Modifying a 13' Critchfield

[TwzteD]

I have a 13' Critchfield hull I'm looking to clean up and modify, obviously the critchfield hull is a rendition of a 13' Allison preffty much same hull as a -delta-rapidcraft etc, very good performing hull in its size range. I'm looking to modify it significantly, not the bottom but more so the sides/transom and top cap. I want to bring up the sides / freeboard a few Inches, raise the transom sides about 3" and the middle about 7". These boats are almost dead flat with no arch. Like the teardrop/airplane wing design seems like it could be a little more areo dynamic also. MOre similar to my bullet in the backround in picture #3. From what I hear the transom angle is not enough some people need to run wedges so I was thinking about tilting it back a few °. One other thing I was thinking is adding a 3" setback with a notched transom similar to the hydrostreams, everybody seems to run jackplates atleast 3" so if I build the transom 20+" tall and run a 15" engine it essentially is the same thing as running a jackplate to get prop shaft near level with the pad. What exactly does a notch help with? Pad is 7 1/2" wide which seems to be ideal for some of the fastest hulls. Anything else that could be added to help performance? Possibly a reversed concave pad similar to the hydrostreams venom? What are your thoughts? With lighter 2 stroke engines in the paxt, newer power is a little heavier, in short looking to make this boat float a little more weight and be able to take rougher water better (higher sides) while possibly adding more performance features if worthy. I know there's some really knowledgeable people on here (Jimboat - aero research) that could point me in the right direction. I have attached a few pictures of a mock up I did with cardboard to get an idea of what it could look like. Black boat is a similar general design I'm aiming for as far as it's shape is concerned. Looking to get as much info as possible. Thanks in Advance. any input, appreciated.

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[TwzteD]

Anyone have anything to contribute?

[Dave S]

Yes why so much not replies?......

[powerabout]

have you got a 15" OMC for it yet?

[sharpeye Mike]

They are good fast boats to start with and they are still winning races. Not sure if your mods will help or ruin the performance of it. Can't hurt to try I guess.

[David]

The Canadian Edition/Hydrostream VooDoo is said to be a Delta with a beak and a notched transom. Either would float with the 60 Merc EFI Formula Race.

[TwzteD]

IM planing to keep the bottom the same, its proven, just looking to add more freeboard and a better looking cap, was just curious regarding adding a notch in the transom. There are many options for 2 stroke short shaft engines, unfortunately with all the 2 stroke bans and no one other than evinrude making them, and none short shaft in a decent hp, the mercury formula race is the only decent option right now in new power. I have one and will be running it on my bullet that is almost completed. I know a guy in Canada that runs one on his rapid craft cyclone, which is basically a critchfield with a new cap, he has seen 66 mph in it with the formula race, thats respectable for a 4 stoke on that hull, not to mention reliable, easy to start etc. Hopefully other manufacturers will follow mercs lead in making smaller hp short shaft engines , hopefully with better gear cases and not big 2.33 ratios. I will likely just raise up the sides, keep everything else the same except the transom angle, i dont think it would effect performance much if at all by raising the sides 7" in the highest spot, but thats why i posted it here as there are alot more knowledgeable people that me in this respect. The bottom is obviously the most important in terms of how the boat performs and id like to leave that as is, just blueprint and clean up the bottom.

[Capt.Insane-o]

Tall sides on small fast pad boats make them much more susceptible to the effects of side gusts and other wind effects.

[TwzteD]

Tall sides on small fast pad boats make them much more susceptible to the effects of side gusts and other wind effects.


I can see that, its not much taller only about 4-7" at the highest spot, But the slightest changes can make a big difference, thanks for pointing it out. The boat will likley be heavier than the ones they race that are tater chips probally 300-350#'s cored.

[hsbob]

add a 1" or 2 to the pad, with a little slope to each side. this will keep the boat from falling off the pad in a corner.

[TwzteD]

add a 1" or 2 to the pad, with a little slope to each side. this will keep the boat from falling off the pad in a corner.

What do you mean slope?

Slope as in rounding the corners or the pad or adding like a reversed chines to the pad?

Like this?



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[powerabout]

I think he means a vee pad so its not flat