Kenneth wrote; (SNIP) > > > For example, if you added 64 lbs of lead to a boat, you would need to > add a 1 cu. ft. air bag to float that lead it if you swamped. It is > just simpler to forget the lead and instead add a 1 cu. ft. water bag to > get the same 64 lbs. of ballast. Lead weighs aprox. 700 lbs. per cubic foot. Thus 64 pounds of lead will only take up 157 cu. inches of space. Since this can be mounted much lower in the boat and centralized fore and aft much less of it can be used to achieve the desired increase in stability or change in trim. A simple calculation of the moments involved will show that 50 pounds of lead mounted on the bottom of a kayak will almost make it self righting. If faired into the hull it will have no noticeable effect on hull resistance. Kevin wrote; >If this is for improving stability, then I consider adding ballast an >inferior approach. The best possible way to improve stability in your boat >is to improve your technique and your fit in the boat. For the latter, >there is a great article in the recent Feb issue of Sea Kayaker, for the >former, I can recommend several ways to improve your balance and edging >skills, from simple exercises to do while paddling, to a full-blown river >kayaking course. This is true for those activities where one is always alert. However, if one is sleeping in the boat or there is a prospect of being at sea for extended periods of time in which one must rest, ballast can provide the required stability and it is safer than increasing the form stability. Also, we have heard from handicapped paddlers who might not have the ability to roll. In this case added stability that actually prevents capsize may be a requirement. For most paddling stores and gear in a boat are a form of ballast that can enhance stability. They can be stored in such a manner as to improve handling and make paddling much less stressful when the weather gets threatening. The obvious problem with stores is that they are consumable and stability suffers with time (unless you have a holding tank aboard). :-) If you are carrying water anyway then it is important to store it as low as possible and outboard to reduce rolling. The containers should be collapsible so the water will not slosh. Of course, the containers should be fastened tightly enough to prevent movement. We used the cheap folding 2 gal. jugs in Labrador. They worked but I never really trusted them and covered mine with duct tape to prevent wearing holes in it. Returning to the origin of this thread, adding ballast specifically to adjust the trim of a boat may not be the most efficient way to do the job but it does work. A sliding seat is much more effective plus it provides flexibility to adjust for less than perfect gear packing. I have used ballast myself on sprint kayaks. We build the boats ten lb. under weight and then shift the lead blocks around to get the best trim. We don't move the paddler because the seats are rather tightly fitted into the best paddling position for control and stroke efficiency. The important thing to recognize through any of these discussions is that circumstances alter needs. One can alter stability in several ways and each method has its virtues and vices. The wise paddler and boat designer will recognize this and use each method in the appropriate manner. To arbitrarily adopt one over the others is to invite problems. Cheers John Winters Redwing Designs Specialists in Human Powered Watercraft http://home.ican.net/~735769/ *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net ***************************************************************************Received on Sat Feb 14 1998 - 06:37:07 PST
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