Hull speed?

[FF]

For those that like to noodle,

Years ago the AYRS came up with a simple method of figuring "hull" speed for a variety of boats.

The old formula was created by looking at fat boats of the time , and doesn't work well for skinny fast boats.

S = L/3b X SQ RT (L)

When run for some theoretical hulls it may be a bit fast , but seems to work.

I have found that boats are priced more by the pound than the overall LOA .

A 35 ft 3 story "wedding cake" will cost more to build than a 65 X 10 single deck fast boat .

With a D/L of about 50 to 100 she should be able co cruise at 12 K on 2 gal an hour or 14K on 3.

Top speed of about 18 would get the usual 1 mpg tho.

This formula is for hull speed , it does not take into account the added wetted surface of real skinny hulls that loose efficiency at lower speeds .

 

[Pete Meisinger]

You are absolutely correct in your theory that boats are generally priced by the pound.

Now lets hear from some boat owners on what they paid for their boats per pound. Be sure to mention the make, model and year of purchase. Include what you think it is worth right now if you care to.

My 36 foot Albin was purchased in around 2000 for about $1.20 a pound (I think around 16,000 pounds). It might be worth a tiny bit more now, say $1.25 a pound due to upgrades, especially the new engine which set me back $20,000 (about $26.00 per pound)

This equation DOES NOT hold very true for evaluating the Admiral. True, she has increased in "per pound" total cost but the investment has been significant.

pete

 

[O C Diver]

I recently purchased a used (1997) Trinka 10 at $12.50 per pound. The Epropulsion outboard was near $50 per pound. But the highest was my Shaw and Tenney oars at around $80 per pound. I'm not sure I like this game.

Ted

 

[Codger2]

I recently purchased a used (1997) Trinka 10 at $12.50 per pound. The Epropulsion outboard was near $50 per pound. But the highest was my Shaw and Tenney oars at around $80 per pound. I'm not sure I like this game.

You can buy a brand new Duffy with all the trimmings for about $15/lb.

 

[O C Diver]

You can buy a brand new Duffy with all the trimmings for about $15/lb.

Not right now. I just sold my charter boat. Down to 4 boats that I have to renew the registration on each year. Need to cull the herd further before acquiring another, unless my wife isn't watching.

Ted

 

[mvweebles]

You can buy a brand new Duffy with all the trimmings for about $15/lb.

I once met a girl at a pub named Duffys. Beer goggles had her at about $10/lb. Light of day had her at around $2.75. Ouch

 

[Lepke]

Using the old hull speed formula, my 83x17 boat comes out at 12+ knots. I run at 10 knots @ 1800 rpm that is max continuous for the 671 Detroits. I guess their hp at about 200. They're more hp than WWII DDs, but very early engines. At 10 knots I average 8.5+gph in the ocean fighting the usual NP swell. That seems to work with the old formula. POs use to run at 12 knots and a few 100 more rpm and about 15gph.
Because I've been running Detroits a long time, mine have some tweaks that give me better mileage.

 

[GFC]

Ten years ago we bought Beachcomber. Figuring out the "real" price is a bit difficult because we had a trade. Counting the value of the trade out of the purchase we ended up buying it for $210,000. The weight (not completely empty but darn near) of the boat was about 58,500.

That figures out to $3.5897 per pound.

That was after just over 3 months of negotiating and it happened to be in the midst of the slump in the economy and the boat was in the Detroit area where unemployment in that area was about 36% because car buyers were nonexistent and auto plants were idle. Boat buyers were also pretty scarce.

I think they got down to where I wanted to be just to get rid of me. I could write a thread on negotiating because there's a lot more that goes into it than just "Would ya sell her for.....?" I'm a professionally trained (FBI) hostage negotiator and the tricks and ideas I learned from that training has proven to be worth its weight in gold.

 

[GFC]

Hmmmm, seems somehow this thread got mixed up with the thread about what was the cost per pound of your boat.