Design Matrix

Criteria	Solution 1	Solution 2	Solution 3	Solution 4	Solution 5	Solution 6
Ease of use	Datum	s	+	+	-	+
Fullfills specs	Datum	+	+	+	-	+
Aesthetic appeal	Datum	-	+	s	s	+
manufacturability	Datum	-	-	-	-	-
Low weight	Datum	-	s	-	s	s
Energy Efficiency	Datum	-	s	-	s	-
Safety	Datum	s	s	s	s	s
Σ+	Datum	1	4	2	0	3
Σ-	Datum	-4	1	-3	-3	-2
Σs	Datum	2	3	2	4	2
Net Score	0	-3	3	-1	-3	1
Rank	3	5	1	4	5	2
Continue or Combine	yes	yes	combine	yes	no	combine

Rationale

Design #1

            Design #1 has a T shaped frame with two wheels and one wheel in the back, and uses the string motor system outlined in the descriptive abstract.  The frame is constructed from aluminum and will not have power steering, measuring in the end at 39 inches long by 29 inches wide.  The wheels are urethane roller blade wheels with ball bearings around the axel.  The width of the frame in the front causes the design to be more stable when turning.  With two wheels firmly on the ground at the front of the frame, the rig will not slide on the testing surface and therefore grant the design sharper turns.  The design has a low weight compared to other designs, and the design will also be more energy efficient with only two string motors and a receiver that need power.  The design also looks professional, as the T shape is common in the market for RC land sailers.  However, this design does not fulfill all specifications, as the land sailer does not have a way to steer with its front wheels.  This means the only turning method will be to move the sail, which will not be as efficient as other designs and their turning methods.  The model will be difficult to create and redesign, but the design principles are useful in other designs.  It will be looked into further in choosing other designs, as this balanced design will make a good datum choice.

Design #2

           Design #2 has an upside down T shape with a crossbeam intersecting the vertical aluminum bar.  This design uses the same string motor system as designs #1 and #5.  The two motors and the boom are attached to a set of strings, which pull or release the string to alter the sail position.  The frame is made from aluminum and the wheels are urethane rollerblade wheels with ball bearings to reduce friction.  The frame is 39 inches long by 29 inches wide.  This design includes power steering, where two bars attached to a rotatable motor are hooked onto the steering column by another, steering wheel like attachment.  Pushing the bar on one side and therefore pulling the bar on the other will turn the column, thereby turning the wheel.  This design fulfills all of the specifications outlined, and requires the same skill level of use as design #1.  However, this design will be heavier, uses more power with two string motors and motorized steering, will be harder to manufacture, and has a structure that could be improved because of the unaesthetic appeal.  All of these are minor faults, as one aluminum bar and one more motor are minor yet necessary.  Regardless, this will be a design that should be looked further into.  This design has an efficient use of the string motor system compared to the other frames. 

Design #3

          Design #3 has the same upside down T frame as design #2 without the crossbeam intersecting the vertical bar.  This design has the same power steering system in the front wheel as design #2 as well.  However, this design uses a new way to control sail position, a single motor next to the mat that turns the entire mast system, not just the boom and sail.  This will work by either a set of gears, a smaller string servo located in the center, or a fan belt style rotator.  The frame is 39 inches long by 29 inches wide.  The frame is made from balsa wood for lightness with aluminum bars for support, and the wheels are urethane with ball bearings for reduced friction and speed.  This design will be easy to use with its simple mast positioning system and fulfills all of the specifications.  The frame also makes this design one of the lighter models featured.  The model has an appealing visual effect, as this framework is common in the RC land sailing community.  However, with so many moving parts in the front and in the mast positioning system, the ability to manufacture the design will not be very good, despite the fact that the intricate string servo system was done away with.  This design incorporates some of the best ideas from all designs, such as power steering, the T-shaped frame, and the central sail servo system.  With that, this design will be looked into further.

Design #4

            Design #4 is designs #1 and #3 put together with some of the ideas put together to form one.  The I shaped frame is a combination of the two T’s, making this design more stable and less likely to fall over during the racing portion of testing.  This design uses the central mast steering method of sail control, and the model also uses the power steering on both of its front wheels.  The frame will be made from balsa wood with aluminum rods for support, similar to design #3, measuring 39 inches in length by 29 inches in width.  The wheels are urethane roller blade wheels with ball bearings.  This design will be easier to use than the others, as the wide ground coverage makes the frame harder to tip.  This design looks more like an RC racing car would with the standard four wheels.   Increased stability will be the main feature of this design, although the frame does weigh more now that there is an extra “leg” to the sailor.  This design also uses a moderate amount of power with two power steering motors and a central motor.  Manufacturability will be much more difficult, as a fourth wheel must be added with the new “leg” and the balsawood/metal rod structure will be harder to assemble.  This design would be good if the three wheeled designs do not function as intended, so this would only serve as a backup design.

Design #5

        Design #5 has a similar functionality to design #1’s T shape, except the horizontal frame at the front will be moved back and the mast socket is moved to the furthest point foreword on the frame.  The frame is made from aluminum poles for durability and the wheels are urethane roller blade wheels.  The entire frame is 39 inches long by 29 inches wide.  The structure was rearranged so that the string motors could turn the boom easier since the axis will be placed in front of the servos rather than behind them.  This design, consumes only a moderate amount of power, having two servos for boom, power steering and a receiver. However, this design experiences the same problem as design #1, being that with the two servos in the way, there is no room for power steering, which will be critical to the functionality of the land sailer.  Additionally, the design may be too heavy in the front, so components will have to be moved to the back to counteract this flaw.  Being so delicate that the design could tip over if the user operates carelessly, this design is not easy to use, and therefore, does not fulfill the specs. The design looks off center, causing the frame to have a poor appearance.  This design does not have anything good or anything better than almost everything else. 

Design #6

          Design #6 combines many of the design elements from previous designs.  The frame will be the same T-shape from design #1, and the power steering usage is similar to design #4.  The frame is made from aluminum poles rather than sheet metal in order to provide a more rigid design than a thin and flimsy structure.  The hollow rod will also be good for housing some of the components, as servos and batteries can be stored on the inside rather than the outside.  The frame is 39 inches long by 29 inches wide, and its wheels are urethane roller blade wheels with ball bearings.  Unlike design #1, design #6 is able to have power steering now that there are no string motors in the way.    Also, with a central motor instead of string motors, the sail has a wider range of turning. With two wheels in the front, the frame will be much more stable during the racing testing stage.  Because of this feature, as well as the simplistic ways of moving, this design is easy to use, and from all other positive attributes, this design fulfills the specs.  The use of poles instead of sheet metal, as well as the simplistic design, gives this frame an aesthetic appeal over some of the other designs.  However, with more mass in the front, the design will be less aerodynamic.  Additionally, compared to other designs this design may be harder to manufacture, being that it will be difficult to mount servos and wheels onto poles instead of a flat surface.  Realistically, this design would be better if the land sailer’s specifications were simpler and required less moving parts.  Because this is not the case, the design will not be very practical.

Conclusion

           After looking over the designs and their individual parts, I have decided that it is best to go with the design #3 with some principles taken from other designs.  The foreword facing T-design scores highest in the design matrix, being that the design will be superior to other designs when looking at ease of use, fulfillment of specifications, and aesthetic appeal.  The design was also only the same level as other designs in weight, energy efficiency, and safety.  However, the previous knowledge that this frame structure is common when building land sailors has influenced the decision on what design to pick the most.  When completing the research portion, the idea was clear that almost all land sailer models used the design #3 T-shape, so real world experience was another factor that was used in deciding which model to use

            Changes can and will be made to the design.  For instance, the frame material will have thickness to it so that systems such as the servos and mast socket can be held more securely.  This idea is taken from design #6, where instead of using hollow metal to house units, solid wood will be cut and fitted for the parts.  This idea takes concepts from two pre-existing features, a wooden and a hollow frame.  If the central motor idea does not work out as planned, the string motor could be put into place instead.  Additionally, the isometric drawings will be redone as the project moves along so that they fit the latest design changes.