Another Way Of Looking At It

[Stingray69]

I am aware that B1's are in need of a nosecone at about 80.
I understand about thinning and sharpening the blades, and maybe reducing the OD of props for speed gains.
I totally get inspecting the hull for hook or rocker and making educated changes to accomodate the power, balance and speed of the boat.
What I have never seen addressed is skeg shape and mods, as in changing the leading edge to a more 'swept wing' shape, like they started to do in the fifties on jets. I have seen more of an angle on high dollar lowers, and custom AM drives, but does no one make any mods to the skeg shape before upgrading to hi-buck setups?

[burtandnancy]

Actually, IMCO does a lot of work on his lowers. He's been fooling around with rake, shapes, entry, bulbs, etc for a long time. The problem is finding out what he knows. You don't just ask someone for their secrets.
Also read somewhere where John Tomlinson (TNT) does a lot of this on the #6's and the numbers prove it. Short of buying someone else's products, you'll just have to figure it out yourself...

[TIMINATOR]

May issue of ***boat. But its not out yet, be patient.... There is some things you can do, but keep in mind: under about 85-90, usually no gains, a nose cone and skeg sharpening will improve the quality/ solidarity of the water to the prop and load the drive harder. Drive loaded harder=wallet loaded harder. TIMINATOR

[Stingray69]

I have a 3000# 21' v-hull, 580hp 502 BBC with a Bravo1. Awesome tq band, done at 5700. If propped up from the worked 23p Mirage there now, speed could be way up there (27-28p). Early blunt B1; '89. As yet unsplashed.
Have needed to run a lot trim, though to get it light. 10' rooster, amount of trim. Worried that all the trim may make a NC more resistant, rather than less, water resistant, due to aim of drive/prop, relative to axis of NC. Figured on sharpening and smoothing the skeg. Unsure about shortening length or thinning front to back dim. Angle of about 45* seems pretty universal.
Is the NC primarily to shape water to prop, or make lower's profile more hydrodynamic, or both?
Looking into it now, for educated tuning changes later.

[TIMINATOR]

Hydrodynamic drag changes with the shape and speed, what works at one speed doesn't work at another. Thats why outdrives are shaped the way they are, look at trolling motors, Bravos, #6s. Different shapes for different speeds. What happens is the water separates from the gearcase at higher speeds due to the inertia of the water, the hole punctured in the water gets larger until the hole is taking water away from the blades and there is not enough bite and thrust drops off and the rpm goes up and the prop is considered to be "blown out". Slap your hand down on the water and you notice that the hole in the water is bigger than your hand. Adding more blades helps, as does a nosecone. Adding more blades adds to drag at lower speeds. The nosecone adds to drag at lower speeds, but usually allows a slightly lesser pitch prop for the same top speed. This helps out of the hole acceleration, but raises the cruise rpm. You need to decide what you need most. Timinator