Foil assisted multihull design

Interesting submission,...then interesting replies on this page
Foil assisted multihull design https://www.boatdesign.net/threads/foil-assisted-multihull-design.48462/page-6

Note: That is approx size of the weekender cat design I am considering. I am also consider a central nacelle of some sort that might help with the support of that hull-to-hull main foil.

 

Foil Shape, Positioning, Depth....
I just read the postings on page 8, Foil assisted multihull design https://www.boatdesign.net/threads/foil-assisted-multihull-design.48462/page-8

Then I looked back at a 2016 article I had read from ProBoat this morning,..entitled The Foil Fix,..
Professional BoatBuilder - 160 - Apr-May 2016 https://pbbackissues.advanced-pub.com/?issueID=160&pageID=42

They took an under-performing 40' sportfisher that during initial sea trials achieved 16 knots at cruise and barely 19 knots flat out. They added a relatively small fixed hydrofoil at the stern (only one) and on the next sea trial she accelerated to a cruising speed of 20 knots, and went to 25 knots full throttle.

There were other gains as well,...she now rides fast and level while consuming 20% less fuel, and the reduction in pitching pleased the owner almost as much as the improvements in speed and fuel consumption.

 

Technically any foils can work. The issue is down to 2 factors that need to be satisfied:-

1. The structural loads
2 Lift v drag

1. If the span of the foil is large then how do you make the foil stiff enough to support the loads?
You i) make it thicker or ii) use a higher strength material or iii) a combo of the two.

2 If you make the foil thicker, is increases the drag. Then the amount of lift you achieve is cancelled out by the increase in drag, thus a zero sum gain.
So selection of a suitable high lift to drag foil is required. These are in variably thin and curvaceous - not so easy for general fabrication.

So, simple answer is yes, but in reality takes a bit more than a simple symmetrical foil between the hulls.

 

Hi Groper,
Appears as thought your last post on this subject was Jan 2014?

Did you ever proceed forward with more foiling design/experiments??