Recent content by chartman

Approaching 40 years ago at Oklahoma State I assisted with a study of long chain polymer drag reduction. We stirred up different batches (different polymers and different concentrations) in a large tub with an oar so we did not break the chains. The fluid was then pumped by air pressure (again...

Prior to the exercise of gathering and analyzing the data I would have agreed with you. But the data showed an exponential fit over the entire displacement mode of operation, then a different exponential fit over the entire planing mode, See the charts below. Those are actual velocity data...

The planing curve going up to top speed immediately reminded me of an exponential curve I used a decade earlier to curve fit a hydraulic heat transfer situation on mobile construction equipment. To fit the boat data I used an ancient version of Sigma Plot and tried multiple kinds of equations...

Brunswick showed a planetary transmission on an outboard in a patent issued in late 2018. US Patent 10,161,482. US10161482B1 - Planetary transmission arrangements for marine propulsion devices - Google Patents https://patents.google.com/patent/US10161482B1/en?oq=us10161482 That...

Wonder is Volvo Penta shutting down Seven production in November 2020 after only 9 months was due to seeing this coming? Mercury's Verado V12 had to be at least partially inspired by Seven, especially with Seven having its origins from Rick Davis. The history of very large outboards is...

We recently published a report modeling recreational planing boat velocity during runs from zero to top speed as a function of the scientific constant e. The velocity curve was split into displacement and planing portions. Each portion was curve fit to the equation in the image below using...

3M riblet film might be on your list. Just google 3M riblet film boats and you can see their miniature ridges that look like a phonograph record (hope you are old enough to know what those are) have been used in aviation, racing yachts, and some other boating applications. Kiss-Cote...

Propeller Accident Statistics To Ike: Thanks for sharing some of your historical experiences surrounding the propeller guard issue. It was nice to see someone talking level headed about the issue. However, you made a major error in the statistics you provided. USCG logs boating accidents as a...

Prop Guard Test Protocol Tank Test w/ No Hull I would be especially interested in any comments you might have about the decision to test the various types of guards for protection levels provided from the front, side, or behind at various speeds, directions, and horizontal center lines...

Propeller Guard Test Protocol draft for comment ABYC (American Boat and Yacht Council) and CED Investigative Technologies were contracted by the U.S. Coast Guard to produce a test protocol for propeller guards. The draft of that test protocol was recently released and is available for public...

RingProp (and several of their predecessors) tried to commercialize that concept (ringed props) out of Australia and the U.K over about a 25 year period and the company failed in 2006. We provide a history of that development on our site, but you will probably find the following link more...

Several companies make ring guards for small outboards. These are generally NOT designed ducts to increase performance, they are just basic ring guards for small outboards. You might just buy one of them, or get some ideas from their designs and try to improve upon them for your specific...

There is an extensive library and some real ships at Mystic Seaport in CT. I have been there. It is a very nice place, plus the food was great at a conference I was at there several years ago. You can view some of their materials from the "Research the Collections" link on their site: Mystic...

I temporarily posted the full 1995 letter from ACT (less the Marine Corps test report I linked to separately earlier). Their letter discusses the drive and provides a propjet vs. prop speed comparison curve for a Zodiac F470 at various weight loads. It is about a 4 megabyte pdf file...