Czmelak building

[Pgoldsmith]

Nice Kevin, awesome achievement...

[lenb]

GO KEVIN.....

Congrats man! You're now the second kit to be built and covered. Quite an accomplishment.

[kjkavaney]

FINALLY...starting to look like this might someday fly !!!...all that putzy stuff has been taking all my time. Len needed a longer cowl as he had to put his motor a lot more forward...I will have the same issue but I have a secret weapon: "Steve Richman Auto Winder" at 2 pounds that I will be putting up to 6 inches ahead of the CG...hoping that will allow me to only need 1.5 inch stand off behind the engine..If I were an Engineer I could do the math, but I am NOT...so time to experiment...
All servos are in...batteries and switches are in...everything is covered and hinged...just need to plumb the fuel tank and mount the landing gear....heck it might fly this year yet …

[ARUP]

That is looking great!

[Mosquito]

Looking good buddy. My airstrip has just about cleared of the latest snow storm so barring anymore storms, we should be free and clear maiden that beast here soon!

[gunny11]

That looks beautiful!

[MarkRobbins]

Good Work Kev!

[MarnochS]

Looking Beautiful .....

[kjkavaney]

Things are finally beginning to feel real on this build. I can see why Pete Stopped using the Pawnee landing gear beyond no longer available. the variance between alignment of thePawnee landing gear bushings are far from great, crooked, so not smooth action. also putting the whole thing together is pretty putzy...
Fortunately i have another set of landing gear and i will see if i can get a better fit from the other pieces...I used the after market McMaster Carr springs and cut them longer so no longer using the spacer as was suggested by Pete...hopefully this will give me more NeuTons...
Used the half scale J cub wheels Pete suggested...added brass sleeves for better hub life.
Next step is a two person job to flip it upside down with the horizontal stab on and see if it is close to being balanced...my engine is out 1.5 inches...Len said he had to go out to 2 & 3/8 inches...
I can't really cut t he exhaust outlets in the cowl till I know for sure how far out the engine needs to come out..
I have left the windows and doors off because I need every entry I have to get at securing stuff...my small hands help...

[kjkavaney]

Still seriously tail heavy even with the Steve Richman auto winder 3 inches ahead of the CG...I guess I really messed up on how heavy my tail is.
I have the motor blocked out to 1.5 inches...so will go to 2.25 or even deeper to balance this. This means that the original cowl provided in the kit will NOT have enough material for this and I will\need a much deeper Cowl. Len told me of a source since he had the same issue as he had to go out to 2 & 3/8"....i suspect i will be even further...

Those of you who are building one of these...be mindful of how much your rear structure is weighing as you build it or you will face the same fate as me !!!!

[kjkavaney]

Put it all together for the first time since it has to be outside as my shop is too small for this monster. Even with the motor blocked out to 3 inches (Pete's plans are for 20mm) I am still way tail heavy and it Is taking 4 pounds on the crank case to get it to balance, which will mean 5 pounds or more of lead on the fire wall.. I already have the approximate weight of the cowl taped to the crank case of the engine.
As i stated before, those of you building one of these...be very mindful of how much wood and such you use in the tail section..One might even entertain shortening the tail section at inch or so ??
The tail section is essentially scratch built as all of those side pieces of balsa are all cut from balsa stock and are not provided already cut in the kit. I made a lot of mistakes and had to scarf a number of pieces of wood and made too many supports than were needed obviously...
Will now make up some lead weights that can be bolted to the firewall...will put in T nuts so things stay in place...nothing would be worse than for the weights to let go in flight and have a severe tail heavy power plane go out of control...

[lenb]

Im not sure where you are holding it from with the line, but all assembled, the CG is at the rear edge of the wing tube, which equals 3/4" further back than the center.
Go with bigger, heavier wheels, an aluminum spinner, and a three blade prop.
oh yeah, the windows are not in.

[JimD]

Decided to check my balance as best I can. Without the wings attached and without the stab on the tail or the prop and spinner on the nose, I lifted at the wing tube and the fuselage is nearly perfectly balanced! Keep in mind that my landing gear is wing mounted. My engine is 1-5/8" out from the firewall. Got 1-1/4" L x 5/8" OD steel spacers for the engine standoffs. They weigh over an once each and makeup the difference in weight between the older DA-150 (like the one in Peter's prototype) and the newer DA-150L version like the one on my plane.

[JimD]

My ignition module, ignition battery pack, throttle & choke servos, and header tank are located between the firewall and the fuselage former under the dash. The radio batteries ate located against the cabin side of the fuselage former under the dash.

[kjkavaney]

Beautiful build Jim. I was shocked at how much the horizontal stab weighs and once it was mounted on my tail, it really put my Cmelak into a tail spin so to speak.....I thought I was okay too earlier this winter.

Len, i am holding the cord at the center of the wing rod, so 3/4" further ahead of what you are suggesing is the balance point.

I have my ignition and it's battery on the front of the firewall and the battery for the auto winder on the back side of the firewall and my Rx's batteries right beside the fuel tank...I can't get any other gear further forward than they already are. I have some aluminum hub tires that weigh more than these J cub ones, maybe I will push the motor out another 3/4" and then add 2 pounds of lead on either side of the motor on the firewall...
I will be curious Jim how yours balance once you put the Horizontal stab on, wheels, prop, and wings on your beast....keep us posted...
kevin

[stevekremer]

Len and Jim,

Don't I remember you guys saying that the dimension that Peter gave for a balance point was without the wings installed?. Are you balancing with the wings on or off Kevin?

Steve K

[lenb]

Guys.

when the plane is all put together, ready to fly minus fuel, you can balance it at the REAR edge of the wing tube. REAR EDGE....

Without the wings, Peter says it the center of the wing tube.

So when you move the balance point to the rear, it takes less nose weight to balance it.


Jim,
You may only need 2 1/2 -3 lbs in the nose if you were able to relocate some of the other items more forward.. That would be good.
With the tail off, I would expected the nose to drop over. so rule of thumb in models is 3-1, so if the stab is a pound, thats three to the nose. Peter says maybe more than 3-1, depends on the leverage arm.

Interesting to see where it comes in.

[kjkavaney]

A Death in the family has created quite a delay in this build. Very close now...they call this Thing a bubble bee, so hence the Callie graphic on the rudder...
My engineer friend suggested a form of a diving board to move everything forward as much as possible to reduce the additional nose weight needed...i am already heavier with the Auto Winder so by putting the ignition battery and some lead right up front...perhaps reducing my extra weight by maybe two pounds...the doors and windows have turned out to be some of the most difficult finish work on this whole project....i have done curved canopies before and hence compound curves...flat windows are a whole new challenge...
Hoping this beast will fly later in the week...working on radio issues as i write this...MXP connectors for the wings inside the fuse...