by James Dreher (1/08/99)

The paper describes innovations in blade design by Durham Boat Company, Inc. since January of 1997. We have done two sweep design enhancement and one sculling blade enhancement and also have come up with a combination of the best features of the Macon and Asymmetrical sculling blade design.

New Blade Designs/Enhancements:

Four blade enhancements/redesigns have been made by Durham Boat Company, Inc. since "New Blade Shapes - Part I" was issued in January of 1997, which are as follows:

• The BB5597 Sweep Blade design completed in the summer of 1997;

• The BB2198 Sculling Blade design completed in August of 1998;

• The BB5299 Sweep Blade design completed in November of 1998 with a January 1, 1999 production release date; and

• The LS1999 Sculling Blade hybrid design was completed in December of 1998, with a January 11, 1999 production release date.

Following are a discussion of the blade design changes starting with the most recent one first:

The LS1999 (large, symmetrical, hybrid) Design: It has been over 6 years since the "Big Blade" or Hatchet shaped blade appeared on the racing scene. Now all racing is done with sculls and oars that are larger in blade area, shorter in length and asymmetrical in shape than those used previous to 1992. Some masters and recreational rowers still use the symmetrical "Macon" spoon shape blade, but the Big Blade has become the norm.

Perhaps now is a good time to revisit the symmetrical blade and see if its performance could be improved equal or superior to the Big Blade. The symmetrical shaped blade had been around forever in various shapes, sizes and made in many materials. Some shapes seemed to perform better than others and the initial tests for sculling blades were rather inconclusive in 1992. That year at the top levels we saw some crews win with Macon shapes and others with Big Blade. With sweep blades it seemed more conclusive. Crews with the Big Blade seemed to dominate. But this may have been misleading. Perhaps just the increase in area made the difference in sweep. The traditional sweep blade may have just been right on the edge of being too small. On the other hand in 1992 tests with Brian Sweener the fastest lightweight U.S. sculler that year actually indicated that the Dreher Macon shape was faster than the CII Big Blade shape. Tests in the U.K. by Peter Haining showed the CII Big Blade shape faster than the CII Macon shape. Since both tests were not done with identical Macon shapes, perhaps the Macon blade shape variance was worth looking at. In fact the CII Macon was narrower and much more curved in the shaft axis direction than the Dreher blade and the oar lengths at that time were 6 cm different - 298cm for the Macon and 292 cm for the Big Blade.

What if we increased the Macon blade area to almost the same as the Big Blade and shortened the length to 290 cm - the typical length of a Big Blade scull today? Would the performance be close, or is there something inherent in the asymmetrical Big Blade design to increase performance? Performance as used here is an all encompassing term which includes maximum speed, ease of entry and exit, constant depth during the drive, balance, etc.

In 6 years of manufacturing Big Blade sculls and oars we had found some design improvements to the Big Blade to enhance it's performance. What if we incorporated these features into the Macon?

This was the design problem that Bob Dreher undertook this year, 10 years after he designed his own sculls in 1988 that were eventually used by him and his partner in 1989 at the World Championship and then again by him and Steve Peterson in 1990 to win the World Championships in the Lightweight Double.

Bob made the blade surface area almost the same as a BB21, just 3% smaller in area. The width of the blade is 19 cm, only 2 cm narrower than a BB21. We had previously had experience with slightly smaller Big blade sculls. Since 1992 we have been making special "Little Big Blades" sculls for a German distributor. He had us cut 2 cm off the bottom edge of the BB21, and his customers swore that they were easier to handle and performed better than the BB21.

Bob made the nominal length of the scull 290 cm, with +/-5 cm adjustment in the handle, the same as a standard Big Blade scull. The proportions of the blade remind me of the "tulip" shape blades in the 60's (i.e., being shorter and wider than the typical Macon shape, but much easier to handle than the heavier wooden "tulips" of the '60's)

Trial rows were very enlightening and enjoyable. Frankly we were surprised to find the performance in all respects equal to a standard Big Blade 21. Entry and exit were very smooth, constant depth was apparent during the drive, it was a joy to row with oars squared, and racing cadence and speed were comparable. Others should do further tests. Perhaps the symmetrical shape could make a comeback and be competitive in the right hands.

As a result of this study, Durham Boat Company completed new tooling for this blade shape to provide for our small, but now, perhaps a growing group of customers who prefer the symmetrical, spoon shaped sculls. The new blade shape has been named the LS1999 (large, symmetrical, 19 cm in width) and presently available (January 1999) on our sculls.

The BB5299 Sweep Design: A New BB5299 enhanced sweep blade shape design and tooling has been completed in November of 1998 and began accepting orders in December of 1998 for January 1999 delivery. The procedure followed was similar to that used for the new BB2198 sculling blade. Many of our customers have been used to the BB52 size and wanted that as an option to the BB55, which was released in 1997. Our goal was to design a blade that was meant to be a smaller blade shape then the BB5597, with improved features to our previous BB52 and comparable or enhanced performance to our BB5597. Similar to the sculling blade changes, the sweep blade changes are subtle. Again, as in the BB2198 sculling blade, our focus was to improve the finish of blades and with only minor changes made to blade curvature and attack angle. Overall the blade shape changes integrate well into the overall sweep oar design resulting in a sweep oar that is very easy to use and has excellent release characteristics, balance, and tracking through the drive. As with sculling blade described above, we improved blade strength and performance with the new edge design. In addition, a more polished blade finish reduces drag on the blades at the catch and the finish.

The BB2198 Sculling Oar Design: A New BB2198 enhanced blade shape was completed at the end of July 1998. After conducting several iterations of blade shapes using a rapid prototyping technique, new permanent tooling was made. Our challenge was to improve what we believe to be the best sculling oar design on the market today. To do that we have in the past and will continue to makes continuous product improvements. In so doing the changes that sometimes are the best are the ones that are subtle changes. In the summer of 1998 we improved the finish of blades and made minor changes to blade curvature and attack angle. In addition, the Dreher blades have rounded and sealed edges that even further increase blade strength and performance. Overall the blade shape changes are subtle and integrate well into the overall sculling oar design resulting in a sculling oar that is very easy to use and has excellent release characteristics, balance, and tracking through the drive. In addition, a more polished blade finish reduces drag on the blades. So far the people that have purchased or tried the enhanced BB2198 are very happy with the changes.

The BB5597 Sweep Design: The sweep blade design was changed to provide a flatter BB55 blade shape with less curve at the tip so that the blade would be easier to release. Also the change in the cord orientation was made to enhance both release characteristics and blade efficiency through the water. The cord orientation change allows the sweeps oars to track in the water more consistently on the drive.