50195Re: [boatdesign] RE: Storm Petrel (Bolger's)
- Nov 19, 2013If I am not mistaken, the Marsh Duck is not ballasted. Where the Storm Petrel is ballasted with a steel plate fin keel. Normally, ballasted boats have a more gentle motion because of their higher mass.I also think that part of the Bolger strategy of Storm Petrel was the very small cabin, which would allow the crew to brace themselves to avoid getting tossed around. 99.999% unnecessary, but 0.001% of the time you could survive a disaster this way.That said, I am not sure that Storm Petrel is my favorite design. Also, it should be viewed as a motor sailor, and be fitted with a small outboard motor for light wind.On Tue, Nov 19, 2013 at 11:55 AM, <nutty_boats@...> wrote:
Thanks, graeme, for the links.
A couple of the links answered a question I long had about Bolger, namely to what school of seaworthiness did he belong. There are two main schools that I know of, most designers ascribe to what I call the barrel over Niagra Falls school where it does not matter how violently the boat acts, as long as it stays in one piece, and the second one where the emphasis is placed on reducing the boat's motion as much as possible for given conditions through good design, because the boat's cargo, the soft, squishy crew inside, can take only so much motion before it is incapacitated, injured or killed. Apparently Bolger ascribed to the first school.
I go with the second school, and as such, Scot's Marsh Duck will have gentler motion than Bolger's Storm Petrel, hence I think it is a superior design.
---In email@example.com, <graeme19121984@...> wrote:
Got to digging up some Bolger Storm Petrel links. Note: this design was completed for Dynamite Payson's Instant Boats, but never appeared in that catalogue of plans. Not quite instant enough maybe, or the slightly non-conformist quirk of deck first assembly in the building guide? Plans are still $50 from PB&F. They are also reproduced in full not to scale in some magazines and books with the instructions...(see links)
So the original keel was 3/8" steel plate. Easy. But Phil Bolger gave out some design pointers for an alternate plywood keel he didn't publish. The plywood keel had about 6" depth lopped off for a draft as shallow as about 14" on the designed WL.
This plywood keel I find interesting. Steve Hanson says his was to be 1.5" thick. He was going to protect it with a steel shoe. Lead equal to the weight of the steel keel plus some extra to counter the plywood bouyancy was to be fitted to have the ballast cog positioned the same as the original. I gather that would be with respect to LOA - easy enough. But that may also be possible with respect to height given the higher density of lead - requires figuring.
Was the plywood keel to be solid plywood? Was it still to be fastened at just the three attachment points? On some Bolger sharpies with sufficient lateral bottom curvature( eg, Micro) a keelson is nailed and glued to the outside bottom then the plywood keel sides are nailed and glued to that - no head logs involved, no floors or other structure required, and the keel is then a strong monococque hollow and flooding box - is that the way to do it on the Storm Petrel? The lead ballast sandwiched between the plywood sides and nails are driven into it too? If the Storm Petrel plywood keel were made 4" thick it would contain a bit more ballast water mass than the mass of the original steel keel and would present a tremendous heeled righting moment at once when raised above the water! Perhaps that ballast water rather than self-draining seawater could even be some fresh supplies?
"I've built a few of Phil's boats already, a Gypsy, Cartopper and what Phil thought was the only Storm Petrel built without alteration's (this was the Storm Petrel that I sold to Marc Lander in S.F. about 20 years ago) ... Anyway, I'd like to build another Petrel ..."
Did Tim ever get the keel done and bolted on? Did he ever get it sailing.
Yes, he made a weighted, plywood keel (one of Bolger's options). It
sails well, but with the "storm" (lateen) rig, it needs a lot of wind to
make it go, as was the point. Next year, Tim wants to make the larger,
lugsail rig for it.....Auke Bay winds are usually light in the summer of
course, and it needs more ooomph. He did have a ball with it though,
motoring, rowing, and sailing.
"The keel will be plywood, fairly thick and with a steel shoe. I'll
have lead inserts with a mass comparable to the steel plate and with
the center of gravity placed where the full steel plate's CG would
It really is an accomplishment to design a boat with the apparent
capabilities and safety of Storm Petrel and only uses 8 sheets of
The reduced keel is not on the plans. I made up a basic sketch and
Bolger added his comments to it. "
I note Storm Petrel at merely $50 may see 2.5+reserve months at sea... beyond the eastern seas lies middle earth... there and back again unseen. The song remains the same...
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