What exactly is meant by the "pad"?

[ripsvin]

Posts that concern setup often talk about the relationship between the "pad" and the prop shaft.

For example: "Level the pad by tilting the trailer with a bubble level on the pad."

What exactly is the "pad"? Is it the transom?

Thank you.

 

[Dhadley]

Re: What exactly is meant by the "pad"?

Boats that have a pad look sort of like they have a ski on the hull. Instead of the hull coming to a V or a rounded V it'll have a flat pad on it. At speed it actually get up on the pad which reduces drag and increases efficiency. Some pads are wider than others and there are other design differences. You basically balance the boat on the pad at speed.

 

[Dhadley]

Re: What exactly is meant by the "pad"?

Here's a couple shots of the pad on my Hewes flats boat. The cut out area behind the end of the pad is called the "step". Some boats have a pad only, this boat has a pad and a step. They also cut steps into the lifting strakes on some larger pad bottom hulls.

 

[Dhadley]

Re: What exactly is meant by the "pad"?

Here's some shots of my Hydrostream YT hull. It has a pad, a step and air entrapment slots.

With these type boats we generally refer to the X dimension as where the propshaft is in relation to the bottom of the pad. On recreational boat the X dimension usually refers the the AV plate (right above the prop) is in relation to the bottom.

 

[ripsvin]

Re: What exactly is meant by the "pad"?

OK, I see. Thank you very much. Very nice boats. The YT hull is new to me. I am mostly a lurker on this forum, and have found answers to all my questions so far, except this about the pad.

My Ali-Craft has a regular V hull with something that may be regarded as a keel. This keel tapers upward the last 3 inches going aft towards the transom. I don't have pictures, my boat is in the water.

As my outboard is set up now, the flange on the stem which is a couple of inches above the AV plate is visible above water at full speed. The AV plate itself is submerged.

I figure I can lift the engine an inch, maybe more, which means new holes.

I bought the boat this spring, but I don't think it's ever been properly set up.

I'm mainly interested in saving fuel, and my thinking is that a proper setup will mean easier "glide" on the water, which again will give me the speed I need (approx 25 mph) at lower RPM.

 

[Dhadley]

Re: What exactly is meant by the "pad"?

Any time you reduce drag you'll increase efficiency. From holeshot to wot. Raising the motor will reduce gearcase drag. In theory, if we could get the gearcase high enough to "hide" it behind the hull, and still keep the prop hooked up, you'd have no gearcase drag at all. Oh wait -- that's a surface drive........

 

[Texasmark]

Re: What exactly is meant by the "pad"?

You know, I was thinking just the other day about a padded boat at 60-70 mph with a twisting screw driving it and not much of the lower unit in the water to counteract thrust, sitting on just a foot or two of pad for stability.

It utterly amazes me how the boats maintain flat (side to side) trim in that situation, but they do.....and do it with just a driver on the "right" side and also with a pair of occupants which you'd thing would upset the balance designed into the critter.

Just Amazing.

Mark

 

[MrBigStuff]

Re: What exactly is meant by the "pad"?

Maybe I'm just getting old but there is nothing quite so terrifying about boating as being on the pad at speed and skidding around a turn rather than "biting" in to the turn. I'm terrifraid of hitting that rogue wake/wave and flipping it. It's not like a car you can take to an abandoned parking lot and see at what point it skids out- getting a feel for what it will take before exceeding its limitations. It seems much harder to know with a boat where the tipping point is and the penalty for guessing wrong is much harsher...

 

[Scaaty]

Re: What exactly is meant by the "pad"?

My old Switzer with a short shaft XS150 surface SS 2 blade 14x28 prop needed some sawing at the wheel to keep it on the pad, and not get into chine walking (it was pretty well self correcting anyway, but squirrly boats can get ya in trouble fast). Its all in good hull design. But the last thing I would have done is give it a good wheel yank at speed to see how quick it would turn!

 

[Dhadley]

Re: What exactly is meant by the "pad"?

Maybe I'm just getting old but there is nothing quite so terrifying about boating as being on the pad at speed and skidding around a turn rather than "biting" in to the turn. I'm terrifraid of hitting that rogue wake/wave and flipping it.

It's not terrifying -- it's a RUSH!! And remember -- there's 2 kinds of race boat drivers. Those that have been wet and those that are gonna get wet.

 

[NSBCraig]

Re: What exactly is meant by the "pad"?

Guess I just wanted to put my two cents in here. I have not found anything any more amazing then running my brothers velocity 410 it is absolutely one incredible machine, very humbling when I return to my Baja 16ss.

The notch your refering to back by the transom is commonly referred to as a notched transom, not a step. I've seen steps in all manner of hulls from fishing boats for the lagoon up to the majority of performace boats today.

Steps ventilate the hull breaking it free from the water, effectively making it float on mussy air not the water. Step hull are the most prone design to do high speed spin outs. You have to set the hull down in the water and make contact again before making anything but a pretty small heading adjustment or your gonna roll.

Hull designs with a pad instead as someone said ski or surf through the water on the pad. If you can get a properly designed hull that uses a step in it to spin out you really have to be trimming it out way to far especially if your chine walking. The pad acts more as a knife in turns then something you can slide on.

Going back to the velocity at 87 mph on the gps there is NO need to adjust trim or anything to spin that boat right around the limit being only how hard you want to be pressed against the side of your seat but there just isn't any way your gonna spin out.

You can find some more info about this on velocity's web site, how much it applies to your boat depends, but Steve Stepp did all his R&D on small outboard race boats and then moved up from there. He even proved that the pad hull with a notched transom is the fastest, most fuel efficent, safest design out there with the vr-1

Wish I had one!

 

[Texasmark]

Re: What exactly is meant by the "pad"?

For what it's worth, years ago when Champion Boats were making their debuit they had a pretty radical hull on their padded bass boats.

They boasted and showed many video's of their boats at WOT make a 180 in the boat's length. Needless to say, there was a lot of spray and the driver obviously was tossed about, but it did it and appeared to not take on any water in the process.

Mark