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Old Oct 10, 2002, 01:34 PM
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Ben74's Avatar
San Francisco, CA, USA
Joined Jun 2001
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Using water as ballast?

anyone know anything about using water as ballast in a glider? i just ordered a kulbutin from hobby lobby. $199 on sale .

anyway, i want to fly it at point fermin, but the landing zone there is really rough. the lift at fermin is insane, so a lot of ballast is called for, but landing the kulbutin there with a ton of ballast on board would be a recipe for distaster. so i'd like to be able to dump my ballast before landing. this is what a lot of full scale gliders do.

the kulbutin seems like a good candidate for water ballast since there's lots of room in the fuselage. my initial thoughts are to install a plastic fuel tank that they use in glow planes, and rig a servo to open a valve that will dump the ballast out a hole in the bottom of the fuse. i don't know if they make those fuel tanks big enough. i may have to use some other kind of container. i'll probably have to make the tank as big as possible to carry the amount of ballast i want.

one problem i see is that if i don't fill the tank all the way up, the water will slosh around. this could have a stange effect on the plane's handling. then again, i may not be able to get as much weight as i'd like with water since it's not nearly as dense as lead. that would mean i would always be filling it to the top anyway. so maybe i don't have to worry about this.

another thought is to use sand. sand is more dense, so i would be able to get more ballast for the same volume. plus it's less likely to leak. come to think of it, this might be the way to go.

i'd welcome any thoughts or suggestions on this topic.

if any kulbutin owners are reading this, how much ballast do you like to fly with? from what i've read, it sounds like people are really loading it up.

cheers,
ben
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Old Oct 10, 2002, 02:49 PM
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USA, CA, Costa Mesa
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I can not directly answer you question but...

It sounds like a good idea. They make fuel tanks in many sizes ie. 4,8,16oz and different shapes. I would imagine that if you had the room, you could switch tanks for different weight needs and always keep them full to avoid the shifting ballast.

I am fired up that you are ordering the Kulbutin. I have been wanting to hear a report on that plane for a while. Let me know when you plan to fly it as I would like to see it fly sometime.

Good luck with it and keep us posted on how it comes along.

Keith
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Old Oct 10, 2002, 06:46 PM
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Duke58's Avatar
Hayward, CA
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Why not just use lead and rig it with a bomb release , maybe tie on a ribbon , or a chute?

Earl
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Old Oct 10, 2002, 08:12 PM
Brett
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So Cal
Joined Apr 2002
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I've heard of folks using the carberator off a 2 stroke glow engine for the water dump valve. Seems like a good idea, since it already has a value actuated by an arm on it.
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Old Oct 10, 2002, 11:30 PM
When the time is right
Duke58's Avatar
Hayward, CA
Joined Apr 2001
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Right , if you must use water try using a ballon bladder, the water will be forced out faster and there is less chance of leaving some slooshing around in the tank , now if you could just find some heavy water.

Earl
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Old Oct 11, 2002, 12:04 AM
Chemically Corrected
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San Diego, Ca
Joined Apr 2001
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Quote:
Originally posted by Duke58
Right , if you must use water try using a ballon bladder, the water will be forced out faster and there is less chance of leaving some slooshing around in the tank , now if you could just find some heavy water.

Earl
I love it! Here you go.
http://www.altcancer.com/h3ointro.htm
Get 10% more weight. LOL.
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Old Oct 11, 2002, 08:15 AM
No fuse too fat
slopeiron's Avatar
USA, CA, Redondo Beach
Joined Apr 2002
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Quote:
Originally posted by Duke58
Why not just use lead and rig it with a bomb release , maybe tie on a ribbon , or a chute?

Earl
Hey Ben,
I agree with Earl. I think using a 'bomb release' type mechanism to drop a chunk of lead is the easiest way to go. As already noted, if you want to use water, you will have to find a way to keep it from sloshing around and also a leak proof valve to release it. Additionally, as you mentioned, water is not as dense as lead. One other thing is that it wouldn't be good if that water somehow got all over your radio gear. (Crash? )

It sounds like a good idea and I think you should be able to rig something up easily enough.

Russ.
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Old Oct 11, 2002, 09:22 AM
David Cairns
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Orange, CA
Joined Apr 2002
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Don't dump the lead

I am not sure dumping lead at Point Fermin is such a good idea. If anyone found out, they would shut the place down until a toxic clean up could be done and gliders would be banned. They have the Point Vicente marine museum closed because they discovered lead from bullets left behind from an old firing range that used to be there. Sure seemed silly to me, it' not like people are sitting around eating the dirt there. But this is California, home of the wackiest environmental laws in the world. There is also the danger of releasing the lead at an inopportune time and flinging a chunk into some picnickers head.
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Old Oct 11, 2002, 10:36 AM
No fuse too fat
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USA, CA, Redondo Beach
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Dave brings up some good points. I suppose there are certain drawbacks to dropping lead ballast also.

I have actually toyed with this idea before, but never got around to doing it because in all honesty, I never thought that it was a terribly compelling problem. Landing at Fermin is really not that hard. Even with heavy planes it is just a matter of getting the technique down. Everyone seems to have their own way of doing it.

Some guys go deep around the top of the hill from the left side and circle back around to the right, making a long approach into the wind and landing up on the side of the hill. Most guys shoot across on the right side, make a left turn into the wind and land on the side of the hill. My approach is a little shorter. I go across on the right but stay higher than most people because I don't like flying through the rotor in the flat area back there. Then I start banking as soon as the plane gets over the road and sort of do a diving pilon turn down onto the top of the hill. The wind is smooth up on the edge of the hill and will slow your plane down pretty well.

Remember, as long as you are pulling on the stick you are causing the wing to plow. This is like hitting the brakes, so doing a long, constant turn back into the wind will really slow the plane down. The key is to do a long, gradual turn keeping the up elevator input for as long as possible. This will slow the plane down better than doing a quick turn back into the wind and going back to neutral. Then it's just a matter of practicing when to start the turn in order to put the plane where you want it in the landing area.

Russ.
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Old Oct 11, 2002, 11:31 AM
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yeah, i considered dropping lead with a ribbon or chute attached, but that seems too dangerous at a crowded spot like fermin. dropping it in the water would be irresponsible, not to mention expensive over time.

the kulbutin is a fragile looking plane. the fuse is fiberglass, but from what i've read it's pretty light glass, and the wings are built up balsa. it may be no problem landing a iron clad plane like russ' spitfire, but landing the kulbutin will be a different story. the airframe will not be able to stand up to less than picture perfect landings. keep in mind that a big glider like the kulbutin will not bleed off speed the way your typical fermin warbird does. especially if it's loaded with ballast.

i am leaning toward using sand instead of water. it's more dense, and i won't have to worry about getting my receiver wet. i'll just build a lite ply box right over the CG to hold the sand. the box might be as simple as two bulkheads, with brass tubes going thru them for the control rods.
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Old Oct 11, 2002, 01:23 PM
When the time is right
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Hayward, CA
Joined Apr 2001
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What's the difference, if you are flying over civilians the degree of control you have over the ballast drop is the same as you have over the plane, you are already going in harm's way by over flying people.

Earl
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Old Oct 16, 2002, 02:05 PM
Free as a bird now.
Brian Courtice's Avatar
United States, FL, Punta Gorda
Joined May 2002
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This ballast question may all turn out to be a moot point as far as the Kulbutin is concerned. It is my understanding that the Kulbutin is designed to be very aerobatic at moderate speed. It is designed more for "gyration" as opposed to speed and penetration. You might find that adding ballast is only going to make the plane heavier, it may have little effect on top speed while detracting from the planes ability to maneuver.

A typical Fermin "lead sled" is designed with a very thin airfoil and stiff airframe. Building them heavy allows the planes to accelerate quicker, and the speed they build up is traded for energy that can be used for those big graceful pumps. You don't see those planes hovering on the lip, snap rolling left and right, pulling tight inside and outside loops etc. For that you want a lighter plane with a thicker more symmetrical airfoil and large moving surfaces with a lot of control travel. To fly like that you want something like a Kulbutin.

When it gets windy at Fermin, try throwing out the Kulbutin UN-BALLASTED. You might find that the extra lift provided by the wind allows you to climb better between rolls and loops. You may be able to hang tighter in the bowl, and keep the plane closer in as you perform one wild stunt after another. If you overdo it and kill all your energy and airspeed, your light plane may just start flying again instead of falling out of the sky.

Sure, the lead sleds will be screaming by as they rip through one huge half pipe after another. If you want to fly like that build a plane like that. The Kulbutin is a different kind of animal. Fly it like it was designed for, and enjoy it for what it is...

As far as the droppable ballast idea goes, I like the idea of a solid droppable chunk as opposed to the water idea. There are just too many things to potentially go wrong with a water ballast system. A droppable weight is a lot simpler. If the toxicity of using lead is a problem, why not use steel? Steel isn't quite as heavy as lead, but it is a lot heavier by volume than water is.
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Old Oct 16, 2002, 02:20 PM
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from what other owners of the kulbutin have said, this plane flies best in high winds with lots of ballast. i'll try flying it without ballast of course, but dave wenzlick seems like a pretty knowledgeable guy, so i trust his opinion.

http://www.rcgroups.com/forums/showt...light=kulbutin
http://www.rcgroups.com/forums/showt...light=kulbutin
http://www.rcgroups.com/forums/showt...light=kulbutin
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Old Oct 16, 2002, 02:49 PM
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Brian Courtice's Avatar
United States, FL, Punta Gorda
Joined May 2002
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I have never actualy flown the Kulbutin, so I may be wrong about the need for ballast. I still think there is going to be a point of diminishing return to ballasting the plane, at least if you want to fly it for extreme manuverability. Keep us posted with your experiences when you get to fly the plane!
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Old Nov 06, 2002, 11:13 AM
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USA, CA, Costa Mesa
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Any flight report?

Ben
Have you finished/flown your Kulbutin yet? I would love to hear what you think about this plane. What did you end up doing with the ballast?

Thanks
Keith
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