About: who writes this, and where the numbers come from
By Itzhak Fuhrman·Built and maintains Knotworth's cost model·Updated 24 August 2026
Most of what a used sailboat will cost you is not in the asking price. It is in the rigging that is nineteen years old, the sails described as "serviceable", the osmosis nobody mentioned, and the survey day you have to pay for before you learn any of it. Knotworth exists to put numbers on that gap before you book flights.
I know that gap because I spent years on the wrong side of it, reading listings and trying to work out what any of them would really cost me.
That only works if you can check the numbers. So this page says who wrote them, what they are built from, and what this site is not qualified to tell you.
Who is behind Knotworth?
Knotworth is built and operated by Itzhak Fuhrman, an engineer who works in data analysis and has spent years trying to answer one question for himself: which sailboat is the right one to buy. This site is the research that question generated, and the product is the tool he wanted and could not find.
That is the honest origin and it explains everything else about how this works.
The problem I kept running into. Every listing tells you the asking price. None of them tells you what the boat will actually cost once the rigging is replaced, the sails are renewed and the survey finds what surveys find. The information exists, scattered across yard rate cards, owners' associations, forum threads and forty years of magazine reviews, and none of it is assembled in one place for the person actually deciding.
So I assembled it. First for myself, in spreadsheets, over a long time. Then properly.
Why an engineer builds this particular product. The costing engine is deterministic on purpose. Given the same boat and the same assumptions it returns the same numbers, and you can see which rule produced each one.
That is a design choice with a real cost, because it means the model cannot be clever. It is also the only version of this product worth trusting with a five-figure decision, and it is the instinct you get from engineering rather than from marketing.
The same instinct runs through the guides. Every figure is a range with its assumption stated, every source is a live link rather than a summary, and the design ratios are computed from published dimensions rather than copied from another site, so you can check the arithmetic yourself. Where two sources disagree, the page shows the spread instead of picking a comfortable middle.
What I am not. Not a marine surveyor, not a broker, not a yard. I am the buyer, and this is a buyer-side tool built by someone who has done the reading.
That distinction matters more than it might sound. It is why the site never tells you a boat is sound, only what it would cost if the listing is telling the truth and what to ask to find out whether it is.
Where genuine marine expertise is required, the correct move is to hire it, and the guides say so. A survey is the obvious case. Knotworth's job is to tell you which boat deserves one.
What are the numbers built from?
Three kinds of source, in order of weight: published rate cards from boatyards and surveyors, current price lists from riggers, sailmakers and engine dealers, and dated reports from owners on sailing forums. Where those disagree, the guide shows the spread instead of picking a comfortable middle.
Published rate cards are the strongest evidence available in this market, because a yard that prints "haul-out to 35 feet, $13.50 per foot, $375 minimum" is committing to it. Forum reports are weaker, but they capture what people were really billed, which rate cards sometimes do not.
Both get cited by name and date in the guides, so you can see how old a figure is and whether it came from your coast. A 2023 California yard rate is useful context and a poor prediction of what a Maine yard will charge you in 2026, and the page should let you tell the difference.
What you will not find here is a number with no provenance. If the honest answer is that the range is too wide to be useful without a quote, the page says that and tells you what to ask for instead. The methodology page covers how estimates are assembled inside a report.
The rules every figure follows
These are the same rules the product runs on, not a separate editorial policy. They are the reason the guides read the way they do.
- Ranges, not point estimates. Every figure is a band with the assumption that produced it. A number precise to the dollar on a boat nobody has inspected is a guess wearing a suit.
- Silence is not a clean bill of health. A listing that does not mention the rigging age has told you nothing about the rigging. That gap becomes a question for the seller, never a quiet assumption that the work was done.
- A real quote beats a model, always. Paste the rigger's actual number into a report and it overrides the estimate. The same applies to these guides: if your yard quotes something different, your yard is right.
- Sources are linked, not summarised. Every rate card and price list referenced in a guide is a live link, so you can check whether it still says what we say it says.
- No money from the sell side. No affiliate links, no broker referral fees, no sponsored placements. Buyers pay once per boat, and that is the entire business model.
What Knotworth is not
It is not a marine survey, not a valuation or appraisal, and not tax, legal or financial advice. It cannot see inside a hull, smell a bilge or start an engine. It reads what a listing says, prices the work that listing implies, and tells you what to ask before you spend real money.
This matters most on the expensive decisions. A pre-purchase survey plus the haul-out that makes it possible runs well over a thousand dollars on a mid-size boat, and no remote tool should be presented as a substitute for it.
What a remote tool can do is stop you spending that money on the third-best candidate. The survey cost guide works through exactly that arithmetic.
Paste a listing URL. The free pre-check returns the specs, the design ratios and the flags, with every figure shown as a range and its assumption. No card until you choose to unlock a full report.
FAQ
Who writes the Knotworth guides?+
Itzhak Fuhrman, an engineer working in data analysis who built the cost model the product runs on. He started this as his own research into which sailboat to buy and kept going. Where a guide quotes a price, the figure is traceable to a published rate card, a manufacturer price list or a dated forum report, and the source is linked in the text rather than summarised second hand.
Why should I trust a tool built by someone who is not a marine professional?+
You should not have to. That is the point of the design: every figure is a range with its assumption stated, every source is linked so you can check it, and the design ratios are computed from published dimensions rather than repeated from elsewhere. The background that matters here is engineering and data analysis, applied to a question a buyer actually faces, and the site is built so you never have to take anyone's word for a number.
Is Knotworth run by a marine surveyor?+
No, and the site never claims otherwise. Knotworth exists to tell you whether a boat is worth paying a surveyor to inspect, not to replace the surveyor. Every report carries that distinction in writing, and the guides link to SAMS and NAMS when the right next step is hiring an accredited professional.
Where do the cost figures come from?+
Published boatyard and surveyor rate cards, rigger and sailmaker price lists, and dated reports from owners on sailing forums. Nothing is drawn from a private database, and nothing is invented to fill a gap. Where the evidence is thin, the guide says so instead of quoting a confident number.
Why are all the estimates given as ranges?+
Because a single number would be false precision. A rigging quote on a 35-footer swings by thousands depending on wire versus rod, roller furling, and which yard does the work. A range with the assumption stated is honest; a point estimate that looks authoritative and turns out wrong is not.
Does Knotworth take money from brokers or yards?+
No. There are no affiliate links, no referral fees, and no paid placements anywhere on the site or in a report. Buyers pay once per boat and that is the only revenue, because the value of a buyer-side tool disappears the moment it is paid by the sell side.
How do I correct a figure that looks wrong?+
Email hello@getknotworth.com with the page and what you paid, ideally with the invoice or quote. Real quotes beat modelled estimates in the product and they beat them in the guides too. Corrections that hold up get applied, and the page's updated date changes.