change deadrise on OB15?

[Tagged]

sorry, its about 7 degree

Joel, I'm interested in how you measure the 7 degrees. Are you measuring one side from horizontal or are you measuring the angle across the keel, which would be double.

Many boat companies use the first measure, and by that calculation, your average bass boat is about fifteen degrees. That is, each side rises 15 degrees from the horizontal.

The reason I ask is because I've always thought the OB boats were closer to 6 degrees, and the Phantoms were closer to 3 degrees. One way or the other, something is confusing me. The OB series has nowhere near the deadrise that a typical bass boat has, so if Jacques is calling it 15 degrees, I'm confused.

Tag

[tobolamr]

BigAl,

StickyStuff put a pad on his PH16. I'd have to search the forums to find it. Here was the latest mention of the Pad build:

http://forums.bateau2.com/viewtopic.php ... hlight=pad

I hope this helps!

[TomW]

Tagged it is the vertical rise of one side measured at the apex and holding the protractor vertically, is the way I was taught it. Only one side is measured.

Tom

[AdamG]

My understanding is a pad is a flat planing surface towards the stern of the boat. You can acheive this by simply "slicing off the keel" parallel to the bottom evenly from the stern towards the bow a few inches either side of the keel line, sort of "squaring it off" so to speak, and putting a flat panel in its place. Of course, this requires reinforcing the pad area that is created significantly, because it will be subject to considerably more force than a V shaped keel. This will save you some small draft, but it will also roughen the ride and let her slide a little more in turns.

[anonymous]

Yeah, I actually thought during the build it would be fairly easy to just lower the angle of the frames going aft, and trim the hull plywood to match the new shape. Find out the deadrise at water entry, decide what deadrise you want (within the ability of the plywood to bend) at the transom, and figure out the tapering heights of each successive frame, using 10th grade geometry to figure out keel depth at transom, given the desired angle of deadrise, and width of the boat. Fit the hull plywood to the frames and call it a day.

[TomW]

Al the basic pad is taken between the stringers and taken forward to the first frame forward. The next size pad extends from the outboard stringers and extends in a parabola that is about 2/3 the width of the base. A pad is never an equilateral trianlgle. It must be level with the keel forward of it, so that the laminar flow is equal on it as it comes off the forward portion of the boat. The main reason for a pad is to allow a higher rise on the motor. It will give you a good 2-3". The other reason is speed you will get a few more mph with a pad than without.

Tom

[anonymous]

The main reason for a pad is to allow a higher rise on the motor. It will give you a good 2-3". The other reason is speed you will get a few more mph with a pad than without.
Tom

Do you mean that it allows you to raise the motor, like with a jack plate, and still get clean water to the prop? I thought it was to allow you to float skinnier when not under power (as most boats squat a little with the weight of the motor)

[Tagged]

Tom you lost me there.

When bass boat and speed boat folks talk about a "pad," they mean a narrow strip down the keel of a v-hulled boat that's about 8 inches wide, flat as a pancake, and runs forward 6 or eight feet.

Here's a link to a picture of a pad built into a PH16.

http://www.bateau.com/boats/PH16/slides ... ottom.html

At high speeds, the flat surface gives more lift than a simple v-hull would, allowing the boat to lift higher out of the water, reducing friction and letting you run fast, fast, fast. It probably does little or nothing below about 45mph, but above 55, you can feel a good boat "pop" up and start riding on that pad. At some ridiculous speed above that, the entire boat may be riding on a small section the size and shape of a water ski.

Having a pad will not allow you to run the motor any higher, but it is true that many of these high performance boats raise their motor to run faster.

And yes, it can get hard to control.


Tag

[TomW]

Tagged we are talking two different types of pads. The ones I mean allow you to raise the motor for more effiecient flow and lower draft without hurting speed and will in fact increase speed some what or the high speed pad like you describe where the boat gets up and is bsically riding only on the pad, scary. Yours is basically an add on, mine is a reforming from the transom and stringers to the keel. Both are viable additions to a boat, but like you said you have to be going pretty fast to gain any advantage with yours. With my pad it comes into play at much lower speeds as the flat area causes the boat to get on plane sooner. I'll be honest most boats don't have them and have only seen them on a couple of offshore boats and in a design class. The idea is intrigueging though and very interesting.

Al it only raises the engine 2-3" you still need a good jack plate to run really skinny.

Tom