Propeller Test: VIPER v. REBEL - Moderated Discussion Areas

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Author Topic:   Propeller Test: VIPER v. REBEL

jimh posted 01-11-2008 01:09 AM ET (US)
Here is some data from propeller tests of the Bombardier VIPER and REBEL propellers. The test data is from a 30-foot boat. The data represents averages of two runs in opposite directions with each test propeller. All the data was collected on the same day, on the same boat, with the same engines.
The results show that there are relatively small differences in the speeds obtained, however there are significant differences in the fuel economy.
VIPER 19-inch
RPM MPH GPH MPG RANGE
500 2.3 0.36 6.3 427
1000 5.4 1.5 3.6 243
1500 7.4 3.1 2.4 163
2000 8.8 7.4 1.2 80
2500 9.8 12.3 0.8 54
3000 16.5 14.6 1.1 76
3500 22.8 17.6 1.3 88
4000 31.2 23.0 1.4 92
4500 37.3 26.9 1.4 94
5000 42.9 35.5 1.2 81
5500 47.8 41.4 1.2 78
5700 48.9 44.8 1.1 73
REBEL 19-inch
RPM MPH GPH MPG RANGE
500 2.2 0.4 6.0 404
1000 5.7 1.5 3.9 264
1500 7.9 3.0 2.6 179
2000 9.0 6.0 1.5 102
2500 14.7 12.2 1.2 81
3000 21.4 14.2 1.5 102
3500 29.0 17.2 1.7 114
4000 35.3 20.7 1.7 115
4500 41.0 24.4 1.7 113
5000 46.2 31.6 1.5 99
5400 48.7 37.8 1.3 87
Just to re-state, this data is from the same boat, the same engines, the same drivers, the same instrumentation, the same day--in short everything was the same except the propellers. I believe that from this data it is possible to make a reasonable inference that the choice of a propeller can have an effect of the fuel economy of a boat and motor combination, even though it may not have a huge effect on the speeds obtained.

Peter posted 01-11-2008 08:19 AM ET (US)
This data is consistent with my own observations of the fuel economy achieved by the Viper versus other propellers.
I suspect that some of the lower fuel efficiency is attributable to blade thickness. While I haven't measured the actual thickness, just by eye and touch the Viper seems to have a relatively thick blade as compared to other propellers I have run on my boat which produced better mid-range fuel economy.
Fuel economy gauges are relatively cheap these days and are very useful tool for finding a good efficient propeller for your boating application.
Sal DiMercurio posted 01-12-2008 12:21 AM ET (US)
Jim, I see a big difference at 3500 rpms in speed.
There's over 6 mph faster with the Rebel, plus over 25 miles farther on the same amount of fuel.
The Viper prop in my opinion stinks.
Never has been one of my favorites, on "any" of my boats.
Sal
Tom W Clark posted 01-12-2008 01:27 AM ET (US)
This test data highlights a few things, most importantly how important a well fit propeller is, but also how, for the vast majority of recreational boaters, top speed is of no importance apart from bragging rights because that is not how our boats are operated outside of top speed tests.
It is something of a shame we tend to dwell so much on top speed when discussing the performance of different propellers when it is the speed ranges we actually operate our boats in that matter most.
This is why, when I counsel fellow boats on propeller selection, I always encourage the collection of good speed and RPM data throughout the range of operation rather than just going out to see how fast the boat goes.
Peter posted 01-12-2008 08:47 AM ET (US)
Here are a couple of pictures of a Viper propeller.
i177.photobucket.com/albums/w231/Whaler-Fleet/Public/ViperPropeller-1. jpg
i177.photobucket.com/albums/w231/Whaler-Fleet/Public/Viper-2.jpg
The "swept-back" Viper has a teaspoon blade shape with a center line that is almost tangential to the hub. This propeller would be characterized as having a high skew.
Here is a thread showing a couple of pictures of the Rebel propeller.
continuouswave.com/ubb/Forum4/HTML/004368.html
Note the Rebel's blades are very rounded, almost soup spoon shaped in comparison. There is more blade surface area. The blade's center line almost comes straight out of the hub. This propeller would be characterized as having a low skew.

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