Guest Terry Winckler Posted July 22, 2003 Report Share Posted July 22, 2003 Now I need some advice on a motor. What's the highest performance outbaord I can put on for maximum speed witthin design tolerances? 4hp is in the specs, but there are more than one such beast. Is there one particular motor that seems to really do the job? As for the boat, which because of builder bozo errors is a bit not perfect, I am terribly thrilled with it. I rpomised by little boys I would build a boat for each if they learned to swim. They did and I did - but with a twist. I did the nesting version and have named each half for one of the boys. The boat's overall name is Dipseydoodle, cuz it has a dip in the front half bottom and a doodle in the stern half. Rows great, though, and I can't wait to get her on plane! Quote Link to comment Share on other sites More sharing options...
Frank Hagan Posted July 23, 2003 Report Share Posted July 23, 2003 Congratulations on the launch! As far as the motor, in that size I don't think there are that many differences between brands. The two things most people look for in a small boat outboard are quiet operation and light weight. Unfortunately, my experience has been that those two things are nearly mutually exclusive! The new 4-strokes are usually quieter in the 5hp range and above, but they are quite a bit heavier. (Honda's 2hp four stroke is, I've been told, just as noisy as its two stroke cousins.) So light weight could be the order of the day, so as not to slow you down while sailing. And the noise will make you hate the outboard, so you'll enjoy the quiet noises of sailing that much more! Quote Link to comment Share on other sites More sharing options...
Guest Terry Winckler Posted July 24, 2003 Report Share Posted July 24, 2003 Frank, thanks for your good insights. Now, I am closing in on building the mast. Is .049 too thin a sidewall for the T6 tubing. Spec sez .065. Quote Link to comment Share on other sites More sharing options...
Frank Hagan Posted July 24, 2003 Report Share Posted July 24, 2003 I'm not sure! I think I'll wait for Graham to chime in on this one. He's usually popping in just at the right time to save me from giving bad advice. There was a post on the Core Sounds that had quite a bit of info on wall thickness, and that might apply. Seems to me it included some sources as well, because people were having a hard time finding the right wall thickness. Quote Link to comment Share on other sites More sharing options...
Designer Posted July 24, 2003 Report Share Posted July 24, 2003 I would stay with the .065" wall thickness. The S11 mast has a smaller factor of safety than the S10 because of availability of standard sections. Quote Link to comment Share on other sites More sharing options...
High C Posted July 25, 2003 Report Share Posted July 25, 2003 The new 4-strokes are usually quieter in the 5hp range and above' date=' but they are quite a bit heavier. (Honda's 2hp four stroke is, I've been told, just as noisy as its two stroke cousins.) [/quote'] I'll second that. My neighbor has a new Honda 2hp, and it is louder than my new 3.5hp 2 stroke Nissan/Tohatsu. The Honda is a little smoother running at idle, but I prefer the Nissan. $200 cheaper, too! Quote Link to comment Share on other sites More sharing options...
Guest Terry Winckler Posted July 28, 2003 Report Share Posted July 28, 2003 Just wondering if a 4 h.p. or 3.5 could actually get the Spindrift zipping along on plane at greater than 10 mph? Quote Link to comment Share on other sites More sharing options...
Designer Posted July 29, 2003 Report Share Posted July 29, 2003 I would forget about 10 knots+ in a Spindrift 10. I have timed my S10 at 6 knots over a measured mile with a 2hp Suzuki with me alone in the boat, which is a speed length ratio 2 (6 kts./sq. root of 9' wl. = 2) which is generally accepted as the beginning of planing. 10 kts. is a speed length of 3.3 which is much too fast for the rocker in the bottom. I once tried one with a 5hp motor, although I had no way to measure speed at the time I believe that it was nowhere near 10 kts, and it made a lot of wake and the motor made a lot of noise. Quote Link to comment Share on other sites More sharing options...
Greg Luckett Posted July 29, 2003 Report Share Posted July 29, 2003 What about motor and speeds with a Spindrift 12? Any more gems to share with us, Graham? Thanks for the info on the 10. It is good to know. Greg. Quote Link to comment Share on other sites More sharing options...
Designer Posted July 30, 2003 Report Share Posted July 30, 2003 You are on the right track Ray. Rocker is more advantageous for boats operating at the lower end of the speed spectrum - rowing and sailing. Rocker makes climbing up onto the plane harder. The ideal planing shape, would be "dead flat" - and to that end when we design true planing hulls, the aft sections are aimed at that. Of course, that means they are inefficient at low speeds - and don't row or sail well. And as you so rightly pointed out, when a boat has to do "everything" you have to try to balance - and (oh boy here is that word again) compromise. With the Spindrift, she has a flatter run aft than most boats of her ilk, which improves her top end speed. Fortunately she is small enough that in low speed sailing, we can trim her down by the bow slightly and heel it to leeward slightly, which eliminates the transom drag, cuts down wetted surface area and gives it more apparant rocker. Which leds us to Greg's question.... Personally I've never had a motor on a 12, so I've had no real life experience on her performance under power. I'm reluctant to give hard and fast numbers because, when you are operating with this type of boat, in that grey zone of beginning to plane there are many variables. The most primary would be the engine itself. To say, generically, that "4HP = X knots" is not responsible. Unfortunately for us consumers "A HP ain't necessarily a HP".... at least i in terms of ratings. Practical Sailor magazine did a test using a single boat and useing different engines of the same "stated" (note not "rated") horsepower - and there were substantial differences in the range from fastest to slowest. So you would need to research "output horsepower" on any given models you were interested in. The second factor is of course, weight, in a small boat like this, the addition of an extra person will reduce or negate the the ability to plane. As a design, I think the Spindrifts cover as wide a range of performance as is possible. There doesn't seem to be another boat out there at this time that can touch her in all round performance. The objective of top end speed under power was never a consideration in the design. We only wanted a boat that would motor well as a tender - moving along briskly with a load and using a minimum of horsepower to do so. To my mind, when using the boat as a tender, the ability to use the smallest, lightest motor (for hauling on board, lifting and stowing) and still get respectable performance is a premium point. It was never about "ultimate" speed, just relative speed. I guess I've just muddied the waters again :roll: Quote Link to comment Share on other sites More sharing options...
Guest Terry Winckler Posted July 30, 2003 Report Share Posted July 30, 2003 Great explanations, Graham, and they help explain what I should and should not expect performance wise. Based on what you say, I probably shouldn't go to a 5 hp as I had planned, and I am better served thinking of the Spin 11 as maybe an 8 mph putt putt rather than a planing speedster. Now, if I could nly find a good deal on a 2 stroke, 4 hp motor.... Quote Link to comment Share on other sites More sharing options...
High C Posted July 30, 2003 Report Share Posted July 30, 2003 I have a 9'4" plastic Water Tender dinghy that has a tri-hull shape, very square at the bow, much like a Boston Whaler has. It's a nice tender, roomy and stable, but it is SLOW under power (3.5hp). I'm very tempted to build the Spendrift 10 as a replacement, bet it'll do nearly double the speed. Has anyone ever tried to squeeze 4 folks into the 10 without sinking? Quote Link to comment Share on other sites More sharing options...
Guest Terry Winckler Posted July 31, 2003 Report Share Posted July 31, 2003 I have a Spindrift 11 that I loaded up with 5 kids and 3 adults plus me, rowing them to shore. Rowed great and kept its stability. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.