A number of vendors sell model ship plans. Unfortunately, sub-par plans are a dime a dozen. Actually, many times you pay a premium and it’s a gamble whether the plan you’ll receive is any good. I’ve spent a lot of money on plans that were incomplete, distorted, or where the original was simply too deteriorated to copy.
Sometimes these plans are salvageable, but they're no fun to work from, and it is always frustrating pouring time into something you feel you already paid for.
Another aspect is poorly researched scale plans. Many plans on the market show every sign of being a historic reference to a ship with quite a provenance. Upon closer research some of these ships turn out to be completely imaginary.
It's not that there is anything wrong with fictional models per se, Hollywood does it all the time. The bigger problem is the deceit. For more on the emotions this can stir up, read more at the Nautical Research Guild website.
Sometimes it helps knowing who drew up the plans in the first place. Here is a list of known quality draftsmen and their respective specialties. Their plans are extremely well researched and, I believe, accurate.
Anyone looking for age of sail plans of British colonial era and North American vessels should consider these plans. The plans can be obtained from the Smithsonian Institution Press. Most of the plans available are published in one of his many naval history books. The price is decent, and quality is generally acceptable.
There is only one rub – you need to get the catalog to be able to order and there are no pictures in the catalog. What I've found to work best is to get the catalog. Then get the book on the subject I’m interested in whether it is sailing fishing vessels or Baltimore clippers etc. Find the illustration in the book and use that as a cross reference to the catalog. Note that not all hull lines plans has a corresponding sail plan, if that matters to you.
David MacGregor has researched and drawn up scale plans of mostly British sailing ships, and some American. He is also an accomplished maritime author.
His catalog spans sailing warships, tea clippers, fore-and-aft sailing ships, revenue cutters and colonial vessels. His plans have largely done for the preservation of the British marine history what Chapelle did for the North American counterpart.
John Lambert is an accomplished author and illustrator. His specialty is allied coastal vessels (destroyers, escorts, torpedo boats, RAF crash tenders etc) and submarines from WW1, WW2 and post war. His plans and books can be ordered directly from his website.
Lothar Wischmeyer is an expert draftsman and model builder. His plans are based mainly on shipyard models preserved in museums in Germany as well as original shipyard documentation. Most of the plans offered are from the Imperial German navy - so late 19th century, WW1. He also offers a few plans from lesser known German WW2 ships. Most plans are drawn to 1:50 or 1:100 scales – which makes for large models.
Al Ross is a seasoned model boat builder who specializes in the smaller warships. He has plans of torpedo boats and sub-chasers from WW2, Brown Navy boats from the Vietnam era, and some detail plans offered separately of the weapons carried by these boats.
Most plans are offered in 1:32 scale, but some are larger - 1:24, 1:16 and 1:12 depending on the size of the subject.
Plans include American PT boats, USAAF air rescue boats and Sub chasers.
His line of model ship plans include Elco 77 and 80 foot as well as Higgins 78-footer, and boats by Vosper, British Power Boat Co and J.S.White Co. He also offers plans of British motor torpedo boats (MTB), gun boats (MGB) and some lend-lease Elco's - all from World War II.