22-2 Flatback at Speed?

[Jack Hart]

I'm in the early stages of a restoration on a 1971 flatback.  It's rigged with a 150 hp Ocean Pro and I was thinking that I would go with a new 175 hp Etec when the painting is done......but when I run the boat now at speeds much over 38 mph, it gets very squirrelly.  I don't plan to make the boat any heavier, actually it will be a little lighter when I'm done with it.  So now I'm thinking even if the 175 weighs the same as the 150, no use going with a 175 cause the 150 is plenty of power and I'm not going to really gain any useable top end.  Also I could save significant bucks with the 150.  If I extended the skeg/keel would that make any difference?   What say you?

[CLM65]

Most folks seem to extend the keel.  I don't recall anyone actually saying how much difference it makes, but seems like a good idea.  Here is a link that talks about power on 222s (not just flatbacks, however).  There are plenty of other posts on here talking about recommended power.

http://classicaquasport.com/smf/index.php?topic=11314.0

[Aswaff400]

HP over 150-175 is a waste on flatbacks, even with full towers, and all the extra add-ons. i have a Merc 225EFI on my flatback and recently splashed her for the first time, and got 47.5 mph not even trimmed and was a scary ride ... it helps if you extend the keel like Eugene does on all of his builds but its the nature of these hulls, they weren't designed for anything over 115-130 hp

[seabob4]

Anybody ever thought about adding a strake or 2 each side of the keel?  Maybe even incorporating a slightly reversed chine?  The hull needs something to grab the water with, a true flat-bottom FB has nothing...so the water is just awash under the stern, going every which way, and taking the boat with it.

Just my thoughts...

[gran398]

Anybody ever thought about adding a strake or 2 each side of the keel?  Maybe even incorporating a slightly reversed chine?  The hull needs something to grab the water with, a true flat-bottom FB has nothing...so the water is just awash under the stern, going every which way, and taking the boat with it.

Just my thoughts...

Good thinking SB. Not really discussed much, but understand they slide at high speed. Like slide out of the channel onto the rocks.

Heard through the grapevine one started sliding down there last year, the operator was by himself upstairs....boat slid so bad with the weight on top he ended up dragging the side of his head through the water. He was thrown out and ended up okay.... the tower not so much.

Great ride and certainly not beating up the boat. Beautiful, awesome boat, began the legacy. The guys all say a sweet cruise is 28 to 30 mph. Not designed to be  a speed wagon.

 Operator error is responsible for 99% of boating "accidents".

For sure as you suggest an extended keel, running strakes at the rear, little reverse chine....anything that gets her to dig a bit in a turn at higher speed.. Makes good sense

[Aquasport Commodore]

I took out my original 1971 Flatback today for the first time and it acted the same as you describe. I also have a 2000 Johnson Ocean Pro 150. Plenty of power and planes nice. Pretty squirrely at speed however. Almost hit a marker due to the sway in the back  Slowed her down a bit and she was more controllable but could feel the rear being a little loose.

Does your have the original steering wheel location (Flat on the console) or has the console been replaced and the angle of the wheel changed? Reason I ask is to see if that helps with handling as the wheel is in a more natural position.

[CLM65]

Anybody ever thought about adding a strake or 2 each side of the keel?  Maybe even incorporating a slightly reversed chine?  The hull needs something to grab the water with, a true flat-bottom FB has nothing...so the water is just awash under the stern, going every which way, and taking the boat with it.

Just my thoughts...

Thought about it...but not really planning on doing anything drastic.  I've also wondered if the boxes on the transom, like Scotty has, would help any.  Maybe they would make the boat act like it had a tunnel back there, and have a little bite in the turns .

[seabob4]

A boat's hull, particularly the stern, needs to feel "planted"...as if, at any speed, in a straight line, you could take your hands of the wheel and have complete confidence that she won't wander, fall off to one side, drift, in short, anything you DON'T want her to do.  With flatbacks, and virtually no deadrise and certainly no strakes or chines, any speed above 25-30 or so and the water will have it's way with the hull.  

We all know about hydrodynamic forces, and how they affect a body in a static state...which is all fine and dandy, extremely predictable.  However, any body of water, at any given time, really is in a chaotic state, and therefore the predictability of the behavior of that body of water is extremely, if not impossible, to describe.  But given a pure dynamic state, we can design into hulls features that can counteract, thus neutralize, equal and opposing forces present in said dynamic state.

Today's "need for speed", getting to the fishing grounds first (and fast), dictates that if the old hulls that were designed to tool along at 18 knots are now asked to do 45...well, some re-thinking needs to be done, to have them perform the way their owner's want them to...

[seabob4]

May I clarify.  Dynamic forces are forces that affect a body in motion...typically exerted by static objects, such as the earth.  Chaotic forces are those that change continuously, instantaneously, that, while one can "predict" the future force, one cannot be certain that said prediction is going to be true, not even predict that it will be "close" to what one thought it might be.  Think "rougue wave"...where the hell did that come from?  Totally unpredictable, yet entirely real.

We have a lot to learn about Mother Nature...

[gran398]

Bob, well stated, both posts.

Craig, the scenario described involves high HP flatbacks at high speed.

The transom bait boxes give planing ability, and for my use (non-drilled) nice flotation for the twins.

In turns with a flatback, yep, the boxes offer a stop for a slide. They run low by design.

Bottom line...the 22-2 flatback can run most any HP.  But be prudent...pull her back and run safely in the turns.

All of the add-ons won't make a hill of beans without good judgement at the helm.

[Aquasport Commodore]

I think Capt Matt said Tabs were a great addition for control and stability in most cases along with using the brain and putting the throttle on a diet at the right times.