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-   -   Home made weights (http://www.rcuniverse.com/forum/questions-answers-154/3628022-home-made-weights.html)

RcKrazy23 12-07-2005 02:19 PM

Home made weights
 
Any suggestions on what I can use that's lying around the house to add weight to correct cg on my airplane?

2slow2matter 12-07-2005 02:23 PM

RE: Home made weights
 
large washers, bolts, etc. Be careful about putting something that is too dense, though! You need the weight (if it's a bunch) spread out so that you don't end up wearing a hole in the balsa, or whatever you put it in. Of course, if you epoxied in a ply box, then whatever goes!

burgh_guy61 12-07-2005 02:38 PM

RE: Home made weights
 
Depending on how much weight is required I have gone from old wheel weights to just some small fishing sinkers to get the lead I needed.

RcKrazy23 12-07-2005 02:39 PM

RE: Home made weights
 
Thanks for the idea. I think I'll spread out some washers in the fuselage and tape it in place wid some heay tape.

red head 12-07-2005 02:51 PM

RE: Home made weights
 
Just remember that it is better to NOT add weight if you don't have to. Sometimes a little extra thought as to moving the items in the plane will keep you from adding. Your local tire dealer probably has a bucket full of old weights and if ask would probably give ya a couple for free. ENJOY !!! RED

Geistware 12-07-2005 02:55 PM

RE: Home made weights
 
Go to a tire shop and ask for their used tire weights.

jaka 12-07-2005 02:56 PM

RE: Home made weights
 
Hi!
Yeah!
Why add weight if it is possible move servos, batteries and RX ?
Regards!
Jan K
Sweden

RcKrazy23 12-07-2005 03:06 PM

RE: Home made weights
 
Some excellent ideas you guys! Think I'll go with asking the tire guys.

Newc 12-07-2005 03:47 PM

RE: Home made weights
 
I believe that the guidance that you got to spread the weight around is wrong.

To minimize the total amount of weight that you need to put in the plane, the weight should be put at the location farthest away from the CG - or if laterally balancing as far toward the wing tip - as is possible. Spreading the weight around and therefore NOT concentrating it where the lowest amount will do the most good will only result in a heavier plane.

As to the comment that the reason for spreading the weight around is "so that you don't end up wearing a hole in the balsa" is wrong also. The only way that the weight will wear a hole in anything is if it is moving and rubbing against a fixed surface, and if it is moving then the plane is constantly changing balance and trim settings.

Finally, I don't agree with simply using tape to install weight, as any tape will loosen from the surface when the g loads of the flight are acting against the weights. It's OK to use tape to hold down something light such as servo wires which have virtually no mass and therefore g forces don't add up to enough to pull the tape away from the surface. I suggest that if possible you connect the weights firmly to the part of the plane where it is needed by bolting it to or through a structural member or at the very least epoxying it in.

kdheath 12-07-2005 04:34 PM

RE: Home made weights
 
I had a vision of the wheel weights flying forward in a minor accident and punching new lightening holes in something important.

RCVFR 12-07-2005 08:10 PM

RE: Home made weights
 


ORIGINAL: JLNewc

I believe that the guidance that you got to spread the weight around is wrong.

To minimize the total amount of weight that you need to put in the plane, the weight should be put at the location farthest away from the CG - or if laterally balancing as far toward the wing tip - as is possible. Spreading the weight around and therefore NOT concentrating it where the lowest amount will do the most good will only result in a heavier plane.

As to the comment that the reason for spreading the weight around is "so that you don't end up wearing a hole in the balsa" is wrong also. The only way that the weight will wear a hole in anything is if it is moving and rubbing against a fixed surface, and if it is moving then the plane is constantly changing balance and trim settings.

Finally, I don't agree with simply using tape to install weight, as any tape will loosen from the surface when the g loads of the flight are acting against the weights. It's OK to use tape to hold down something light such as servo wires which have virtually no mass and therefore g forces don't add up to enough to pull the tape away from the surface. I suggest that if possible you connect the weights firmly to the part of the plane where it is needed by bolting it to or through a structural member or at the very least epoxying it in.
What he says is good advice. Concentrate it, and securely fasten it.

poppy2 12-07-2005 08:12 PM

RE: Home made weights
 
RcKrazy23-

I have used old tire weights I get from the tire stores. They work fine. Drill a hole through them and screw them to the wood. Won't be going any were. I think some tire stores will be reluctant to give them to you because they are suppose to expose of them properly, due to the fact that they are lead. Good luck.


Poppy2

2slow2matter 12-07-2005 09:43 PM

RE: Home made weights
 
OK, "wearing a hole" in the balsa was the wrong wording, but it still applies. Rubbing is not what I was talking about. However, this guy is new. He will have many rough landings ahead. Why don't you put about 4 or 5 ounces of very dense dead weight epoxied to the balsa floor of a model, and make a few rough landings. I guarantee you, inertia will take over, and the floor of that model will eventually break apart.

If you don't believe me, then try it. By spreading the weight around, I wasn't suggesting a weight here, and a weight there--eveny distributed between the CG and farthest point fore or aft. It was merely an attempt to suggest using lower density weight. Any moron with any sense at all could figure out to put it as far away from the fulcrum as possible--in order to minimize the amount needed.

I also recommended doubling the floor with some light ply, or even a ply box epoxied into place to help strengthen the area where the weights will be placed.

Crap, guys, he may only need a washer or two. He didn't even say how much we're talking about here.

Also, taping the weights in place is perfectly acceptable--especially for a temporary solution. If you had real hobby weights, you could just tape them in place (even on the outside of the fuse) for a few test flights. Then, once you are satisfied with the location of the CG, then you can more permenantly mount the weigts into the INSIDE of the fuse--by any one of the methods mentioned above. You are on the right track. Use some common sense.

iaclmac 12-07-2005 10:40 PM

RE: Home made weights
 
Well ... in the old days we use to use pennies. That's right ... good old fashion US coin of the realm. The US penny weighs about 1/10 of an ounce. So, for each ounce you want to add will be 10 pennies. I use to stack them with a dab of 5 minute epoxy between each one. I never had them come apart. Nowadays pennies don't buy a lot .... seems they are the cheapest thing next to free

mirwin 12-08-2005 12:10 AM

RE: Home made weights
 
Another 2 cents worth: The farther away from the CG you can put the weight, the less weight you will need.

Mike


mirwin 12-08-2005 12:14 AM

RE: Home made weights
 
I like the penny story. Hey, wait! If you needed 10 pennies, you could use a dime and save space. No, wait! Never mind. . . .I'm losing it. Must be cabin fever.


RcKrazy23 12-08-2005 03:58 AM

RE: Home made weights
 
More brains = better ideas then one any day!:D

MinnFlyer 12-08-2005 10:09 AM

RE: Home made weights
 
I also use Tire weights.

Go to any garage where they sell tires. When they balance tires, they remove the old lead weights and toss them into a bucket for recycling. In fact, I just stopped in on my local tire shop last week and asked for a few handfuls. A few minutes later I walked out with VERY heavy pockets.

PS, use epoxy or screws (or both) to hold any weights in place!

huggins 12-08-2005 12:18 PM

RE: Home made weights
 
A friend of mine put a trailer hitch ball in the nose of a Skybolt and old D-cell batteries in the tail of an Extra. Not what I would recommend, but resourcefull don't you think.;)

Mike

2slow2matter 12-08-2005 12:32 PM

RE: Home made weights
 
A trailer hitch ball? My gosh, that thing must weigh several POUNDS!

I definitely wouldn't recommend the battery, though, since those things tend to start corroding over time.

Resourceful, yes, defintely.

Gringo Flyer 12-08-2005 02:47 PM

RE: Home made weights
 


ORIGINAL: huggins

A friend of mine put a trailer hitch ball in the nose of a Skybolt
That seems like an incredible amount of weight.

I cant imagine what kind of build would require that much weight or even where you could put a trailer hitch ball inside of an airplane.

huggins 12-08-2005 04:00 PM

RE: Home made weights
 

ORIGINAL: Gringo Volador



ORIGINAL: huggins

A friend of mine put a trailer hitch ball in the nose of a Skybolt
That seems like an incredible amount of weight.

I cant imagine what kind of build would require that much weight or even where you could put a trailer hitch ball inside of an airplane.

It is indeed true. It is a Great Planes Skybolt which I believe has a reputation for being a little tail heavy anyway. He is a great flyer and a great friend, but a craftsman.....he ain't! He covered it with fabric and then painted it. Oh, I don't believe he used any sandpaper during the build either. It came out incredibly tail heavy. Anyway, it took a that much weight to get it to balance. I don't think that it flies that great either......maybe it has something to do with being so heavy:D I always refer to it as his "Skybrick". He did eventually put a bigger engine in it and removed the hitch ball, but he still had to add dead weight.

2slow2matter - I agree with you on the battery issue. I was a little concerned about that when he told me about it. Like I said.....resourcefull!

Mike


gtmattz 12-08-2005 06:06 PM

RE: Home made weights
 
I used pennies to balance my Daydream 2M sailplane. When I was purchasing everythiing for the plane I read in the manual that installing mini servos would reduce the weight and allow for better thermal soaring... Well as it turns out, the design of the plane ends up being fairly tail heavy, so I ended up having to put about oh.. 2 full size servos worth of pennies in the nose of the plane...
go figure ;D. AFTER I got all done I read the reviews for the plane on this page, 2 people said to use normal servos as you have to add nose weight anyway... Live and learn, right? To keep the pennies together, I used black electrical tape at first, then after I had the final amount, I epoxied them all together. I keep them in place in the plane with a large chunk of velco so that I can move the weight around to get my hi-start launches correct depending on wind conditions (I think.. going to be doing my first hi-start launches this weekend.. if there is sunlight to keep the rubber warm :D )

feep 12-10-2005 10:02 PM

RE: Home made weights
 
One thing no one has mentioned about tire weights is that they can be melted down and shaped very easily. A torch and a tin can can be used to melt lead. Take a wire coat hanger and wrap it around the can for a handle and press the lip of the can to make a spout and you're ready to go. You can simply pour the molten lead out on a flat surface to make a sheet and than cut it into strips or you can take some clean sand and press a cowl or other complex shape into it to make a crude mold that you can pour molten lead into to take the shape you want.
You just want to be careful around it. Aside from the obvious danger from molten metal, lead should not be handeled without some precautions. Rubber gloves and washing your hands after handling are two that would be wise. If your melting it down I would be careful about breathing in the fumes also. That would be best done outside.
Lead is one of the heaviest elements and as such, adds more weight per square inch than any other material you can lay your hands on.

jstrawn 12-10-2005 10:22 PM

RE: Home made weights
 
I've used Lead Shot and Epoxy. My LHS also sells re-loading supplies, so they always have a lot of shot around. The shot also makes good weights for building (to hold down wing sheeting, etc).

For the airplane weights, I'll put it into a mixing cup, add some epoxy, and let it dry. Then I'll run it thru the drill press, and screw it to the firewall (backside or front side, depending on the space)


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