Marine Technology Group

Ventilation Tubes 

 
VENTILATION TUBES

Ventilation tubes allow the surface piercing propeller to draw air into the back of the propeller.  These are used in many cases to assist vessels through the pre-planing range.

The purpose of the ventilation tube is to allow the ingestion of air onto the backside of the propeller.   Since Surface Piercing Propellers are designed to operate with approximately half of the propeller out of the water, some applications require premature venting of the propeller to allow the vessel to reach a planing state. 

H/RI offers the following information so that builders an owners can fabricate their own ventilation tubes.  Due to the wide variations of transom configurations, H/RI offers to make ventilation tubes for customers on a custom basis only.  Detailed transom layout information is needed in order to insure a successful installation.

The low pressure developed by the back of the propeller blade will be sufficient to cause the propeller to ventilate for most applications equipped with a ventilation tube.  The ventilation tubes should extend above the free surface of the water so as not to ingest large amounts of water during normal maneuvering ahead as well as astern.

If a ventilation tube has to be extended from the transom in any direction, care must be taken to avoid loops where water can become trapped.

GENERAL VENTILATION TUBE INFORMATION

The ventilation tube should terminate no more than 1 in. (25.4 mm) in front of the propeller.

The Ventilation tube can be fabricated out of rigid or flexible material with a diameter of approximately 2 in. (51mm) for the ASD 8 and ASD 10 and 3 in. (76. mm) for the ASD 12 and ASD 14.

NOTE 1.  Insure that the flexible section is adequate to handle both angular movements from trim as well as the angular and axial movement from steering.

NOTE 2.  Insure that the flexible section is adequate to handle the angular movement from trim.