Unorthodox way of Acheiving CG??
 

Hello,

I have acheived the proper CG for my Sig Kadet senior today. It was about 10 oz tail heavy. I did this by epoxying 10 lead .50 cal musket balls (1 ball = 1oz, convienient, huh?:)), with 30 min epoxy, onto the inside of the Seniors cowl (5 on each side).
I was aware that the epoxy itself added weight, but I calculated 10oz to bring the plane to level, and the epoxy would make it barely nose heavy as I intended. It worked well.

Because this is my first trainer, I decided to avoid more complicated solutions, such as mounting the engin forward, etc.

I was sure to move the battery and reciever as far forward as possible, and also purchased a somewhat heavier Aluminium spinner. Oh, and a muffler or manifold extension was needed which added some weight as well.

My question is this...

Although they seem pretty dang solid, will they hold under heat and vibration?

If the epoxied .50 cals work, then I should have only one more balance problem to solve. My Kadet is a little heavy on the right side. Can I epoxy a bit of lead under the left wings Aileron servo hatch? Or would it be wise to avoid puting anything that may interupt the servo, if it should break free?

Thanks for any help!

Noah

RE: Unorthodox way of Acheiving CG??
 

When I have to add lead to a plane I epoxy it and have had no issues. I use flat pieces though; not sure what the round balls look like or how well they will hold.

To balance a plane laterally, I usually put a little piece of lead at the tip on the bottom side, and either paint it or cover it with a piece of covering. The further out on the wing you put the lead, the less lead you will need.

I just had to add 4oz of lead to the nose of my newest plane and still may need more, all this after moving everything forward, using heavier servos, heavier muffler, etc. Not so happy about that one:eek:

RE: Unorthodox way of Acheiving CG??
 

Oh bother! That is what I was avoiding!:) I want my first plane to be as simple as possible.

Yeah, I had a ton of old lead musket balls, so I figured I'd use 'em. They are in there pretty solid. So I am glad to here It will be ok and that heat or vibration won't be a factor.

Thanks gaRCfield



~Noah

RE: Unorthodox way of Acheiving CG??
 

You might want/need to reinforce the areas around the cowl mounting screws...with all that weight in the cowl, it will probably crack around the screw holes in a relatively short period of time.

And, with a rough landing, and the cowl is gonna want to keep on going...all by itself :D (you're going to have bending and shear loads, etc. on the mounting points )


Your idea is not a bad one...just that I think you are going to need to beef up the cowl a bit. (1st time I've heard of using muzzle loader ammo for ballast...:D )

RE: Unorthodox way of Acheiving CG??
 

yes it will work , provided you used enough glue

RE: Unorthodox way of Acheiving CG??
 

Musket balls or bell shaped fishing weights can also be easily flattened with a ball peen hammer to almost any thickness which provides versitility in ways or places to attach. I recall on one pair of warbird pylon racers I prepared which had scale struts under the stabilizer, needed just a quick touchup to the rear and flattened musket balls on each side paper thin was just wrapped around the struts with a bit of thin CA dripped on. Worked nicely and was just about invisible.

John

RE: Unorthodox way of Acheiving CG??
 

Ahhh... I see! Great point! I will look into reinforcing the Cowl mounting screws. I don't want to add too much more weight though. So maybe a few more screws will help hold it more securely.

Yeah, the ballast is in abundance and free! My father works for an auction company and one of the departments there sells fine antique firearms. One of the lots was an old Flintlock Kentucky rifle (Beautiful! sold for $8,000+) and it came with a ratty old wood box with about 800 musket balls in it. The buyer decided to part with the ratty old box and leave the auction with the rifle only. He was driving a Saab, if he had taken that ratty box, he would have draged his muffler all the way back home!:D My father has a one ton van and decided to take them... why? I couldn't tell you, but I have found a use for them.

RE: Unorthodox way of Acheiving CG??
 

The Kadet Senior ARF is notorious for coming out tail heavy. With mine, I lined the firewall with lead and still needed some lead on the cowl! All told about 12 oz. Just keep a close eye on the cowl mount screws or add a couple of extras as suggested. You're going to love this airplane! Probably the best trainer ever produced, IMHO.

RE: Unorthodox way of Acheiving CG??
 

If this has a plastic cowl that screws on, it will not work. The extra weight added to the cowl, combined with the vibrations will pull tha e cowl loose in about one or two flights.

Remove the weights from the cowl and epoxy them into the tank compartment.

Or (what I often do) melt them down with a torch (Beware of fumes) into a single, flat block and epoxy it to the firewall. Then put one or two screws through it for extra measure

RE: Unorthodox way of Acheiving CG??
 

OkadaKeisuke:

Light models fly and maneuver better.
Weight is additional inertia and stress to the structure.

Always try eliminating weight first; there is always something to lighten.
Half a pound added to the nose equals lees weight than that taken away from the tail, just because the distances to CG are different.

Try to locate extra weight as far as possible from the CG, and for a trainer, as low as possible as well (to improve stability).
Attach it well to a structural part.
Removable weight is better, at least a portion of it, since the CG shown in the drawings is seldom the best for your particular model, and the freedom for later adjustments is a good thing to have.

http://www.rcuniverse.com/forum/m_8605287/tm.htm

Many happy flights for that Kadet!

RE: Unorthodox way of Acheiving CG??
 

While the second half of this statement is true, the first is not.

Heavier planes handle MUCH better in windy conditions and give you more control over the elements.

And as far as adding weight goes, if your plane can't handle an extra few pounds, you built it wrong :D

RE: Unorthodox way of Acheiving CG??
 

Mike, I'm so glad you stated that, I don't want to get into the weight thing but the people that have been selling the ARFs that are built with as little wood as can be done have been able to sell the lighter is better idea to a new breed of public and they are buying into it. There is a point in models where too light is too light and too heavy is also too heavy. I have yet to see a pattern plane built ARF light and there are good reasons for it. Adding usless dead weight to a plane is another thing too, I would have gone with a 6 volt sub-C battery mounted up front. Round lead marbles are probably going to vibrate out with just epoxy holding them in. On a hard trainer landing they may decide to do what they were intended to to be used for. Flat wheel weights with the doubel sided tape and a couple of servo screws mounted to the motor mount may have been a better idea?? I remember my decoy anchor weights didn't work out the way I had planned!!:eek: That is a story all it's own!!:D

RE: Unorthodox way of Acheiving CG??
 

Out of experience I will go with getting something flat. The weights which the use too balance wheels work the best (think it was mentioned by someone here). When balancing my Edge we used a couple of different weights and this just works the best hands down. You don't need a lot of space too put them - just a flat surface. You can even bend them to fit around a corner if it needs be.

I will add one more thing though if you intend using it - I would not just rely on the double sided tape too make it sit. I had a deadstick just after take off and put it down a bit hard on the ground - one of the weight sticks came loose and fell off - if I didn't have a look at the ground after picking up the plane I wouldn't have noticed it. I used epoxy too just make them glue better and only at the ends of the sticks.

RE: Unorthodox way of Acheiving CG??
 

without a doubt flat is better than a round ball for attachment, I happen to have some lead strip scrap from a Xray room I built for a client, when I need a little weight or in some cases alot I make my weight by folding it and pounding the lead flat to fit in whatever space I need it to fit into.

this P-47 has about 6oz of lead in the nose, not attached to the cowl, the spitfire has over a pound bolted to the engine mount, there total weight is about 11lbs each.

most cowls can't handle much more than a oz or 2 at the most, the firewall or engine mount is a good place to give you a solid mounting surface, you don't want the lead shot to pop off either and change the CG in flight rolling around in the engine area, wouldn't be too cool.

you could also make a weight box, just a small box to hold the lead to put your shot into then pour epoxy into it then either drill holes for screws or just glue it into a convienent place.

if my memory serves me right the senior is a fairly good sized plane there should be some room in the front to glue something into place like that.

RE: Unorthodox way of Acheiving CG??
 

Oh bother! I was hoping the cowl weights would work. But it seems that it is far too much a risk then I want.

I suppose I will remove the weight added to the cowl and move them back to the fire wall. I believe will have to add an ounce or two more since I am moving the weight closer to the CG point, but it will be alot more safe attached to the structure as opposed to the cowl.

I am not worried about adding too much weight to the Senior Kadet, considering it's light wingload and ability to perform with extra systems added (Camera, drop pod ect.)

Also, I didn't think about the malleability of lead... DUH!:eek: I can custom shape these ball weights as needed.

I guess the only question I should ask, is there an easy way to remove epoxy? Will debonder work on epoxy? I know it works on CA, but 30 min Epoxy?

I wish I thought about this problem and posted this thread BEFORE I did anything![:@]:eek:

Well, thanks again guys. Much appreciated!

Noah

RE: Unorthodox way of Acheiving CG??
 

Heat, if you have a covering heat gun then just heat up the lead balls and they will fall off.

RE: Unorthodox way of Acheiving CG??
 

Suggestion from one who has used the exact same thing: (Musket balls)

Flatten them, I simply put a hole in the front of my SPADstick (Corugated plastic fuse) the right size and epoxied the ball into the hole. Well.. One hard landing too many and one of my three lead balls is somewhere in the field next to the runway, I assume it popped off on impact when I screwed up a harrier landing in a heacvy wind and let it nose over. (No plane damage of course, its a SPAD after all!)

If youve the melting equipment (I make my own lead shot for my muzzle stuffer) you could fashion a flat mold from something and make flat weights, but do it OUTSIDE! (Duh you say, well I know folks who melt lead on the kitchen stove...)

RE: Unorthodox way of Acheiving CG??
 

+1 for gluing weights to the plane, not the cowl. I must have missed that late last night:eek:

RE: Unorthodox way of Acheiving CG??
 

Yep, it was late... No problem gaRCfield!:)

RE: Unorthodox way of Acheiving CG??
 

Nah! That's not unorthodox. I've seen a guy tape a wrench to the belly of his airplane. Needless to say, the flight ended quickly. :eek:

RE: Unorthodox way of Acheiving CG??
 

Here are two 50 cal musket balls. Takes just one minute to make paper thin with a ball peen hammer. They can be wrapped around anything or easily tucked into almost anywhere and just about any old glue, school muselage or rhino snot will hold just fine.


Agreed with all always moving things around first to ballance but when you just can,t this is how to shape any lead.

I do a heck of a lot of maidens and darn if the Wx is nice its almost daily with something and getting the CG far enough forward is where what many folks fail to do. I have on many occasions taped on externally cresant wrenchs, pliers or any manner of other things to be able to fly a high percentage of them and it illustrates the need to truly ballance their airplanes and to make it ballance where it is with all that stuff before bringing it out the next time whether or not the do it by shifting stuff internally or using lead or whatever.


John

RE: Unorthodox way of Acheiving CG??
 

I only had a hair drier, but it worked great! The epoxy got somewhat soft and I peeled it off the cowl.

Thanks for the tip Gray Beard!

Noah

RE: Unorthodox way of Acheiving CG??
 

My first trainer was a Sig Kadet Senior that I built. I also had to add weight to the nose. Strip lead bolted to some fairly thick brass sheet mounted between the cheek cowl brought it into balance. Think I needed 4 ounces. But it flew great even though it was powered by a Thunder Tiger GP42! I still have it, I should try to fly it.

RE: Unorthodox way of Acheiving CG??
 

I hear a lot of Veteran RC Pilots say the same things. This is one of the reasons I picked this as my first. And hopefully its fate is fair, as to allow me to say "I still have it" a dozon or so planes down the road.

RE: Unorthodox way of Acheiving CG??
 

Hi OkadaKeisuke
In your first statement you say that a 1/2" diameter lead ball weighs one ounce. As I recall from my interest in skeet shooting, the diameter of a 16 gage shotgun barrel is defined as that diameter of a lead ball, 16 of which equals one pound. That works out to about .66 inches, and one lead ball of this diameter equals one ounce. Your .50 diameter balls weighs a bit less. I'm not nit picking. It's just something I remember. At my age of 73 I have forgotten a lot, but somethings are still there. I move heaven and earth not to add lead to balance my planes. To do that I have the CG in mind at every step of the build. If you make it the last step, as many people do, you may already be trapped.