Tunnel sponson Pad Spray Rail

[Infoless Racer]

Can someone enlighten me of the benfits/effects of adding a spray rail on the tunnel sponson pad...

[Mark75H]

Spray rails add lift. Water flying up as spray is wasted energy that can be reclaimed by spray rails.

If you are interested in this kind of thing, you will be very happy with Jim Russell's Secrets of Tunnel Boat Design book.

[MN1]

Can someone enlighten me of the benfits/effects of adding a spray rail on the tunnel sponson pad...

It is not used on the pads very often. But there are some out there now.
I put some on a Formula 100 tunnel boat back in the 70's and it made the boat porpoise. I've also seen them used to help in how the boat corners, mostly when coming out of the corner.
Testing is the key!

Mark N

[JohnsonM50]

Most of the PWC's have them & most of the hydros seem to have them starboard-aft helps keep the corner from digging.

[Infoless Racer]

Thanks, dont think jim's program covers spray rails on sponson pads more on the tunnel walls but the comments make sense...

[Jimboat]

Thanks, dont think jim's program covers spray rails on sponson pads more on the tunnel walls but the comments make sense...
Update - TBDP/VBDP performance software Version 8 (http://www.aeromarineresearch.com/tbdp6_features.html) now includes spray rails, lifting strakes and trim tabs (http://www.aeromarineresearch.com/tbdp6/strakes_and_sprayrails.html). (plus a bunch of other new features (http://www.aeromarineresearch.com/tbdp6/tbdp_v80_new.html)!)

Spray Rails are normally on chine/sheer and can improve hydrodynamic lift at lower CLW's (lower velocities) and reduce induced (whisker) spray drag. Lifting Strakes are usually on planing surfaces (like sponson pads) designed to have a surface generally flat (zero deadrise) to water surface, and generate increased lift at improved efficiency under some conditions due to more efficient lifting surface area.

TBDP/VBDP accounts for above-chine spray rails, below-chine spray rails, lifting strakes and trim tabs....and a big list of other new features (http://www.aeromarineresearch.com/tbdp_updates.html).