adding keel to deep v

The biggest and most dangerous problem with adding a keel is heeling outboard when turning. It will react like a sailboat. However, at those speeds, the crew will fly off the boat.

 

Has anyone ever actually seen a real keel on a deep V planing hull?

 

No .

 

Okay, now we're done it. So, what constitutes a "deep V". If 18 degrees of transom deadrise is a deep V, then I've seen a keel on one, though it wasn't an external appendage, but in fact a real, honest to God keel. It had floors bolted to it, stringers laying parallel to it, yep a real keel. It even had a keelson on top of it, meaning apparently it had offspring too . . .

 

I guess many would use 18 degrees as the lower edge of deep keeldom. Still, I can't think of why one would be useful on an 18 degree 35 knot planing hull. On the other hand, we have seen some much more weird things on the water.

 

I was pointing out a construction detail, again, it wasn't an appendage, but a backbone.

 

Not a whisker less than 20 degrees at the transom. That was Renato Levi's definition and it's one that my personal dictionary adhere's strictly to.
Nothing pisses me off more than seeing marketing hype describing 15 degrees as a deep-vee....

 

Gt, if it is more fins you were referring too like you pictured then there are advantages on a planning hull. If it was jet driven then even more so as the increase in directional stability would be dramatic, minimal at rest though. If they are placed near the transom they can be built to ventilate the back of them and release some of their drag. Sucks is you have props behind them. This can allow you to have more effective area than a keel possibly with a greater T moment for the same drag.
The guys at Humphree in Sweden make such items and they work fantastically.

 

Sorry for the delay guys. See the link to the boat with skeg/keel thing. Although almost semi displacement or deep v dependant on opinions, these boats seem to have breathtaking handling throughout the model range, see the youtube clips..... I am gob smacked at their ability to sit on top of breaking waves, and our local harbour master has a large modelshown in video as southampton ABP, and it is truelly phenominal.

What im confused by is HOW they can sit ontop of breaking rollers, beam seas etc as in videos, and what the advantage of the skeg is, of you browse the web site through models and gallery you will se some have skeg, some dont, some have keel, some dont...... I am trying to way up the merits
either way

http://www.safehavenmarine.com/GENESIS%2037%20development%20page.htm

 

That is a fairly substantial skeg, and aside from protecting the propellor, substantially shifts the CLR towards the stern, which will mean harder to broach. The extra drag would irk some, but to drive over the front of breaking waves, you need all the help you can get. This is one of the areas where well designed power cats shine, they can be pushed hard downhill and not go tearing off course. Another reason they are beloved of rescue organisations.

 

Aw, I don't know Will. Maybe the buyer thinks he wants a deep V for the local lake and the seller tells him that the boat is a deep V but doesn't say it is 15 degrees. Everybody should be happy. The seller gets a sale and the buyer gets a better boat than the one he thought he wanted.

 

i love the reaction you can stir up by quoting a typical figure as a guideline on this forum. hours of fun! i was making a distinction, not asserting a hard and fast rule. also, "adheres" does not have an apostrophe. proofreading it seems is a lost art. as is irony.

Tim B.

 

i think so too

 

The referenced boat has a deadrise of about 22 degrees amidships and 15 degrees at transom.
Deep V?

js

 

That boat is a shaft drive with a partial recess for the propellor, presumably to get a shallower draft and better shaft angle. The affect of the skeg on stability is that of directional stability, and it is not a deep vee hull.