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Old Apr 09, 2014, 06:55 PM
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Canada, AB, Calgary
Joined Oct 2012
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Weight of various bulbs

I'm designing a custom RC sailboat, and looking for a lead bulb around 15 lbs. What is the standard weight of a Marblehead bulb? 10R bulb? I54 bulb? Any others that are in that range?
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Old Apr 09, 2014, 06:57 PM
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Dick L.'s Avatar
Minnesota, USA
Joined Aug 2002
2,255 Posts
Some will be much less than you expect - deep keel, less weight for same RM required.
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Old Apr 09, 2014, 07:14 PM
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Monterey Bay California
Joined Feb 2004
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I-54 fin and bulb are a two sided 'glass molding, bonded together (no separate bulb/fin). All up, the bulb/fin together weigh 9 pounds and change.

Tell us more about your boat, 15 pound keel sounds intriguing
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Old Apr 09, 2014, 07:32 PM
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United States, MA, Wenham
Joined Jan 2007
1,494 Posts
There are no two Marbleheads that are the same.
Even the ones that are the same.

With that Said, You'll find Ms with ballasts as low as 5.5lbs (IOM bulbs retro fitted to M foils) and probably all the way up to almost 15lbs. Definetly 10. There are hundreds of designs. Some fat, some skinny some red, some blue, some tall, some short.

The question is more specific of, what M are you talking about, and what is the ballast that goes onto that M?


You'll find the majority of Ms between 6-8lbs of ballast however.
Good Luck.
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Old Apr 09, 2014, 09:49 PM
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Australia, TAS, Penguin
Joined Mar 2012
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Not sure if this helps, but my A Class weighs 15.1 Kg all up, the fin & bulb would be around 13.5Kg of that. Draft is 299mm, so the distance from hull to bottom of bulb is probably 230-240mm.

So I guess this is an example of a lot of weight on a comparatively short fin
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Old Apr 10, 2014, 07:21 AM
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Wick Smith's Avatar
United States, MI, Grosse Pointe Woods
Joined Aug 2011
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15 lb Bulb

The 1.7 Meter boat that I produce has a 16.5 lb bulb. It is poured in two halves so I can pour to any weight you want. 15 lbs is well within range for this mold. PM me and we can talk more.
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Old Apr 10, 2014, 07:58 AM
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Here's a shot of our bulb for the 2 Meter AC OD. 19 lbs cast in halves (hose clamp is temporary...;-)) Curious what your buildling as well, love the bigger RC boats.

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Old Apr 10, 2014, 10:17 AM
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Canada, AB, Calgary
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Still in the early planning stages. I will start a build thread once construction is actually underway.

Wick Smith - you have PM.
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