Great Loop Trawler/Cruiser - Concept

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rick berrey
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Re: Great Loop Trawler/Cruiser - Concept

Post by rick berrey »

Most of Atkin seabright hulls have ballast on them , but Two Brothers has none as far as I can tell . The hull looks to be the same basic hull design as smaller surprise and big surprise both with CBs , and big surprise with a larger hp power requirement than Two Brothers which is 6' longer . So why would two brothers not have ballast , and is that the reason for the lower 12 HP ? If the power requirements are correct this hull scaled to the lower 30' range should only require hp in the low 20s . With some kind of rig for a para sail to give down wind sailing ability I think this type hull would fit many of requirements + some . The more I look at seabright hulls the more I like them .



fallguy1000
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Re: Great Loop Trawler/Cruiser - Concept

Post by fallguy1000 »

rick berrey wrote: Sun Feb 21, 2021 9:48 pm Most of Atkin seabright hulls have ballast on them , but Two Brothers has none as far as I can tell . The hull looks to be the same basic hull design as smaller surprise and big surprise both with CBs , and big surprise with a larger hp power requirement than Two Brothers which is 6' longer . So why would two brothers not have ballast , and is that the reason for the lower 12 HP ? If the power requirements are correct this hull scaled to the lower 30' range should only require hp in the low 20s . With some kind of rig for a para sail to give down wind sailing ability I think this type hull would fit many of requirements + some . The more I look at seabright hulls the more I like them .
I don't see any ballasting in the plans. Bit I did notice the construction is robust, beefy hardwood timbers. So she gets plenty heavy in the traditional build. Most likely, a version built in another fashion may require ballasting. Of course, a water tank ballast might be the magic for tuning, or extra fuel would be good as well.

As for the beam, the designer suggests "she be built with no changes of any kind" in the last line in the article. I certainly don't know enough about these boats to comment on the beam. The question would be how to build the center bigger.. I don't see much value in widening the deck.
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rick berrey
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Re: Great Loop Trawler/Cruiser - Concept

Post by rick berrey »

From what I have seen so far all the Atkin seabright in that size range are built with 3/4 lap and oak , so there must be something else . The rig is more of a get home rig so may be no ballast needed for it , but the other 28' seabright hull has I think 2000 or 2500 lbs ballast , so maybe less hull vol . On build materials being already heavy , extra glass and epoxy on the bottom of these hulls could replace some ballast , make the boat bullet proof , make the builders who always want to build it heaver happy , and BBC could sell more epoxy and glass .

rick berrey
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Re: Great Loop Trawler/Cruiser - Concept

Post by rick berrey »

" Learning Freeship with Atkin Suprize Mortorsailor " on Wooden Boat forum compares the Atkins seabright hulls that are the same basic hull . The lines for Two Brothers are done and may be in the public domain , or a $100 domain to the Atkin site might be in order . As Two Brothers sits it is rated at 11 mph with 12 hp , beam is 8'8" so could be trimed to 8' 6 " , scaled in length only 10% it would be 31.5' with 16 hp , just right for me . Big Surpize is rated at 20 mph with 22 hp , so the hull form can be pushed to our 13 mph goal with a bit more hp , maybe a 20 hp on a 10% + length only version . It carries a get home or down wind sail for an option , and may be could be towed at 6100 displacement as designed , or 8100 disp . + 10% . Interior would have to be redesigned . Seabrights seem to be wide at the bow so a forward birth would be roomy . So my question is , with the hull lines done would it be possible to sell a redesigned set of interior plans and offer the original plans on the free plans with all material conversions left to the builder ?

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Re: Great Loop Trawler/Cruiser - Concept

Post by fallguy1000 »

rick berrey wrote: Sat May 15, 2021 4:11 pm " Learning Freeship with Atkin Suprize Mortorsailor " on Wooden Boat forum compares the Atkins seabright hulls that are the same basic hull . The lines for Two Brothers are done and may be in the public domain , or a $100 domain to the Atkin site might be in order . As Two Brothers sits it is rated at 11 mph with 12 hp , beam is 8'8" so could be trimed to 8' 6 " , scaled in length only 10% it would be 31.5' with 16 hp , just right for me . Big Surpize is rated at 20 mph with 22 hp , so the hull form can be pushed to our 13 mph goal with a bit more hp , maybe a 20 hp on a 10% + length only version . It carries a get home or down wind sail for an option , and may be could be towed at 6100 displacement as designed , or 8100 disp . + 10% . Interior would have to be redesigned . Seabrights seem to be wide at the bow so a forward birth would be roomy . So my question is , with the hull lines done would it be possible to sell a redesigned set of interior plans and offer the original plans on the free plans with all material conversions left to the builder ?
Not sure I follow the question, but making the boat shorter makes her slower.

I get 7.5 knots at 31.5'. I need to undersrand how Big Surprise gets 20..
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rick berrey
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Re: Great Loop Trawler/Cruiser - Concept

Post by rick berrey »

Two Brothers is 28'9.5" so you would not make it shorter at 31'6" , the mph and hp are on each plan as per Atkin . If one hull can get to 20 mph , another hull with the same lines only bigger should also be able to reach the same speed or greater , one would only have to do the math to find the required hp . Problem,s with J designing a great loop boat is time , another is interest , redesigning the interior and deck of an already designed boat might be doable .

rick berrey
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Re: Great Loop Trawler/Cruiser - Concept

Post by rick berrey »

There are now study plans from another designer that fits our 8'6" tow option , he might be spying on our tread . LOA 33'10.75" , beam. 8'.75" , Draft 1'2" with outboard up , disp. 7,100 , 60 to 115 high-thrust outboard . Down side are you are not docking her by yourself as there is no door on the side . I am not sure how a high thrust outboard will function long term running at low rpm,s . The company I was working at replaced our outboards with suzuki 90 hp , we burned one up the first day , and had issues with the others making oil . The rep came out and told us our problem with the ones making oil , we were running them at displacement or just over . He told up to run them wide opened whenever we could and it solved our problems . We ruined a merc running it back and forth across the river at idle speed . So will a high-thrust motor last on a boat pushing disp. speed , or running at low rpm,s on an extended trip such as the Loop ?

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Re: Great Loop Trawler/Cruiser - Concept

Post by TomW1 »

Rick a Hi-thrust motor has a final gear ratio of 2.33 to 2.38 compared to a regular ratio of 2.0 to 2.07. This is for a 60HP motor. I don't know if you can even get one in a 90 and have never seen one in a 115. So you still have the problem of not being able to slow the motor down enough to operate at displacement speed. The Hi-thrust motors were designed for heavier loads to operate in an economical range of around 3500rpms and still get good speeds.

The thing you need to do is add a second trolling motor on in the 9.9 to 18HP range and attach it to the main motor so it can be controlled by the main steering, and provide fuel from the main tanks. This is done by the Walleye fisher men on the Great Lakes when they fish all day. The trolling motor size will depend on the displacement of the boat.

There are lots of places you can use the 90 on the Great Loop like the Mississippi, but I know there are a lot that you can't and you need displacement speed.

Well that is what I know about it.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

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Re: Great Loop Trawler/Cruiser - Concept

Post by Fuzz »

I am with Tom here. A big outboard to go fast and a 10-20 hp kicker to do the slow stuff. Plus you can put run hours on the smaller/cheaper motor. I have a 22 foot boat that weighs around #6000 with people when fishing. My 9.9 will push it 5-6 knots around half throttle. And not burn much fuel to do it. I think that is a better way to go than midsize twins would be.

rick berrey
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Re: Great Loop Trawler/Cruiser - Concept

Post by rick berrey »

I agree with the kicker , but if you used the kicker much of the time why would you need the primary large hp outboard for this design concept ? It would be like needing two different motors , one for displacement speed , one for semi displacement . If twins will not do the job then are we back to an inboard ?

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