Minimum hardware required: PI 133, (64 Mb for Win NT)
Operating system(s): Windows NT, 2000, XP
Most recent version date & number: January 2006 , 5.20
Number of installations:


What is Hydrocomp PropExpert ?
PropExpert is a software tool for the sizing and analysis of propellers for work boats and pleasure craft. It provides the tools needed for the proper selection of propulsion system components - engine, gear and propeller - and has been selected as the principal propeller sizing tool of many of the best known manufacturers and distributors of marine engines and propellers

  Capabilities and New features

PropExpert :

Analyze the selected propeller "on-the-hull"
In its simplest form, all propeller software can select diameter and pitch given only speed, power and RPM. This, of course, assumes that the speed is accurate and that the engine is capable of driving the hull to that speed.

PropExpert runs a two-stage calculation. First, it makes an optimum recommendation for the design speed, power and RPM. Then, it analyzes this propeller against its defined thrust requirements (its predicted drag curve) and modifies the design speed as required until a proper match is found. This analysis determines not only achievable top speed, but thrust, power, efficiency, cavitation and even fuel consumption.

Remember, a propeller selection is not just running a few numbers through a formula. It is finding the best propeller that meets the needs of a vessel, and the only way to know this is to explicitly evaluate how the propeller will actually perform on the vessel.

Solve for the best gear ratio
Sometimes we have the opportunity to help determine the best gear ratio, as well as the best propeller. There are different ways that this can be performed, but typical methods do not always point to the most efficient ratio. Based on our work for the large motor yacht industry, we have developed and incorporated into PropExpert unique algorithms to find this most-efficient gear ratio [see Professional Boatbuilder Dec/Jan 1997].

Evaluate cavitation and blade strength
It is fairly simple to determine the amount of cavitation on a propeller, and whether there is adequate blade area to handle it. As more-and-more of our applications are for highly loaded propellers, however, it is altogether something different to predict the effect of excessive cavitation and also whether the blade material can handle high thrust loading.

PropExpert can evaluate the amount of cavitation as described above, but it can also determine if the propeller is likely to develop "thrust breakdown" due to excessive cavitation. It contains formula to calculate the reduction in thrust and power accordingly. In other words, with PropExpert you can actually see the "overspin" typically found with fully cavitating propellers. You can also check if standard blade material is adequate for the application, or if you need something higher strength, such as nickel-aluminum bronze.

Provide for different propeller styles (e.g., Gawn)
In 1975, a Dutch research institute produced the first numerical formula for marine propellers. These formula formed the basis for virtually all propeller software. Th e propeller style (called the B-series) was typically used on ocean-going cargo ships, but it also saw use on tugs, trawlers and other vessel types. Also known as the Troost style, it is a well-used, efficient design.

Many programs base their calculations for all propellers on these B-series formula. Unfortunately, not all propellers are of the B-series type. In fact, for work boats and pleasure craft, the vast majority of propellers are not B-series. Why? B-series propellers are prone to early cavitation and thrust breakdown. To handle growing levels of cavitation and thrust loading over the years, alternative designs, such as the Gawn (or ogival) propeller, are now much more popular. With its flat face, the ogival propeller is easier to manufacture and repair.

What this has to do with propeller software is simply that you get wrong answers trying to size a Gawn propeller with a B-series formula. The difference in recommended pitch, for example, can be greater than 5% - a huge difference if this is 5% overpitched and the engine is now overloaded.

Allow you to consider alternatives, such as 5 blades or cupping
Contemporary solutions to the excessive cavitation we see with highly-loaded applications include higher blade area propellers (like that found with the newer 5-bladed propellers) and cupping. It is not widely known that these 5-bladed propellers require different design criteria, such as a lower tip speed limit to account for the greater water restriction between the blades. Also, it was not possible until recently to determine the effect of cup on thrust and power performance.

Both of these features need to be explicitly evaluated. PropExpert employs proper criteria for these more contemporary options, and is the only commercial product that considers the effect of cup. (Not only does HydroComp create the software, but we also develop the technology. We did the new development of the numerical cupped propeller performance model, presented to the 1997 Propeller Symposium of the Society of Naval Architects and Marine Engineers.)

Optionally use sea trial data to predict speed
As we noted above, getting the proper design speed is critical to the proper selection of the propeller parameters and gear ratio. Reliably predicting speed is therefore very important. When you have very little data about the vessel, it is difficult to get a confident result.

While PropExpert allows you to use an "average hull formula" to predict speed - which has proven quite good - an even better way is to "correct" this average speed prediction based on results of a sea trial. When doing a repowering analysis, for example, we often know that the boat was making a certain speed at a given RPM. We know its engine, gear and propeller. PropExpert can take this data, "back-engineer" its actual thrust-making and power-absorbing performance, and use this thrust and power to anchor the speed prediction to this know real-world performance.

For a boat with a poorly-operating propeller, it is this feature, as much as any, which insures that the proper propeller correction can be determined the first time. With PropExpert, those days of trying two or three propellers before you got it right are gone.

Incorporate engine power curves into the calculation
Propellers for towing vessels have been traditionally sized with a bollard calculation - where the speed is zero and the RPM is the engine's rated value. Then the thrust calculated at this condition is represented as the "bollard pull". While this is a simple calculation to compare vessels such as tugs, it is a completely fictional scenario. Water speed into the propeller is never zero (there is some advance velocity), but more importantly, an engine does not always have the power to run the engine up to full RPM. This is particularly true when a propeller has been sized for some intermediate compromise speed and the propeller is actually somewhat overpitched for the bollard condition.

PropExpert utilizes an appropriate engine power curve for its towing calculations. You can even enter specific values for any engine, as you might do with the new electronic control engines. You can see cases of engine overload as PropExpert finds the equilibrium RPM where the propeller needs what the engine is actually capable of delivering.

  Why Do You Need PropExpert ?

Who should use PropExpert ?

While appropriate for anyone needing sizing capabilities, PropExpert is expecially designed to suit the requirements and constraints of propulsion equipment vendors. Boat builders and yacht designers, too, will find PropExpert a valuable addition to their suite of tools

Which types of vessels can PropExpert evaluate ?

 The general categories of work boats and pleasure craft fit the scope of PropExpert. This would typically include motor and sailing yachts, tugs, trawlers, patrol craft and sport fishing boats. Only a few data items are needed to adequately describe the vessel, PropExpert's various calculations, include max speed, equilibrium towing or free-running analysis of the selected system.

What types of propellers can I use with PropExpert ?

PropExpert can determine optimum diameter, pitch, blade area and RPM for virtually all commercially available inboard propeller of 2 to 5 blades, from about 450 mm (18") diameter up to about 2 meters (80"). Both flat-faced (Gawn) and foil-section (B series) propellers are supported, as are ducted propellers (Kaplan).

Can I use PropExpert to estimate vessel speed ?  

PropExpert offers three techniques to estimate the speed of a vessel. The most accurate method is to base the prediction on a prior trial of the same vessel. The trial of a similar vessel can also be used. When suitable trial data is not available, you can use PropExpert's native speed estimation formula.

  How Does PropExpert Work ?

What makes PropExpert different ? 

PropExpert shares the reliability and reputation of HydroComp's NavCad™ performance prediction package. Exhaustively tested in the office and in the field, PropExpert offers the most up-to-date techniques presented in an easy-to-use, yet powerful, package. Special features have been implemented to support the needs of propulsion equipment salespeople. Minimal hull data requirements, automatic preparation of hydrodynamic properties, clear and concise data entry, and extensive database capabilities make rapid sizing and review very easy.

What database capabilities are found in PropExpert ?  

All data storage uses integrated databases - there are no disk files to open or save. PropExpert includes databases for jobs, vessel trials, default settings, propellers and engines. (These files can also be read by most popular database programs.) PropExpert also links to the World Marine Engine DataBase and HydroComp Stock Propeller DataBase products. These add-on files can be ordered with PropExpert as options.

What kind of support is available ?  

HydroComp PropExpert includes both on-line and printed User's Guides and Help systems, which can generally answer most questions. In addition, 90 days free maintenance and telephone/fax/e-mail support are included with the purchase. The annual maintenance and support subscription offered by HydroComp and Design Systems & Technologies will insure that you will continue to receive all updates and in-depth technical support. On-site or seminar training, as well as special contract consulting services, are available.

What do I need to run PropExpert ?

PropExpert is a Windows application. Depending on your current system configuration and installation options, PropExpert may require a pentium processor, 16 Mb ram and up to 15 MB hard disk space.


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