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How to Select the Correct Prop for Your Boat

Maybe the biggest improvement that can be gained in performance with your RC Boat is the selection of the correct prop!

First Step:

Ask questions of persons who are running the same class and boat you need to prop(and running well). Find out the pipe length and pipe that they are using. Ask if they are using stock or raised timing in their engine. If they use raised timing, you will need to lengthen the pipe a little. Set your boat with the same pipe and length that they are using. This will be a documented starting point that you know will work well. ALL of these questions also can be asked of the participants on the Listbot (you may have to do some sorting). Visual selection and comparison is by far the best. Choose your model carefully.

Second Step:

Find out which prop(s) the people running well are using on their boat. Ask the weight of the boat you are comparing against. If your boat is of a similar weight, their prop will be a good starting point.

OK lets define RUNNING WELL:

Does that person have a boat that is fast and will slow down and mill well before the start of the race. Does the boat ALWAYS come on and off the pipe easilly during racing? Are they winning races or finishing close to the front of the pack? This is RUNNING WELL.

Third Step:

Apply the steps #1 and #2 above and run your boat in several races to find out what is the "weak link" of your boat. I use the testing pond to do this, and if you have the time, the application of testing AND a few races is the best way to place yourself in a position to improve the performance from your "base point".

Fourth Step:

NOW you are ready to make your boat perform BETTER than the boats that you observed and used as your "baseline setup"! Look at the specifications on the baseline prop you are running (pitch diameter, lift characteristics, etc). Document these specs. You now should categorize the prop, as fitting into one of three classifications. (Non lifting – high efficiency prop, medium lifting – medium efficiency prop, straightaway prop.

The X series Octura props fit in the first category, the 1400 and 1600 series Octura props fit in the second category, and many straightaway props fit the third category. ABC props numbering system won't tell you the application or category. They do have a cross-reference chart that will show the equivalent prop with the Octura Series (also the pitch and diameter specifications). They also have the H series props and the S series props. These are primarily props that Andy Brown optimized from the standard ABC line of props. Many of the H Series props are excellent for the hydro classes.

Study – study – study, the props that Octura and ABC offer in terms of classification, pitch and diameter. Buy several props that seem to fit closely with the prop you have been running. NOTE: Over the years you will buy MANY props that won't work well, keep them and you will find a use for them sometime in the future! If you are running X Series props, you may be able to change to 1400 or 1600 series Octura Props or H series ABC Props. The deciding point will be how much weight you have on the strut. If there is very little weight, you probably will have to stay with the X Series Props. Outboards run VERY well with 1400 series props! (Takes a little setup change)

Fifth Step:

The quickest method to enhance your performance is to buy a Prop Duplicator, which will allow you to bend a prop, which is as good as many of the front runners, use. The Duplicator is made off of the best props that the front runners use! This device will allow you to duplicate as many props as you want. Another way is to purchase a prop from Competition Marine Designs (Andy Brown). Andy is as accomplished at modifying props as anyone in the hobby. He can provide a prop that will be much better than a stock prop.

Sixth Step:

Now that you are moving into an area, very few people explore, you need to document your findings. When you test, have several props selected to try. Use a radar gun and a stopwatch to time your turns and document each of the props. DON'T forget to make your selection one that will race well. If you have a prop duplicator as your base point, you can pound several shapes and even different props on the same Duplicator. I have found MANY times, that several props of different shape and blade area pounded (bent) on the Duplicator produce vastly different props. Here is an address for a little spread sheet application that I developed to keep track of my props. I have included the current listing of ALL my props for your information.(a zipped file for Microsoft Excel) http://nitro-engines-rc.com/propdoc2.zip

Until next time……. (Tech Notes Guest : Andy Brown on Straightaway Setup and Running)

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Other notes for EAP Registered Users:

Brian Callahan and I have developed a little auxiliary spreadsheet program to calculate the exhaust port area. This is an input item in the newest version of EAP for calculating the ideal tuned pipe. If you would like this little program you may download it from http://nitro-engines-rc.com/exhport.zip

Other images that may spur your imagination are located at http://nitro-engines-rc.com/liner.gif and http://nitro-engines-rc.com/nrpiston.gif and http://nitro-engines-rc.com/osmixture.gif



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