Decided to throw something together about rake length with some numbers. It seems that whenever rake length is brought up, all the builders question wether or not its good. So I decided to put some numbers on paper for a "just see" purpose. That and its f'n raining and I'm bored.

So, what we are looking at when we look at rake is the amount of surface area that is in contact with the water surface, thus friction. Now there are several factors to consider when doing this, wave friction, air, wind resistance. But all things considered, Boat A & Boat B will have to travel in the same conditions, so wave and air resistance are eliminated.

The basic formula for friction resistance is similiar, but manely R=Cf x S x V2.
R = Resistance in lbs
Cf = coefficient of friction using Reynolds Number
S = surface area in ft2
V = speed

The Reynolds Number for:
15' hull = .01093 (lots of factors went into this)
20' hull = .01052 (lots of factors went into this)

So if we have 2 boats A & B

Boat A is 18'48" with a 7.5' rake
Boat B is 18'48" with a 6' rake

R = Cf x S x V2
Cf on 18' hull is .01069
S on 7.5' rake = 18' - 7.5' = 10.5' of actual "wetted" surface area
S on 6' rake = 18' - 6' = 12' of actual "wetted" surface area

This is to say, how much hull is in direct contact with the surface, not up the sides, but surface. So to eliminate another factor, lets put the hull on dry land on a level surface. How much of the hull is in direct contact with the ground, the "wetted surface".

So since were not moving, we will use V as 1 so V2 = 1.

Boat A 7.5' rake
R = Cf x S x V2
R = .01069 x (10.5' x 4') x (1)2
R = .01069 x 42 x 1
R = .44898

Boat B 6' rake
R = Cf x S x V2
R = .01069 x (12' x 4') x (1)2
R = .01069 x 48 x 1
R = .51312

Doesn't seem like much but there is a difference. Now figure in wave resistance, "riding in a chop". The longer rake has more of a gradual slope that the shorter rake. Thus the shorter rake has more of a blunt surface and is much more prone to "plow rather than skim. Everytime a wave hits the short rake, the hulls slows down. And take into consideration that I negated speed. The faster your hulls moves, the more of a difference. Remember the speed is V2

Boat A
1 mph R = .44898
20 mph R = .44898 x (20)2 = 179.592
30 mph R = .44898 x (30)2 = 404.082

Boat B
1 mph R = .51312
20 mph R = .51312 x (20)2 = 205.248
30 mph R = .51312 x (30)2 = 461.808

The faster you go, the less drag and the more the gap get between the two.

Now most on here will argue that it really doesn't make that big a deal, but a little friction goes a long way. Why the hell is Frog selling that fantastic product, it reduces friction. So now when you hit a grass patch or lillies, your hull won't slam on the brakes, it will skim through that shit. Thus Gatorglide has lowered the coeffecient of friction between your hull and the water surface.

Again, this was just to throw some numbers out there for discussion or clarification.

I have no business poking on this subject, but what comes to mind for me with the longer rake is illustrated below. Lol @ illustration!

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Lol u get what im saying!!
So with the longer rake its more susceptible to plowing. Ur boat obviously runs well.

My $0.02....about a week or two before Nonk-J started fab on my hull...which was going to be a hybrid Vee rake...I got to take a PD 1860 out fishing in Grand Isle. I had to cross some pretty rough water with that CC rig. What I realized was that the PD rig stayed on top of the wave crests and never really dipped in/out or had much bow slap to talk about. So, I figured the length was adequate enough that I did t need the Hybrid Vee rake. Was able to opt out of it with J and save a few hundred $$. But, compare the Uncle J rake...which we all know is a very long rake...to the short rake of the PD X Series. Not saying my rig is bad in rough water...because it definitely is NOT...but, I feel the PD stayed on top the crests with less bow slap than mine.

My argument about rake goes back to my LT days....when I had/have the mindset that more length in water helps getting on step and minimizes "squatting" at take off.

I know that will probably create another debate!


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Because of displacement shouldn't the water line be higher on a longer rake vs. a shorter rake. So your water line would be higher up so essentially both hulls would have close to the same square inches in wetted surface.

Actually, I think my longer rake has more rake length in the water than the shorter rake would. In fact, my boat will hold water between the console and front deck bulkhead after a rain...could have something to do with usually having 12 or more gallons of gas in the bulkhead?? If I had less rake, I think it would sit more level....just my thoughts.

Okay other than running vegetation there can't be any difference in rake length. Wind might do something but that probably very minimal. Where your running on step half or better of the boat is out of the water right? So the rake has nothing to do on step. But when I hit someone's wake that's a different story. It fells like you slammed on brakes!! And mine are mostly around 6'.


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You really have to put boats with long rakes vs. short rakes into better perspective.

Rake Boats.jpg

Are y'all sitting down?

8' 2"....edit

Mine is about 6' 9''

Seriously, with two batteries in the back, anything over half a tank of fuel and trolling motor on it, this boat drafts lower in the front than the back. It's very annoying when I'm fishing by myself.
I'm counting the pointed bow as part of the rake. But, from the start/stop weld button to the point, horizontal distance 8'-2".




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How long is your point? 14"?


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Also, don't you have 24" sides?

That will make the rake angle steeper than a shorter sided boat with the same rake length right?

Point probably closer to 16"...and yes...24" sides. That would certainly explain a little extra rake length!




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I have the same trailer as you my boards stick out about 1 1/2" past the transom. I asked for a " normal " rake I didn't want a real long one. Notice how mine starts past the bunk boards.

Measure from the stern, using a straight edge....how much flat running surface before the rake starts? My 18'8" boat has 11'6" of flat bottom (appx. 62%).

9'-1" from the transom to the weld button....and yes, my bunks stick out past the transom 2".

Just doing math in my head...17'-4" of bottom length. I know from top of transom to tip of point is 17'-10".

Well your rig looks really good though!

Have you run that thing with no gas or batteries up front just to see? Aux. tank maybe? Wondering if it would help your speed any.

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Your math does not account for load. A long rake boat seems more sensitive to load than a short rake boat (as long as the short rake boat does not plow).

When I redid my Kevlar Marsh Master I added a foot to running surface by adjusting the rake where it meet the mod v
bow.

When loaded down before the mods it was sticky in the mud the nose kinda plowed. ( too much load per SQ inch of surface area) .

I also added some width and 6" of length. I don't feel the nose plow any more

It is all a balance. Narrow boats need less rake, wider boats can get by with a longer rake, its all about sq" of boat in the water. The fewer sq" of boat in the water the more HP and prop trust to push the load.

I can't prov it with math, but years of playing with these boats have taught me this.

JD

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Banded, what is the motor difference between yours and Will's old pd?

Bout the same. I think he has a little more decking on heads.


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Crazy pictures over emphasizing a rake?? I have no idea what you're talking about! Well, maybe I know a little bit about that.

My boat length is 51% flat surface and 49% rake....so, I didn't draw my picture quite to scale...but it was close!


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