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  Detailed Analysis of Hydrofoil effect on Montauk ride, in reference to SF Bay waters.

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Author Topic:   Detailed Analysis of Hydrofoil effect on Montauk ride, in reference to SF Bay waters.
Salmon Tub posted 06-07-2004 11:43 AM ET (US)   Profile for Salmon Tub   Send Email to Salmon Tub  
It helps a lot!!! Like night and day!!!


P.S. Tony (Elaelap) get a second opinion from Gunther, but I think you may want to look into one for your 18'. I installed a Stingray.

JohnJ80 posted 06-07-2004 04:48 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
This seems to have become a hot topic lately. Can you give us some more data like how much trim range do you have now, the motor, where the motor is mounted vertically, etc...?


Salmon Tub posted 06-08-2004 12:27 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
I guess I should add a few more details into the "detailed analysis". The funny thing is, the previous post pretty much says it all. As for my boat, it is a 2000 Montauk, with 2000 Nissan 90 2-stroke (300+/- lbs). I raised the motor one hole up from lowest position last year.

Here are some notes regarding the effect of the Stingray on my hull and motor:

Right from the start, when motoring through the 5 MPH zone, I noticed a difference in the way the boat handled. The effect on planeing speed was different than what I expected. Previously, the bow would raise high, then come down as you approach approx. 18-20 mph. What happens now is that the bow does not seem to lift at all, rather than the whole boat seems to lift up. In other words, if previously, I would have a tackle box on the side of the console, it would slide down torwards the transom upon acceleration, now that same box does not shift at all. Regarding the effect on power trim, I noticed that if previously, power trim had little effect on the boat's attitude at speeds of less than 15 MPH, such as in rough seas or slow speed zones, I was now able to see it's effect at slow speeds such as 5-8 mph. Even in the 5 mph zone, I was able to see the bow rise and drop when using the power trim, and this helped to reduce the wake of the boat. At idle there was no noticable effect on the trim of the boat as I had expected. Regarding the effect on speed, I did not have an oppertunity to test the boat out at WOT, but I was very impressed with how quickly the boat was able to reach cruise speed. One other interesting note regarding speed, at first glance, it seemed that the boat lost about 10% to 15% speed at any given rpm range, i.e., if previously 4000 rpm gave 26 mph, now it was at aprox 23 mph at the same range. This at first was discourageing, until I confirmed the speed with the GPS, which did indicate that the speed was about 26-27 mph. I have come to the conclusion that this is because I have a paddle wheel style speedometer whith the wheel mounted at the large chine on the transom. The speedometer is set at -15% since before the foil, it would lie and show that much more when compareing GPS to Speedo. I had always atributed this to the fact that the wheel was probable close enough to the prop to pick up some of the slippage. It seems that the foil had created a physical block and that the wheel now had "truer water" spinning it. Reseting the speedo back to 0% correction eliminated the discrepancy. Regaridng rough water handleing. This is where I was most impressed. We have some rough waters in out bay. On Sunday, test day, we had some of the biggest tide swings of the year. In some areas currents reached 6+ kts. We also had a good layer of wind on top of that to funny things up. I went through flat water with slow rollers of about 1 to 2 ft., as well as the stacked almost motionless waves we belovedly call the potato patch of about 4 ft. The effect of the foil is simple, it is like a shock absorber. The first impression I had was wow, the boat rides the water like my boss's catamaran. The boat seams to hug the water and when going into the waves. In essence, the foil eliminates the top 20% of roughness. If previously, you had a carbonated drink on the console that would fizz every time you hit a wave, and try and topple from the changing angle of the boat, now, it may still try to topple, but you no longer get that fiz because the edge has been eliminated.
Regarding control, it enhances the control of the boat, which gives you the impression that you have less control since slight corrections are now more visible. Also, with more keel in the water, you feel the effects of the waves a little more, even more so when in following seas. You feel this more in the bow rather than stearn, but I never felt even a bit out of control, and the trade-off of rough pounding for this would be a no brainer.
I was hesitant for a long time because I didn't want to put holes in the motor for a useless accessory. Now, I can not be happier. I spoke to the guys at Doel-fin and Stingray regarding performance and they both seem to say that they are not for ever hull, flat bottom boats such as Jon boats, and super soft vee boats that are extremely low profile do not handle foils well. That may be why engine manufs. do not make these as part of the lower unit. It may cut out a segment of the market. Also, it may create shipping problems since most motors are shipped laying down in crates.

1. Motor had more splash on it than before.
2. that is about it.

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