chucksaw812

Hi everyone,
I have a Dynaflite super decathlon with an OS 1.20 pumped for the engine. I've built about 20 airplanes in my lifetime and been flying about 25 years.
To get the Decathlon to balance out, I have to add ONE POUND of lead to the front to make it balance!..I've never had anything come close to that!
Has anyone else had to add that much weight to get it balance before?
I have the battery and radio and servos as far forward as I can.
any ideas?
thanks in advance!
chuck

BobH

My Feedback: (2)

What ever you need to make the CG is what you need.. pound or two pounds... doesn't matter.
Unless you want to rebuild the tail group super light?? I don't know what else you can do.. Save putting on a heavier engine.

chucksaw812

Those were the only two options I could think of too and neither one sounds like an easy task.
Ok,..a pound it is....ill add it.
it just seems like such a lot to add just to get it to balance but hopefully the OS 1.20 will be enough.
thank you Bob for your advice.

dbacque

My Feedback: (3)

Do you have any servos in the tail? If so, move them as for forward as possible and use very stiff, well supported pushrods. Where is the battery? Move it as far forward as possible. Every ounce moved forward is several ounces removed from the nose.

That being said, I had a plane with a half pound of lead on the tail. I put the weight it needed and it was one of my favorite planes of all time. When I built the second copy of it, I shortened the firewall. That one still needed a quarter pound on the tail. Still flew great.

Do what you can with the equipment and then add weight as necessary.

Dave

smithfj

Yes sir, that's the Dynaflite Decathlon menace. Mine took an awful lot also and when I sold it my flying buddy added even more. I have a giant scale RV-4 that is lighter than it was. It flies good though.
Frank

chucksaw812

There are three servos in the tail. One for each elevator and one for the rudder. I was going to add a pound of lead and go with it because to move the servos forward would require a three foot pushrod run! I'm not crazy about the plastic tube in a tube pushrods and I'm not crazy about a three foot balsa pushrod either but I guess that's what I'll have to do. Just not sure which would be best for a long run like this .
I just can't stand the idea of having a pound of lead in the front if I don't absolutely have to have it. I bought the plane from a good friend and it was already built and covered. Guess I'll have to take some of it apart because I definitely want it done right. Thank you for you advice!

chucksaw812

Which engine did you have in your Decathlon?

Pylonracr

A pound of lead?? Holy Crap! My personal limit for ballast is 1Oz. Before I would add any ballast to your plane I would move those servos to the front. Darrol Caddy sells some very nice carbon fiber pushrods if you are not used to making your own. Carbon arrow shafts make nice pushrods, as do 4-40 rods with carbon graphite sleeve laminated to them. What ever is easiest for you, but move the servos!! If you have to, you can place the battery ahead of the firewall; either attach to the motor mount or build a small bracket. Can you remove a few ounces from the tail? Anything will help. Remember, the lighter the plane is - the better.

When you move the servos, if you still need a few ounces, lighten the tail. You will be removing overall weight from the plane instead of adding to it.

Scott

foodstick

I have never built a model that needed more than 6 pounds of lead

1 pound of lead now is better than 1 pound of epoxy after the tail heavy crash...

Light is better but balanced is a must ! have fun with it when she flies..

chucksaw812

Yeah!..I've never had to add more than an ounce or so before and most of the time just repositioning the battery would do it. But, I bought this plane from a friend and he already had it built with a 2 stroke Aviastar 1.50 in it. I wanted a 4 stroke for this plane so I put an OS 1.20 in it. I thought for sure it would be heavy enough and that I would actually have to add weight to the tail but no!, a pound to the front!... I can't have that...I'm definitely going to have to move the servos forward..
Carbon fiber rods are an excellent idea! Thank you!..and arrow shafts would work great I'm assuming....thank you for the tips. Much appreciated!

chucksaw812

Gonna have to move those servos forward for sure I think...don't like the idea of a pound of lead at all!

JCOKEEFE

My Feedback: (2)

I completed one about a year ago and had to install about the same amount of lead weights on the front of the fire wall held in place with epoxy. Engine wise, I installed a Saito 1.25. However, a Saito 1.50 or 1.80 would be more ideal for this aircraft.

speedracerntrixie

My Feedback: (29)

Forget where the plans say to balance it. The Decathelon has a constant cord wing so re figure the balance point at 30% to 33%. See how much additional weight is required to hit this balance point. Moving at least the rudder servo forward and running pull pull cables to the rudder will greatly reduce the required ballast up front. Shopping for a lighter tail wheel assembly would also help as well as moving the RX battery as far forward as possible.

Pylonracr

Shawn

Good call on the pull - pull cable for the rudder. Simple to retrofit. I would still move both aileron servos due to the amount of weight needed to balance.

TFF

Worst I ever heard was 12 lbs on a 50 lb twin. Scale tends to need weight vs just a model. A Spitfire is a good example; the Merlin engine is 2/3s the weight of the real thing. So that would mean a 20 pound plane is suppose to be 6 pounds with a 14 pound engine. Extreme example but with scale do everything to minimize the need for weight. All the servos on my WW1 planes tend to be almost on the firewall.

TomCrump

I use 3 and 4 foot nyrods frequently. I never have a problem with them. Pull/pull systems work well, too.

sensei

Now that is great advice right there...

Bob

k3 valley flyer

My Feedback: (18)

Sounds like two options are add 1 lb or move servos forward and maybe rebuild tail feathers. On a plane that size and that much power I personally would add the weight. Some of my bigger heavier WWi warbirds with very short nose needed up to 5 lbs. Do what ever it takes to get the CG right, matter of preference as I doubt either method will impact flight performance adversely.

beepee

Chuck,

Not surprised. My DSD flew with a Quadra 42 on magneto and it still needed some lead on the firewall. Put the lead that is needed in the nose and fly. It can handle it. You will gain some by moving any weight possible forward. Truth is, the Dynaflight Super Decathlon is a notorious for coming out tail heavy. Despite that, it is a nice flyer.

Have fun!

Bedford

philakapd

Could you add something useful to the front? A camera, larger battery or landing lights?

raptureboy

If you get lead shot from a gun shop and then mix it into epoxy and pour it into the cowl you can reduce the lead to 10 oz or so. I've done this before with my biplane. You need to be sure you spread it around evenly to distribute the weight. Not unusual to have to add this much weight on a short nosed airplane.

pkoury

My Feedback: (7)

If it is ready to fly I would add the lead and fly the model to set the CG to your style of flying. Once the CG is where you like it you can decide what to do in regards to moving servos.

loopdeeloop

My Feedback: (4)

I built a1/4 DSD a few years ago and powered it initially with converted weed whip motors. Started with a 25cc Homelite, then a 30cc and it currently has a DLE 30. The airplane needed a fair amount of weight (as I remember, about 8 ounces) to balance it. I built a contoured balsa box that fit at the bottom of the fire wall. Filled the box with BB's and epoxy. It is screwed to the firewall so it can be removed and changed if necessary. Rudder and elevator servos are in the tail, separate ignition and radio packs both of which are far forward. The airplane was covered with Sig Koverall and painted with Rustoleum and then clear coated. It tips the scales at 19# unfueled. I will be flying it Wednesday. Not too much you can do to reduce tail weight during construction other than relocate the servos. The weght is in the cabin area. Some lightening holes in that area could remove a little weight. I don't remember the wing details but seems to me there could be some weight reduction there if one thought about it a bit.

Stick 40

if you decide to move the servos forward, think about carbon fiber push rods. light and strong. I had to do the same thing on finished plane and the carbon rods did the trick


stick

DavidAgar

My Feedback: (108)

The Dynaflite Decathlon and Chipmunk all need a ton of weight to balance them. Move everything as far forward as you can, balance it and fly it. Good Luck, Dave