 plate was added and then the engine bolted in place.