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Old 26-04-2003, 23:58   #1
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Custom Modifications

I am considering three modifications to my FP Tobago 35, and would love to hear opinions from others, experienced or not, that might enlighten me regarding these:

1. A "bow sprit" that extends forward to allow deployment of larger headsails. I have heard that this is not uncommon, and that the Tobago could stand to have more sail forward.

2. Extension of the keels forward and aft, to allow improved upwind performance. My idea, after assessing performance. Mind you, I am more used to the upwind performance of a Hobie 21.

3. Holding tank for the toilet and the greywater. There are more and more areas, especially in North America, where they require the use of holding tanks. As yet, I cannot envision the best place and configuration for such an installation.

I would appreciate anything from a 2-bit opinion to an experienced evaluation, regarding a Tobago or similar boat.
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Old 03-02-2011, 06:48   #2
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FOUNTAIN PAJOT TOBAGO 35´ ENGINES

I own a Fountain Pajot Tobago 35´year 1994. I want to improve two things in my boat. The speed when going under power, and the speed and pointing ability upwind under sail.
I have two Yanmar 18 HP, original ones from 1994. I can not gain a decent speed from the engines. Any idea what should be the maximum speed with the pair of Yanmar 18 hp I can obtain for this boat or any similar cat?
What is the average rpm for cruising I should keep not to hurt the engines in the long term?
Any idea how to improve my speed? Changing to a different propeller? Changing ghe engines to larger ones?

Regarding the upwind under sail, what is the maximum angle achievable for a cat like this one? 45 degrees? What can be done to improve upwind perfomance? I see Catana´s have two "daggerboards" that can be lifted, I suppose that improves greatly their upwind perfomance?

All comments on the two subjects are greatly appreciated.
regards,
FUAD
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Old 03-02-2011, 07:10   #3
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How fast does it go under power?
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Old 03-02-2011, 07:32   #4
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Faud,

I can relate to you some Mahe 36 real world performance. Since the Tobago 35 & Mahe 36 are similar, this may help you.

Performace & fuel burn http://www.cruisersforum.com/forums/f136/fuel-consumption-18475.html

Engines http://www.cruisersforum.com/forums/f136/engines-38677-6.html#post514970

Sail Drives and Props http://www.cruisersforum.com/forums/f136/sail-drives-and-props-38652-5.html#post600742

Mark
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Old 03-02-2011, 16:28   #5
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Answers

Moondancer thanks for your interest. In calm water inside the bay, I would say 3 to 4 knots, but when I am going against the wave and wind, I barely advance, I would say 2 knots. This makes cruising under power eternal!! Regards,
FUAD
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How fast does it go under power?
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Old 03-02-2011, 17:10   #6
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FUAD

Mark, thanks alot; i will review the sites.
regards,
FUAD

Quote:
Originally Posted by Cotemar View Post
Faud,

I can relate to you some Mahe 36 real world performance. Since the Tobago 35 & Mahe 36 are similar, this may help you.

Performace & fuel burn http://www.cruisersforum.com/forums/f136/fuel-consumption-18475.html

Engines http://www.cruisersforum.com/forums/f136/engines-38677-6.html#post514970

Sail Drives and Props http://www.cruisersforum.com/forums/f136/sail-drives-and-props-38652-5.html#post600742

Mark
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Old 24-02-2011, 18:17   #7
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Re: Custom Modifications

Fuad,

I own a 1997 Tobago 35. I bought the boat used 9 years ago and replaced the small holding tank it had with a long aluminum tank fitted in the cockpit locker. (mostly to the port side unde the seat) Its enough to last for serveral days between marinas here in VA.

Concerning boat speed under power, I have the same engines. I have no problem motoring in flat water at 6-7 kts @ 2700 RPM on the stock 2 bladed props. The key is a clean hull. When CAT NAP's hulls gets gunked up she's a dog.

CAT NAP
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Old 25-02-2011, 07:29   #8
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Lightbulb Re: Custom Modifications

We have a FP Athena 38 with 2 18 HP Yanmar GM 20s and we get 6-7 kts as well with standard 2 blade props, and about 5 kts with a single engine. The clue to your problem will be what engine RPM you can get at full throttle, it should be at least 3000 rev/min. If you get less than that, are you emitting black smoke from the exhausts? If so that would indicate the engine is overloaded which could mean its overpropped (prop pitch too high), boat is fouled or the boat is significantly overloaded. Overpropping is likely if the props are non-standard. If both engines give about the same speed individually, it would seem unlikely that they are the cause unless you have made a modification to both such as changing the exhaust arrangement
Cat speeds under motor can drop significantly in adverse conditions because the wind load is proportionally greater than for a mono. I have heard good reports from people fitting the Brunton autoprop which can allow you to use higher power by automatically reducing pitch when the prop is highly loaded in such adverse conditions. However, thats an expensive way of making up for a conventional prop /engine combination that is not optimised.
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Old 26-02-2011, 07:23   #9
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Re: Custom Modifications

I have a 1994 in 10-15k I can point to 40'.
Have though of a bow sprit.
The holding tank sits over the port side. Aft just over engin cover and under steering arm.
I have vovol md2010 and get 6-7k.
When both are running. how do you remove the port engin.
I am thinking of cutting a big hatch in the deck. Then lifting out with the boom.
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Old 26-02-2011, 08:43   #10
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Re: Custom Modifications

Not reaching rpm can also be a semi blocked exhaust. This usually happens up near the water mix or elbow. Injection timing and or injectors that need cleaning.
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Old 28-02-2011, 05:14   #11
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Re: Custom Modifications

Quote:
Originally Posted by CAT NAP View Post
Fuad,

I own a 1997 Tobago 35. I bought the boat used 9 years ago and replaced the small holding tank it had with a long aluminum tank fitted in the cockpit locker. (mostly to the port side unde the seat) Its enough to last for serveral days between marinas here in VA.

Concerning boat speed under power, I have the same engines. I have no problem motoring in flat water at 6-7 kts @ 2700 RPM on the stock 2 bladed props. The key is a clean hull. When CAT NAP's hulls gets gunked up she's a dog.

CAT NAP
Thanks CAT NAP for sharing your information. I am next to taking the boat to the periodic hull bottom anti-fouling paint, so I will do some maintenance on the engines and will have the mechanic check on the engine´s rpm. I think my problem is with the engine twin control system. It is hard for me to take the levers all the way down to large rpm numbers. Also, I cleaned the hull and it improved quite a bit. Thanks again.FUAD
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Old 28-02-2011, 05:18   #12
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Re: Custom Modifications

Quote:
Originally Posted by Rapanui View Post
We have a FP Athena 38 with 2 18 HP Yanmar GM 20s and we get 6-7 kts as well with standard 2 blade props, and about 5 kts with a single engine. The clue to your problem will be what engine RPM you can get at full throttle, it should be at least 3000 rev/min. If you get less than that, are you emitting black smoke from the exhausts? If so that would indicate the engine is overloaded which could mean its overpropped (prop pitch too high), boat is fouled or the boat is significantly overloaded. Overpropping is likely if the props are non-standard. If both engines give about the same speed individually, it would seem unlikely that they are the cause unless you have made a modification to both such as changing the exhaust arrangement
Cat speeds under motor can drop significantly in adverse conditions because the wind load is proportionally greater than for a mono. I have heard good reports from people fitting the Brunton autoprop which can allow you to use higher power by automatically reducing pitch when the prop is highly loaded in such adverse conditions. However, thats an expensive way of making up for a conventional prop /engine combination that is not optimised.
Rapanui: Thanks for the explanation. Just came yesterday from a 2 day trip to nearby islands and with a cleaned hull and forcing a bit the twin lever control handle bars, I could get to 2,500 rpm and perfomance improved alot. No black smoke or any of the other problems you described, I think it is mostly in reachiong the rpm because of an improper twin control system and cables instalation. Thanks. FUAD
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Old 28-02-2011, 05:25   #13
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Re: Custom Modifications

Quote:
Originally Posted by cnj View Post
I have a 1994 in 10-15k I can point to 40'.
Have though of a bow sprit.
The holding tank sits over the port side. Aft just over engin cover and under steering arm.
I have vovol md2010 and get 6-7k.
When both are running. how do you remove the port engin.
I am thinking of cutting a big hatch in the deck. Then lifting out with the boom.
Thanks CNJ for sharing your comments. Regarding using a bowsprit, I have been thinking also of it, a bowsprit or a pole, to better use the jib going downwind in a wing and wing configuration. Also to better control the spinnaker. If somebody has used it on a Tobago, your comments are welcomed. Regards, FUAD
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Old 01-03-2011, 01:12   #14
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Re: Custom Modifications

Fuad,
From what you say then you are down on engine speed and hence power at 2500 rev/min. From memory, the 2 GM 20 max power is 3600 and continuous max power 3400 rev/min. Given that the torque curve is pretty flat, then the maximum power you can generate would be about 2500/3400 of the nominal 18 HP, quite a big reduction on what is already a relatively small amount of power available. Headwinds, fouling etc will make it worse.
Normally, you would match the prop so that you can get somewhere just below max power rpm lightship, no fouling, calm water. Then adding load, fouling, wind etc you should still get close to max continuous power should you want to, but more importantly at cruising speeds of say 2200 to 2500 rev min you will have a large margin of power available so that you can maintain a reasonable cruising speed in adverse conditions.
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Old 21-09-2012, 06:32   #15
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Re: Custom Modifications

Re: the original post: Bow Sprit: I've rethought this one, and have abandoned the idea. Here in the Caribbean, where I have been spending the last few years, I have not used the gennaker at all, and really have very few occasions when I would dare. Yes, there are times when the wind drops for a bit behind the bigger islands, but then it can swoop down in a sneaky way and cause real problems.

Besides, when I used the gennaker back in Canada, I enjoyed the flexibility of running the tack line through a pulley from either bow. This would not be possible with a bow sprit.
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