Sweep Oar Design Features::
The APEX Blade Shapes for Sweeps were introduced at the 1999 Head-of-the-Charles Regatta. This is the "Next Generation" of blade shapes for both sweep and sculling. These blades have both a smooth front surface, and most importantly, a smooth back surface to provide better hydrodynamic lift. Today the APEX-Sweep is the most popular sweep shape selected.
The theory of a smooth faced blade causing less disturbance to the flow of water over the front face of the blade seemed to us to be in direct contradiction to basic hydrodynamic theory. Potential gains in hydrodynamic lift could be achieved if the back, not the front face of the blade, is free of impediments to the smooth movement of water in the direction of flow. It is not the front, but the back of the blade with its longer curved surface that accelerates the water flow and should provide a lifting force as the blade traverses out to the 90 degree stall position and back again during each stroke. By making the back surface "smooth" with the spine, or shaft attaching ridge parallel to the water flow, the blade would be more efficient and easier to handle.
The APEX blade shape is a significant design improvement. What we have done is to move the attachment spine to the top of the blade on both the front and back parallel to the direction of water flow as the blade traverses out and back from the boat. The spine was changed to a smooth contour and the volume calculated to effect a displacement enough to give the correct buoyancy as well as the right weight and weight distribution which affects the balance point. In addition, the blades can now be made just a hair above the FISA minimum thickness of blades to provide (i.e., of 3 mm thick blade; 2 mm in from the tip) more efficient blade work.
A BB5299 enhanced sweep blade shape design and tooling has been completed in November of 1998. 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 BB55 with improved features to our previous BB52 and comparable or enhanced performance to our BB55. 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. This is our 2nd most popular blade shape sold and continues to show up on the podium.
The Dreher APEX RG Sweeps: The latest improvement of this design is a modification of the Dreher APEX blade shape which rounds the profile of the blade, slightly deepens the blade at the center of pressure, and improves the cant angle at the catch to further enhance its hydrodynamic performance. Below are some photographs.
This blade shape is observed to be more efficient from both a hydrodynamic and aerodynamic basis. The action of the blade through the water seems to allow greater lift. The vortex generated on the back side of the blade retains contact longer with the blade before shedding and forming the puddle. Consequently, this is theorized to increase hydrodynamic lift. This benefit will increase as the speed in the boat increases. Because of the rounded edges, especially the bottom two edges of the blade, there is less turbulence observed at the finish with the easier release of the water from the surface of the blade at the finish. Just as with any high performance oar, the better the rower, the greater the potential benefit with this design. Many of the advances of this oar design would be most obvious at approaching race pace and above and not noticed as having any perceivable difference when rowing at a steady-state pace or less then full boat of rowers at a time. Also, the oars must be rowed enough so that the crew becomes used to them.
Priming/Painting Service: Durham Boat Company, Inc. offers oar purchasers with the option of priming with a flat gray or priming and painting oars with one base color of choice as an option or no priming or painting. We have had a number of customers request this service so we offer either priming only or priming and painting done professionally.
Sweep handles: Sweep handle are are offered in two sizes several grip wrap options of sythetic suede in red, navy blue, granite, gray, black or yellow. (i.e., an inboard wrap only, a full length wrap, and an inboard wrap with an STS rubber grip at the outboard end or choice of full length rubber grips (gray, black, blue or orange).
Ever since we begin manufacturing Dreher sweep oars in 1991, we only offered the carbon handles. We designed the adjustable sweep oar with the adjustment feature in mind. In so doing we could save about 1 pound per oar from the traditional wood designed oar. Our design includes a shaft with no taper at the point where the constant diameter of the handle mates up the the shaft. Because there is no taper to the shaft along the entire shaft/handle interface, there is no movement or lost energy during the drive.
The Synthetic Suede wrapped has been the most popular grip wrap and with a little practice the easiest to install than other oar surface handle treatments. The wrap is gentler on the athletes hands than existing grips on the market today, while still providing a excellent grip on the oar.
We are no longer offering the wood over carbon as an option. The wood over carbon design was offered to provide the traditional wood feel with the strength, stiffness and light weight of carbon. It is now apparent, that for the most part, the sweep market has moved onto synthetic wrap over a composite handle with the adjustable length feature.
Other Relevant Information: For more information see:
A technical discussion of the Apex-R Blade Theory & Practice.
Dreher Adjustable Length Carbon Sweeps
+/- 5 cm of continuous adjustment standard.
For additional information call, write or e-mail:
C. M. Fuerst
Durham Boat Company, Inc.
220 Newmarket Rd. (Route 108)
Durham, NH 03824
Phone 603-659-7575
Phone 603-659-2548
Contact: Cfuerst@cris.com
For German and other European customers call or e-mail to obtain prices:
BBG Bootsbau Berlin, GmbH
Müggelseedamm 70
Berlin-Reiedrichshagen, 12587
Germany
+49 (0) 30 /64 55 374
+49 (0) 30 /64 55 251 Fax
Contact: E-mail BBG
For UK customers call or e-mail to obtain prices:
Dreher UK
7 Vicarage Close
Waterbeach
Cambridge CB5 9QG, UK
+44 (0) 79 7073 4330 Rebecca Caroe
+44 (0) 79 7026 6180 Grant Craies (Cell)
Contact: E-mail Dreher UK Information
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Contact: E-mail Dreher UK Service
For other related links on Other Dreher Carbon Fiber Products manufactured and sold by Durham Boat Company, Inc. see the following links:
Home Last Updated: December 12, 2005