Adding weight for CG
 

Hi All,

Iam about to install my engine in my Tiger 60 and wanted to use the engine to setup the CG.
It seems that the plane it still way tail heavy even with the engine on and it looks as if Iwill need to be adding about 6 - 8 ounces of weight in the front of the plane.

Does this seem excessive at all? The last plane Ibuilt was spot on without adding anything.

Any suggestions will be appreciated.

Thanks in advcance.

RE: Adding weight for CG
 

6 to 8oz? How about a pound and a half?

Shift what you can shift, then add whatever is needed. Don't let the "Experts" tell you that adding weight is a sin. The Tiger is a fabulous plane - balance it properly with whatever amount of lead it takes and you will have one sweet flier!

RE: Adding weight for CG
 

G'day

Most planes I have built have had to have some lead up front to get the CG right. I start by putting everything as far forward as I can, I use a heavier engine if one is available and then I add some lead as far forward as I can get it.

There are also available heavy spinner nuts which are useful. As they are right at the very front of the plane, they are very effective and don't need to be as heavy as lead added at the firewall.

I usually add the lead either to the sides of the engine mount ( nut and bolts to hold) or I epoxy sheet lead inside the front cheeks of the model. The trick here is to fix slightly too little so you can easily trim it with a bit extra if you need to.

One model I have, Hanger 9 Sopwith Camel, has a box provided to put lead in. I don't know how much I added but it was quite a lot.

Cheers - oh and remember "Nose heavy planes fly badly, tail heavy planes fly once".

Mike in Oz

RE: Adding weight for CG
 

Hi!
Adding weight is a tremendous sin!:D

Serious..try to move everything else lika servos , receiver and batteries as far forward as possible and replace heavy tailwheel/gear and try to carve away as much of the wood to the rear as possible using a Dremel.-That's what I do;)

RE: Adding weight for CG
 

If you have to add nose weight, you're not using a big enough engine!

Brad

RE: Adding weight for CG
 

Brad,

APC propellers are heavy and can help too.

Is there any way to add lightness to the tail?

One ounce shaved there are two less to add to the nose.

Ase explained above, do what you can do to keep it light, but over every other consideration, do balance the plane properly.

Good flights!

RE: Adding weight for CG
 

Hi _brad_
Having built many kits I eventually learned that the correct location of the CG must be kept in mind VERY EARLY in the build. I tape or tie everything near its location and make adjustments very early, and repeat this as needed. My aim is to never add balancing weight, but if needed, I add the weight. I have used the heavy brass nose cone in place of the standard nut, and never saw a problem.

RE: Adding weight for CG
 

Thanks for all the tips and help.
I had not added the prop or spinner, so perhaps I need to add those as well before adding weight.

I was spoiled when my last build was so perfectly balanced without doing a thing.

RE: Adding weight for CG
 

Irepresent that remark! Iusually have to add tail weight.

I'd prefer not to add 8 oz to a .60 size model, but you do what you gotta do. Get the engine and battery as far forward as possible. Shiftingthe receiver doesn't help as much as it used to.

A Harry Higley nose hub will putweight as far forward as possble so you need less.

http://www.sigmfg.com/images/yy1HIGNIN007.jpg

RE: Adding weight for CG
 

Adding weight is not a Sin - Nor is moving things around a Sin;)

When ones chooses to add weight here is a simple safe way to get the weight (lead shot) all the way forward where it will do the most good without the disadvantages of hanging it on the crank shaft.

When one chooses to move things around here is a simple safe way to do the same with the battery which will do the most good.

John

RE: Adding weight for CG
 

I would add that an over-sized battery can be more useful aboard than a dead piece of lead. :)

RE: Adding weight for CG
 

The things you can do with a 6 volt sub-C!!!;)

RE: Adding weight for CG
 

Obviously moving the weight the furthest in the direction needed will be the most effective. With that being said, it's often necessary to make and mold your own ballast.

Take some scrap balsa, and build a "cast." Be it in the shape of a square, rectangle, triangle...whatever you need. Make sure that it is water-tight, because you're going to pour molten lead into it.

Hit up your tackle box, or head to the bait shop for some split shot, or heavy sinkers, or whatevers most available and economical. Go into your pantry and eat a small can of corn, or beans...just make sure it comes out of a tin can..or whatever metal it is. The metal in this can will withstand the same heat that will cause lead to melt.

Clean the can. Squeeze/deform the can as to make a little "spout," resembling something that you see on a juice pitcher.

GO OUTSIDE.

Put your balsa mold on the ground, put the lead in the can, and take a blow torch and heat the lead until it becomes molten (This doesn't take very long)

Once it's all liquid, put the torch to the side, and using a channel locks, or something to hold the can, pour the lead into the mold.

ONCE AGAIN...Go outside for this! Obviously be careful with the torch and the molten lead.....but be more careful not to breathe any fumes, and wash your hands when your done. Always wash your hands when your finished handling lead.

RE: Adding weight for CG
 

<p class="MsoNormal" style="MARGIN: 0in 0in 10pt"><font face="Calibri" size="3">I buy a 7-day medicine plastic container from Walgreens for 99C. I cut it into 7 boxes. I fill one box up with small sinkers and I pour epoxy in it. I close the plastic lid and I have a 1 ounce weight box. If I have to put it on the tail, I attach a small line to it, put epoxy all around it and let it drop slowly as far as I want to the back of the fuse. No matter how it falls, the epoxy will stick forever. Voila!</font></p>

RE: Adding weight for CG
 

I offer an alternative method which I utilized recently, Secure a fishing weight in a vise and saw off a piece with a hack saw and then pound it with a hammer until it resembles a fat quarter. Then drill a hole through it. Mount it with a bolt and locknut through the fuselage as far foreward as possible. By this method, I got approximately 2.5 oz per weight.  I have learned that weight is not as bad as I have been told. The plane still flies well but next re-build I will be more conscious of the consequences of strengthening the plane too much. Since, the rebuild however the plane is much less susceptible to the consequences of a rough landing. .....Wayne

RE: Adding weight for CG
 

How about a scratch built Bipe. Any scale plane that had a round engine is going to require weight in the nose. In this case I had everything moved behind the fire wall I could move. I even have a sub-C 6 volt battery behind the fire wall. It took about 3 pounds of lead in the nose to get the correct CG. I used epoxy and lead shot and floated it inside the engine cowl/ring. This is NOT the way to do it with most planes, the cowl will crack and break off. I made this cowl and the way I set it up there was no problem. Some planes no mater what you do will require lead, in this case it was a lot of lead.

RE: Adding weight for CG
 

Watch out for melting lead in a steel can.  If it's a soldered can the solder will melt right along with the lead.  No fun to drop the bottom out of a can full of molten lead into your lap!

RE: Adding weight for CG
 

Fantastic tips - I would never have thought of most of them.
I have been fishing and would never have thought to use sinkers to do the job - just brilliant.

Thanks so much to everyone.  I have decided to complete the plane and then add the weight as necessary.  Everything is as far forward as possible, so we shall see what happens when it is complete and how much I will need.