Full Pilot house on a GS28X or PG25C Panga?

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rick berrey
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Re: Full Pilot house on a GS28X or PG25C Panga?

Post by rick berrey »

I couldn't find a panga less than 29' with a pilot house when surfing the web , I think if looking at a pilot house on the 25 J would have to be consulted . He already has the plans for the 28 and it puts him in the range of where he wants to be with intended use , performance , size and cost .



barrelroll
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Re: Full Pilot house on a GS28X or PG25C Panga?

Post by barrelroll »

So an idea is to steal a page out of the Renn Tolman design book and add 3" chine flats to a Panga widening the Panga to 7'9" at it's widest point. When Renn Tolman started adding cuddy cabins to his original 7' wide Standard skiff he determined it wasn't enough boat to support the weight so he added 3" chine flats creating the 7'6" wide widebody to better support the weight of cabins and pilot houses and also cut down on spray. He kept the same bottom and stringer design just widened the boat 6" total with the addition of chine flats. I picked up a set of Panga plans and have started to attempt to learn sketchup to play with the idea. I think the plan is to add 6" to the beam width at the gunnels add a 3" flat where the bottom meets the side on each side tapering the chines down from station C forward. It's going to require some new lofting or some cut to fit parts.

rick berrey
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Re: Full Pilot house on a GS28X or PG25C Panga?

Post by rick berrey »

Scaling a boat to around the 10% ranges has few risk to the form and function of the boat , I am not sure I would do a redesign of the beam on a boat that size , it,s a lot of money and work to risk . The 28 is already designed with a pilot house option , you might be able to scale it down length only 3% to 5% if you want a shorter boat and keep the 8'2" beam

TomW1
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Re: Full Pilot house on a GS28X or PG25C Panga?

Post by TomW1 »

Duplicate, sorry. Tom
Last edited by TomW1 on Thu Sep 29, 2022 12:45 pm, edited 2 times in total.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

TomW1
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Re: Full Pilot house on a GS28X or PG25C Panga?

Post by TomW1 »

Rick, Jacques said time after time that you need to scale in both length and width if you scale. He does not recommend scaling in only one direction. By widening the hull to 7'9" you are actually widening it by 10.7%. You should then lengthen it by 10% and your back to 27.5' and you might as well build the GS28. I am not sure why you keep bringing up the PG25 all the 25 but it is not the boat for him.

Tom
Last edited by TomW1 on Thu Sep 29, 2022 1:36 pm, edited 1 time in total.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

rick berrey
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Re: Full Pilot house on a GS28X or PG25C Panga?

Post by rick berrey »

Tom , to clear up the issue of scaling , many designers allow their designs to be scaled in length only , Jacques among them , you will find many examples for length only on these forums . What I was suggesting was that if he wanted a panga with a wider beam then he should scale down the 28 in length only , 3% is only around 9" and might not affect form and function . I would not widen the 25 without scaling in length as well , building the 28 with the pilot house is do able and scaling down the length 9" to 1 foot I would think is a better option that scaling the 25 .

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Re: Full Pilot house on a GS28X or PG25C Panga?

Post by TomW1 »

rick scaling even only by length has its foibles. See this article from Jacques part way down is the scaling by length only section. https://boatbuildercentral.com/support- ... -plans.pdf You will need to adjust the frames, the boat will sit lower in the water as her waterline displaces 10% less water you will need less HP on her by a factor of 80-85%, less gross weight on board will be less and the motor well cut out may need to be adjusted. These and other factors must be taken into account when you down scale a boat. Down scaling has more problems than upscaling per Jacques.

Tom
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rick berrey
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Re: Full Pilot house on a GS28X or PG25C Panga?

Post by rick berrey »

Tom you are right in down scaling risk , that's why I threw out 3% , and I would ask Jacques before I did it . If you look at Jacques comments on scaling he talks about 30" frame spacing to 40" spacing , that example is well above the 10% rule of thumb range in excepted scaling length only , he is using it as a " redesign the boat if you scale too much" . That being said there are boats here like the Nina that I would not scale length only without Jacques blessings .

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