Fairing machine

A powered fairing machine having a pair of flexible arms formed in a cross configuration with an abrasive material on their lower surfaces is described. A power source with a rotary output drive is connected to the intersection of the arms to impart a circular motion to them.

This invention relates in general to an apparatus and method for sanding 
curved surfaces, and more particularly to an apparatus and method for 
power fairing of simple curved surfaces or compound surfaces. 
BACKGROUND OF THE INVENTION 
A flair surface is one which is free of bumps and hollows. Fairing is a 
sanding process that does not simply smooth a surface. Rather, it is a 
process which removes bumps or hollows from the surface being treated. It 
has application, for example, in the finishing of boat hulls which usually 
include a variety of compound curved surfaces. A variety of methods have 
been employed in smoothing the surface of hulls. These include rotary 
sanders, orbital sanders, random orbital sanders and the like. However, 
these perform simple smoothing functions and not, properly speaking, 
fairing functions. One device that has been used for fairing is called a 
long board. It consists of a relatively long, perhaps 3 feet, flexible 
board with sandpaper or other abrasive surface attached to its bottom 
surface and handles at either end. It is then worked by hand in a push 
pull motion or a diagonal motion to perform fairing. As is apparent, it is 
highly labor intensive and not entirely satisfactory in terms of 
performing the function. 
It is a primary object of the present invention to provide a power head 
fairing apparatus to be used as a fairing tool, not only on simple curved 
surfaces, but also on compound curved surfaces. 
SUMMARY OF THE INVENTION 
Broadly speaking, the present invention employs a pair of crossed arms 
coupled to a high torque, relatively low speed, rotary drive power source, 
such as a hydraulic motor, with the crossed arms being formed as flexible 
arms or battens having extended, generally rectangular shaped, planar 
surfaces. The arms are capable of flexing in the direction perpendicular 
to the planar surface and the lower planar surface includes an abrasive 
covering, such as sandpaper. In this arrangement the arms can flex to 
conform to curved surfaces. The arms are coupled at a longitudinal 
position close to their midpoint at the cross intersection to the rotary 
output drive of a power source, such as a hydraulic motor, and the cross 
is driven in a circular motion to perform the fairing function. The 
operator holds the apparatus and guides it over the surface by means of 
handles attached to the power source. 
In one configuration a second pair of cross arms are coupled to the rotary 
drive at a position displaced along the axis of rotation from the first 
pair of arms, to support the first pair of arms which have the abrasive 
coating. The second cross is general congruent with the first cross and 
has its outer ends fastened to the upper surfaces of the ends of the arms 
of the first cross.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The fairing apparatus in FIG. 1 is suitable for fairing not only concave 
surfaces, but also convex and compound curved surfaces. It includes a 
first pair of generally rectangular arms 11 and 13 extended longitudinally 
and having planar lower surfaces 15 and 17. These arms 11 and 13 are 
formed in the configuration of a cross. A second pair of arms 12 and 14 
are also formed in a cross configuration and are attached at their 
intersection to the rotary output drive 20 at a point displaced along the 
axis of rotation from the point of intersection of the first pair of arms 
11 and 13. The rotary output drive 20 is powered by a high torque motor 22 
(shown in phantom), or other suitable power source. The rotary drive 
output 20 may be formed, for example, with a key to lock with a slot in 
the shaft of the motor 22. 
In the configuration shown, the first pair of arms 11 and 13 are maintained 
in a cross configuration by any suitable adhesive or mechanical structure 
(not shown). The outer terminal ends 11 and 13 are fastened, in the 
illustrated embodiment, to the second pair of arms 14 and 16 though 
flexible couplings 33, 35, 37 and 39. These flexible couplings may be 
formed of a material such as rubber pads. The couplings may be attached to 
the surfaces of the arms by means of a suitable epoxy adhesive. The lower 
surfaces 15 and 17 of the arms 11 and 13 carry a suitable abrasive such as 
sandpaper. Typical dimensions for arms 11 and 13 are a width of three 
inches, a thickness of one-eighth inches, and a length of twelve inches. 
While in the embodiment of FIGS. 1 and 2 flexible couplings have been 
employed, it will be realized that the second pair of arms 14 and 16 may 
be fastened directly to the first pair of arms 11 and 13, without 
intermediate resilient materials. The arms 11 and 13 are formed of 
suitable flexible materials rendering them flexible in the direction 
perpendicular to the planar surfaces 15 and 17, which carry the abrasive 
material. Suitable materials for these arms are plywood, other flexible 
boards, or a unidirectional glass fiber, epoxy composite. In the 
embodiment shown in FIGS. 1 and 2, flexible rubber pads are used to join 
the outer ends of the first pair of arms 11 and 13 to the second pair of 
arms 14 and 16, but, other suitable forms of fastening may be employed, 
provided that they do not extend below the abrasive surface to interfere 
with the fairing process. A suitable hydraulic motor for this application 
is a Char-Lynn "J" Series Motor. These motors are available from Eaton 
Hydraulic Division located at Eaton Prairie. Minn. 
In FIGS. 3 and 3A there is illustrated an embodiment which may be used for 
fairing concave surfaces only. Again, in this embodiment the arms 31 and 
33 will be formed by a material that provides flexibility in the direction 
perpendicular to the planar surface of the arms. Because the apparatus is 
used only for fairing concave surfaces, the second pair of arms are not 
needed and the rotary drive output 20 is shown directly coupled to the 
arms. 
In FIGS. 4 and 4A, the fairing apparatus of FIGS. 1 and 2 is shown with a 
generally dish shaped cover 40 mounted to the motor housing 42, such that 
the cover does not rotate, but remains fixed with respect to that motor 
housing, allowing, therefore, the arms 11 and 13 to rotate. The cover 40 
is fastened at its center to the housing 42, such as by a collar or other 
appropriate mechanical fixture. The motor housing 42 has gripping handles 
45 on either side of it for manipulation of the entire sanding apparatus. 
The housing 42 is generally cylindrical, typically formed of either 
fiberglass or metal and has space around the enclosed hydraulic motor 
allowing for gas and entrained particulate material to pass from 
underneath the dome through the housing to a vacuum hose 46 connected to a 
suitable vacuum motor 48. The diameter of cover 40 is sufficient to extend 
beyond the outer ends of arms 11 and 13 in operation. The position of 
these arms may need to be adjusted to assure that the cover skin 41 
extends to the work surface without interfering with the sanding process 
when the cover is flexed. The cover skirt 41 may be formed of a brush, 
thereby allowing air to pass through it without particulate material 
escaping. This arrangement then provides for extraction of the sanded 
material, thus providing for improved safety and health considerations, as 
well as cleanliness of the operation. Hydraulic hoses 43, which are 
coupled to the hydraulic motor pass out from the assembly through the 
vacuum hose 46. At a suitable point, such as ten feet removed from the 
cover, this hose may be divided in a Y-configuration, with one leg of the 
Y going to the vacuum motor 48 and the other carrying the hydraulic hoses 
going to a source of hydraulic pressure. The cover itself may be formed 
from a suitable light weight metal such as aluminum or a suitable 
thermoplastic material such as acrylonitrile butadiene styrene. 
It will be understood that the invention is to be defined by the attached 
claims.