How come? Does it make the boat more unstable?

Hard turns or in nasty water where one sponson fly’s, Turning IN you have one prop trying to push the boat over, this instead of pulling it back down like when they turn OUT, Now back in the day I saw huge pressure on the old hydraulic tie-bar system, we used, that gave me a “Clue” to the forces involved.

Myself no way.

Thanks! I understand now

thanks for the insight Steve....not to get to off topic, but do most teams run with them spinning inwards now? Is there a sped advantage of them spinning in vs out?

That is a good question; I have seen a couple flips that look suspicious.

i see it in the pits on a few boats here an there and as i mentioned pretty much all but one accident since i have been keeping track was spinning in. The way i understand it is when the boats get loose the action of the prop while spinning out pulls the bottom of the boat into the turn and back underneath itself. Spinning in has the opposite affect working the bottom of the boat against itself in a turn making it get violent quickly. We have put the green boat into a slide many times and all i have to do is keep the sticks in the kitchen and Ed can steer right out of it, you can feel the boat settle right down with throttle. On the other side of the coin when we tried spinning the props in in the 30 DW SS cat it was very hard to stay ahead of it in turns but it did accelerate much better. We only did one race like that and went swimming, thats when i started paying more attention to that. I think it is slightly faster spinning in so in a bracketed class its not necessary but in spec classes like SC or SCL i can see the need to go after that last few mph. I think the long and short of it is when the boat gets loose or on the edge of control the props spinning out helps settle it down where the prop spinning in push it more out of control.

Below is a report regarding the failure of the canopy on the Victory team in 2009.
Basically, if a boat ends up upside-down (same as Big Thunder) the weak points are the hatch, which as shown in the report below collapsed INTO the cockpit, and the unsupported areas of the deck which also collapsed into the cockpit.



Structure & Component Failures and assumed timeline
1. The main impact forced the cockpit canopy top hatch past the hatch retaining flange within 0.04 seconds from initial impact, in which broke the hatch in half, shearing the fwd mounted hinges and bolts, allowing the water under pressure to enter. The hatch was found further most fwd from the debri that entered the canopy and went through the front bulkhead of the cockpit fig 1,2,and 3.
2. Simultaneously from the force of water and the impact, the aft bulkhead is blown into the void behind the cockpit; however it still remains mainly intact and connected at the base. At this point the bulkhead ring frame has failed and sections can be found in the cockpit fig 4.
3. 0.08 seconds after impact based on cockpit pictures the cockpit is fully immersed in water (pictures on file not shown) boat is still traveling backwards at speed in the water
4. Rear deck section aft of the canopy bulkhead collapses into the void behind the cockpit.

Pics to accompany report

This new double flange design was adopted after the Victory crash.



I'm not sure why this would be better then other designs? Any ideas?

I was wondering about that graphic as well, it could use a little more detail. My only thought is the added ramp is to break laminar flow and to keep the water from getting under the lip of the hatch flange. My personal thought is there should be a ramp surrounding a recessed hatch but that may be what this shows. I also think there should be a sacrificial ramp mounted behind the hatch. This would be a break away piece bonded on to the outside of the surface laminate. Basically it would blow off in the event of a forward hit but in the event of coming in backwards (like the BTM accident) it would ramp the water over the rear lip of the hatch in the initial hit. I have seen scoops similar to this on boats currently but do not know if there are functional air scoops or intended as i have described so they may already be in use. My thoughts is the canopy should be featureless except for elements to divert water pressure. Its important to preserve laminate continuity on the surface to strengthen and limit any feature that may allow water pressure to breach. Limited scoops/hatches/ports/etc. Integrity of the canopy depends on managing and diverting pressure rather then trying to stop it.