super fin - long post

[superpop]

Re: super fin - long post

I was not trying to be a naysayer but rather pointing out what I thought might be a design problem. If you have ever watched an IO prop as you are slowly moving around, it creates a round conical thrust pattern as it moves through the water. You are forcing a lot of PSI in the form of a round shape into a square box. I would think a round tube just behind the prop would be far more stable and secure, but again just my opinion. My other concern and the reason I asked about WOT performance is if you are getting a lot of movement or shuddering, you could damage something, such as the fins on the drive that you are mounting too. I have also heard that devices like this and whale tales, put undue upward pressure on the outdrive.

 

[cpubud]

Re: super fin - long post

A round tube would act more like a jet drive only adressing 1 problem . what I have done is improve performance all-around. and you keep saying box what I have is not a box, more of a top plate with 2 rudders.

 

[steve201]

Re: super fin - long post

if I might add my 2 cents...you have 3 things going on here where people are trying to address in the hydrodynamics world......1st is the maneuverability at slow speed as well as high speed....with 2 rudders pointing down you do get increased rudder authority....now the question is, is this the overall point of adding the twin rudders behind the prop....2nd, for better speed effeciency, latest generation submarines of the US Navy has used a propulsor for the past 15 yrs and gets incredible effeciency out of them....for your idea...going to a circular tube style propulsor behind the prop would require you to make the propulsor style add on more conical thus giving a funnel look to it..making the water accelerate as it passes thru the tube..giving more top end...a propulsor puts incredible stress on the drive and will need reinforcing to keep it from parting with parts of the drive..
finally 3rd....your adding dissimilar metals to the drive....yeah..it's stainless..but your running an aluminum drive...extreme care is going to have to be taken to keep corrosion to a minimum...........your also going to have to inspect the drive and it's components more often for corrosion....
if it were me designing something like this....I'd extend the skeg aft some to allow for it to be attached to your device...then I'd make the twin fins out of aluminum and concentrate on rounding your edges more and making solid welds instead of spots....they will hold better....

just some observations on my part...it's a good idea but difficult to do....ever wonder why mercruiser hasn't done it??....too expensive and difficult to do..easily prone to dock damage....

Steve

 

[cpubud]

Re: super fin - long post

well I have been running it all season long and love it no problems.

 

[Fireman431]

Re: super fin - long post

well I have been running it all season long and love it no problems.

Then it's perfect.

 

[dan t.]

Re: super fin - long post

So the piece that you built seems to work well and stand up to normal use also, this is good.But , I think you may be fighting a different problem. From your pics it looks like your prop has a lot of rake, a raked prop gives bow rise. I beleve your boat uses the same hull as my 2452. From several years of expermenting I have found that a large blade area non raked prop works best on these hulls, they improve hole shot,hold better at low speed, and add steering controle at docking speeds. Low speed wander is a normal thing and I have learned to steer to avoid it,most people overcompensate and make it worse. good luck with your foil/rudder,hope it continues to work well,but consider trying a non raked prop

 

[JBF 1962]

Re: super fin - long post

It'd be interesting to see how in worked in a lake such as my boat lives, which is to say, more weeds than water. lol BTW, TABMAN, the Bennett guy on here, recommends 18 x 12 trim tabs on boats this size

 

[jayhanig]

Re: super fin - long post

well I have been running it all season long and love it no problems.

Since you've finalized your design, how about some updated pictures?

 

[cpubud]

Re: super fin - long post

Im running the first one I made. I have tried 2 others but none worked as well.

 

[Stachi]

Re: super fin - long post

fill us in on what ya did...curious minds need to know !

 

[Mark42]

Re: super fin - long post

well I have been running it all season long and love it no problems.

Its really great to hear that something you designed yourself has been working well and meeting or exceeding your expectations. Gives the rest of us incentive to go ahead and try fabricating the ideas we come up with.

Have you given thought to having them manufactured and selling them?

 

[cpubud]

Re: super fin - long post

they already are being sold under the name Super fin.

 

[jeepnsam]

Re: super fin - long post

Round Prop Guard claims the same thing
http://www.propguard.net

 

[jonesg]

Re: super fin - long post

The propguard might work better with reverse airfoiled stators to remove prop swirl.

 

[Fireman431]

Re: super fin - long post

My personal opinion that propguards should be a requirement here in Florida. We have so many idle zones that they blame on wildlife injuries, when in fact, it's because the property owners on the water have more pull with the lawmakers.

Welcome to Florida...where manatees and turtles have more rights than your child.

Good job on the inventions!