Bang-for-the-buck factor

[frank pedersen]

I have followed many threads in which opinions are traded back and forth about the relative merits of different boat designs. These exchanges often include evaluations of cost and performance. Since we are familiar with quantitative factors like D/L and SA/D, I propose a new index: the bang-for-the-buck factor, or B:B. For performance-oriented designs, it is computed by taking the square root of the cost and multiplying it by the PHRF rating (see www.phrfne.org for a list of ratings); then divide this quantity by 1000 to get an easy range of numbers. Of course, you get a "better" score with low values, so you can subtract that score from a constant, say 100, to have the psychologically satisfying idea that bigger is better. According to my casual estimate, a 210 has one of the best B:B scores (which is what Ray Hunt designed her for). Square root of cost is used because costs go up exponentially with size. For smaller boats, especially one-design classes, you can use Portsmouth ratings rather than PHRF scores. This leaves out aesthetic factors, but I believe they are largely in the eye of the beholder.

[johnw]

I should think the cost would go up with the volume. That would be the cube, not the square. Of course, longer boats tend to be leaner, maybe that's the thinking. It's an interesting concept in any case.

[StevenBauer]

22.25 for our Ostkust, or 77.75 if you subtract it from 100.

Anyone else?


Steven

[rbgarr]

16.5 for my Shields or 83.5, (including capital costs since purchased: used trailer and sails).

14.9 or 85.1 without.

A solid "B" grade, which sounds about right.

[johnw]

I know there is a way to convert between PHRF and Portsmouth Yardstick, but I can't remember it. I suspect dinghys would do very well. I spent about $2,000 on my Snipe, including sails, but a new one would cost about $8,000. Which number should I use?

[johnw]

Okay, I found the formula. If I bought a new Snipe, at about $8,000, it would come out to 19.86. Based on what I've actually spent on the boat, it comes to 9.93. It could be I'm right about the square root being the wrong factor, or it could be that dinghys are just a better value for speed (and catamarans a still better deal.) When I raced against the big boats a couple years ago at the Seattle wooden boat festival, I finished ahead of the 30-35 footers, and behind a well-sailed Thunderbird and a Blanchard Senior.

[rbgarr]

Use the 9.9 figure. By your report it seems like your boat certainly rates an "A-" in "speed-bang for the buck".

[johnw]

Use the 9.9 figure. By your report it seems like your boat certainly rates an "A-" in "speed-bang for the buck".

So for an A+, you buy a 6 meter cheap? Dunno, it seem like it should have more to do with the cost of building. I got my hull for $200, my mast for $500, my main for $800. The jib was cheap because it is on its last legs.

Claiming races could be the solution.

[johnw]

Another factor. My particular Snipe weighs 460 lb., compared to 381 lb. minimum weight for the class. It's not too competitive, but because it is a Snipe it has the rating.

So I'm going to build a new hull for the rig to go in. Cost of materials will run about $700. It won't be a Snipe hull, because I want a boat that a person with a bad back can pull up on the dinghy dock. I'm shooting for about 250 lb. I'm designing a hull that can carry more people -- 3 or 4 instead of 2. I'll then have a boat I can sail by myself, or with several friends. If all goes well, I'll have a boat about as fast as a competitive Snipe, but a number around 10.9 instead of 9.9. If I could afford to have someone else build the boat, it would have a higher number. So it seems to me that there are a lot of factors not directly related to speed that affect this formula.

[rbgarr]

Not a lot of factors: just cost, however you want to add it up, and a handicap rating.

It doesn't take aesthetics of any kind or pleasure in ownership into account. A simple "handicapped speed for the dollar rating" for what it's worth, which may be 'Not much' to many. The truly best bang for the buck will always be OFB (Other Folk's Boats).

That's enough pinhead dancing for me.

[Noah]

Yeah, this idea is totally whacked. It only values cheap boats. It will rate a cheap slow boat way higher than a fast more expensive boat.

Frank, is this another thread so you can say how great your "spirit of tradition" boat is?

[bamamick]

So, if I put down what I have invested in the Dragon, by this formula my b:b factor is 43.2. Exactly what is that supposed to mean? If someone owns a new Petticrows Dragon his b:b factor is far different (and worse, I assume, by this scale) since a new boat costs 2.5 times what I have in mine, yet in anything except light air the newer boat will have a distinct advantage.

I tried to do a thread like this on Dinghy Anarchy and was bombarded by people telling me that there is no effective way to measure the true value of a boat in comparison with other boats. All I was doing was trying to see how people felt about their boats and which classes were considered a good value for the money (by and large, beach cats seemed to be the consensus winner. Surprised me). Didn't go over too well.

Mickey Lake

[rbgarr]

The formula, such as it is, kind of mimics the thought process I went through when getting my boat. Minimum cost to purchase, moor, maintain while able to get under way and sailing quickly. Also fast enough in light wind to be really enjoyable.

I track my annual cost per hour of sailing and try to get it to $10-20 per hour. That's roughly 80 hours of sailing in a good summer: four hours during a week's afternoons and four on a weekend for ten weeks.

A close friend was bemoaning the fact that tough business conditions kept him away from his boat this summer. He has a J-32 and the six hours he sailed cost him @$750 per hour. He and his wife know that's insupportable.

[Daniel Noyes]

interesting
I think this rating will only be informative if applied to boats kept in tip top condition.
I bought a windsurfer and rig for $75 at a yard sale a few yrs back and had the boat sailing at 12-15 knts. regularly but it was sun rotted and the skin of the board kept breaking and needing patches, I trashed it 4 yrs later.
I suppose you could own a reall performance keel boat for very cheap and have a great rating but spend all your time fixing gear and leaks rather than sailing.
How would I work out the rating for the new Alpha dory I have for sale?
Dan
http://dansdories.googlepages.com

[frank pedersen]

I think I was pretty clear that the 210 seems to provide one of the better combinations of performance and affordable price. Trying to quantify performance and price (however imperfectly) also highlights the many other considerations that enter into choice of a boat, e.g. aesthetics, pride of ownership, historical value, comfort, etc.

[rbgarr]

I suppose you could own a reall performance keel boat for very cheap and have a great rating but spend all your time fixing gear and leaks rather than sailing.

Personally I'd include that time spent as a cost in the formula, perhaps a multiplied cost (!), if it was time spent fixing when you would otherwise be enjoying sailing the boat.

I wonder what formula might be similar for power boats? A "comfort index" of some kind?

[bamamick]

WHICH 210? What price? It matters.

As Noah said, all this does is reward cheap boats, which may or may not even be sailable at anywhere near their phrf or PY number. But I guess that it does give us something to talk about since the thread seems to be doing well.

Mickey Lake

[rbgarr]

Designer Ted Brewer developed a 'comfort index', basically a relationship between displacement and the area of waterplane, i.e., if the boat weighs alot and has a small but well distributed waterplane area, then it will resist movement from passing waves and therefore be more 'comfortable'.

Displacement (in lbs.)/[0.65 x (0.7 LWL+0.3 LOA) x (BD to the 1.33 power)]. BD is max beam at the deck. Not sure I have that exactly right. Could someone check the math and see if the number for the J-24 below seems correct? I don't know how to do the last part: raising to a power.

A lower number is jumpier.

Thus J/24 = 12.9, while Hans Christian 48 = 45.7

[frank pedersen]

rbgarr: My TI hand calculator has a "yx" button (actually the x is an exponent). To calculate BD to the 1.33 power, you enter the BD value, hit yx and then enter 1.33, and then the equals button. Re your comment on power boats, please try to work in a carbon footprint factor. At least in a sailboat, that is nil.

[johnw]

Of course, If you're racing in a one-design fleet the absolute speed of the boat is irrelevant. It's the speed relative to the people you are racing against.

[frank pedersen]

Yes, 12.9 is correct for a J/24, but it sure is a complex formula.

[rbgarr]

Frank,

Thanks. BTW, how does your boat work out by that formula?

[MiddleAgesMan]

The only PHRF rated boat I've owned AFAIK was the Alberg 30. Using what I paid for it almost 30 years ago ($16-17K) it rates 29.7 or 70.3... If the same boat sold for $10K today the rating would be much better.

[frank pedersen]

rbgarr: Well, stick with me for a moment. My boat is pretty jumpy at 11.4. Your value for the J/24 is 12.9, which I confirmed with displacement at 3300 lbs. A recent issue of Sailing World, which gives specs for lots of boats in connection with Harken advertising, lists the J/24 displacement at 3000 lbs. That would make the comfort index 11.8. A 210, which has a displacement of only 2300 lbs, has a comfort index of 12.5 (I thought it would be higher). Your Shields comes in at 25.9. None of these computations includes crew weight in the displacement value, and that would raise the numbers a little in proportion to how much crew weight contributes to total displacement. One other thought about waterplane area: a relatively high ratio of waterplane area to displacement contributes to a boat's ability to surf and plane, but, as you point out, it adds to jumpiness. Conclusion: you can't have everything in just one boat. I find that fascinating because it points out how every design is ultimately some sort of compromise.

[rbgarr]

Your boat must be light and strong. Nice.

[Tom Hunter]

Ted Brewer's comfort calculator was intended to be tounge in cheek, but humor often has a basis in truth, and this certainly does.

I'm not sure how well it works with smaller one design boats, I get the impression he was thinking of boats you that people would sail overnight, either racing or cruising. It is still fun to compare, even if it does not cover all possible boats very well.

[john welsford]

That formual is way too complex, makes far too many assumptions as to shape of hull so can only be valid for certain hull shapes and will only be an approximation. A better one is simply displacement over waterplane area, even that will produce a curve as the hull is depressed as the flare in the sides and ends increases the waterplane area.


JohnW

Designer Ted Brewer developed a 'comfort index', basically a relationship between displacement and the area of waterplane, i.e., if the boat weighs alot and has a small but well distributed waterplane area, then it will resist movement from passing waves and therefore be more 'comfortable'.

Displacement (in lbs.)/[0.65 x (0.7 LWL+0.3 LOA) x (BD to the 1.33 power)]. BD is max beam at the deck. Not sure I have that exactly right. Could someone check the math and see if the number for the J-24 below seems correct? I don't know how to do the last part: raising to a power.

A lower number is jumpier.

Thus J/24 = 12.9, while Hans Christian 48 = 45.7

[rbgarr]

I think we all know these formulae are approximations. We're just noodling around.

[CundysHarbor]

Since the cost of a boat is really only the down payment (consider annual maintenance) I question the value of the bang for the buck equation. I have owned and built a wide assortment of boats and really believe that the plastic kayak gives the most fun for dollar spent. BUT, I still build boats and enjoy the associated labor. There are more important things than cost!
Dave