rcdude7

My Feedback: (264)

I am in the final stage of finishing my 28% extra special and I'm nose heavy. Please help me come up with a cleaver way of moving the CG aft without adding dead weight to my plane that is already on the porky side of the scale. I did build with a weight bias towards the rear, so here goes..........

In the nose I have a stock G-62 with a CH ignition, J&A pitts muffler, cup mount, 1200 mah NIMH 4.8 ign. batt (light weight), 3 1/4" tru-turn, 22X8 mejziik prop. Stock LG with light weight H9 3.5" foam wheels.

In the tail I have three digital hitec servos, 4-40 push steel/CF push rods (built as per WH instuctions), stock tail wheel assy. w/2" klett tail wheel (heavy). Single 2700 NIMH 6V RX pack mounted way way aft (as far as I could, can't go any farther) in the fuse. Plus, a few extra robart hinges in the rudder and elevators.

I still need to move the CG aft at least another inch. I do not want to swap the engine for some thing lighter!
I have considered cutting off the rear crankshaft stub. I don't know if this will trim much weight though. I can't see any other weight that can be trimmed from the engine.
I have also considered switching to C/F LG as it is forward weight. I have'nt even mounted the wheel pants yet.....whew.
I can put lead shot into the stab tube to get my CG right but this will be used as a last resort only.
Thanks in advance for your ideas and sorry no pics.

Mike

jongurley

My Feedback: (29)

What is your target CG from the leading edge of the wing tips,,,

rctom

I'd start with a CF spinner, that will have a big effect on balance. Also, you should be using 2 servos on the rudder in a push-pull, the second servo will move the CG back about 1/2".

If you do both of these things you should be pretty close.

Tf

Dangerous Dan

My Feedback: (1)

CF Spinner followed byCF gear would be the easiest, the spinner is a ways forward.
Might also move your throttle and choke servos further back.
shorten your engine standoffs so you only have 1/16 clearence between the spinner and cowell.

Is your true turn the lightned backplate version?

rcdude7

My Feedback: (264)

My target is about 3.5 inches back. I am at 2 inches now.

I have not mounted a throttle servo yet. I have a mini futaba servo that I plan to mount in the fuse though. I am going to use a manual choke setup.

My cowl to spinner clearance is 1/8" and the engine is bolted directly to a built up 3/4" fire wall. I cut a 2 inch hole in the center with a hole saw to remove weight there.

I am going to get a lightened spinner back plate from tru turn. The TT cone itself is very light.
I would like to avoid spending $80 on a CF spinner if I can.

I mounted one strong servo for the rudder to avoid the geometry problems of setting up two that will probably fight each other. I don't have a hitec programmer to adjust deadband width of my servos. I may take the plunge and do this anyway if all else fails.

I'll remove the engine and cut off the rear crankshaft stub. This has got to help a little.

I have been thinking of getting a TBM wingtube as they claim a 7oz weight reduction and my stock tube is .017" out of round. I know this won't do anything to correct the CG though.

Keep those ideas coming

Mike

Dangerous Dan

My Feedback: (1)

DO NOT USE MINI SERVO FOR THROTTLE

The gears can not withstand the vibration use a standard size servo. I had to land my 28% at 1/4 throttle on the maiden and I used a Mid size servo HS85.

jongurley

My Feedback: (29)

I have a 5475 digital hitec,, 30 something odd dollars and it is digital, probably doesnt' make a difference but maybe it is alittle more precise than a regular old standard,,

cstevec

My Feedback: (1)

Change your engine mount to shortest possible hardwood dowels & bolts, change to a carbon fiber spinner, mount the ignition battery back under the wing tube & you should be there. If not, go ahead & go with dual servos on the rudder & just be carefult to get the linkages correct. You won't have an issue with the servos fighting each other on the rudder if you are careful about setting up the linkages.

The carbon fiber stuff is nice but it is not going to help you get the cg back.

Tired Old Man

My Feedback: (1)

A fiberglass spinner from Bisson goes for $65.00. Leave the heavy aluminum one off or sell it to someone that wants it until you can afford the glass or c/f version. All metal spinners are heavy! The lightened back plates will deform pretty easily if you put a little too much oomph into the spinner screw. If you have a roll of True Red Ultracote you can move the battery back as far as you want to. The TBM wing tube weight is a fact. Tom is also now carrying C/F wing tubes so you may want to talk with him about them. Lighter main gear will only reduce the weight a little and have little effect on the balance point. If you have a choke servo up front you may want to think about that again. Is it really necessary?

Airbike

My Feedback: (6)

How come no one mentioned switching to a wood prop instead of the carbon prop. They are generally lighter.

Tired Old Man

My Feedback: (1)

I forgot that!

Dangerous Dan

My Feedback: (1)

I actually weighed a 22x8 MSC and a 22x8 Mejzlik and they weighed the same I got close to 1,000 more rpm's from the mejzlik on a BME 50.

I have saw a 28% extra special fly with a G-62 and it pulls it nicely.

There is no comparison between a aluminum and a CF Spinner. The backplate will deform like Pat said if you lighten the backplate, because the pressure you put on the backplate when you tighten the screw. In this reguards that Is why aluminum spinners must have a thicker backplate.

On calibrated scales

3.5" TrueTurn Standard Backplate 4.5oz

4.0" Troy Built Models Carbon Fiber 2.4oz

If yoe decide to put the battery in the tail be careful ti use heavy guage high quality extntions, don't want wire and connectors robbing preacious electrons.

kgp1

My Feedback: (13)

I bought a 300 from a club member and he wasn't happy with it's performance. G62 with 4 tail servos and nose is still too heavy. what is the correct CG? 2 1/2, -3???? can anyone help me with this problem? KEN

rcdude7

My Feedback: (264)

The instruction book states 2.5-3 inches. I am going to try 3" for my maiden flight. I went with carbon gear, a light-weight wingtube and lightened my TT backplate by cutting 4 9/16" holes and re-balanced it on my dubro balancer. I added 2oz lead to the stab tube to get the CG @ 3 inches.

Tired Old Man

My Feedback: (1)

Use 3-1/2" for the C/G. At 3" even, it will still want to land a little fast. At 3-1/2", you still maintain full control without it being twitchy at all, and the snaps will be more predictable. Landing approaches will be flown at a casual speed in a pretty flat attitude. 3D will be A LOT better!! Those that have gone with 3-1/2" will pretty much all agree with the above.

Pat

Jaketab

My Feedback: (2)

I'm having the same balance problem with a 300 LX and DA-50. I put the 2 Rx bats next to the rudder servo and put the ignition battery directly over the landing gear. I plan on getting a fiberglass spinner which should move the C/G aft of 3 inches. I thought the DA's were light, but you couldn't tell by my plane.

For time being, I'm going to stick 1/4 to 1/2 oz lead on the tailwheel assembly to get it to balance out.

Question - Can anyone forsee a problem with putting a small amount of lead on the metal part of the tailwheel assembly?

Bobby Folsom

No problem at all. That is exactly how I balanced my WH 260. It would have kept working great except for the big boune the plane took when I ht a hole in the road and the tail of the plane jumped up and slammed back down on the deck in the trailer (before I used a bungee cord to strap the tail down - dumb me)!! It broke the metal tail wheel bracket at the first bend. I replaced the original tailwheel mechansim with a plywood block and a Haight-style tail wheel. The whole new mechansims weighed exactly the same as the weight I had added plus the original tailwheel setup. There are some photos on the 260 pictures thread.

Bobby

kgp1

My Feedback: (13)

Just wanted to say that I found another way to get 3.5 in CG with a G62. I decided to move firewall back 1in to get CG right. thanks for everyones help.-kgp1

Bob Pastorello

My Feedback: (198)

I'm gonna chime in here now on MY nose-heavy sled Extra..... I have a BME 50, H9 alum mounts, J&A Pitts w/a, tried the single rudder in the fuse pull/pull per recommendations.... 4 cell 2700mah NiMh RX batt is on the shelf behind the canopy rear bulkhead. Everything else dead stock, Dave Brown 3.5 spinner, BME 21 x8 wooden prop.

It is SO friggin' nose heavy, I'm not sure it will balance if I put TWO 8611's in the tail. Since I only have one, I'll try it back there and see what happens....

NO - I will NOT put anymore money in this....and NO, I will not fly it spinner-less. If I cannot get it close without spending more $$$, I'll sell the thing, and let someone else invest in this not-quite-an-Edge-OR-an-Extra-260-300-sorta-looks like an aerobatic airplane...

On a different note - I learned a couple things about Ultracote on this airplane.... one, it takes a LOT of heat, and TWO - practically NONE of it was stuck down between the bubbles and wrinkles from the Thai Guys....took more time fixing the covering than rigging out the plane, and that's no shugar.

Frankly, I'm thinking I already should have invested my money elsewhere. Let me hear from some of you guys flying these and tell me about how great they fly, so I won't die of buyers' remorse.

Dangerous Dan

My Feedback: (1)

aerobob,

I have a BME 50 on my extra special. H9 aluminum mounts Trueturn spinner, lithium side of motor bok, J&A pitts. Dual lithium reciever batteries behind the wing tube. 1 rudder servo pull pull. CF wing Tube and Gear. Mine weighs 17lb dry and flies like a dream. I have 210 flights on mine and the covering still looks really good. I spent 30 minutes shrinking when I first assembled and spend 1 hour cleaning and shrinking around flight 150. This plane is awsome. THE BME 50 is a powerhouse! It funs perfect every flight and keeps getting stronger It has ran over 50 hours! What CG are you trying to get Mine is at 3 and 1/4" and flies IMAC and 3D really well. A friend has one totally stock with a DA 50 and all three lithiums in the motor box! His balences at 2.5" Little nose heavy for my taste but It flies well!

Tired Old Man

My Feedback: (1)

Aerobob,

One of the things people need to do before they start affixing stuff in any plane is to attach the engine and then lay stuff on the plane to get an ide of how it will balance out lter. Move the stuff around to get a feel for the parts locations. An easy way to do this is to "trial" assemble the plane and leave the gear off. Put a piece of 2" diameter PVC pipe on the floor, set the plane on it, and find the balance point. Too easy!

You plane should easily balance at the "sweet" spot of 3-1/2" aft of the leading edge at the tips. One servo in the tail should do just great, but you may have to move a battery from the front if it's there.

Dan,

Still running that 3-1/4" c/g? Shame on you It flys even better at 3-1/2".

Pat

Bob Pastorello

My Feedback: (198)

dntmn - thanks for the testimonial/experience. It gives some hope. Except for me not using Lithiums, and the Tru Turn you're using, these two should be pretty comparable. Appreciate it.

Silversurfer - appreciate your tutorial on equipment placement. In my original post, I stated where I had already placed the batteries as a starting point. Ignition battery on the landing gear is as far aft as it is going, period. Rx battery was as far back as I could "easily" place it without a bunch of screwing around building crap inside the tail. Rudder servo location was told to me to be *the* correct place. I don't mind mounting it in the tail with a single pushrod, and will do that to see where it gets me.
As far as "affixing stuff", without major modifications to the nose/cowling, the engine placement is pretty will "Fixed" by design. Same with elevator servos. Same w/ Landing gear. So the only really "movable" components are the batteries and the rudder servo.

Maybe installing a 1/4" threaded rod with a threaded lead mass in the fuse is in order....

cstevec

My Feedback: (1)

Aerobob, if you do the above & still have a nose heavy plane, you can always fill the stab tube with "something" to add weight to the tail of the plane. On my 260, with a BME 100 in the nose & rudder servo's set up pull-pull, I wound up placing the ignition battery on the back side of the wing tube & the flight pack batteries on a little fabricated shelf in the turtle deck accessable from the hatch. When I want tail weight I take a bunch of pipe cleaner twisted together & soaked in epoxy (liquid steel actually) & slip them into the stabilizer tube. Easy in, easy out & it adds 1.5 oz. to the tail. The pipe cleaners move the cg back 1/2 inch & make hovering a hands off thing. I was able to set the transmitter on the ground in a hover at 4.5" cg with the 260. ('course it didn't stay there long) The Wild Bunnies are very stable once you get 'em dialed in.

Dangerous Dan

My Feedback: (1)

Aerobob,
What CG are you trying to achieve?
How are you checking it?

Pat,
Call me lazy I fly 95% precision and 5% 3D. After 210 flights with my Cg where it is I just never took the time to move the bateries around...

I am at this point buying time until my 260 comes in..It is gonna be sweet

Dangerous Dan

My Feedback: (1)

airborne curiously where is your CG on your 260? is it an IMAC or a 3D CG?