Szolack withdrawing from Shootout Action
10-20-2016, 08:13 PM
#151
Platinum Member
Platinum Member
10-20-2016, 09:03 PM
#152
Registered
Hi Naut, long time.
Found this old picture which I think helps visualize your explanation?
[ATTACH=CONFIG]560682[/ATTACH]
Red dot is the CoG position, green rectangle is the CP in ground effect, magenta is where the CP can travel as the boat moves with 6 degrees of freedom.
P.S. Still blows me away too...
Found this old picture which I think helps visualize your explanation?
[ATTACH=CONFIG]560682[/ATTACH]
Red dot is the CoG position, green rectangle is the CP in ground effect, magenta is where the CP can travel as the boat moves with 6 degrees of freedom.
P.S. Still blows me away too...
Last edited by kidturbo; 10-20-2016 at 09:06 PM.
10-20-2016, 09:24 PM
#153
Registered
10-20-2016, 09:26 PM
#154
Registered
I knew Jim melley when I was a kid. I grew up down the road from him. I haven seen him in years and it's very sad to me to see this happen. Jim was always a speed guy. Started in motocross... Funny thing is many many years ago before motocross flat track bikes got faster and faster until the out profoarmed the tire technology. People where getting hurt and worse. Things advanced and got better because of science and learning from failure . But to keep putting yourself in this ( roll the dice) actions of flying a ( plane) with no controls nothing will be safe. Every time I have seen the posts or people from fiore to Garth and Jim ......it's to much to soon. I feel horrible for ALL the family and friends along the way... Congrats to anyone who knows that they are fast enough. It's hard to come to turms with that natural human instinct to be better fast stronger.
10-20-2016, 09:47 PM
#155
Gold Member
Gold Member
Planes get 1/3 of their aerodynamic lift from under the wing and 2/3 from suction above the wing.
A tunnel hull boat however, gets most of it's lift from under due to the compressed air through the tunnel and the hard surface (water) below.
The point of maximum lift is somewhere around the cockpit when the boat is running nicely.
As the bow lifts slightly, the point of maximum lift moves forward.
When the bow lifts up more severely, the point of maximum lift moves further forward and leads to an inevitable blow-over.
He summarizes by saying the tunnel boat has no way to control where the lift is centered, unlike an airplane wing. The boat is like a fixed wing being pushed further without altering shape to allow for higher speed.
Sounds like it's not possible to overcome the 'ground effects' lift from underneath because a boat is always running close to the water.
Please let me know if I've misunderstood and I'll correct/delete.
RR
Last edited by rak rua; 10-21-2016 at 01:58 AM.
10-20-2016, 11:57 PM
#156
Registered
When in middle school I was a crew member on a 7 Litre Hydro Team. (I washed the boat and held it in the water waiting for the 5 minute gun) - anyway this boat had a system in where it would fill the sponsons with water should the front get light. So it would work like this...coming out of the turn, the driver would get on the gas, and start letting water out. If the boat felt good, he would continue to let more water out to "fly the hull" they called it all the way to the turn, at which time he would fill them back up so it would settle down really quick, could drive deeper into the turn, and could turn fast without rolling over. If going down the straight the driver felt the front getting light and rising too much, he would open the inlet, and it would fill the sponson up almost instantly. During the few years I was doing this I saw at least 12-15 boats go over, ours never did, and it held the lap speed record for whatever the course length was I don't remember.
Of course I realize a big difference between a 22 foot boat weighing almost nothing running about 145 MPH, and a 40+ foot boat running 175+, but a way to control weight in the front very quickly is perhaps something to think about?
Of course I realize a big difference between a 22 foot boat weighing almost nothing running about 145 MPH, and a 40+ foot boat running 175+, but a way to control weight in the front very quickly is perhaps something to think about?
10-21-2016, 07:12 AM
#157
Gold Member
Gold Member
Think about what these guys are doing. Its all starting to make sense with all this "lift" talk... Consider that a Cessna cruises at about 140 and tops out at 185!
10-21-2016, 07:40 AM
#158
10-21-2016, 07:54 AM
#159
Registered
Great input and conversation from folks in the know. Very enlightening.
10-21-2016, 08:26 AM
#160
Gold Member
Gold Member
Agree with ^^^^.
Interesting and informative thread, some pretty 'clued-up' guys with lots of great info!
RR
Interesting and informative thread, some pretty 'clued-up' guys with lots of great info!
RR
