Sailing towards the neck
If you look carefully, you will see that almost all ship models in bottles have the bow facing towards the neck of the bottle. This makes it easy to insert them and erect the masts (see my page on how it is done). So one challenge is to make bottled ships that are perverse. Here is 1893 America's Cup defender Vigilant, in a really prize Slivovitz bottle. No, I am not going to give away how it was done. I will only say that the hull was too big to fit through the neck and was made in two parts, reassembled in the bottle. Vigilant statistics: 124' LOA, 86'2" LWL, 26'3" beam, 13'6" draft. Sail area 11,272 sq ft, crew of 70. She also carried a centreboard!
The easiest to understand is big bottles. You can put so much more detail in, and three and four masted ships are easier. There is a foray into a 2 litre (1 gallon) jar the main ships-in-bottles page.
There are three challenges here. Firstly to make something that will fit inside, then something detailed enough, and then small bottles also have proportionally smaller necks. Here are four of my small ships-in-bottles.
The brigantine and the gaff cutter are both inside 100mL (one nip) spirit bottles of the kind they serve in aeroplanes.
The three yachts under spinaker were a real challenge I set myself, in a 75mm (3") miniature gin bottle. The neck is really tiny (as is the bottle); the hulls are made of aluminium strip filed to shape and painted, set in an blue epoxy sea. Making the right mast height for each yacht was a significiant challenge as the bottle glass is not of uniform thickness and there is little clearance.
The spritsail cutter is in a 80mm food coloring bottle. The coin is an Australian 20c piece. The hull and stand are of Huon pine (Lagarostrobus franklinii) which lives to 1000+ years in South-West Tasmania. If you look closely, you will see a helmsman standing up to the tiller (height 9mm). This model is also on the port tack (another challenge).
Wind on the starboard side
Again if you look carefully, you will see that almost all ship models have the wind coming on to the starboard side of the ship or boat. Why? Well almost all sewing threads are twisted in the same direction (right-handed lay), and when you pull on them to erect the masts, the thread untwists slightly under tension. If the ship is on the starboard tack, the fore-and-aft staysails swing in towards the centreline and look good. If it is on the port tack, they stick out at a most unnatural angle. So here is another challenge to thwart this trend. My main ships-in-bottles page has two models which are on the port tack.