# How do I calculate prop slip for my six pack test?



## suns22 (Mar 10, 2002)

Hi,
My name is Richard Montgomery and I just recently purchased Get Your Captains License second edition. I love the book and have only really had one problem. I may be blind, but I can not find any information on how to calculate the apparent prop slip of a vessel. I have noticed that this question is often asked in the navigation problems section and since I will be taking my test in one week, I was hoping that someone could point me in the right direction. I would be extremely grateful for any help. Thanks!!

Sincerely,
Richard Montgomery
[email protected]


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## TSOJOURNER (Dec 16, 1999)

Richard...use your search engine (Google, for instance) and enter Propeller slippage. There''s a number of sites that deal with this but the board won''t permit me giving you the addresses. Cheers.


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## TSOJOURNER (Dec 16, 1999)

Richard,
This question concerns the relarionship of the prop''s pitch and its actual travel through the water at any given speed. You need to know this to accurately calculate the hull speed of a vessel at a given engine and therefore the prop''s RPM.

Slip in % = 100 X ( Prop pitch in feet X prop rpm - vessel speed in knots devided by prop pitch in feet X prop rmp )
This is one formula to estimate prop slip, I''m sure there are others. 
Good luck. JEF


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## Denr (Feb 7, 2001)

I took the examination two weeks ago, hear me now believe me later, this is not a part of the test. Spend your time studying the rules (90% grade is required for this portion of the test) and Colregs for an international endorsement, rather than spinning your prop trying to understand this useless subject. Naturally, I passed all six modules, which was a total of 160 questions. It is only 120 questions if you just test for the OUPV license. You should probably consider taking the sailing test as well as the auxiliary towing modules to get these endorsements on your license.


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## TSOJOURNER (Dec 16, 1999)

denr,
I plan to gor for my uopv liscence and wonder if i could pass by using a book from the bookstore alone or is it worth the 600-900 bucks to take a course from some captian. I hate to spend money I don''t have if a little reading is all i need to do,?


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## Denr (Feb 7, 2001)

You can try it but I personally don''t think it’s possible. I bought one of the self-study courses and studied for a year. I then paid the money, attended a class, and learned more in 5 days than I did in the year of self-study. You''re probably much brighter than I am so you may feel that it is not necessary. I''m certain I would not have passed. I now hold a USCG 50-ton Masters License. For the OUPV license, your test will consist of 30 rules questions, 20 charting and plotting questions, 30 navigation questions and 60 deck general questions. The test was NOT a cake walk and as stated in my previous post, a minimum score of 90% is require to pass on the rules portion of the test. 

The application process to the Coast Guard is quite involved; you''ll need to get the physical, drug test, fingerprints, 3 character references, documentation of sea service and probably other things I''ve forgotten! Start this process as soon as possible if you''ve not done so already. Good luck, you''ll need it!


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## TSOJOURNER (Dec 16, 1999)

Ahoy mateys! This post goes out to all! I''m interested in getting a six pack license also! I would appreciate any info about this process. Denr, I like to pick your brain also, you seem to know what your talking about in other posts. And since you took test a few weeks ago, I''d think you could help me out. As a kid, I sailed with my Dad alot on the Jersy shore. I plan to purchmy own boat next winter. With that said...I probally know just enought to be dangerous! I have heard some many different things about the six pack license to the piont that they don''t do it any more. I will say I am a newbie, But we all have to start somewhere, and you all are all I got! To all who want to put their 2 cents in....I Thank You,Taylor...Blue skys and High [email protected]


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## tsmith409 (Feb 28, 2002)

RICHARD;
I AM AMAZED THAT YOU COULD HANDLE THIS BEING THAT YOU ARE BLIND
TONY


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## klem (Oct 16, 2009)

Back when I took the test, I do not believe that prop slip was a part of it. The formula given by JEFryar is the easiest way to get it. You can basically think of it as a measure of how far you should have gone(determined by the pitch and the rpm) and how far you went(determined by boat speed) expressed as a percent.

For those of you debating between studying on your own and taking a course, unless you are a really good book learner on a budget, seriously consider taking a course. You will end up spending less time in the end and it is a really good way to meet other people interested in doing what you want to do. Check into the specific school that you are thinking of beforehand because there are stories of really bad teaching but also some of really good teaching. I was not going to take the course but got talked into it by a friend and feel now that it was definitely the right thing to do.

Out of curiosity, those of you looking at license, what are you planning to do with the license? Are you actually going to put it to use or just have it and consider it a good educational experience?


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## Boasun (Feb 10, 2007)

As an instructor of OUPV/100/200 ton Mate/Master. I only explain prop slippage and don't go into the math for it.
The MAIN thing to study is Rules of the Road and ColRegs. Nav Plotting for the 200 ton. Both require 90% in order to pass. OUPV & 100 ton Nav Plot is only 70%.
Nav General is 70% for passing.
Deck General/Safety is 70 Questions and needs only 70% to pass. This is where you would find the prop slip question if they had one in the exam.
So that are the four exams you would be taking for you license...oops excuse me... your Merchant Marine Credentials.
Also note: The R of R / ColRegs have gone from 30 to 50 questions per exam and still 90% to pass...
So have fun studying.

Please notice that I home studied for my first, second, third and fourth license. Which were 100 Master, third Mate unlimited, Second Mate unlimited and 1600 ton Master. The last three are all Ocean endorsed. Then you have the STCW, GMDSS (radio license), and Able Body Seaman. Plus Radar on all of that is necessary fot the upper level licenses. And this with an ex who was as supportive as a lump of clay while I studied.


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## Waltthesalt (Sep 22, 2009)

You can learn more than you ever wanted to know about prop slip calculations from David Gerrs Propeller Handbook. Basically to do it empiracally by running a measured distance at a fixed rpm to get a good accurate speed. Then you calculate the difference betwnn the actual speed and the speed you would have if there were no slip and devide that difference by the theoreticla slip free speed.. The fromula is aparent slip = (Pitch in inches/12 times RPM) - (Actual knots times 101.3) All divided by (ptich/12 times RPM)


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## Sailblu (Sep 30, 2011)

*OUPV Exam*

I have looked everywhere for the answer to this question: are the Deck General questions the same for both the 6 Pax and the 100 Ton exams? I know there are less questions in the 6 Pax. It would be great if you knew the answer to this question because I would then have more time to concentrate on the relevant subjects.

I would greatly appreciate a reply.
Thank you,

Tyler


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## tempest (Feb 12, 2007)

Hi Tyler,

This thread is 9 years old, looks like it was revived again in 2009. However, I think the best advice here regarding this came on post # 4.

I'll try to answer, The OUPV is good for up to 100 tons. Depending on the type of waters you have documented your sea time on you can obtain an " Inland" or a "Near Coastal" License. Near Coastal requires appropriate time served beyond the Boundary line, which is not necessarily the same as Colregs line.

The Deck General for the OUPV is 60 questions and for a Masters Lic. it's 70.
You need a 70% passing grade in either.

I honestly don't remember, what the material difference in the questions were other than the number. My guess is that they might add some CFR questions regarding " inspected" vessels.

IF you go to the USCG site Deck Exam Guide - USCG National Maritime Center
It lays it all out for you.

All the subjects are relevant. However you really do need to Nail the rules of the road..that's where I've seen people fail the most. You need a 90% on the rules 30 questions. Which means you can't get more than 3 wrong.

The approved courses are good in that they will help focus you on what you need to know.
In other words, (for good or bad) they'll teach to the test. They will also help you with the paperwork.


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## jrd22 (Nov 14, 2000)

Good review Tempest. I'll just add that you can study on your own and pass the test (I did), but it's MUCH (four months of intense study for me) less time to take a class and you will probably retain more useful knowledge that way too.


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## Sailblu (Sep 30, 2011)

*Oupv*

Tempest,

Thank you very much--the link was very helpfull. I took the Deck General exam today and it was fairly easy (92%) since I had studied for the 100 ton exam for the past month. I was really worried because I had not nailed all the formulas and the math but ends up there was nothing like that in the 6 Pax exam. I studied using this website: Boater's Tests by BoatFix.com


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## tempest (Feb 12, 2007)

Tyler, Congrats! 

Nice link too..!


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