FAQ: PROPELLERS

What’s the secret behind VENTRY propellers?

Our props are manufactured on-site, one-by-one, using state-of-the-art proprietary technology. We utilize the ideal number of blades (two) and the ideal composition (wood, Kevlar and fiberglass) for optimum efficiency, air volume, and safety with minimum noise.

Are VENTRY Propellers safe?

In our 21+ year history, we have never had a VENTRY Fan propeller fail. Delamination and prop failure of wooden props is an erroneous rumor that has surfaced over the years, believed to be perpetuated by those with no knowledge of aircraft technology, our production process, our materials, or our safety record.

VENTRY Fan blades are extremely safe. They are designed to be fail-safe, meaning that they will disintegrate in a controlled and limited manner when safety necessecitates, such as in the case of a catastrophic accident. For instance, one time a firefighter stuck a pike pole through the guard on his way out of a structure. The propeller turned into toothpicks with very little momentum. The department was able to simply replace the propeller and were back in business - with minimal expense, no engine damage, and no firefighter injuries. See our propeller page, near the botom, for a picture of that propeller.

Click here to visit
the Propeller page

Why do you use wooden propellers on your fans?

Our propellers are not solid wood but actually a composite of cedar (at the core), Kevlar, and fiberglass. Many people hold misperceptions about the wood component, thinking erroneously that metal props would be better than wood. In fact, the opposite is true. Thanks to the composition of our propellers, no blade in the industry is safer, more durable, or more efficient.

Here’s how John Neils once answered the question of “Why wood? Wouldn’t a metal propeller be better?”:

There are a multitude of both engineering and production reasons for using wood cores on our props. First, wood is light and the cellular matrix dampens vibrations much better than metal. Every time the gasoline engine generates a power stroke it is resisted by the mass of the prop. By keeping the prop mass low, we lower vibration which cuts down on fan walking. [VENTRY Fans are known for being extremely stable.]

Wood also enables us a fail-safe design; when an accident occurs, wood will splinter and turn into toothpicks which don’t have enough energy to force their way through a guard. Wood allows us to design the props so that in a strike situation they fail progressively from the tip instead of failing at the root with catastrophic consequences. In such a case, the engine crankshaft will not bend or fail so repair is easy. Wood is easily fabricated, giving us the flexibility to design and then fine-tune the pitch and airfoil to match the engine and desired airflow characteristics.

Metal does have one advantage over wood and that is durability. That is why we developed a process that pressure bonds Kevlar and fiberglass to the wood core. With this coating, our propellers enjoy the safety and unique characteristics of wood while meeting the durability of metal. Our fans’ performance is proof of the efficacy of the design.

Our props require a fair amount of hand labor but the effort is worth it. Every once in a while, someone accidentally tests their safety characteristics, and we get a telephone call thanking us for the fail-safe characteristics of the prop.

Hope this answers your question. ~ John Neils

Please see also our page entitled, “SAFETY PROPELLERS: The Secret to Safe, High Air Volumes.”