Re: Step Sharpie/Box keel
I meant to add that PCB also says of Bell's Puffer ( from a 40+ year
development theme):
"The volume of this cutwater and keel carries her displacement far
forward, with a similar effect on her wavemaking, to these penis-
like bulbs that are some times stuck onto bows to compensate for a
bad basic shape. The bad shape is often the consequence of insisting
on a sharply-raking stem profile and producing it by shortening and
blunting the waterline instesd of stretching out the deck. The box
does not have a high drag because its profile is matched to its plan
view, with the corners of the box lying along the lines followed by
the water flowing around the sides and bottom of the box."
"This is a conservative design. The hull shape is different from
other boats, but its a natural development of a line we've been
pursuing for 40-odd years since the early box-keel Striker steel
production boats"
Graeme
PS. An interesting aside, " With the total input of letters by
Roger Bell on this commission amounting to just about two pages,
the "man of few words" has not yet let us know about progress
building or cruising. He might steam into Gloucester tomorrow."
MAIB Vol12 #11, 15Oct99
Has he yet?
--- Inbolger@yahoogroups.com, "graeme19121984" <graeme19121984@...>
wrote:
development theme):
"The volume of this cutwater and keel carries her displacement far
forward, with a similar effect on her wavemaking, to these penis-
like bulbs that are some times stuck onto bows to compensate for a
bad basic shape. The bad shape is often the consequence of insisting
on a sharply-raking stem profile and producing it by shortening and
blunting the waterline instesd of stretching out the deck. The box
does not have a high drag because its profile is matched to its plan
view, with the corners of the box lying along the lines followed by
the water flowing around the sides and bottom of the box."
"This is a conservative design. The hull shape is different from
other boats, but its a natural development of a line we've been
pursuing for 40-odd years since the early box-keel Striker steel
production boats"
Graeme
PS. An interesting aside, " With the total input of letters by
Roger Bell on this commission amounting to just about two pages,
the "man of few words" has not yet let us know about progress
building or cruising. He might steam into Gloucester tomorrow."
MAIB Vol12 #11, 15Oct99
Has he yet?
--- Inbolger@yahoogroups.com, "graeme19121984" <graeme19121984@...>
wrote:
> another property of the box keel is to shift displacement to theends,
> preventing a hull from wallowing in its own waves, and allowing
> increased speed. See PCB&F write-up of their design #635, Col H G
> Hasler.
Hi Nels,
another property of the box keel is to shift displacement to the ends,
preventing a hull from wallowing in its own waves, and allowing
increased speed. See PCB&F write-up of their design #635, Col H G
Hasler.
Does the forefoot of the keel necessarily have equal curvature of the
chine in plan and profile views in the planing step sharpies, similar
to the sailing displacement box-keel models. Planing might require the
cutwater bottom to exert more pressure than the sides, no?
Graeme
another property of the box keel is to shift displacement to the ends,
preventing a hull from wallowing in its own waves, and allowing
increased speed. See PCB&F write-up of their design #635, Col H G
Hasler.
Does the forefoot of the keel necessarily have equal curvature of the
chine in plan and profile views in the planing step sharpies, similar
to the sailing displacement box-keel models. Planing might require the
cutwater bottom to exert more pressure than the sides, no?
Graeme
--- Inbolger@yahoogroups.com, "Nels" <arvent@...> wrote:
> ....A box keel is a long hollowed keel with the bottom open rather
than
> filled with lead or whatever....
Although there are some grey overlapping areas, (Like Fast
Motorsailer) the way I visualize the difference between a step
sharpie and a box keeled boat is;
A step sharpie has a wider, roomier hull perched atop a fast narrow
hull that is quicker and more easily driven as the speed increases
and the hull rises to be mostly supported by the narrow hull. Bolger
claims on page 355 of BWAOM that if a Wyoming is built like the
modified Sneakeasy it could have a beam up to 27 feet!
A box keel is a long hollowed keel with the bottom open rather than
filled with lead or whatever.(And more deadrise in the main hull
than a step sharpie.) It's purpose is to help resist leeway in a
motorsailer while at the same time allowing heavier contents to be
stored low down in the bottom of the keel, adding to the righting
moment of the hull.
It also has the benefit of allowing the inboard engine driveshaft
to be under the waterline and aligned parallel to the water surface.
It can also provide standing headroom down the centerline on a boat
that would not normally have standing headroom.
The trade-off is that it performs best when the engine is running to
maintain way as the keel is not that aerodynamically efficient,
compared to a fin. The rationale is that most sailors use their
engines more than they care to admit to according to PCB. So why not
have one that is efficiently located?
FMS has leeboards added to a planing "semi-stepped sharpie" hull?
MacGregor seels a planing motorsailor as well
http://www.macgregor26.com/index.html
Nels
Motorsailer) the way I visualize the difference between a step
sharpie and a box keeled boat is;
A step sharpie has a wider, roomier hull perched atop a fast narrow
hull that is quicker and more easily driven as the speed increases
and the hull rises to be mostly supported by the narrow hull. Bolger
claims on page 355 of BWAOM that if a Wyoming is built like the
modified Sneakeasy it could have a beam up to 27 feet!
A box keel is a long hollowed keel with the bottom open rather than
filled with lead or whatever.(And more deadrise in the main hull
than a step sharpie.) It's purpose is to help resist leeway in a
motorsailer while at the same time allowing heavier contents to be
stored low down in the bottom of the keel, adding to the righting
moment of the hull.
It also has the benefit of allowing the inboard engine driveshaft
to be under the waterline and aligned parallel to the water surface.
It can also provide standing headroom down the centerline on a boat
that would not normally have standing headroom.
The trade-off is that it performs best when the engine is running to
maintain way as the keel is not that aerodynamically efficient,
compared to a fin. The rationale is that most sailors use their
engines more than they care to admit to according to PCB. So why not
have one that is efficiently located?
FMS has leeboards added to a planing "semi-stepped sharpie" hull?
MacGregor seels a planing motorsailor as well
http://www.macgregor26.com/index.html
Nels