SetBack / Offset more or less?

[whipper]

Hears a question ive often wondered but never experimented to much with. Would an Allison be more or less Susceptible to hook with more or less setback? Im thinking less prone to hook with more setback as theirs more leverage with more setback. Also what is the most setback you have ever seen anyone run on an Allison? The whole fulcrum aspect comes into play hear as part of the design. So load driver size and gear would also play a large factor. Heavy drivers, should they use more setback then lighter drivers. and if so what setback and difference per pound would indicate an inch more or less setback.

Some time ago i remember some engineer guy had some load figures and the effects of setback and how best to maintain fulcrum. but another question would be what is or were is the best fulcrum or CG point for different Allison hulls? In other words how far aft of the hulls true centre or fore can you go before running into what type of issues. Anyone have some experience or information they can share on this.

 

[whipper]

Paul I think when the bow drops it doesn't drop as far down the keel line toward the narrower sharp vee as much with more setback i was thinking. I know when ever i have hooked the bow looked like a pivot point and was almost buried . Fulcrum if I remember right for a GS is right behind the front seats? I sure want to sling up my hull with me in her to see exactly were the teeter point is buy gently lower her on a round padded log or something like that. That way with lets say a 250xs I could find the right offset to match the teeter point the 2.5 had. It could be very useful information changing motors of any kind. Even the 225X and 200xs ros are quite a bit heavier. Then a 260 very close to a stripped 225pm and 280 about the same as a promax again because of the 40 amp stator. When i have my motor off next time to install the new mid i might go back out again. I can go almost to 14 with my adjustable Allison plate. 13 and a bit. Im 225lbs add a passenger of 185 to 200 lbs and she takes alot trim to get a good angle of attach at 11.

 

[FloridaGS]

When I got my boat it was bare empty, and for my comfort too weight sensitive. I loaded two batteries in the rear starboard, toolbox in the rear port. 12 inch bass box in the rear starboard with a charger too..about an extra 150 pounds...the boat now is more rearward balance, comes off a high speed run better...I do suspect the sharp bow as the hooker...also when you ventilate the foot, you do have a prop that will tend to cartwheel and pull the rear to the right once it does grab... so here's a few thoughts, do most hook to the left? Would a three blade tend to hook less? I think we all agree more weight or setback helps

 

[SLOmofo]

Every time I hooked mine it's been to the right =clockwise, 15+times. I have had it go to the left (once or twice)but that was only turning left and then having it bow steer =Counter clockwise. Almost sucked up a center divider buoy (2 55 gallon drums welded one on top of the other) got my attention real quick! set back 7" or 8". 3.3 JohnRude X front half =heaver, with a 16" Taylor mid =heaver. No I don't know how heavy. If I could get closer I would, but the Hyd steering and a 1994 XB 2003 transom don't allow me to. Barely make it with the trim system I have.

 

[FloridaGS]

Now that's the biggest number I read so far...how violent were the hooks, and what was the speed..all over 80 90, 100 etc...and any threw you? you use a pfd and or a helmet? thanks for sharing the info...I felt mine begin a few times, gently let off, so no damage yet, but I want to be prepared and aware.

 

[SLOmofo]

Differently not a brag, as one would be enough for me! Almost all at 95 ish. Felt and knew they were going to happen. Not smart enough to wear a helmet. Life Line vest with ballistic material in the sides. Only one threw me out was at 100.9 a personal best high speed if that counts. I don't like to go fast I like the acceleration. Long story on the "why", bazaar to realize "I am 3' under the surface of the water. Looking up. I need to swim to the surface!" All except for the last were slow motion. "Oh, I feel as though I'm going to hook the boat. I should grip the steering wheel. Grip. Yes, it's hooking. Is this the time I'm going to get wet? as the boat goes around 180 degrees, scrubs off 75 mph in 100 feet as it turns facing the opposite direction. An ever decreasing spiral like a whorl pool.
The time I did get wet was... "I'm hooking,!!! grip !!!"thought I only half gripped the steering wheel" I found out 3 months later I had bent the studs that hold the helm into the dash, cracked the dash." next thought was swim or drown! I thank the Life Line for saving my life or at the very least my ribs. Other then ego, my only damage was very slight surface cuts hand and a nasty pulled back muscle.

Fun Stuff! If you live to tell!

 

[FloridaGS]

Well I am glad your ok...only pdfs I have are jet ski types..at least it may have limited safety, I need to wear it for sure...and yes you can feel it, I have been lucky, but I am jot hoping to count on it.

 

[Bobalouie]

When I had my boat I had to change from a 7" jackplate to a 10" to get her to fly right and be responsive to trim. The previous owner was probably in the 180 lb range and I was 300 or so at the time. So, I dont know if it would hold up in every case and it is certainly not scientific, but on my XB02 that equated to 1 additional inch of setback necessary per 40 lbs of driver weight. As for load, my hull was an ultra light and probably weighed as much fully loaded to fish as most XB02's stripped down to run. (I didnt carry the kitchen sink with me when fishing) All of my weight was also carried as far back to the rear of the boat as possible and anything in the rod lockers was balanced to the pound side to side. Nothing ever up front under the deck.

Mine was a downright handful to drive for me with the 7" plate, and I almost hooked it twice, both times running in the low to mid 90's. One time was due to a throttle chop due to debris in the lake, in which I got lucky. When I chopped the throttle the bow dropped like a hammer and I thought I was in for a ride. It hooked about 20 degrees to the right before I slammed the gas back down which popped the bow back up and I missed the debris. With the longer plate on, the bow never dropped as suddenly as it did with the shorter plate on.

There was no noticeable difference in holeshot, although, I am sure that if I had been on a drag course there would have been some increase in trap time.

 

[FloridaGS]

Good point on the bow drop when coming off speed. I had that in mind when I decided to add another 150ish to the rear of the boat in hope of making it more manageable, and anti hooking..

 

[whipper]

Gary SLOMO Florida has one of the biggest baddest omc 450+hp motors on the planet hanging of the back of his 03. His Allison does 0-100 in well lets say blinding acceleration break neck times. LOL he is a very experienced Allison owner . Just goes to show it can happen to anyone. NOW dont let that scare you but it accually is a reminder for you to get a better vest! My hooks were less violent than some of Garys and i new it was going to happen also. But could hang on no problem. There are guys that have never hooked also. You have to respect these hulls as they are the pinnacle of high performance Vee hulls in the world. You can compare them to not a Mustang GT500 but a Lamborghini Gelardo. On the street both are just fine being compliant. Take them to the track and you better have your safety gear on as anything can happen.

If you can get a life line awesome! But there are several 100mph rated vests that will work. You need the type with a high rear collar. On Allison web page Darris sells some ok vests with the Allison logo on them and can get a colour match. Best advise on speed is never giver to the limit with passengers. Make sure you have two vests like yours at least. A buddy who knows the risks might agree to a speed run. But know your limits and your hulls. Its one thing to hook by your self its another with a friend on board. Ill go to mid to high 80,s with certain people in the passenger seat. With more than one passenger i just take it easy 80 tops. Im sure if i had a 260 or 280 those numbers would be higher as the speed limits are higher with the same amount of trim.

One last thing Bobalouie mentioned somthing that has worked for me also. A few times when {oh panda}happens I nailed the gas. You will hook from letting off to fast, over trimming,prop beak, or wave a few others but these are the main reasons. Wave is like letting off to fast if the prop breaks surface you slow to fast. Thats why some say wave dependant just stay in her and hope for the best.

For an ULTRA high performance boat they are really very forgiving. its just stupid pet tricks that cause the issues but that would apply to any very high performance boat. i much rather hook than blow over!! All these threads with all this info is what will save your arss. All great points so far...

 

[FloridaGS]

10-4, always wary about any passengers, had owned 90 MPh plus boats since 1988, though the Allison is light to the extreme and can run the foot to its cavitation limit, thus hooking.
Other boats I have owned, like a 19 Action with a 280, would never hook, so the hull is the difference here.

A thought I had earlier today is to bolt on some strakes to keep it straight like a Nascar does...run it out to the foot's limit, the hull falls down but the stakes keep it straight until you can get the prop back on it.

Though to bring this thread back to setback, the hook is always a concern of mine when fiddling with the hull dynamics, so thanks for addressing the concern .
looking forward to the suwannee river run Sat Nov 12...maybe the group will stop in rockbluff my HQ...I will be there.

 

[90 5.0]

My 03 drove very well with 14" of setback @ 1/4 above. Since the 03's and gs have a similar hull if it was me I'd move it back some and see how it feels.

Especially since you have the adjustable Allison plate, only takes a few minutes to do.

 

[SLOmofo]

Well I am glad your ok...only pdfs I have are jet ski types..at least it may have limited safety, I need to wear it for sure...and yes you can feel it, I have been lucky, but I am jot hoping to count on it.

At least get a jacket that has straps that go between your legs, that way it should stay on if you go in feet first. My fear for the type that's like yours is ......feet first, arms up and the jacket gets stuck around head height pinning your arms so you can't swim. The Life Line isn't Coast Guard approved but it's one of the only ones that will float an unconscious person face up. I have a approved jacket stuffed in the forward compartment.

 

[90 5.0]

At first the lifeline was a bit uncomfortable, now feel naked without it wearing a normal pfd. Kind of like not wearing a seatbelt

 

[Scott in MN]

The more setback you have the higher you run the case. When the bow drops and it pivots around the transom the higher your skeg will be out of the water and the less control you will have. The only time I hooked my bass boat was with 19 inches of setback which is the way I bought it. Best driveability was with a 10 inch plate. I now drag it with a custom setup that is about 7 inches back.