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Cockpit construction

Old 11-13-2011, 09:09 PM
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aex
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Default Cockpit construction

My thoughts and prayers go out to the families of the men we needlessly lost in Key West this week .
The tragedies that have struck our community this have prompted me to rethink my resto project .
As some of you may be aware , I am presently having my old Chris Cat restored in it's original form and livery .
In 1989 we constructed a reinforced cockpit with F16 canopies for the boat . It basically consisted of a cored drop in cockpit liner with a bolted and glued on cored canopied deck .
After the project was finished I remembered sitting in the new womb looking around and commenting to my driver how we now had protection in the event of a stuff however in any other impact we could be in trouble . We went on and fortunately ran pretty hard with no mishaps but I always told guys the canopies gave a false sense of security .
Yesterday I contacted my builder and asked him about engineering an actual drop in survival cell or perhaps I should just install the original three man open cockpit as many guys have been tossed overboard with no injuries .
I suggested an elliptical structure consisting of an aluminum or perhaps chromemoly cage , the canopy bolted to it and a cored composite cockpit wrapping that drop in structure .
In retrospect our 1989 cockpit had some good attributes , the liner we fabbed acted as a cocoon of sorts . Many of the cockpits I've seen just use the hull's existing deck and bulkheads to segregate the cockpit .
Any input or collaboration on this project would be valued .
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Old 11-13-2011, 09:18 PM
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Those are some good points. I would like to know what the top of the canopies are made of? Are they all made out the same materials? Kevlar, carbon fiber?

Didn't Fabiola buzzi have a copit/canopy system that detached from the boat in the event of an accident?
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Old 11-14-2011, 05:02 AM
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Sorry for wall of text, but here is some of my thoughts on the subject.



When designing a safety system for a race boat there are three main areas that need consideration.

§1. Cockpit integrity
The occupants needs to be protected against oncoming water. Windscreens, outer shell and structural supports needs to be strong enough to withstand high speed contact with water.

§2. Restraints
If §1 is successful you need to protect the occupants against the g-forces that occur during deceleration in a crash.

§3. Life support and rescue

If §1 and §2 is ok you need to make sure that the occupants don't drown and that evacuation is possible.


If these three areas are properly engineered you will have a good safety system for your race boat. But if any of these areas fail you will be in deep trouble.


Going back to §1, cockpit integrity.

How do you design an outer shell that is light but strong enough and cost efficient? For that you need some data.

How fast is your boat?
What type of crash will put the most force on the cockpit?
How size will your cockpit be?

Those three questions will help you estimate the maximum force on the Cockpit. Estimations can be done by hand (pen, paper, calculator) or by computer simulations. There are some excellent software's on the market but getting the work done usually costs a few dollars.
If you need, I can support with information on how to do the calculations by hand.


When you have an estimation of the forces that will act on the outer shell of the cockpit you can start with the structural design.

A complete safety cell or a "top hat"?
Metal frame cowered with a composite skin?
Monocoque?
Wind screen design, thickness, fixation, etc. Polycarbonate is a tricky material to work with.
Hatch design, hinges, locks, etc

Many important decisions to be made…
The devil is in the details!


Next on my list is verification of your design, i.e. testing.
As far as I know there is very little testing of safety cockpits/capsules?
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Old 11-14-2011, 07:59 AM
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I'm with you on a separate structure from the boat. As a matter of fact, the superstructure could be a standard design across the industry and all boats built and/or retrofitted with the design.

It's hard to control safefty in our sport but if there was a single design, over-engineered for safety, perhaps that would be better???
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Old 11-14-2011, 08:31 AM
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I' d go with a monococque capsule. Sideby side sitdown config therefore stuff and rollover would have equal area of attack.
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Old 11-14-2011, 08:53 AM
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What type of capsules do the drag boats use? Their driver's survival rates seem to have gone up dramatically since implementing their use, and the speeds are quite high.
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Old 11-14-2011, 09:35 AM
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A drag boat capsule uses a steel frame/cage and a single skin outer shell.
The roll cage uses 1 1/4"x0.065 normalized CrMo steel (SAE4130N) tubing.
A minimum 1/2" thick composite shell.
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Old 11-14-2011, 06:57 PM
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[QUOTE=Gripenland;3549154]Sorry for wall of text, but here is some of my thoughts on the subject.

How do you design an outer shell that is light but strong enough and cost efficient? For that you need some data.

How fast is your boat?
What type of crash will put the most force on the cockpit?
How size will your cockpit be?

Those three questions will help you estimate the maximum force on the Cockpit. Estimations can be done by hand (pen, paper, calculator) or by computer simulations. There are some excellent software's on the market but getting the work done usually costs a few dollars.
If you need, I can support with information on how to do the calculations by hand.
/QUOTE]




Thank you for your offer .
A spec cockpit is the answer , a pair of capsules that could be inserted in any hull would make retrofitting existing hulls feasible and would split the surface area . Two man canopies are out .
I anticipate speed in excess of 130 in my vessel .

Last edited by aex; 11-14-2011 at 07:06 PM.
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Old 11-14-2011, 07:04 PM
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You definitely need a dedicated cockpit .
Hulls , decks and bulkheads will fail . They are not designed to withstand the loads these types of accidents present . Like a car they should absorb energy as they fail and the capsule should protect the pilots .
I'm proceeding with caution but proceeding .
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Old 11-14-2011, 08:33 PM
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It reminds me of NHRA rules. Depending on the class your car falls into you have to meet certain regulations just to set your tires on the track.

If I myself were the owner of a offshore racing orgnaization I'd do the same. I couldn't live with the guilt of knowing or allowing someone on my course with substandard equipment. I think they need to either make the cockpits safer or slow the boats down.

Sorry, this stuff this weekend really had me thinking and wondering what could have been done better...
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