A Pound of lead!!
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A Pound of lead!!
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
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
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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.
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.
#4
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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
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
Last edited by dbacque; 09-11-2016 at 11:48 AM.
#5
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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
Frank
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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!
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!
#8
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
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
#9
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..
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..
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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!
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!
#13
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.
#15
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.
#16
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!
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!
I use 3 and 4 foot nyrods frequently. I never have a problem with them. Pull/pull systems work well, too.
#18
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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.
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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
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
#21
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.
#23
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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.
#24
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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
stick
Last edited by Stick 40; 10-06-2016 at 03:54 PM. Reason: spelling