Tech Talk: Skidfin Setup
By Nelson Holmberg – Skid fin technician – U-40 Flav-R-Pac
It’s just a 300-pound slab of steel that hangs off the back of the left sponson, and helps hold an arc in the turns, right?
Yes — sort of.
Most hydroplane racing fans already know that the skid fin’s purpose is to help the boat hold its arc around turns, so that drivers can “paint the buoys”, or simply hold their lanes at speeds upward of 140 m.p.h. through the turns.
Did you know, however, that the skid fin also has another very important function in the straightaways? A hydroplane’s alignment (like your car) is significantly influenced by the skid fin.
For that reason, it’s critically important that the fin has a nearly perfect alignment with the inside of the air trap. To find that alignment, some use lasers from the back of the skid fin to a carefully measured target at the rear of the boat. Others use good old fashioned string lines and tape measures to get a parallel measurement between the back of the fin to the airtrap, measuring multiple points between the fin and the transom. There’s really not a wrong way to set the alignment, as long as the measurements are correct.
In the turns, the 3-foot tall by 3.5 foot long, one-inch-thick skid fin throws a majestic “second roostertail” 50 feet into the air representing the force created by the gravity against the fin, and the skid fin must withstand up to as much as 13 tons of force in side load.
These forces are transmitted into the boat via two very stout assemblies: the skid fin bracket that extends from the rear of the left sponson, which the upper portion of the skid fin is bolted to, and the rods that tie into the lower portion of the skid fin. The tie rods are the main carriers of the force generated by the skid fin, and these are attached to the “skid fin box” – a series of vertical plates that attach to the rod mounting plates and the main structure of the hydro.
Because of this extreme force generated in every turn, skid fins are frequently inspected and tested for cracks and faults. Team members who work on skid fins also check all tie rods, bolts and fittings after every run of their boat to make sure nothing is slipping or loosening.
In order for the skid fin to keep it’s settings and to not allow any adjustments to shift after the boat leaves the dock, all of the rods that tie it into the boat are set to apply tension at all times, as any unloading of that tension would allow for the possibility of the adjustment nuts to loosen – which would be catastrophic.
Twice in the past 17 years, an H1 Unlimited hydroplane has had failures of the the skidfin, and both caused significant damage – in 2007, the U-1 Elam Plus with Dave Villwock driving suffered a failure in Valleyfield, Quebec, landing the boat on the rocks; while the most famous failure was in the 2010 APBA Gold Cup in Detroit, where JW Meyers, driving the U-37 Miss Peters & May ended up crashing into the seawall in front of the Roostertail Restaurant, destroying the boat:
Obviously, the skid fin is just as important to an unlimited hydroplane as any other part is. Without it, the modern engineering marvels we know as hydroplanes would not be able to safely maneuver the race course.
Speaking of the race course, there are certainly differences between each different race site, and that sometimes means changes for the skid fin set up. Sometimes a driver wants more control in the turns, other times he wants a little more freedom in the turns.
What that means for set up is that we can make any number of changes for the driver. Skid fins can be set down (or deeper into the water) to provide more grab. Or we can set the fin higher for a little more freedom. We also use angled shims to provide different angles of attack on the fin based on the radius of a turn, or driver preference, to improve boat ride.
It’s just a slab of steel…but it’s so important to have just the right set up.
To learn more about what makes an Unlimited Hydroplane one of the fastest boats on the planet, check out the Hydros 101 page.
By Nelson Holmberg – Skid fin technician – U-40 Flav-R-Pac
It’s just a 300-pound slab of steel that hangs off the back of the left sponson, and helps hold an arc in the turns, right?
Yes — sort of.
Most hydroplane racing fans already know that the skid fin’s purpose is to help the boat hold its arc around turns, so that drivers can “paint the buoys”, or simply hold their lanes at speeds upward of 140 m.p.h. through the turns.
Did you know, however, that the skid fin also has another very important function in the straightaways? A hydroplane’s alignment (like your car) is significantly influenced by the skid fin.
For that reason, it’s critically important that the fin has a nearly perfect alignment with the inside of the air trap. To find that alignment, some use lasers from the back of the skid fin to a carefully measured target at the rear of the boat. Others use good old fashioned string lines and tape measures to get a parallel measurement between the back of the fin to the airtrap, measuring multiple points between the fin and the transom. There’s really not a wrong way to set the alignment, as long as the measurements are correct.
In the turns, the 3-foot tall by 3.5 foot long, one-inch-thick skid fin throws a majestic “second roostertail” 50 feet into the air representing the force created by the gravity against the fin, and the skid fin must withstand up to as much as 13 tons of force in side load.
These forces are transmitted into the boat via two very stout assemblies: the skid fin bracket that extends from the rear of the left sponson, which the upper portion of the skid fin is bolted to, and the rods that tie into the lower portion of the skid fin. The tie rods are the main carriers of the force generated by the skid fin, and these are attached to the “skid fin box” – a series of vertical plates that attach to the rod mounting plates and the main structure of the hydro.
Because of this extreme force generated in every turn, skid fins are frequently inspected and tested for cracks and faults. Team members who work on skid fins also check all tie rods, bolts and fittings after every run of their boat to make sure nothing is slipping or loosening.
In order for the skid fin to keep it’s settings and to not allow any adjustments to shift after the boat leaves the dock, all of the rods that tie it into the boat are set to apply tension at all times, as any unloading of that tension would allow for the possibility of the adjustment nuts to loosen – which would be catastrophic.
Twice in the past 17 years, an H1 Unlimited hydroplane has had failures of the the skidfin, and both caused significant damage – in 2007, the U-1 Elam Plus with Dave Villwock driving suffered a failure in Valleyfield, Quebec, landing the boat on the rocks; while the most famous failure was in the 2010 APBA Gold Cup in Detroit, where JW Meyers, driving the U-37 Miss Peters & May ended up crashing into the seawall in front of the Roostertail Restaurant, destroying the boat:
Obviously, the skid fin is just as important to an unlimited hydroplane as any other part is. Without it, the modern engineering marvels we know as hydroplanes would not be able to safely maneuver the race course.
Speaking of the race course, there are certainly differences between each different race site, and that sometimes means changes for the skid fin set up. Sometimes a driver wants more control in the turns, other times he wants a little more freedom in the turns.
What that means for set up is that we can make any number of changes for the driver. Skid fins can be set down (or deeper into the water) to provide more grab. Or we can set the fin higher for a little more freedom. We also use angled shims to provide different angles of attack on the fin based on the radius of a turn, or driver preference, to improve boat ride.
It’s just a slab of steel…but it’s so important to have just the right set up.
To learn more about what makes an Unlimited Hydroplane one of the fastest boats on the planet, check out the Hydros 101 page.
Tech Talk: Skidfin Setup
By Nelson Holmberg – Skid fin technician – U-40 Flav-R-Pac
It’s just a 300-pound slab of steel that hangs off the back of the left sponson, and helps hold an arc in the turns, right?
Yes — sort of.
Most hydroplane racing fans already know that the skid fin’s purpose is to help the boat hold its arc around turns, so that drivers can “paint the buoys”, or simply hold their lanes at speeds upward of 140 m.p.h. through the turns.
Did you know, however, that the skid fin also has another very important function in the straightaways? A hydroplane’s alignment (like your car) is significantly influenced by the skid fin.
For that reason, it’s critically important that the fin has a nearly perfect alignment with the inside of the air trap. To find that alignment, some use lasers from the back of the skid fin to a carefully measured target at the rear of the boat. Others use good old fashioned string lines and tape measures to get a parallel measurement between the back of the fin to the airtrap, measuring multiple points between the fin and the transom. There’s really not a wrong way to set the alignment, as long as the measurements are correct.
In the turns, the 3-foot tall by 3.5 foot long, one-inch-thick skid fin throws a majestic “second roostertail” 50 feet into the air representing the force created by the gravity against the fin, and the skid fin must withstand up to as much as 13 tons of force in side load.
These forces are transmitted into the boat via two very stout assemblies: the skid fin bracket that extends from the rear of the left sponson, which the upper portion of the skid fin is bolted to, and the rods that tie into the lower portion of the skid fin. The tie rods are the main carriers of the force generated by the skid fin, and these are attached to the “skid fin box” – a series of vertical plates that attach to the rod mounting plates and the main structure of the hydro.
Because of this extreme force generated in every turn, skid fins are frequently inspected and tested for cracks and faults. Team members who work on skid fins also check all tie rods, bolts and fittings after every run of their boat to make sure nothing is slipping or loosening.
In order for the skid fin to keep it’s settings and to not allow any adjustments to shift after the boat leaves the dock, all of the rods that tie it into the boat are set to apply tension at all times, as any unloading of that tension would allow for the possibility of the adjustment nuts to loosen – which would be catastrophic.
Twice in the past 17 years, an H1 Unlimited hydroplane has had failures of the the skidfin, and both caused significant damage – in 2007, the U-1 Elam Plus with Dave Villwock driving suffered a failure in Valleyfield, Quebec, landing the boat on the rocks; while the most famous failure was in the 2010 APBA Gold Cup in Detroit, where JW Meyers, driving the U-37 Miss Peters & May ended up crashing into the seawall in front of the Roostertail Restaurant, destroying the boat:
Obviously, the skid fin is just as important to an unlimited hydroplane as any other part is. Without it, the modern engineering marvels we know as hydroplanes would not be able to safely maneuver the race course.
Speaking of the race course, there are certainly differences between each different race site, and that sometimes means changes for the skid fin set up. Sometimes a driver wants more control in the turns, other times he wants a little more freedom in the turns.
What that means for set up is that we can make any number of changes for the driver. Skid fins can be set down (or deeper into the water) to provide more grab. Or we can set the fin higher for a little more freedom. We also use angled shims to provide different angles of attack on the fin based on the radius of a turn, or driver preference, to improve boat ride.
It’s just a slab of steel…but it’s so important to have just the right set up.
To learn more about what makes an Unlimited Hydroplane one of the fastest boats on the planet, check out the Hydros 101 page.
By Nelson Holmberg – Skid fin technician – U-40 Flav-R-Pac
It’s just a 300-pound slab of steel that hangs off the back of the left sponson, and helps hold an arc in the turns, right?
Yes — sort of.
Most hydroplane racing fans already know that the skid fin’s purpose is to help the boat hold its arc around turns, so that drivers can “paint the buoys”, or simply hold their lanes at speeds upward of 140 m.p.h. through the turns.
Did you know, however, that the skid fin also has another very important function in the straightaways? A hydroplane’s alignment (like your car) is significantly influenced by the skid fin.
For that reason, it’s critically important that the fin has a nearly perfect alignment with the inside of the air trap. To find that alignment, some use lasers from the back of the skid fin to a carefully measured target at the rear of the boat. Others use good old fashioned string lines and tape measures to get a parallel measurement between the back of the fin to the airtrap, measuring multiple points between the fin and the transom. There’s really not a wrong way to set the alignment, as long as the measurements are correct.
In the turns, the 3-foot tall by 3.5 foot long, one-inch-thick skid fin throws a majestic “second roostertail” 50 feet into the air representing the force created by the gravity against the fin, and the skid fin must withstand up to as much as 13 tons of force in side load.
These forces are transmitted into the boat via two very stout assemblies: the skid fin bracket that extends from the rear of the left sponson, which the upper portion of the skid fin is bolted to, and the rods that tie into the lower portion of the skid fin. The tie rods are the main carriers of the force generated by the skid fin, and these are attached to the “skid fin box” – a series of vertical plates that attach to the rod mounting plates and the main structure of the hydro.
Because of this extreme force generated in every turn, skid fins are frequently inspected and tested for cracks and faults. Team members who work on skid fins also check all tie rods, bolts and fittings after every run of their boat to make sure nothing is slipping or loosening.
In order for the skid fin to keep it’s settings and to not allow any adjustments to shift after the boat leaves the dock, all of the rods that tie it into the boat are set to apply tension at all times, as any unloading of that tension would allow for the possibility of the adjustment nuts to loosen – which would be catastrophic.
Twice in the past 17 years, an H1 Unlimited hydroplane has had failures of the the skidfin, and both caused significant damage – in 2007, the U-1 Elam Plus with Dave Villwock driving suffered a failure in Valleyfield, Quebec, landing the boat on the rocks; while the most famous failure was in the 2010 APBA Gold Cup in Detroit, where JW Meyers, driving the U-37 Miss Peters & May ended up crashing into the seawall in front of the Roostertail Restaurant, destroying the boat:
Obviously, the skid fin is just as important to an unlimited hydroplane as any other part is. Without it, the modern engineering marvels we know as hydroplanes would not be able to safely maneuver the race course.
Speaking of the race course, there are certainly differences between each different race site, and that sometimes means changes for the skid fin set up. Sometimes a driver wants more control in the turns, other times he wants a little more freedom in the turns.
What that means for set up is that we can make any number of changes for the driver. Skid fins can be set down (or deeper into the water) to provide more grab. Or we can set the fin higher for a little more freedom. We also use angled shims to provide different angles of attack on the fin based on the radius of a turn, or driver preference, to improve boat ride.
It’s just a slab of steel…but it’s so important to have just the right set up.
To learn more about what makes an Unlimited Hydroplane one of the fastest boats on the planet, check out the Hydros 101 page.