I think that the reason model boat bits are difficult to get in shops is a compound one
1) Amount of damage: Model planes and model planes get wrecked easily. Most model fliers carry a roll of bin liners in case of unexpected landing, and even the best pilots write planes on a predictiably regular basis. When I was learning to fly, and training for my A certificate, I wrecked three planes and 2 IC engines. Equally with R/C cars, the amount of damage they sustain is pretty awesome. At any given race, at least 3/4 of the racers would destroy something fairly important, and that meant that the spares sales are very high.
Comapre this to the amount of damage you build up in a single year on your crash tender. It's very small in comparison.
My local model shop reckons he pays the rent, bills and salary for himself and his wife with R/C cars and their spares, and any other sale is a bonus to him.
2) Ease - As mentioned already, you can go into any local model shop and by a ( at least local ) competition quality car, and a Nationals quality plane, both of which can be ready in an evening work and another evening programming the Tx. While it's possible to get RTR boats, they are generally not very good, and there are no real "competition grade" RTR boats available at the "average" local model shop. There is nothing in my local shop that I could take to a OMRA or tug towing event and not get laughed off the pond with
3) Lack of gadgets. This is the reason why I personally ( and all my school friends who were into models ) gave up on boats - there's nothing that demands instant blwoing of your sataday job money on. In planes there is ALWAYS a new Tx, a new set of batteries, the latest plug in mixers, those new carbon fibre servo horns. Equally in model cars, theres always a new shock kit coming out, new tire compounds, new upper chassis rails etc. All of these offer miraculous powers that will turn your low end model into something that has is faster/stronger/longer than anything else in the planet. ( obviously it can't, but everyone likes to think that it might ..) and it's all accessible with your sataday job money or your bonus, or your over-time cash. There's not really anything like this in the model boating world. This means that there is less money being spent on upgrades and bits for boats than for cars and planes - so the shop owner is making less money out of these lines.
4) Lack of, for want of a better word, "sexiness". Have a look, next time your in the newsagents getting MMI, at the difference in style, layout, content etc, even just number of pages, between for example RCME ( Planes )/Model Racer ( cars ) and MMI or Model Boating. Attend a model boat club meeting and your either in a pub with the same group of 10 chaps you see every month, or your at a huge meeting run along the lines of an AGM, with minutes, apologies and a argument between 4 different guys on the whether to use Cyano or Aliphatic for gluing a keel to a former.
Attend a model areoplane meet and theres talks on aerodynamics's from chaps in the aviation industry, study classes for your A and B certs, Jet Turbine demostrations etc. Attend a model car meet, and you have the tamiya or Team Losi reps letting you have a go of next years models.
I'm 26, and I work with a group of people of similar age. I could take any one of them, even the women, to an aero meet or a car meet, and they would be buying a car, or signing up for training on planes, the next day. Or they might flick through a magazine with an interesting cover, and go and by an ARTF plane, crash it, go get a new one and this time take lessons. This just isn't going to happen with boats. They just don#'t have a lot of "sex appeal".
That means that less new people enter the hobby, so less sales are made to them, making it less profitable to keep a stock.
There are a lot of other reasons - the fact that boaters are usually older, so less likly to splurge money on silly things, the fact that they are generally more capable of scratch building small tools or components, so need to spend less money, the fact that boats have such a diverse number of possible models, so the shops have to make small orders of 100's of different things, which means low discounts and lots of space taken up etc etc etc.
But mainly I think it's becuase the ethos of boating is different. There is, compared to current day planes, and especially cars, a far, FAR higher level of pride and quality about boats. A guy will spend 2 weeks building up a set of railings, and another 2 weeks cutting out the windows. These don't add ANY value to your local hobby shop. In the time that an R/C car fan has brought 10 liters of fuel, 3 new sets of front shocks, a new battery set and 2 new tires, the boating guy will have blunted a few scalpel blades, and maybe needed to buy some more solder or flux from the DIY shop.
The big shops CAN, and probably WILL survive, such as Westbourne, but where you have a small space and a mixed stock, they shop owner has to take the route that gives him the most people walking through his door and the most sales. And, due to the image issue, the number of people who thik "I'd like a model - I'll have a boat" is much smaller than those who decide on a car or a plane, and that means that this trend will continue.
Steve
BTW: I don't want it to sound like I'm not a fan of model boating - I am, and I love it. But I love it becuase it poses a difficult and complex challenge, and I know that I can get support for questions at this forum, so I keep at it. I'm considered "Too young to take boating seriously" (actual quote from lake ) at the local boating pond, and the 2 local clubs both had me head butting the table, due to frustration or boredom. So I build by myself ( with the help of you guys ) and I sail by myself. But I'd be much more enthused if boating was as accessible as flying or R/C cars, and a lot of others would as well. And that would drive up sales.
