Lumenier RB2205C-12 2400KV SKITZO Ceramic Bearing Motor
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Old Jan 27, 2013, 10:45 PM
klkirkman is offline
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Tungsten ballasts


I thought I had mentioned this before, but one of the places that the Bones pushed the limits were in the use of tungsten in the ballast bulbs. We sought an interpretation of the rules of that day about use of materials heavier than lead, and were told that the rule in place then was aimed specifically at spent nuclear fule and mercury to keep someone from contaminating a farm pond. Having said that, I support the ban of heavier than lead as a thoughtful ,limitation due to the high cost of tungeten

We looked into machining tungsten bulbs and found that machining the material was nearly inpossible using normal shop facilities even if one looked the other way at the costs, so we made our bulbs by casitng bundles of tungsten welding electrodes in the center of cast lead keels. One thing we did was to leave a long center electrode protruding to the long pointy end of out laminar floe bulb bodies as this fineness was too extreme to to stand up to being handled if cast in lead; in essence we were using tungsten reinforcing rods.


Karl
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Old Jan 28, 2013, 01:21 AM
bigpat is offline
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Karl,
I can see the day where lead is banned due to health risks. And having lead lying at the bottom of ponds is no better!

It may be the day soon, where we'll have to use steel as bulbs.....

From the sounds of it the Bone concept pushed the boundaries of the class over there. I think over the years, it has been incremental improvements to the class. I still think that carbon isn't essential to build a competitive M. I've built one out of fibreglass, and I know a particular boat built from glass with aluminium masts, which is as quick as anything out there.....
Old Jan 28, 2013, 05:46 AM
Gregg28 is offline
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Banning tungsten, or lead for that matter, would do little to impair the developmental aspect of the Marblehead. It is a material of construction restriction. The use of tungsten does not allow you to make new construction methods possible. The only thing that it does is to allow the ballast bulb to be smaller. Yes, a boat with a tungsten bulb is probably a little faster than a boat with a lead bulb, but with 10 more years of innovation, it is hard to imagine that it would build on this advantage.
Old Jan 28, 2013, 06:20 AM
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Agree 100%...
Old Jan 28, 2013, 06:26 AM
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Originally Posted by Gregg28 View Post
Banning tungsten, or lead for that matter, would do little to impair the developmental aspect of the Marblehead. It is a material of construction restriction. The use of tungsten does not allow you to make new construction methods possible. The only thing that it does is to allow the ballast bulb to be smaller. Yes, a boat with a tungsten bulb is probably a little faster than a boat with a lead bulb, but with 10 more years of innovation, it is hard to imagine that it would build on this advantage.
But who has the capabilities or the money to use tungsten as a bulb. I use tungsten for counter weights but there are already pre made.
Lead even though it is not safe is easy and cheap to mold.
Last edited by 8387mike; Jan 29, 2013 at 12:29 AM.
Old Jan 28, 2013, 12:02 PM
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There is another metal that is even denser (heavier) than tungsten and has a much lower melting point of just over 1000 C. It's gold - and a 6 lb bulb would only cost about $160,000.

Seriously, even in an open development class, there have to be some sensible limitations.

John
Old Jan 28, 2013, 12:13 PM
Mike Denest is offline
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6 lbs. of gold is nice but a lost hatch cover is worth more than the boat.
Old Jan 28, 2013, 01:33 PM
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Mike,
I agree with your post completely; another innovation we introduced was a molded FRP hatch cover slide mechanisn that permitted the hatch cover to slide in place and be essentially waterproof, but which could be augmented by a small piece of tape at the aft edge to be fully waterproof.

Karl
Old Jan 28, 2013, 06:27 PM
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Milton Thrasher offers an IOD 50 inches long that can be sailed in the M Class
Old Jan 28, 2013, 06:37 PM
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hass-alfed and bass-ackwards
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Originally Posted by klkirkman View Post
... we made our bulbs by casitng bundles of tungsten welding electrodes in the center of cast lead keels. One thing we did was to leave a long center electrode protruding to the long pointy end of out laminar floe bulb bodies as this fineness was too extreme to to stand up to being handled if cast in lead; in essence we were using tungsten reinforcing rods.


Karl
That was almost exactly what I was thinking. I know from previous work that tungsten is extremely difficult to work, and I had no intentions of trying to cast or machine a bulb because of this. I did consider hitting up one of the fishing weight places to see what it might cost to have them cast a weight, but since it's not allowed, there's no point in even looking up their phone number.

P.S. I think I have one of those style hatches on my boat, but I didn't build it. It was built by George Baldacchino, who has a reputation (at least around here) for knowing how to build a fast boat.
Old Jan 28, 2013, 08:55 PM
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Visit a commercial roofing company. They still use lead sheet for lots of flat roofs near gutters, and other through-roof fixtures. Take a visit to RCSailing.net and do a search. Claudio "D" has posted a method of cutting a variety of shaped pieces and then gluing them together, finally filling and filing for final shape. Basically you are building a bulb like they used to build Marbleheads (Bread 'n Butter) and you can even use those spendy CAD drawings to shape each layer of the bulb.
Old Jan 28, 2013, 09:24 PM
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Originally Posted by bigpat View Post
From the sounds of it the Bone concept pushed the boundaries of the class over there. I think over the years, it has been incremental improvements to the class. I still think that carbon isn't essential to build a competitive M. I've built one out of fibreglass, and I know a particular boat built from glass with aluminium masts, which is as quick as anything out there.....
Great conversation in general, but I agree with this entirely.

Most of us are at the stage of using round carbon tubes for masts. I've been staring at them saying, why the heck are those not airfoil shaped aluminum masts?

Not only more aerodynamic, but also less expensive.
Usually things are one or the other. The tungsten is better, but a huge cost increase.

Why are we not using aluminum masts? It's a win-win.


With the proper equipment there's no reason why you couldn't suck all the resin out of a fiberglass hull and make a hull pretty well competitive in comparison to a vaccumed carbon/Kevlar one... and again at a big price reduction.
Old Jan 28, 2013, 09:32 PM
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hass-alfed and bass-ackwards
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With an aluminum airfoil shaped mast, does the mast twist or spin on a shaft relative to the sail position or direction of the wind?
Old Jan 28, 2013, 09:48 PM
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It's dependent on how you have it set-up. On my EC-12 I have goldspar aluminum masts, and they do pivot off the centerline just a tad to meet the wind direction... that's with stationary shrouds, or a "Traditional" rig

The M-Class and it's swing rig in paticular might present a bit of a challenge with the airfoil masts..... Not sure I Haven't attempted to build one. But hey, this is a developmental class. surely someone could draw up something



I should also add that i have two other Ms that would take an aluminum airfolil mast right now without any extra throught.
My Vintage M already uses a deck-stepped airfoil mast. It just happens to be made of laminated pine.
My Classic M has a deck-stepped round carbon tube for a mast.

There isn't any sense for me to put aluminum masts on either of these boats, as I already have rigs, but there's no reason why I couldn't... and it would be easy as pie.

Want pictures? Just ask.
Last edited by breakwater; Jan 28, 2013 at 09:56 PM.
Old Jan 29, 2013, 11:46 AM
Mike Denest is offline
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Quote:
Originally Posted by klkirkman View Post
Mike,
I agree with your post completely; another innovation we introduced was a molded FRP hatch cover slide mechanisn that permitted the hatch cover to slide in place and be essentially waterproof, but which could be augmented by a small piece of tape at the aft edge to be fully waterproof.

Karl
Right. I have those on my M and several other boats. The one thing to be careful with is I've seen M's try to imitate a U-boat and implode the hatch cover. That's why I tape it up all around the perimeter.


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