Sunfast 35 and light Ballast/Displacement Ratio

Switchtack

Switchtack

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I'm looking at a 2004 Sunfast 35 online and the specs show the B/D ratio to be around 26. That seems very low. I've noticed that many Beneteau's and Jeanneau's specs are all down in the lower range. Can anyone shed some light on the reason for designing them that way? Does having an iron keel have anything to do with that?

The D/L is around 167 and the SA/D is 22.2, which shows it has some horsepower. You would think you would want to have a little ballast to keep the boat on it's feet. These figures come from Sailboat Data.

Does anyone have any thoughts about the Sunfast 35? What little there is on the web keeps calling it a cruiser/racer. Sure, it has a nice interior, but these numbers seem to be much more racer/cruiser. Cheers.
 
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psycho tiller

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Switchtack said:
I'm looking at a 2004 Sunfast 35 online and the specs show the B/D ratio to be around 26. That seems very low. I've noticed that many Beneteau's and Jeanneau's specs are all down in the lower range. Can anyone shed some light on the reason for designing them that way? Does having an iron keel have anything to do with that?

The D/L is around 167 and the SA/D is 22.2, which shows it has some horsepower. You would think you would want to have a little ballast to keep the boat on it's feet. These figures come from Sailboat Data.

Does anyone have any thoughts about the Sunfast 35? What little there is on the web keeps calling it a cruiser/racer. Sure, it has a nice interior, but these numbers seem to be much more racer/cruiser. Cheers.
Click to expand...

I don't know that boat model specifically but many of the Sunfast models during that time period were the same exact hull and interior as the cruiser model just with a bigger keel and larger rig/sail plan bolted on. Without getting rid of the extra weight and hull shape of a dedicated cruiser boat there's only so much you can do with bolt on tweaks. These sunfast models have almost nothing in common with the newer Sunfast models that are specifically built for performance and racing from the ground up.

There are certainly some limitations to this type of quick and dirty tweaking of a boat including some specs that may not make a lot of sense but still in the right conditions and for certain uses they're decent, fun boats. Maybe not the first choice for heavy weather, offshore sailing but for many typical buyers it's still a good choice that serves their needs well.
 
Crash

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1669705836718.png


Like Sloop said. Relatively deep bulb, and good sized bulb too, means you don't need the same amount of ballast to get the same righting moment. Also fairly beamy stern meant some added form stability. But your right re performance. A J/109 rated 75 (OD config) and the Sun Fast 35 rates 108. So slower than the numbers might suggest. Of course the J boat weighs 1300 lbs less, yet carries 600 lbs more ballast.
 
12 metre

12 metre

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Not quite as powered up as the OP has been led to believe.

SA/D is one number on Sailboatdata that is sometimes incorrect - at least the number given near the top of the chart. I ran the rig and displacement numbers and came up with 17.6, which is on the moderate side - particularly for a frac rig - albeit this one is close to MH.

If you look further down the chart (under Rig and Sail Particulars) you will see the correct number - 17.6

B/D is on the low side at 26% but she is quite beamy with beam carried well aft - so what she lacks in ballast stability is likely made up by form stability. Which in my view is fine for coastal sailing.

She also has a good 7 ft of draft which may also help. As SJB alludes to - location of ballast is as important as amount of ballast.

Lombard is a good designer - so I would trust him with regards to designing a boat fit for it's intended purpose. Providing the marketing gurus haven't exaggerated things.
 
Lynch

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The 32 and 37 from the same time make good cruiser racers and are pretty sturdy as well
They’re not deep water cruisers but are good for club racing and coastal cruising.
 
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psycho tiller

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When comparing the B/D of 26 for this SF 35 to other performance boats with bulb keels and of relatively similar size, beam and draft it's still a very light B/D ratio.

Doesn't make it a bad boat, just probably have to reef a little earlier. Probably a much nicer and spacious interior than most other comparable performance boats. Certainly numbers on paper don't explain everything but for comparison of B/D ratios (only because I collected this data a few years ago while drooling over new boats):

The SF 35 in the OP is 26
-Tartan 101 is 40
-J/109 is 36
-J97 is 34
-J/99 is 40
-Sunfast 3200 is 38
-Sunfast 3600 is 46
-Ben 10R is 38
-A35 is 45
-JPK 1080 is 45
-J105 is 44
-Sydney 36 is 43

Maybe the light b/d is not too different than many production cruisers which I think is more of what the 2004 sunfasts are anyway. I'm not familiar with those numbers though so maybe I'm wrong.

Years ago I owned a 2004 sunfast 32i which is probably very similar to the one the OP mentions. I really enjoyed the boat and had tons of great days on it. However, to call it a "Sunfast" and market it as a performance boat, although not entirely wrong, is maybe slightly misleading. Of course every boat has limitations and for the right purpose and buyer the SF35 would be a fantastic boat. You don't buy a Ferrari to go off road 4 wheeling or the grocery store and you don't buy a Hummer to go on a race track. You buy the Ferrari for the babes and you buy the hummer because you lack size in other areas! Wait, what were we talking about again?? :)
 
Jambalaya

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There was a trend in IRC for a while to go for fin keels ... I remember them on some Archambault 35s and the original Sunfast 3200. It is possible this design has no bulb just an iron fin ?
 
Jambalaya

Jambalaya

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Switchtack said:
I'm looking at a 2004 Sunfast 35 online and the specs show the B/D ratio to be around 26. That seems very low. I've noticed that many Beneteau's and Jeanneau's specs are all down in the lower range. Can anyone shed some light on the reason for designing them that way? Does having an iron keel have anything to do with that?

The D/L is around 167 and the SA/D is 22.2, which shows it has some horsepower. You would think you would want to have a little ballast to keep the boat on it's feet. These figures come from Sailboat Data.

Does anyone have any thoughts about the Sunfast 35? What little there is on the web keeps calling it a cruiser/racer. Sure, it has a nice interior, but these numbers seem to be much more racer/cruiser. Cheers.
Click to expand...
Is that the correct model name and do you know which rating rule the design was aimed at ?
 
Zonker

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Ballast to Displacement ratio is a pretty dumb number (well except for maybe identifying design outliers that a very outside what is "normal").

As others have already pointed out the stability of a boat is governed by righting moment. Which is a combination of form stability and the VCG of the keel. The amount of ballast is pretty unimportant. NAs are concerned with "how much right moment does it have" and what is the AVS. How we got there is usually decided in the very earliest days i.e. wide beam/bulb keel with low B/D or wineglass hull with encapsulated keel and 45% B/D.
 
The Dark Knight

The Dark Knight

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Crash said:
View attachment 556524

Like Sloop said. Relatively deep bulb, and good sized bulb too, means you don't need the same amount of ballast to get the same righting moment. Also fairly beamy stern meant some added form stability. But your right re performance. A J/109 rated 75 (OD config) and the Sun Fast 35 rates 108. So slower than the numbers might suggest. Of course the J boat weighs 1300 lbs less, yet carries 600 lbs more ballast.
Click to expand...
When I was racer shopping, I woulkd refer to the ORC rating certificates for the actual boat or a sister ship.

Registration is free https://www.orc.org/

Here is a SF35 club rating cert.

 
Somebody Else

Somebody Else

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You draw a boat with a given displacement and then you throw in a condos-worth of furniture and what you got left is how much ballast you can bolt on.

These harbor queens that substitute a working cockpit for headroom in the aft cabin just are not meant to be pressed into service as weekend warriors. Dragging that fat ass around in light air is not going to be anyone's idea of a fun time. And in heavier breezes, you'll need a 2 full offensive front lines crammed together on the rail to keep from sailing sideways. At least you have the facilities to feed them moderately well...
 
The Dark Knight

The Dark Knight

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TUBBY said:
At least you have the facilities to feed them moderately well...
And you say that like it's a bad thing!
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The fridge on my SO40 was permamently on over summer and was always stocked with beer. On windy days the downwind legs were beer legs, light days, all legs were beer legs.

Kept the crew happy.
 
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