What makes a good V-bottom?
 

Now that I've got all the bugs out of my new engine, and found a prop that seems to work well (no more blowout issues), I think I've managed to put good power into a floating brick.

Since this is my first fast boat, I'm happy to chalk this up to "lessons learned" so that I am better equiped to move up at some point.

The lesson I am trying to learn right now is: What makes a good conventional V-hull? I mean, in a short boat with no steps, it's hard to figure out why one boat would be fast and another miserably slow? Assuming the bottom is straight, what other factors are there?

Obviously V angle plays a big role. The deeper the V the softer the ride, the shallower, the faster. Someone told me that in a fast V, the inner strakes won't extend all the way to the transom? What else?

Any good examples of good fast V bottoms in the 24-27 ft range? I remember at one point reading a comparison test of small single engine Offshores, where the Velocity outran all the other boats in the test, even though it didn't have steps.

Thanks

The 27 Activator can be very fast with the rite power. MRD has a yellow 27 now that goes well over 100. How fast do you want to go ?

My 26ft/280 Velocity has a full length pad and 4 full length strakes. It rides vary high and flat in the water. It is a vary fast hull by comparison to your Powerquest.
I have only driven my boat 3 times thus far so I'm not sure how it will handle the rough water...

Velocity makes a great hull. In my experience (true 26') on lake MI they handle the big stuff with ease. With the pad they are very fast. I personally would not buy a V without a pad. Without a pad a lot of boats run very wet.

well I definitly belong in the brick catagory..so no help here....

Yeah. I'm a member of the brick family as well.

• The less deadrise the faster it will be (but won't cut as well)
• The wider&longer the pad, the faster it will be.
• The lighter the hull is, the faster it will be. (especially if light in the bow)
• Lifting strakes are supposed to help but seems minor compared to deadrise,pad, and weight.
• The hull also needs to be straight. if there's a hook in the bottom, that will slow you down, plus it won't be as responsive to trim which will hold you back even more.

The fastest 28 single I've heard of is Tuffmarine's Tuff28. Ran 95+ with a stock 525. I think it weighs less than 4000lbs. Has a less than 24degree deadrise, maybe a pad too? no cabin, so light up front. That puppy flat hauls azz. The low freeboard/lower profile is not for everyone, but I think it rocks.

To answer your question there is a mix of many factors that make a good V. Design, balance, construction, set up, driver to name the basics. It is hard or impossible to appreciate the differences with out driving or at least riding in them. Even apparently identical boats will act different. The best ones have been refined over time. Also regionally boats are different to match the local water conditions. So if you ask a dozen people what one is best you are likely to get 11 different answers.

There are few great boats, many good boats and too many "just a boat" boats out there. Ride in as many as you can so you can appreciate a good or great boat when you ride in it.

strakes, weight, chines, balance, propulsion efficiency

24*deadrise!


I am not so much into speed as I am the boat's ability to get through rough chop.

I guess I am oldschool.

Like the older Magnums/Formulas/Cigs/Donzi's/Scarabs/Fountains.

I also like the ride of a 38 TG and Formula with steps.

The stepped bigger (42- 47' Fountains) are fine.

I'm trying to picture what "a full length pad" looks like? The bottom of the boat is flat for some width of the boat all the way from the transom to....where?

Do the strakes run through the pad? are there 4 strakes and two chines, or are you counting the chines as two of the strakes? I was told Strakes provide lift, but ad resistance and hence cost speed?

Anyone know of a Velocity that is sitting out of the water anywhere around me? I'm not looking to buy anything right now, just more looking to learn. The engineer in me is never going to just "use" the boat to go boating. That much I know of myself.

Besides everything previously mentioned the X dimension is very important. If the prop is running too deep, trim response will be poor and the boat will run wet, (too big a footprint).

At speed wake should be breaking at or behind the helm. Maybe a Bravo "shortie" will help.

Seems like pretty much everything has 24 deg deadrise. DIfference seems to be in how much pad.

I'm also wondering if steps are even necessary in a boat that small? They obviously help a great deal on the bigger boats you mention, but do they do anything on a fast, small boat that only runs on the last three feet anyway?

What does that mean "wake should be breaking at or behind the helm"?

The x-dim or more importantly the distance of the prop shaft from the bottom of the boat was another question I'm looking at: If you're going to run a modern "normal" 4 blade prop (Like a bravo1) how far would you put it below the hull bottom? I assume the kind of water you run in plays a factor in this. You obviously don't want the prop coming out of the water on every wave.

How far below does velocity put their props? Anyone know?

The X on my outlaw is a makes-me-sick-to-my-stomach 7"
I'm currently working to improve that somewhat.

Here is a bad pic ( only one I have) of the bottom of my 26 Corsa. If you click on the pic and enlarge it you can see how wide the strakes are. The bottom strakes end a few feet before the transom. I set my X dimension at 18 1/4". That puts my drive shaft around 3 1/2" below the keel. This hull runs extremely well in the rough.

[QUOTE=bcarpman;2631597]What does that mean "wake should be breaking at or behind the helm"?

When you are on plane and driving, look over the side and see where the wake is coming off the hull. If it is forward of the helm, you may be running the hull too wet. If you can't trim the outdrive enough to pull the wake aft, chances are the prop is too low or you are getting too much stern lift.

They, (Corsa), obviously were very influenced by the 28' Cigarette!

thanks

3.5 inches? Wow, I think I'm about 12 inches. Doesn't that put part of the prop out of the water? Is it a surfacing prop?

I would add that the boat needs to be "still" with 2-3 degrees to bow lift...ideal balance. Nail this balance with the perfect X and an average production hull with a straighten/flat bottom can make amazing speed with superior hull efficiency. Reggie spends more $ on dialing in the right set up on Fountain's production boats than most.

On my Velocity, the "full length pad" is a basically flat area on the bottom instead of the bottom coming to a V. It runs from stem to stern and is 12-14" wide.
My hull also has 4 full length strakes not counting the chines.
Most old school V bottoms have 2 full length and 2 that start at the bow and end 1/2 way back.
The hull also has a notch transom so the drive can be mounted higher and still get clean water to the prop.
The Velocity does have a 24° dead rise bottom, but rides up on the pad when going fast.
This is the first boat I've owned that is not an old school straight V. I went this direction so that I could have a bigger boat that would still run pretty fast with mild power.
Here is a running pic from the last owner.
Like I said earlier, I'm learning the boat and the jury is still out...:cool:

Yeah, that runs pretty high on the water. amazing with a full length pad it doesn't slam hard when the water gets rough.

Be interested to hear your thoughts once you get more time in it.

How is the degree of bow lift defined? In one of my boat books it's defined as the change in attitude from the way the boat sits off plane, but that doesn't make sense at all as my boat sits with the bow WAY up off plane.

I've had two people tell me two different things about the effect of prop depth on bow lift. One said a deeper prop will raise the bow and another said the oposite.

I don't really know exactly how you measure the degrees of bow lift. I am thinking it may be as compared to the angle of the strakes...like on the trailer. Our pursuit of the ideal X was all trial and error. We started by raising the "X" 3" by raising the extension box 1" and adding a 2" shorty lower. We first tested with 3" spacers to confirm a base line and the efficiency of the Imco lowers vs the std Bravo lower. Next we changed to a 2" spacer, then 1" , and then no spacer. As the boat may handle differently at different X-dimensions, it is possible you could also have to adjust the bottom, strake length, etc to achieve the right balance and attitude. This process , including finding the right props added over 13+ MPH. This was the biggest Home Run we every had in 20 years of pursuit of more speed.

Just thought I'd post some details on just how bad my hull must be (I say "must be" because we can't think of anything else that could be at fault).

The boat came with a stock 330hp 454. I would run 53gps on a good day with a light load.

If you put 5400 lbs, 300pshp into:

http://www.go-fast.com/boat_speed_predictions.htm

and you get a hull constant of 223 which would seem about right for a conventional V of this vintage.

So then I drop a "330 on Roids" in that dynoed at 460hp and the boat barely hits 59or60 gps (Speed calculator says it should hit 63). Oil pump goes south on that engine after about 20 hours with the predicted consequenses. (still no idea what happened)

Drop a Tyler Crocket built 502 with 540hp and the boat still feels like it's bouncing off a wall at 60mph (speed calc says it should hit 69mph). The last 30% of throttle yields no speed increase.

No amount of drive trim will loosen up the bow.

Stock boat used a 21p 3 blade. Newest motor can't even turn a 24p 4 blade despite an extra 210hp. If I run a 25p 3 blade, it blows out before WOT.

I really do love this boat for everything other than top speed (It's a really spacious boat for it's size), and everyone commments on how nice it is both outside and in. So I'm not sure what I'd buy that would be as nice. Can't stand the baja's and you have to step up to a 30plus fountain/formula with twins to get a cabin/cockpit that's as roomy and as of now I can't afford that (business has been slow this year). Compromises!

Oh well, just rambling now.

Many boats like yours have wedges or hooks on outer chines to make the boat plane easily and cruise flat and nice. The things that make it cruise nice hurt at higher speeds. In addition to that the drive is probably buried in the basement. It is not as you have seen how much power you have; it is more how much drag you don't have. You can change the bottom ,add trim tabs, steering, Fill transom raise motor buy props and on and on.

Enjoy it for what it is. You can spend endless effort and money changing things and likely still be dissatisfied. If speed is important get a fast boat.

It takes a bunch of power to go fast in a straight V. I had a 27ZX (non-step) Donzi with a Procharger. It would break 70 on a good day. I figured that it would hit a wall in the mid to high 70's with bigger power. The ride and handling was unbelievable. The snottier the water the better. I played around with a Shorty and it did not like it. It takes lots of bow lift in a v. I probably gave up 3 mph due to running a 4 blade vs 3 blade with a conservative X but would have lost around 7 in cruise.

I wanted to go a bunch faster so I went with a step hull. And yes, it is much faster. I did sacrifice some ride and handling.


Enjoy the v-hull. :ernaehrung004:I would have one again. Spend some time dialing it in and you may get a few more mph. I would not do anything permanent since not everything works with every hull. You don't see Magnums and V hull Cigs breaking speed records but they are still cool and have a great ride. The only way to really make them fast is to make them very light. If you want to do that then get a race boat.

Don't let the pad V guys confuse you. Those boats are a good bit different and can go fast. I have never driven one but have run with a few. I am pretty sure that they did not have they same ride I had as they bounced across the top of chop at 70.

yes, this hull does have built in wedges on the outside of the strakes. Another 257 owner said his are out of the water with enough power, but mine aren't. You'd think that would show in the slow speed hull constant, but I guess it's non-linear.

I already put homemade 20inch trim tabs on in place of the stock insta-trim and they do work very well so I'm sure I don't need the built it wedge.

So far I'm treating this boat as one big learning experience. I figure once I'm ready to move up to something really fast, I'll not only know what to buy and not buy, but I'll know how to drive a small boat fast in rough water (two weeks ago I was running 40mph in a 5ft random chop, something I would have never done just a year ago) which I would guess is a skill that will help me drive a faster bigger boat as well.

I've already put way too much money into the engine, and bought a well built drive to hold up to the power. Both bad investments in this boat in retrospect (Should have just built another "330 on roids"), I'm not going to put a bunch more money into the boat: paying someone to redo the hull, or a shorty drive, but I MAY experiment some this fall.

I've built many composite car parts including entire race cars out of fiberglass/kevlar/carbon fiber, so I know what I'm doing. If I really feel up for experimenting I may take off the wedge, blueprint the bottom, and raise the drive/engine.

I know, it's a lot of work for a boat that's never going to be particularly fast, but I figure I'd learn a lot from it and it'd be fun (yes, that's the kind of stuff that I enjoy).

Would be kind of fun to have a 70+mph 257 powerquest sleeper. I already get the weirdest looks as I idle around in what is obviously not a stock boat. :) Came out of the harbor last week just ahead of a guy in a VERY fast boat. Got on plane well ahead of him and it was funny how he made sure to pass me before he slowed down to cruising speed (slower than I was cruising). Not sure if it was the sound of my motor, how fast I got on plane and up to 50+ or the fact that it was him and his buddy, and I had four girls with me. I got a chuckle out of it though.

I know a fellow that took the hooks out of his late 80's 24' Formula and it made a big difference. That boat had a 330HP 7.4L Alpha. I think it went from a top speed of 52 to 57.
Then he bolted in/on a 575HP 540cube and Bravo drive. I think the boat then topped out around 70, maybe in the low 70s. He did not add external steering though and the boat became a real handfull.
Anyway, I think you will see a decent gain in top speed by taking those hooks out. You'll need to make sure your steering is tight and use the tabs.

Actually a 17' Bayliner with a gorgeous woman is what makes the best hull! :cool-smiley-011:

Carp,
I agree with Jim, you could get the boat to run 90-100+ MPH but today most of your set-up is not for top speed. To get significantly more speed, it will take major changes that are not in the engine compartment. My 1987 Scarab will run over 100 MPH but I could buy a new 39' Outerlimits with twin 1075's for less than I have spend over the last 20 years clawing up the wall.
Ben

I bet my hull is similar to yours i seem to have a 60 mph wall 23 ft rinker 3900lbs , 502 carb. best gps 59.x with a couple people in the boat. I went out and looked at the "pad on my boat it is about 2 inches wide only.

Try calling Boca Marine, in Harrison Township, ask for Tom.

He's got a 30 sitting inside that he used to race, he can give you all the info you want and then some on Velocity. Google the number as I don't have it handy.

My 280 Velocity was a fantastic boat, you need to get back on the throttles right before you land to soften the landings, once you learn to throttle it right you're gonig to love it.

The 280's corner like a go-kart, non-stepped hull.

I had the same boat with a (330 HP) 454 Mag...21P Merc Mirage prop.

60MPH GPS


You should be going faster.


My boat used to porpoise a lot. If I still had it I would go to 4-5 blade prop with more cupping to control the nose and get the weight from the motor up. That boat is very transom heavy from the motor and a heavy built transom. If you can get the back up you will pick up speed.

A very heavy (in comparison) Wellcraft Nova 23' with a 454 used to go 60 with a 24* deadrise and no pad.

I think that boat is better off with a lighter 350 CI Engine Whippled.

My .02

Yeah it seems to need a lot of trim. Do trim tabs help?

Something doesn't add up. You should definitely be running faster than that.

I ran mine in Lake St. Clair..on Sundays with a 3' chop I felt out of control in it. Not enough weight or deadrise upfront to knife the chop and too much weight in the back. It bounced like a basketball.


I always ran with my tabs all the way extended downward (when in chop) to keep the nose from bouncing up and down.

I gave up and sold it. However, in calm waters I used to have a blast doing donuts around a 4-5 mile imaginary circle course.

If I still had it I would most likely contact a custom prop shop and explain the problem(s) and see what they could do. I think the prop needs a lot of blade surface to get the back end up and out and to keep it level.

It felt like a 4,000 pound boat with 3,000 lbs in the mid to back section. A balance act is required to get it running right. Work on getting the right custom prop.

Yeah, but now you have an '87 Scarab that will run 100. Anyone can go out and buy a new outerlimits :) (this coming from a guy who just got back from bike night on his twice restored '85 honda saber)

Carp,
If you want some good advice and honest perspective, there is a guy close to you in MI that can help you. Dave Goodman, Tiger Fiberglass, Maryville, MI (810 364 8875). Dave has the experience and can do all the necessary F/G work. He can help you with the necessary X-dimension changes, rigging, bottom work, strake lengthening, etc. Dave is an ex-racer and and is very experienced in set up. He has helped numerous race teams improve their programs. He can also participate in the actually testing and dial-in until it is right.

This thread has been a lot of help. Thanks to everyone who chimed in.

Two questions I still haven't got answered:

1. Will raising the prop increase bow lift or decrease it?

2. What do the strakes do? they increase surface area which is bad for speed, right? but they provide lift which can be good? Do they provide any stability or resistance to chine walk? Would flattening then out at the stern help with my lack of bow lift?