Recovery Pad design
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A short history of the recovery pad....
I discovered the use of pads in 1980 with the help of a TV news camera that was filming a story for a local TV station.
They were doing a story on local RC Boat racing.....I was test running a boat for the camera and it was spinning out at will every time I attempted a fast corner....
I had the sponson design right for a damned fast boat but it wouldn't turn with confidence at speed....
I asked the camera man if he could show me the footage in slow motion and that is when I discovered what was causing the erratic turning problem....
It became obvious I was going to have to hold the nose of the boat up in the corner mechanically....I built a pad right there out of repair materials and 5 min epoxy and put it on the right side of the boat and
shazaam the boat turned like it was tethered to a post.....The camera showed that Coanda water attachment and Bernoulli was causing the boat to roll up
on its nose in a turn pulling the motor skeg out of the water allowing the boat to snap spin faster than you could see with the naked eye.
With the skeg out of the water the boat had no rudder [directional control] and around it would go faster than you could see....That was the day I learned about Bernoulli and Coanda...[but that's another story]
My first boat race I entered was the NAMBA NATS in Burnaby B.C. in 1983....I won the 3.5 OPC class with a boat that had pads on it....I had built probably 15 test boats by that time with all
different designs and sizes of pads and the boat I ran was a killer at the Nats.....Bobby Tom of K&B saw the boat run and asked me if I would be open to talking to Tommy Lee in Cullman Alabama about the pads.
That next week Tommy called me and that was the beginning of a long and lasting friendship between Tommy and I that continues to this day.. Over the next year the XT460 was designed.....The first production XT460's ran at the NAMBA NATS in Reno in 1985 and the rest has been history....
Rod Geraghty
Note;Unless you like spending time in a retrieve boat, pads make running a tunnel a lot more fun......
This will give you something to think about when designing "pads" for your boat....As a result of about a zillion trips to the pond to test,a lot of the old tunnel racers know what they need
for pad design but not many know why they work.....This is a prime example of answering a design question will cause about 50 new questions to be formulated....
Understanding this law of physics also helped tremendously in the design of the JAE hydros.....
It is all so simple when you understand how & why water attaches to a surface and how to get rid of it when you want to....
I discovered the use of pads in 1980 with the help of a TV news camera that was filming a story for a local TV station.
They were doing a story on local RC Boat racing.....I was test running a boat for the camera and it was spinning out at will every time I attempted a fast corner....
I had the sponson design right for a damned fast boat but it wouldn't turn with confidence at speed....
I asked the camera man if he could show me the footage in slow motion and that is when I discovered what was causing the erratic turning problem....
It became obvious I was going to have to hold the nose of the boat up in the corner mechanically....I built a pad right there out of repair materials and 5 min epoxy and put it on the right side of the boat and
shazaam the boat turned like it was tethered to a post.....The camera showed that Coanda water attachment and Bernoulli was causing the boat to roll up
on its nose in a turn pulling the motor skeg out of the water allowing the boat to snap spin faster than you could see with the naked eye.
With the skeg out of the water the boat had no rudder [directional control] and around it would go faster than you could see....That was the day I learned about Bernoulli and Coanda...[but that's another story]
My first boat race I entered was the NAMBA NATS in Burnaby B.C. in 1983....I won the 3.5 OPC class with a boat that had pads on it....I had built probably 15 test boats by that time with all
different designs and sizes of pads and the boat I ran was a killer at the Nats.....Bobby Tom of K&B saw the boat run and asked me if I would be open to talking to Tommy Lee in Cullman Alabama about the pads.
That next week Tommy called me and that was the beginning of a long and lasting friendship between Tommy and I that continues to this day.. Over the next year the XT460 was designed.....The first production XT460's ran at the NAMBA NATS in Reno in 1985 and the rest has been history....
Rod Geraghty
Note;Unless you like spending time in a retrieve boat, pads make running a tunnel a lot more fun......
This will give you something to think about when designing "pads" for your boat....As a result of about a zillion trips to the pond to test,a lot of the old tunnel racers know what they need
for pad design but not many know why they work.....This is a prime example of answering a design question will cause about 50 new questions to be formulated....
Understanding this law of physics also helped tremendously in the design of the JAE hydros.....
It is all so simple when you understand how & why water attaches to a surface and how to get rid of it when you want to....
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Kris Flynn
Well-Known Member
- Joined
- Mar 11, 2002
- Messages
- 4,340
You are THE man Rod, I had a hooking issue with my design when running over the wake of another boat in the corners during a race (would run spot on by itself out on the course). By adding some blocks (in the right place after a few goes) the issue was sorted and I am very happy with my design
Lennard Cuenco
Well-Known Member
- Joined
- Feb 24, 2010
- Messages
- 578
the other part of this "optimal cornering equation" is canting the motor right or left, experiment til the boat stays in the groove in the turn
- Joined
- Nov 14, 2005
- Messages
- 339
Yeah great thread...
Yes.....Tommy and I have probably had no less than 100 different recovery pad designs that we have tried over the years....
Really this is probably the ultimate turning tuning tool for a tunnel....You want some water attachment [COANDA] designed in when the pad touches the water in the corner....
This pulls the sponson and pad down and keeps the inner tunnel sponson wall firmly sunk to the pad depth...remember the turnfin on a tunnel is the vertical inside sponson wall .....The better that vertical wall holds the better the boat will turn at speed....That is why a tunnel will turn equally well left or right....
Note:Food for thought.....
Go look at that you tube video again...this is what the bottom of a tunnel sponson and recovery pad are doing when you turn the boat...
The back of the teaspoon is the bottom of the sponson and the bottom of the recovery pad....
There is no rocket science here ...when Coanda and Bernoulli are applied,the sweet spot of the boats handling characteristics is about 1/2 mile wide.....It is all so simple when you understand Coanda and Bernoulli......use
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