Re: halp determining transom angle
This looks like it's related to your other post. My response there is related to this question too.
<br /><br />13 degrees sounds about right. That's about what most transoms are (+-).<br /><br />8"(side opposite angle)/37"(hypotenuse)= Sine of X angle. So inverse sin of 8"/37" = 12.48 degrees. That's about your 13.<br /><br />There are several ways to figure your required shaft length, but with a transom that tall, you should obviously go with the longest shaft you can. These days 30" shafts are found on the bigger motors. 25" are also common. I don't think you can get longer than 30" though. Outboard brackets make your motors susceptible to the elements, another reason to go as long as you can.<br /><br />One way to measure is by knowing your transom angle (13 degrees) and the length on your transom from the bracket rest to the keel (37").<br /><br />The cosine of 13 degrees X 37" = 36" = shaft length.<br /><br />Or, if you don't know your transom angle you can use a level or a plumb-bob to find it. Make sure the boat is level. Attach a string with a weight at the end, to the outer edge of the transom where the motor will bracket. Let it hang. Now measure the distance from the boat transom at keel to the hanging string.<br /><br />Lets say you got 8". Using the same trig....<br /><br />Sine of angle = measurement opposite angle desired/ the hypotenuse.<br /><br />So... the Sine of some angle = 8"/37". The inverse sine of 8"/37" = 12.48 degrees.<br /><br />You can also use a (long) level, by touching one side of the level against the transom where the motor will bracket, leveling the level, and again measuring the distance from the keel to the same side of the level as touching the transom mount. Again, this would be the measurement opposite the angle desired which you can plug into the trig stuff. The boat needs to be level first.<br /><br />I would have your outboard bracket fabricated so it's flush with the keel and hull of the boat on the bottom. Using a common 12 degree transom angle and a 30" shaft motor, you would need to make the transom bracket mount at about 31" long (@ 12 degrees). But check the rigging specs of the outboard. It may not have a shaft of exactly 30". You can figure it this way:<br /><br />Cosine of 12 degrees = motor shaft length/bracket length.<br /><br />For a 30" shaft........ Cosine 12 degrees=30"/X". This = 30.7".<br /><br />So when measuring the bracket from motor mount bracket rest to keel, it would be 30.7".<br /><br />Hope this helps.
