The Physics of A Boating Accident.
 

Oh Here goes,, I want to learn about scenerios, how to see a telltale sign of an on comming accident, how to properly react, (maybe a noise from a drive at high speed that would indicate a drive failure seconds away) (how to tell a stress crack is serious) (delaminating) ( tabs and when where and how to use them) (water depth) (wave types) any and every thing that has been picked up from years of experience on the water. Thanks in advance for your stories, scenerios, and solutions.

Re: The Physics of A Boating Accident.
 

I want my impeller back.........:D :evilb: :evilb: :evilb: :evilb:

Re: The Physics of A Boating Accident.
 

Ohh Yeaaa,,
Its not my fault you decide to go to Vegas,, the one weekend,, I finaly get my boat over to your slip,, not to mention get kicked off the dock by your manager, because I would buy a non refundable one year slip rental,, just to tie up at the one spot that was deep enough.:rolleyes:

Im going to go to the boatshow again this weekend even though it sucked,, they had some great sail boats :cool: ,, I'll bring a few impellers and buy a few beers,, if you want to drop by.

Dayum and I worked so hard to get this one thread started , that you Hijackedd, :D

Re: The Physics of A Boating Accident.
 

only missfortune I have had so far (power boating not blow boating) is that the props go thump thump THUMP when you get too close to the sand bar, then you take them to the guy who goes bang bang grind grind, while his cash register goes chinga chinga...was out in some nasty stuff (lake erie, big storm)runnin down hill, trimmed up a bit and was gassin it hard (to try and lighten the bow) every time I thought I was gonna stick it..I survived but have know idea if that was the right thing to do..was fun as hell though...

Re: The Physics of A Boating Accident.
 

stuffed a 12'-14' wave once very ugly respect the sea she bites

Re: The Physics of A Boating Accident.
 

Alot of time the smell of oil will indicate a drive that is ready to fail the upper seal goes and it pumps itself into the bildge anyone in back seat usually smells it
also burning rubber smell is a sure sign of a coupler failing

Re: The Physics of A Boating Accident.
 

I think there are too many different conditions in the world of boating, to rely on information from others for "just in case it happens to me" help.

Re: The Physics of A Boating Accident.
 

The attached picture shows a hull right after either stuffing or passing through a huge wave. Notice the water rolling off the rub rail and deck. A huge amount of energy at work.

ed

Re: The Physics of A Boating Accident.
 

It all starts with basic high-performance seamanship. One has to understand how to operate the craft properly before any "what not to do" makes any sense to them. Let's throw out for the moment the "unavoidable"- that rogue wave or hole you just didn't see or didn't have time to correct for because there's usually no way to prepare for those.

The most common thing I see in newer boaters is the lack of knowledge/ability in managing boat attitude. It sure ain't a car- no point and throttle here. Understanding what the controls do and how they affect boat attitude is key. Then you have wind/wave issues to understand. If you've got a moderate to strong headwind, your boats controls need to be set differently that if you're running out of the wind. When you get into quartering seas or combinations (waves, wind, currents, all going different directions- big on the Great Lakes) it gets even more complicated. Let me interject here- if you have a performance boat that doesn't have accurate, easily readable tab and trim indicators, you're wasting your time. They also need to be blueprinted, for lack of a better word. If the indicator shows +3 and the drive axis is parallel to your bottom, your experiences won't translate to another boat you may operate. Also, if they differ, you're really screwing yourself up- if one drive or tab is off a bit but you thing their set neutral, you'll have a tough time applying information to attitude. You really need to be able to draw a correlation between how these devices are set. what the wind/water conditions are and how the boat is performing. A big issue is understanding what the trim and tabs do to your boat's attitude. I see tabs misused many times in keeping the bow down. Of course there are extremes where you need to pull the drives to neutral and help the nose-down with tabs. Pretty much though, tabs are better uses to correct for yaw, by being set opposed to each other, not identically. There's no substitute for spending time in your boat in different types of water conditions. I know, most people want to toss in the cooler and cut right to the fun part. Doing that right off in big water is alot like signing up for karate lesons and on the 3rd day challenging the local black belt. You're probably going to get your a$$ kicked until you develop some experience and skill.

Good thread idea! I'll let someone else chime in now.

I look forward to talking about structures, preventative maintenance and responsible boat prep.

Re: The Physics of A Boating Accident.
 

I'm one of the "newbies" to performance boating, I've been boating for over 10 years, but only in "run-a-bouts" & ski boats. I now have a Donzi 26ZX, & am very much looking forward to "learning" how to handle it. I'm certainly not one to just hop in the seat & see how fast I can go. I do ask alot of questions, & I have learned alot from this site, & the folks that post here on the forums. I have considered Tres Martins school, I just have to see what my schedule for the summer is.
I do have a couple of questions about trim & tab positions. I understand that the Donzi "stepped" hull is much different than straight "V" hulls, & I understand the step hull likes alot of positive trim....That much I got....in the sharp turns, (river running 30-35mph) will I experience the cavitaion that I normally do in a straight "V" hull? If I do, will I be able to trim down a bit for the prop to be able to bite? ORRR, do I just ride it out thru the turn?....During all this, should I just leave the tabs up?....Sorta the direction I had planned with the tabs, until I get comfortable with them, is to leave them all the way up....Is this a mistake?...
Sorry for the "rookie" questions, but like I said....I do ask alot of questions....:D ....After all, my family will be in the boat with me....I don't like the idea of my wife throwing things at me if the boat starts to act "weird".....:eek:

Re: The Physics of A Boating Accident.
 

You're right in wanting to know how your boat performs in differing conditions. You've hit on a common issue- someone moving from a highly maneuverable boat and into an "offshore" style boat. Offshore boats are made for hammering waves straight on- that means compromises in turning. Adding to this issue is the stepped hull of your boat. First, your Donzi wasn't designed to "carve water" and the physical stresses of doing so and exponential vs. a ski boat. That being said, 30 or 35 mph isn't fast- unless you want to do full-lock, full power turns at that speed. Second, stepped hulls need to be turned in the proper procedure. If your wife might go off with a boat acting "weird", think of what she'll do after getting the experience of a high-side ejection from the boat. I can't give you specifics on your boat but most steps like to be settlled then powered through turns. I'd suggest hitting one of the Donzi forums and getting with some folks who own your specific boat. I don't mean to scare you but more than a few experienced racers have been tossed in turns from not cornering properly. Also, my step-V experience isn't near what many on here have so they may be a better source of specifics. My only experiences have been a few turns at the wheel and one trip as an eject-ee.

On Tres' school- it's probably a tremendous idea but I also think alot of it might be lost on a newer perf boater. It's sort of an MBA in high speed. No one says you can't go back for a second trip, though.

To your question on tab position- you'll want to use the drives to control nose up/down. Tabs are more for yaw- if you're getting cross wind and it's sterring you off-course, drop the opposite tab and straighten the boat up. Some boats need a touch of tab at neutral drive position especially running into a head wind. You'd probably want to keep your tabs neutral when turning. Tabs will give you a little more "effective bottom" basically adding a small amount of bottom running surface to your boat. There are times that you can get better top speed by trimming out until you lose lift (bow porpoising) and tab it down just a little bit. Sometimes youll do better like this rather than neutral tabs and less drive trim- but that's really dependent on your specific boat and load- that's the fun of experimentation.

Re: The Physics of A Boating Accident.
 

Great info so far. Im really at a dissadvantage. I dont have any indicators for my tabs so I have to work them from the seat of my pants. Fortunately I do prettymuch all my boating on the rivers here so navigation and crosswinds is not an issue. I will use the tabs to help get on plane and then to counteract any porpoising. If I got the tabs too high, the bow will do this then I drop them till it smooths out. I also use them to level the boat off so its not listing to one side or the other depending on occupants etc.. So they are not always even.

The one big question I have is how much is too much trim for the drive?? I usually keep mine low enough, on smooth water for top end runs, that its not throwing a roostertail. I have a Bravo 1 drive. Nothing fancy. I have played with it some with a portable gps and have overtrimmed to throw a tail, but never noticed any gain in speed. Did notice a different feel for how stable it felt in the water. Now I know some drives are designed to throw a roostertail. But I dont believe a Bravo 1 is. So what is the highest I should trim it in desirable conditions?? Highest possible spot without loosing speed or control?? BTW. I have an old Baja 240 sport. Straight heavy hull.

Re: The Physics of A Boating Accident.
 

You can trim to where you porpoise or where you lose speed. You can trim it to where you lose stability or at least start to feel like it's going away. If you're going from neutral to rooster tail and not seeing a climb in speed or rpm, there's a problem. I don't recall the Baja having an over-conservative x-dimension so you may be in need of a better prop.

No drive is really designed to intentionally throw a roostertail. Surface drives just do but that's irrelevant here. Unless you're dealing with big power, throwing water into the air is likely more counter-productive than anything. Lots of performance boats have Bravos on them. They're actually faster than the TRS they eventually replaced but a bit less durable as you near max power. They are usually mounted at a decent x-dimension and typically uitlize a cleaver prop. That means that they can be trimmed up until just the bottom of the prop engages the water and the top actually comes out as it rotates. That's where you'll find the least amount of drag and the highest efficiency.

Someone smarter that I will have to explain how different prop designs and dimensions affect bow and stern lift and how to properly size a prop to a specific boat. It's a little science and alot of art.

Re: The Physics of A Boating Accident.
 

I appreciate the info. The factory speedo doesnt always work. So I only get to test when I borrow a handheld GPS unit. Most of my observations are seat of the pants. And you can feel when the boat gets really loose and when you get more bite from lowering the drive a little. As for the X dimension. I have no idea. Im running the stock setup on the boat which I bought used and have been happy with. IE, no money to mess with it. :)

I would have to think that once you trim too high, despite it looking cool, you are gaining too much slip and loosing performance potential. And I do know there's a difference between my cleaver and Mirage props. Thanks for the info.

And by the way.. When hitting big wake or rough water.. Make sure to trim down the drive and tabs so the nose doesnt point to the sky. Learned that one the hard way. Closest I came to loosing it. I backed off the throttle but didnt get the drive and tabs down in time. Bow went near vertical from a wake that was bigger than it looked. Kept popping up till I could get everything trimmed down and throttled down. Scariest ride I went on. Did manage to keep the boat straight though.

Re: The Physics of A Boating Accident.
 

my old boat doesnt have tabs, amd the drive trim guages work when the want too..fixing things as I learn how..right now Im driving it by feel, trim em down to get on plane, then I trim up untill the boat starts to feel lighter and seems to be working easier and adjust so its level side to side...how about a basics trimming 101 post from somebody..running flat water, bumpy water, big ugly water..running uphill, downhill etc.....

Re: The Physics of A Boating Accident.
 

Eddie Hill said that is why he stopped racing drag boats and got into car drag racing.

Re: The Physics of A Boating Accident.
 

So far there is some really great info,, Chris,, thankss!!,, I hope every one feels free on this thread to just spout on about what they know or have experienced with out any sharp shooting,, just a friendly exchange,,, I know alot more people have questions,,, and so far I have learned alot about how little I really do know,, and that helps in being cautious and responsible when out on the water. I Really Liked seeing the figures,, and drawings, that showed up in the other boat accident thread towards the end,, thats what really got me motivated to start this discussion,, hopefully we can get some of those here as well. If your a member here who has a safety class or has the experience on some of the basics, please chime in. Please remember,, alott of people even non members read through these threads,, so if this helps a guy who goes out and buys a $400k 130mph,, or even a guy whos on his first $45k 70mph type of boat,, see that there is alittle more to it than just hammering the throttles.
Thanks so far and lets keep the ino going. :D

Re: The Physics of A Boating Accident.
 

I bought a copy of "Fast Boat Seamanship" by Dag Pike, as recommended on OSO. I've found it to be very useful, especially with respect to wave conditions and the like.

Re: The Physics of A Boating Accident.
 

ROLLWITHIT I have a 88 baja 240 sport ,the x is very deep on these I put a new drive together this fall went to a 2'' shortie boat handles nice flies flatter when you see a rooster tail you are way over trimed not good, i have owned this boat since 1990 and have made lots of changes now it got 670hp 83.2gps more this spring:D SO If you want to talk I will leave my cell on this post

Re: The Physics of A Boating Accident.
 

Where did you purchase it from? Sounds like something I would like to read.

Re: The Physics of A Boating Accident.
 

I very much appreciate your input, I have really learned alot from this site. Everything from maintenance, to tips on driving. I can't wait to get out on the water & start learning. I will be doing alot of boating in the Gulf, so river runs will only be for days of rough water. I will use the tabs sparingly...& speed will only come with experience....I look forward to learning much more from you folks here on the site :D

Re: The Physics of A Boating Accident.
 

Just did a search on Amazon.com to get the book. I got it used from someplace back east for about $30.

Re: The Physics of A Boating Accident.
 

Found it, thanks for the info, can't wait to read it. It has lots of good reviews....

Re: The Physics of A Boating Accident.
 

One thing that needs to be said. Virtually all learning on a fast boat needs to be done in little bits. 99% of the time when someone has an issue it is because of extremes. Too much speed for conditions, too much or too little drive trim, too much tab, too hard a turn, too little common sense, or too big a set of balls. Each of us has a different learning curve and each boat does too. A simple rule of thumb is do things in small increments, run faster 5 mph at a time, play with tabs and trim one notch at a time, etc. Getting the feel of a boat is one of the most satisfying experiences out there and what we all pay such extravagant sums of money for :D

Re: The Physics of A Boating Accident.
 

Finding out what setting work best is a danger if you dont understand the parameters. Self taught boaters instructing other boaters how to operate boats is also a danger when they dont understand how other hulls may work. That is why we put 2 other classes together to help all performance boaters in all size , speed, and configuration learn the proper way to use your craft. Using a process of discovery has to have boundaries and technique to maintain proper control. If not damage or injury may happen.

Re: The Physics of A Boating Accident.
 

"typically utilize a cleaver prop" That would be the last prop to use on a bravo especially on that guys baja. Cleavers are best used on outboards that are mounted very high on lighter hulls (generally), not on heavier sterndrives. I would listen to Tres when it comes to learning about high performance boating safety.

Re: The Physics of A Boating Accident.
 

there used to be a book called everything you need to know about propellers. I think Quicksilver published it. Not a bad place to start to learn about the basics of boat propolsion.

Re: The Physics of A Boating Accident.
 

Have you been to a boat show, marina or dealer's showroom in the last 20 years? I can't recall more than a handful of times when I haven't seen a cleaver on a sport boat.

Re: The Physics of A Boating Accident.
 

Im sure that if the tabs and drive are tucked too low it will give too much stern lift coming off the wave or wake and will set you up for a bow down entry, setting you up for a stuff. The key is having the tabs and drive set right. I do know that if they are too high, the bow tends to point up too high. Thats what happened with my incident. I under-anticipated the size of the wake and did not get the tabs and drive down in time to keep my exit and entry level enough.

Re: The Physics of A Boating Accident.
 

Airtime. Ive followed the project on your 240 quite a bit. Nice to see one of those old tubs can hit 80 plus with the right power and setup. Not sure if I wanna put the money into mine or just save it for a bigger boat. I appreciate the help. I'll pm you.

Re: The Physics of A Boating Accident.
 

I agree with Tres you have to understand theory of how a hull works and what trim and tab changes do.This way it is easier to make proper changes not try to remember to do this and this when the boat is doing that.Plus a traditional Vee bottom is total different than a stepped hull Try to turn a stepped like a traditional Vee and you are calling your insurance company or worse

Re: The Physics of A Boating Accident.
 

A very intersting thread and great to see communication as it does breed awareness.

I have of course a few observations; First, in determining the physics of a boat accident there are more often than not any absolutes. It is usually discovered a sequence of events transpired leading up to the incident determined to be an accident. This is why we always stress checks and teach situational awareness.

I too have read Dags book and know he wrote a fast boat course for the U.S. Coast Guard. There is a lot of information some of value some not for our performance applications. Some things in the book we do not support.

When you operate any craft at extremis you must be able to recognize when something isn't right and develop/teach yourself inherit instict to be aware, acknowldege the problem, and act to create a sloution all within seconds or you will find yourself in a very bad spot.

Re: The Physics of A Boating Accident.
 

Great point Brad. Another thing that we teach in diving is pertinent too. If you have a little problem, correct it quickly or stop. Don't let it go on and then have another little issue pop up, then another, and another until you have a REAL situation on your hands. In analyzing dive accidents and mishaps this is a common thread. A small anooyance occurs and you ignore it, then something else happens and your concentration is split again. By about the third "little" thing you are starting to be really distracted and mistakes can bite you hard at this point. Any further without stopping and fixing the issues simply puts you closer to disaster. Since boats are such complex machines there are all sorts of things to nag at you, add to that friends or family on the boat, weather issues, traffic, water conditions, etc. and you have a real potential for danger if distracted.

Re: The Physics of A Boating Accident.
 

ya, I have. Show me a boat test on a sport boat with a stern drive using a cleaver prop. It would be a terrible prop to use on a submerged Bravo ( Like what you were talking about) Again, a cleaver would be used on a lightweight sport boat, where the drive is set very high. "Typically" on an outboard. You might be confusing cleaver with stainless steel maybe. I'm not sure, but a cleaver has a flat trailing edge and extreme rake. Plus they have a different hub than traditional props. here is a quote straight from the mercury racing site on cleaver's:
"Mercury Racing produces a variety of cleaver style propellers for small 30 hp outboards through 300 hp V6 engines. The cleaver style propeller, inspired from racing, are designed to run at the water surface for maximum efficiency. They work best on lightweight hulls which have natural bow lift. Three blade models for the 30 hp engines feature through hub exhaust. Larger three and four-blade models, available for V6 outboards, feature over hub exhaust."

"Propeller hub reliability is improved with the use of a new steel square-bore hub standard on all Mercury Racing Cleaver, Lightning E.T. and Chopper II propellers."

Not designed for Bravo's at all.

Re: The Physics of A Boating Accident.
 

good stuff here- I hope to take one TRES' classes someday, worthy investment IMHO.

Another nod for having your tabs /trim marked/ calibrated so you know what's really happening with your settings.

A digital, easily readble GPS is good for "enhanced feel" of settings at cruise and slower speeds where many of us spend the majority of our time. You can easily determine just how much trim past/near neutral is the sweet spot- increased trim will gain no results for a period and then then eventually rpm's will climb and speed will drop a few digits. I like (does not make me right though) the point where increasing the trim stops yielding benfits in incremental speed gains- seems like it would be more hull in water for evasive handling and avoiding the overtrimmed launch opportunity on wakes and waves.

Trying to go by the rooster is a mistake, as boats and setups vary. My 25' Daytona (cat) had an agressive x, liked trim barely above neutral and had minimal rooster (or perhaps it was "washed" by the tunnel wate/spray). My 28 Pantera also liked just one tick above neutral (though I always thought big single un- notched v's would want more) and the rooster was near non existant.

A friend on the lake has a 28 Daytona, Ilmors, agressive x, Imco's, 5 blades- he runs around throwing so much rooster that many perf boaters- myself included thought he was just a newb not knowing how to trim the boat.... Then I went and bought a mild powered 30' Daytona, mild X (shorties about to go on) and put 5 blades on- at neutral trim there is a good 3' of rooster... lesson learned on judging rooster.

That said- the one thing that I do suspect in many milder x perf boats is too much trim for conditions- which can be confirmed through methods above- sorry for the rambling- think there's some good stuff in there though.

Can't say enough about awareness though- peripheral vision, don't be trying to entertain and hold conversations while underway, maybe a good mate next to you just to announce overcoming traffic from their side. I go way wide of areas infested with tubers/boarders and waterbikes- their courses are just toooooo random. On nice days there will be rogue holes and wakes from Cruisers you can't even see cause they are around the corner now- just slow down some so you have extra margin for WHEN you encounter them:D

Re: The Physics of A Boating Accident.
 

Very good thread. Lot's of good information.
In the original question, you were looking for anything to look for, not just driving
So I thought I would chime in.
Get a good feel for your boat, and LISTEN to your boat. If something sounds different or "funny" - better check it out right away.
About 10 years ago I took my then wife, and a buddy to Cedar Point for a weekend - he caught a room, and we camped on the boat. 1st season with the boat, '86 Baja 250 Force, 330/TRS. It was late in the season, and I had put numerous hours on it in the season, and had many years experience on Erie.
We had to leave for home on a Monday, and woke up to 5's out of the west (we were heading to Toledo).
After beating ourselves up for about 30 minutes, but still running ok, I'm noticing a strange noise, almost sounded like a bad ground on the stereo coming through the speakers, kind of a hum, keep hearing this for a few minutes, so I backed off and raised the hatch. The motor didn't have thru-bolt offshore mounts, just bolted to the top of the stringer with lags. I had crushed the Starboard stringer, and the motor is listing down about a 1/2".
AND, I've got water coming in from the transom assy.
Bilge pump is keeping up, but I knew if I could keep the boat moving, the Transom won't have any water on it to come in.
Headed as quickly as reasonably possible to Put-In-Bay to tie up and get the boat in a sling.
Everything worked out alright, no-one was hurt, and no-one wound up wet (except from wave spray).
Got the boat slung up.
then came the fun of taking the Jet Express back to mainland. Getting picked up by a friend. Picking up my truck and trailer. Driving back to Miller's ferry to cross to the Island. unloading the boat onto the trailer, and just barely making the last ferry of the day with truck, trailer, and boat.
It really sucked sitting in my truck on the ferry, with my boat on a trailer behind me.
The decisions I made kept us safe, and everything worked out fine, but there certainly were flaws in what I did.
FIRST - My ex-wife was the only one of us three to don a life vest. I should have required this of my other passenger, and out of common sense for myself. I was in a frantic situation, and also was trying to keep the ex-wife calm - like everything is going to be fine. I forgot my first responsibility KEEP EVERYONE SAFE!
SECOND - I didn't contact the Coast Gaurd to let them know I was having trouble. Had the motor conked, or I started taking on more water than I could keep up with, they wouldn't have known to even look for us.

I'm sure someone else can chime in on other flaws in my actions, if you feel the need to feel free. If it keeps another boater safe, I'm all for it.

Sorry to be so long, but my simple point is LISTEN to your boat, and if something sounds wrong, something probably is wrong.

Re: The Physics of A Boating Accident.
 

I agree that with experience most of us can get a decent feel for our rig,s and how they handle and or react in most conditions.
Not that this isn't an informative thread and we should continue sharing our experiences, however.
If you really want to learn the physics of how your hull is reacting , where your trim should be , tabs etc as well as real life scenarios of how to quickly avoid an accident, pre- check drives ,hull and much much more.
Take the Tres Martin school, I learned more in two days than in all my 30 years on the water.

Re: The Physics of A Boating Accident.
 

Thanks! The only way to make a difference is to get right imformation! Everytime another acciddent on the water happens, all policies are in jepardy of a hike in price later down the road. Besides, the course is fun and very entertaining!

Re: The Physics of A Boating Accident.
 

I'm a pleasure boater not a racer or an expert but maybe this will be of some use to you.With the o/b's on my boat I could cruise at 100 but I can't read the water past 80 so I keep it to that and only in good water and in a straite line.This allows me to monitor and adjust for the conditions in front of me as they change.Since I don't race,unneccesary sharp high speed turns are something I don't do because it's a fast way to get into trouble with little or no chance of correction.However if I have to make the big turn I give and take gas from the motors thru the turn.This tells me the margine of error for the boat in THAT turn in THAT water at THAT speed.The boat is a 26 ft tunnel,not a v bottom.Good luck to all.

Re: The Physics of A Boating Accident.
 

REGGIE did a show on how to drive a vee hull back in 94, I think it was a good show, if I find the tape, maybe I can put it on here it was for nonstep hulls. I learned a lot from it and a throttleman ex world champ:D , not going to say who he is:D . because he took me out in rough water with my boat, I think it was with the 590hp motor and said he will run it at racing speed. thats because I wanted to race it at that time. it was at least 4 footers, but watching him drive and throttle was cool he had it running a lot harder in the rough than I have, but at the time I just couldn't run it the same speed as him. I just had to learn by myself.[Taking classes is fine in the class room but I would want the teacher to tell me instead of show me]when we got back to the dock he was impressed with the motor, he said he figured it would break:rolleyes: , well the deck did move, found out it got water between the core from the hatches. that was fixed and done better than baja did back then, the new ones 06,07 seem to be state of the art in design and lay up ect, a 35 with standard lay up is running 105 plus with 700s a true 35:D its not dialed in yet so thats the same as some 38footers with built in swimplatforms.