everyone on this thread are starting to get the idea of where we need to go from here. The wing section through the tunnels is intentional but I dought that that section has ever been analized with respect to ground effect, faster speeds, angle of attack etc. Though wind tunnel testing would be real interesting we have had years of test flights wih brave (or testosterone induced bravery) test pilots with pass after pass with no data aquisition. We are now starting to get that data but it needs to be put into a computer model to see what happens if... X,Y, or Z. without hurting someone. With the stuff we have talked about in his thread I think it's about time to build scematic model #3 and see what you all think. Issues I will try to address are weight & balance, Capsule design, Aero with controls, Sponson to tunnel angles hull strength etc.
Wizard612,
Just to keep things straight here, at least in my mind .....
From your posts I get the impression that the design your working with is for a Comp Jet, or, a Roundy Round Type Boat and not a Purely 'Point & Shoot' 1/4 Miler. Am I correct in my understanding?
Wizard612,
Just to keep things straight here, at least in my mind .....
From your posts I get the impression that the design your working with is for a Comp Jet, or, a Roundy Round Type Boat and not a Purely 'Point & Shoot' 1/4 Miler. Am I correct in my understanding? Im not sure also. If its a Drag Boat I think its going the wrong way.
yes, this thread started out as a comp jet concept over on the 'compjet is back' thread.
I think to do both with the same boat is not the idea but I think doing both with the same design with modifications is the idea I'm going for. The sketch on youtube more closely resembles the drag boat but as this thread continues the design in my head is changing a bit.
Thanks for the clarification.
In this clip you can see the effects of the chop, on the hull, resulting in flight. http://www.youtube.com/watch?v=OQKHv...eature=related
I think minimizing the surface contact would be key to absorbing ripples in the water
That video is scary to watch for a couple of different reasons. It basically shows that even with a tunnel that's running flat, a small hop across rough water is enough to push the bow up with enough positive angle to blow the boat over.
It tells me that even the guys who run their tunnels flat are susceptible to blowing over. not as much as the guys that like to fly the nose, but its a definate possibility.
That video is scary to watch for a couple of different reasons. It basically shows that even with a tunnel that's running flat, a small hop across rough water is enough to push the bow up with enough positive angle to blow the boat over.
It tells me that even the guys who run their tunnels flat are susceptible to blowing over. not as much as the guys that like to fly the nose, but its a definate possibility.The underside of the "airfoil" if you will, isn't in purely clean air when the boat's on the water. I think what happens isn't due soley to the increased angle of attack, but I think it's also about allowing more air under the boat and getting the airfoil up in clean air where it actually creates more lift than desired, and the boat begins to literally fly. Becuase of the weight and balance, and without the drag of the water to stabailze it, the natural tendancy for the airborne hull is to go nose-up, and fly over backwards. Even an airplane will do this. Here's an example...I used to fly gliders out at El Mirage, and it would get so windy that I could actually ground fly the glider. Sitting in the cockpit, I would pick up the tail, level the wings, and balance on the single landing wheel. Thing was, that if I didn't have the dive brakes open killing the lift on the wing, the plane would leave the ground, and instantly flop straight over on it's back. Not exactly sure why, but I bet the two behaviors are very related.
That video is scary to watch for a couple of different reasons. It basically shows that even with a tunnel that's running flat, a small hop across rough water is enough to push the bow up with enough positive angle to blow the boat over. .
if that were true, every one of them would blow over at every race.
It tells me that even the guys who run their tunnels flat are susceptible to blowing over. not as much as the guys that like to fly the nose, but its a definate possibility.
anything -can- be susceptible to blowing over, but attitude is only one attribute, and not necessarily the most important. dynamic c/g, or balance, for the intended speed is the most important factor.
the boat in this video began to climb for no apparent reason which indicates to me that it was not set up properly, balance wise, for the intended speed. lift is good, climb is bad.
would love to take a daytona to a wind tunnel to have some experts take a look at it. I think there is something to the shape of the top deck of the daytona that creates lift. Its shaped like the top of a wing in between the pickleforks and I wonder how much lift is generated by that shape at 100? 135? Not sure if a wind tunnell would tell you that or not but i think that shape creates problems for the faster daytonas.
the problem is that the dynamic c/g shifts further and further rearward the faster you go. this has to be accounted for as the boat goes faster and faster. at some point, options are limited other than adding weight or significantly modifying the area you're talking about, which wizard's design does do.
there is nothing wrong with lift - as long as no climbing occurs simultaneously. if the nose begins to climb, you are done as it turns into a sail.
in '01 at red bluff, we ran the fastest that boat ever went, 134.9, and the boat hit a small roller right at the end of the lights. the whole boat lifted, and settled right back in - no climb. the dynamic c/g was correct for the speed/power applied (and it looked bitchin too).
Cheyennes dont have that shape and dont seem to have the problems eliminators have and are able to run positive nozzle angle unlike most daytonas. dont mean to hijack the thread, its kinda related...I hope.
i would say, ask joe barnes about that (rip 239), but you cannot. cheyenne's can blow over just as easily as daytona's can - they may be able to run safely at a designated speed with a little more [I]attitude[I] than a daytona, but it still boils down to having the correct dynamic c/g for a given speed/power applied. greater attitude doesn't necessarily equal quicker/faster; lift does.
bp- I'm confused, please give me your best definition of dynamic CG. to me the center of gravity (or more appropriatly the center of mass) is not a dynamic location unless something in the boat (ie. mass), is moving. CG does not shift with speed. lift changes with speed and the center of lift might well change with speed. Center of lift can also change with the angle of attack as it pertains to speed. but the mass of the boat as it pertains to the boat only stays put. ( well ok it is moving in the same direction of the boat but it is in the same XYZ coordinate within the boat).
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