Lower Unit Shapes...

[Kris Flynn]

Has anyone here experimented with thinning down the lower units, for less drag, cutting the Skegs down and shaping the lower more like a 'Wing' as the real ones are (I think)?

Anything at you have done to try and improve performance ffrom your stock K&B lower?

Kris

 

[TimD]

Kris,

One thing worth checking is that the prop shaft is stright compared to the fin. I have heard of them being drilled / tapped crooked and that can rob a lot of performance.

Also, don't sacrifice strength by thinning the fin down too far! A sharp leading edge is also useful.

Cheers,

Tim.

 

[Ian Inverarity]

Kris,

Re: shaping like a wing, this is not necessarily a good idea for surface piercing appendages. This is a very good article on the subject:

http://rcboat.com/527_3.pdf

Ian.

 

[Jeff Torgalski]

If you can endure reading it and try to skim through the vocabulary, it's alot of good information. Great find, Ian!

 

[Ian Inverarity]

Jeff,

Oops, I am a mechanical engineer, I kind of forget sometimes that some of this stuff is a bit hard for many people to read! : Ignore the formulas, the useful stuff is in the text.

It is from the past tech papers section of rcboat.com

Ian.

 

[[email protected]]

Kris,

When I've broken off the lower skeg in the past I use thin but strong aluminum in the shape of an "L", works great.

 

[Jeff Torgalski]

That's awesome Ian, I am studying chemical engineering. I am in my 2nd year. Taking 1st semester physics right now, and I plan on taking fluid dynamics and the like next fall. I can make a little sense out of it,

Cool, bro,

Jeff

 

[Kris Flynn]

Tim, do you mean make sure it is square to the trailing edge of the fin/skeg?

It is actually for a 12 cell FE Tunnel project i am slowly wrking on...i have the lower so i am begginning to get it ready to use, even though i probably wnt have a boat ready to use (No one has seen a Villain in Aus yet have they???) suppose i will have to wait and see...

Anyway, so the strength of the lower isnt as important with this project as it would be with the vibration of a nitro OB...so i want to try and remove as much weight as possible, and also make it perform better and more efficient

Thanks Ian, if i get some time i will try to read it, looks interesting at a glance though!!

also what is the verdict with the leading egdes of the skegs/turn fins? Are they better straight, or curved (from a side on view)?

Kris

 

[TimD]

Kris,

Have a look at an article by Rod Geraghty on this page http://rcboat.com/news.shtml - about 2/3 way down the page.

As for Villains in Oz - I haven't seen one but that doesn't mean much - try contacting Paul Stirton as he's importing Grim's stuff. His email is [email protected]

As for side on view of L/E - I've always run them on an angle but straight - no curve. Never had the courage to try anything else on a perfectly good fin.

Tim.

 

[Kris Flynn]

Thanks Tim! i will have to check mine out...

I just saw a thread on RRR frum about the diffent shapes and i thought that it might be interesting to see if anyone had experimented with see if either worked better than the other on an OB...

Kris