Running Surface at Plane

[Darkside]

I'm planning to wax our new AR195 this weekend. I don't won't to slow the boat down so I need to know how large the pad is where the boat runs at plane so I don't get wax there. I know this will vary at different loads. Has anyone searched through pictures to determine how far the pad extends forward or to the sides at say 30 mph. Thanks

 

[2kwik4u]

This is about the best I can get you from my photo archive. This was taken at ~18-20mph or so.



screen grab from this video

 

[Darkside]

Thanks @2kwik4u . I had looked at several videos but none in smooth water. The wetted surface extends a lot more forward than I would have thought. I picked up a couple of mph. top end, when I cleaned the mold residue (wax) from some of the bottom but I didn't go that close to the bow. My wife would probably get upset if I dulled the surface with scotch brite pads or 1200 grit paper that far forward.

 

[Maccam26]

how much of a speed decrease we talking about here?

 

[Darkside]

how much of a speed decrease we talking about here?

Not sure. I don't have reliable data one way or the other. Boat wax will cause high surface tension between the surface and water. They make some spray on expensive stuff to reduce the tension but I'm not going down that road. In sail boating you could gain 10% in speed by dulling the surface with a scotch brite pad. But that's apples and oranges here. Designing a tight fitting cover for the bimini that started at the front edge of tower would probably increase top end more. I just like to know I'm getting the most out of the boat and maybe save a little $$$ in fuel along the way. I could probably save more money by hording gasoline. I do have an empty above ground pool out back.

 

[d_coyne1984]

I think the speed loss at what these boats can achieve is going to be negledgable. I always wax my bottom. It makes it easy to wipe clean. If there was any speed loss, I couldn't notice it. She would still do 49-50 wide open until the day I sold her.

 

[gthh]

@d_coyne1984 practically in our recreational boating case, I concur.

This has been batted around the forum for years with no real substantive conclusions.

I personally would not scuff up a perfectly good gel coat for a debatable performance increase but would use the theoretical justification as an excuse not to any work on that half of the boat! ...for [HASH=3630]#$@[/HASH] sake there is enough area on my boat that can use the attention my hull is not getting! (...cracking open a beer at this moment)

 

[dshscarab]

Not trying to start a debate here but when I waxed mine, I thought I actually gained a mph or 2. Plus, the bottom has some protection on it.

 

[Darkside]

I personally would not scuff up a perfectly good gel coat for a debatable performance increase but would use the theoretical justification as an excuse not to any work on that half of the boat! ...for [HASH=3630]#$@[/HASH] sake there is enough area on my boat that can use the attention my bottom is not getting! (...cracking open a beer at this moment)

You may have hit the nail on the head. I'm kinda lazy and trying to find an excuse not to get under the boat on my back. ( " on my second beer already, you need to keep up") ??

 

[Wright2e]

This is about the best I can get you from my photo archive. This was taken at ~18-20mph or so.

View attachment 118203

screen grab from this video

Super cool. Hardly every get to see a lake that smooth.

 

[Julian]

Yeah....a scuffed hull is supposedly better...but it's probably a tiny impact. Found this explanation online:

Professional boat racers prepare the bottoms of their hulls by lightly scuffing the surface at a 45 degree angle to the keel. Its difficult to explain why (i'll give it my best chance here), but waxing the bottom will actually create more friction that a lightly scuffed surface. Your example of a freshly waxed car is a good example. The water does bead from the surface with minimal effort...but have you noticed how a dull, faded car will actually hold a sheet of water on the surface and not let it roll off? When you have that surface of water sticking to the bottom the hull, the water passing underneath the hull can actually do so easier because water-to-water friction is less than water-to-hull friction no matter how smooth or well waxed the bottom is. I dont have back-to-back proof (like gps data) but I figure if its good enough for the teams that spend major dollars to go boat racing, its good enough for me I have heard its a 1-2 MPH on a full size boat. I do wax the topsides for easy cleanup after a trip to the lake though.

 

[Maccam26]

I’ll spend less time underneath now

 

[robby76]

Hello there. My hobby in the 1980’s -90’s was building and racing radio control boats out of wood then fiberglassing. Waxing the hull underneath made the hull stick to the water decreasing your speed, planing, and turning. I always took some 600 wet sand paper and sanded the bottom of my boat hulls.
Then I tried some “Rain X” windshield water repellent on the bottom of where I had been wet sanding and it was like ball bearings, wouldn’t stick to water and slide out in the turns having to change out my turn fins. I still have my boats from back then. It’s a great hobby.
Disclaimer: this procedure worked on radio control boats less than 42 inches long and weighing less than 15 pounds.