The biggest overall issue lies in the visual design, page layout and navigation system. The site gives users the impression that you're running it out of your basement and that it's your first attempt at running a website. While this may in be the case, it's not the message you want to convey.
In addition, PayPal "Buy Now" buttons don't make the grade in terms of professionalism, nor does the "Visitor #" page counter. At present, you're suffering from a complete lack of trust, confidence and credibility as far as online stores (ecommerce sites) go.
With only 2 products for sale, your ability to attract new customers is severely handicapped. You're running a niche site where your users will most likely want a "one stop shop" where they can find just about anything and everything they're likely to require in pursuit of their hobby. The likelyhood of your site gaining any sustainable traffic is extremely limited because you've got such a small amount of content and because your product offerings are so narrow.
Were I you, I'd find a supplier(s) who can provide an assortment of tools, plans, supplies, books, guides, glue, paper, decals, RC controls, engines, ready-made kits and so forth. This would allow you to expand your product offerings and attract a wider client base.
You'd do well to consider providing users with detailed guides on RC and glider flying and a link resource where users can find related information. Perhaps even a forum where you can establish a community of loyal users.
As has already been suggested, take a look at your competitors sites to do some market evaluation. See if you can't source the same products, or better quality products, at a reasonable price. With the knowledge you already posess, shop their sites and make notes on how things are presented. Go through an entire purchase and actually buy something. This will allow you to evaluate their processes for yourself.
Once you've assembled an inventory of items you can sell, implement an actual shopping cart and set up a payment gateway that will allow you to run with the "big boys".
At present, you've got nothing to lose and there are plenty of easy to implement free shopping carts available that will work on any server with just about any type of database.
Don't worry too much about improving what you've got, your efforts would be much better spent in a complete redesign with an integrated shopping cart.
These links ought to help you get started:
Basic Guide to E-Commerce (Doing Business Over the Internet/Web)
E-Commerce Guide*-*SBDCNet - National SBDC Information Clearinghouse
Good Luck.