Boat with rotatable wheel keel for resistance to leeward movement in water and for sand transport

A rotatable wheel is mounted under a sailboat or other boat and shaped in a manner such that it will be efficient in developing a hydrodynamic lifting force to function as the boat's primary keel to resist leeway and provide directional stability. The wheel or wheels can also be used to ramp launch or haul the boat and to roll the boat about on land. In order to reduce hydrodynamic drag, a tire fitted onto the wheel forms a continuous and fair surface with the wheel wall.

BACKGROUND 
1. Field of Invention 
The invention relates to the new use of a wheel as a keel for a sailboat to 
resist leeward movement in water and for transportation of boats over 
land. 
2. Description of Prior Art 
Prior devices for ramp launching of boats include trailers and other 
wheeled devices. Such devices normally would be detached at water's edge, 
and thereby create a storage and security problem while the boat is in use 
on the water. Some small vessels have permanently mounted wheels for ramp 
launching, which, due to their unstreamlined design, create tremendous 
undesirable drag when the vessel is moving through the water. 
A sailboat must have a keel or similar device (i.e. centerboard, 
bilgeboards, or leeboards) to resist leeway when sailing upwind. In order 
to serve this function, the keel must be streamlined to minimize drag 
against forward motion; yet shaped to effectively resist leeward motion. 
This requires a keel with a small frontal area, a hydrodynamically smooth 
and fair surface in the direction of motion, and relatively large 
transverse projected area. A keel is also used on other types of boats to 
aid in directional stability. Heretofore this device was always separate 
from the wheeled device used for launching. 
A user of such a boat has to roll the boat into the water, float the boat 
off the trailer or detach or retract the rolling device, tie off the boat 
while such user runs up to store the trailer, return to the boat, lower 
the centerboard, and finally sail away. Haul out is a reversal of these 
steps. 
Therefore, a user would appreciate a device which would allow such user to 
roll the boat directly into the water and sail away without having to 
perform the above complex and tedious procedure. 
OBJECTS AND ADVANTAGES 
Accordingly, we assert the following objects and advantages of our 
invention: the provision of a boat with a keel which is sized and shaped 
to be hydrodynamically efficient in resisting leeway, yet which has 
greatly improved ease of launching and haul out, and elimination of the 
security risk of a trailer left on shore. Other objects and advantages are 
to provide a boat with reduced drag for greater speed in the water, 
reduced risk of damage due to grounding, easier rolling on land, and the 
potential for rolling over the bottom in shallow water where other boats 
might get stuck. 
Readers will find further objects and advantages of the invention from a 
consideration of the ensuing description and the accompanying drawings.

DRAWING REFERENCE NUMERALS 
6 wheel and tire 
8 side wall of wheel 
10 tire 
12 axle 
14 hull 
16 rudder 
WHEEL SHAPED KEEL--DESCRIPTION 
In accordance with our invention, we provide a boat with a keel which is in 
the form of a wheel, which is rotatably mounted, and which is 
hydrodynamically shaped for stabilizing the boat in water and enabling it 
to travel easily over land. 
FIGS. 4 and 5 show boats with wheels as they might be mounted on a sailboat 
in place of a conventional keel. Two wheels would be normally mounted, 
either alongside the hull(s) 14 as in FIG. 4 or recessed into the hull 14 
as in FIG. 5. The wheels are mounted such that axle 12 is recessed into 
the hull 14 or projects minimally into the water when the sailboat is 
afloat. Wheels 6 in FIG. 5 have less than fifty percent of their diameter 
projecting into the water, and wheel 6 in FIG. 4 has seventy percent of 
its diameter projecting into the water. 
The wheel side wall 8 is a solid and continuous surface, and as shown in 
FIG. 3, fits flush and tangent with the exposed surface of a tire 10 which 
is mounted on the perimeter (rim or circumferential edge) of sidewall 8. 
As shown in FIG. 2, a radial section through wheel and tire 6 from axle 12 
to perimeter is shaped like a narrow ellipse divided at its minor axis or 
like the forward portion of a symmetrical wing section with the maximum 
thickness of the wing section being at axle 12. The mathematical curve 
describing the outside surface of this sectional shape is a mathematically 
smooth and continuous curve, with no abrupt changes in radius of 
curvature. The curve is parallel to axle 12 at the perimeter; and 
perpendicular to axle 12 at the axle. Maximum thickness of wheel 6 is at 
axle 12 and the ratio of thickness to wheel diameter is 1/8. 
WHEEL SHAPED KEEL--OPERATION 
A sailboat with wheels mounted as shown in FIGS. 4 and 5 can be easily 
rolled about on land; or when a launching ramp is available can be rolled 
directly into the water. With the wheel keels, the usual step of removing 
wheels and lowering centerboard or other keel device is eliminated. The 
vessel may be sailed directly away from the ramp without adjustment. 
The vessel will be able to sail upwind with no keel other than wheel 6 to 
develop necessary sideforce. The high ratio of hydrodynamic lift to drag, 
or of sideforce to resistance, required of upwind sailing are achievable 
due to three factors unique to this new wheel shape. First, wheel 6 has a 
low ratio of transverse width to diameter and of projected frontal area 
exposed to the water flow to transverse projected area. Second, the 
surface shape is mathematically smooth and continuous, with no abrupt 
change of radius of curvature. Third, because no more than seventy percent 
of the diameter of wheel 6 projects into the water, axle 12 and hence any 
attendant mounting apparatus is recessed into the hull or projects 
minimally into the water. Consequently there is little or no parasitic 
drag due to the mounting apparatus. 
Under sail wheels 6 may spin in the water. We believe this action will 
reduce frictional boundary layer drag relative to a conventional keel or 
leeboard. This is, because the surface of wheel 6 will move through the 
water at a rate less than the speed of the boat. 
When the user has completed sailing, the vessel may be rolled directly out 
of the water on its wheels 6. If the boat becomes grounded in shallow 
water, or hits a submerged rock or the like, its keel wheels will enable 
it to roll over the bottom or the obstacle without damage to its keel or 
hull, thereby avoiding the damage which would occur to a boat with a 
conventional rigid keel. 
SUMMARY, RAMIFICATIONS, AND SCOPE 
While the above description and accompanying drawings contain many 
specificities, the reader should not construe these as limitations on the 
scope of the invention, but merely as exemplification of the preferred 
embodiment thereof. For example, a vessel might have only one wheel on 
centerline, or might use a wheel as a rudder for steering purposes such 
that a three point suspension gives full stability on land. A hole may be 
made through the wheel wall for the purpose of locking the wheel against 
rolling or for some other purpose. The wheel rim section might be 
elliptical in cross section, with the center area of the wheel largely 
open. The use of a wheel shaped keel need not be restricted to sailboats, 
but can be used on any floating craft which has a need for rolling ability 
on land and directional stability in the water. 
Accordingly the reader is requested to determine the scope of the invention 
by the appended claims and their legal equivalents, and not by the 
examples which have been given.