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Full Pilot house on a GS28X or PG25C Panga?

Posted: Fri Sep 09, 2022 4:06 am
by barrelroll
It's probably easiest to start this question out with a picture.

Here's some really bad sketches of what I'm thinking

A PG25C with a pilot house added, the top one I believe is way too short and wouldn't fit 4 people
Image

Here's the same concept on a GS28X, I couldn't find a straight shot with the jump cabin so I just threw a small normal style cuddy on it
Image


How much will adding a full pilot house effect the performance of a PG25C or a GS28X? Rough math is about 300lbs for the pilot house with a 60" floor from cuddy bulkhead to rear bulkhead and a 70" interior height. Interior would be an open floor with just 2 permanent mounted helm seats on pedestals, maybe some battery boxes that double as foot rests, v-berth and no other "furniture."

Looking at the GS28 study plans it says not to add a cabin though the GS28X shows a jump cabin, large console, leaning post, and tower, I can't see that setup being much lighter than a lightly built cabin.

I really like the simplicity of the Panga 25 Would adding a flotation bracket help or hurt the weight balance? After reading about adding a bracket to a P25 moving the center of gravity too far after I'm wondering if a bracket would help offset the weight of the pilot house. I'd do a main with a kicker in the 500-600 pounds range. As nice as it would be to have a self bailing deck it's not mandatory

Would the GS28 be a better option for adding a cabin?

I live in southeast Alaska and am getting close to done with my 23' Tolman Widebody. After building my first boat I'd like to do a lot of things differently and am starting to plan the next one. The door on my shop is the biggest limiting factor as to what I build next. If I pull the trim off the garage door on my shop I can squeeze out a 8'4" wide by 7' 1" tall boat. With our weather a fully enclosed pilot house makes life much more enjoyable on the water.

Here's the want list for the next boat
-25-28' long
-Max width of 8'4" and height of 7' 1"
-Full enclosed lockable pilot house and a V-berth, 60" from cuddy bulkhead to rear bulkhead
-Range of 200+ Miles
-Cruise at 30mph in calm seas, 20ish in 2-3 footers, slow and not sketchy in 4-6 footers
-Single main with kicker

I think either of the boat will do that with a 140 or 150 on the 25 and a 200 on the 28 or am I dreaming?

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

Posted: Fri Sep 09, 2022 5:11 am
by OneWayTraffic
It's not just the weight, it's the location of it, and how high in the boat it is. I feel that the designer would never approve; if he thought it viable he would have designed it.

For those climates I'd recommend either the P21 or the DE23 or 25. I'm not sure about width off the top of my head though.

I'd imagine that the Pg25 would look better, but it's a narrow boat. If I were putting a top on it, I'd go for a t-top with wrap around clears, or a pilothouse console built light.

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

Posted: Fri Sep 09, 2022 9:19 am
by fallguy1000
Well, the idea of a pilothouse on a Panga is terrible. Sorry, but the boat is really narrow and stability and trim would be affected.

The GS28 could certainly be done with a house. I never understood the 8'2" dimension on the boat. Is that for a 2" rubrail each side? Perhaps. Any house would need to be made super light with foam core 12mm and db1700 glass each side with high density inserts as needed for hardware. But...

The front section of the GS would then be inaccessible. And the house would get very hot in Florida or the Gulf of Mexico. So, scope screep is rapid and you'd be adding a pass through door or extra bilge pumps/scuppers for the forward section, air conditioning, etc.

More conversation would be needed than a one paragraph reply.

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

Posted: Fri Sep 09, 2022 9:22 am
by fallguy1000
Build a DE style.

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

Posted: Fri Sep 09, 2022 10:35 am
by barrelroll
fallguy1000 wrote: Fri Sep 09, 2022 9:19 am
The front section of the GS would then be inaccessible. And the house would get very hot in Florida or the Gulf of Mexico. So, scope screep is rapid and you'd be adding a pass through door or extra bilge pumps/scuppers for the forward section, air conditioning, etc.

More conversation would be needed than a one paragraph reply.
The idea is to link the cuddy/ jump cabin to the pilot house so you wouldn't have an open area up front. If you need to access the bow the shelves would be wide enough to walk around. I've got a drum anchor winch going on my boat in progress and don't plan on accessing the bow often. I live in Alaska, no need for ac though depending on the direction you go most marine heaters are around 20 pounds + a couple gallons of diesel or a bbq propanetank.

The pilot house on my tolman is built pretty light with marine plywood. The lower sides are 1/4", the upper sides/ windshield frames are 1/2", rear bulkhead is 3/8", door is 1/2" with a big lexan window, and the roof is 1/4" with some support beams that double as hand rails. Everything is getting covered in 4oz besides the outside of the roof which will get 10oz glass.

There was lots of talk about a bracket moving the center of gravity too far aft on a panga. Wouldn't adding a bracket help offset the weight of the pilot house?

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

Posted: Fri Sep 09, 2022 10:53 am
by barrelroll
fallguy1000 wrote: Fri Sep 09, 2022 9:22 am Build a DE style.
That might be the better option. For some reason I thought it was too wide, designed to cruise much slower, and an inboard boat. Its an outboard and 8'4" wide so i could probably squeeze it out of the shop. It's not designed to cruise faster than 30 according to the study plans topping out at 29-33mph with a 150, a 200 which is the same weight as a 150 would probably get me a high 20's cruise speed. Our current skiff cruises at 18-20mph and our favorite halibut spot is a 30 mile run, causing near 30mph would get us an extra hour on the fish each trip weather permitting.

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

Posted: Fri Sep 09, 2022 11:29 am
by fallguy1000
barrelroll wrote: Fri Sep 09, 2022 10:35 am
fallguy1000 wrote: Fri Sep 09, 2022 9:19 am
The front section of the GS would then be inaccessible. And the house would get very hot in Florida or the Gulf of Mexico. So, scope screep is rapid and you'd be adding a pass through door or extra bilge pumps/scuppers for the forward section, air conditioning, etc.

More conversation would be needed than a one paragraph reply.
The idea is to link the cuddy/ jump cabin to the pilot house so you wouldn't have an open area up front. If you need to access the bow the shelves would be wide enough to walk around. I've got a drum anchor winch going on my boat in progress and don't plan on accessing the bow often. I live in Alaska, no need for ac though depending on the direction you go most marine heaters are around 20 pounds + a couple gallons of diesel or a bbq propanetank.

The pilot house on my tolman is built pretty light with marine plywood. The lower sides are 1/4", the upper sides/ windshield frames are 1/2", rear bulkhead is 3/8", door is 1/2" with a big lexan window, and the roof is 1/4" with some support beams that double as hand rails. Everything is getting covered in 4oz besides the outside of the roof which will get 10oz glass.

There was lots of talk about a bracket moving the center of gravity too far aft on a panga. Wouldn't adding a bracket help offset the weight of the pilot house?
The Panga is a narrow boat. He has a sleeping berth design, but that is all it is. The Panga has an immersion rating of 510 pounds. Add a bracket and larger engine and pilothouse and very soon the boat is an inch below her design lines. Add a few nice halibut and some leads and rigs and another inch. It will not serve you as good as the Tolman.

As a person who enjoys fishing, I understand your wishes for the right boat. My guess is your greatest desire is safety, second dry ride. The Panga with a cabin is a mistake in every way. The center of mass of the boat will rise forward; destroying that which makes the panga so good in high seas; stability. The boat will rock horribly abeam as well. It is an epic error; believe me. Terrible for drifting for but. Erase the house and the Panga is a great trolling boat and less rocking drifting abeam.

The DE offers you 30mph with a 200hp engine; dry ride; room to stand even in the house. Set it up with autopilot and a small radar alarm and you can cook/eat breakfast underway. Catch a bucket of warm water off the engine output and warm your hands even. It is a really great boat.

All boats that go faster have a tradeoff! Fuel economy always drops once on plane. Keep that in mind if you are worried about the boat being too slow. Jumping from 150 to 200 on the DE is going to cost more money for engine and running both.

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

Posted: Fri Sep 09, 2022 1:22 pm
by Cowbro
Since you are already looking at large boats and 200hp outboards, how about the CS25? The only thing that doesn't fit your criteria is the width, but the widest part of that boat is the flare in the topsides that you could easily modify the shear and trim it up a little to stay at or under 8'4". Just leaving the rubrail off and going with a heavier inwale might get you what you need. That boat will handle the seas, the weight of the cabin, etc no problem, at the trade off of more weight, slightly more involved build and worse fuel economy.

Phil

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

Posted: Fri Sep 09, 2022 3:55 pm
by rick berrey
GS28X options state " a light pilothouse based on the tower tower style and dimensions is possible " . So you can build a pilot house so long as it is the shape and size of the tower , and light . I think the issue will be weight and performance , a total foam build and maybe S2-glass or carbon on the cabin and pilothouse could be an option . So as per the study plan , yes you can build a pilothouse .

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

Posted: Sun Sep 11, 2022 8:33 pm
by TomW1
There have also been one DE25 lengthened by more than 10% and one being lengthened by 10% at this time. Check there are plenty of ideas in their builds in each build. Tom

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

Posted: Mon Sep 12, 2022 10:40 pm
by Matt Gent
I spend a lot of time in a DE foam pilothouse and warm temps are a non-issue. Only need 3-4 kts of breeze and it ventilates well. Surely would be fine in Alaska.

IMO the Panga is too small for a functional pilothouse, much less for 4 people.

I’d think the GS would make a great pilothouse boat, just being careful not to move the Cg fwd too much. Based on the hull form it looks to me much more comfortable than a DE in heavier seas.

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

Posted: Tue Sep 13, 2022 7:10 pm
by rick berrey
I think intended use needs to be factored in when looking at the panga 28 and DE25 . The study plans say the Panga,s top priorities were economy and sea worthiness , without the pilot house it is a fishing machine , that was what it was designed for . The DE25 is a picnic hull , it is designed with some comforts , and would be great for both fishing and hunting trips . I did find some pangas with skinny pilot houses , 29' was the shortest of the bunch , so the 28 would be on the low end . There have been many times I have wished I had a jump cabin or pilot house here in the south . If I were in Alaska and building a boat in that size range a pilot house would be a must . If I were going to make a long run , purpose driven to fish or hunt I would have to go with the panga , 4 people could fit in a skinny pilot house . I would consult with J before I ruled it out , as it is listed as a build option .

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

Posted: Wed Sep 14, 2022 8:28 pm
by barrelroll
I think you guys have me convinced the panga isn't enough boat for my needs. I bought the gs28x and de25 plans. I've got 14 hopefully quiet night shifts coming up to do some research.

I forgot everywhere else doesn't have 50 degree rainy days in the middle of July. Just about every Alaskan fishing machine has an enclosure to get out of the weather, even my 17 footer has a windshield and full canvas enclosure.

We use our boat a fair amount, usually 200 hours a year on the main with a lot of time on the kicker and on the hook halibut fishing. Use goes from a close afternoon fishing trips to 150+ mile trips and staying on the boat for multiple day trips. Range needs to be a minimum of 150 miles + reserve, 300 miles would be perfect.

The more I read about the de25 I'm not sure if it's the right boat between the cruise speed and bad weather handling.

I need to do some more research on the gs28. A 6' long pilot house fits nicely on the jump cabin model. I think I can get pilot house weights down pretty close to the tower console and get fuel close to the same spot it is on an open boat.

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

Posted: Wed Sep 14, 2022 9:31 pm
by Matt Gent
Here's an overlay of the DE25 and PG25. The PG is a full foot more narrow at the station of the DE helm.

Image

I've been in the DE in all kinds of water. I've always felt safe, but I've often felt uncomfortable. The shallow deadrise carries well forward, making for some hard slapping/pounding particularly in quartering seas. It would be great in larger period waves; we deal with a lot of wind chop. It does not want to broach (large keel, shallow entry). The skiff bottom is great that I can take fully-loaded trips with 140hp, but it comes with some compromise. I consistently get over 3mpg and carry 60 gal; 100gal would be easy to fit. Cruise depends highly on the water conditions; generally between 17-24mph is OK.

My ideal cruiser would be a Dorado 30 converted to pilothouse with a large single OB and a kicker; I think the GS28 is pretty close to that hull. Unfortunately the Dorados are really hard to come by.

Image

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

Posted: Wed Sep 14, 2022 9:59 pm
by barrelroll
Matt Gent wrote: Wed Sep 14, 2022 9:31 pm
I've been in the DE in all kinds of water. I've always felt safe, but I've often felt uncomfortable. The shallow deadrise carries well forward, making for some hard slapping/pounding particularly in quartering seas. It would be great in larger period waves; we deal with a lot of wind chop. It does not want to broach (large keel, shallow entry). The skiff bottom is great that I can take fully-loaded trips with 140hp, but it comes with some compromise. I consistently get over 3mpg and carry 60 gal; 100gal would be easy to fit.

My ideal cruiser would be a Dorado 30 converted to pilothouse with a large single OB and a kicker; I think the GS28 is pretty close to that hull. Unfortunately the Dorados are really hard to come by.
Thanks for the response. We deal with lot of close 1-2 foot afternoon wind chop. We almost never see widely spaced rollers. I have a boat that's safe though uncomfortable in those conditions currently. That's why I was drawn to the gs and panga. Pounding into a 2' head sea for 15-100+ miles at 10-15mph is getting old.

Between the handling in rough weather and the common weather we have on the inside passage I'm thinking the de25 is too much of a paint shaker for me.

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

Posted: Wed Sep 14, 2022 10:02 pm
by TomW1
Why has no one mentioned the CX25 which can be stretch 10% to 27.5'. It is an ideal offshore fishing boat and has a full pilot house with sleeping area and kitchen for overnight trips. One buillder used a 300 HP motor on his build and had plenty of power. Recommended fuel tankage is 110 gallons but you could add more or less. Well food for thought. You won't have any paint shaking with this boat. :D

Tom

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

Posted: Thu Sep 15, 2022 9:21 am
by rick berrey
Tom ,The cs25 was mentioned but not the cx , i would agree it would be a better option than the de25 . A 27.5' CX25 would have the panga beat in the comfort zone for an overnight trip , it would be the other design I would be looking at if it can be scaled up and if beam wouldn't be an issue if it had to scale both L/B . Intended use and cost would dictate my pick as performance of either would do the job .

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

Posted: Thu Sep 15, 2022 5:25 pm
by TomW1
Jacques is pretty particular on scaling L/B, but this boat is already 8.5' wide, and he may let you get away with just length. Scaling width would take you to 9.3875'. Less than a foot wider. Since Jacques is retired ask Jeff to ask Jacques his opinion on scaling the CX. Or buy the kit as is and have the boat ready in a much shorter time.

Second concern on the GS28X. Even using Divinycell the added weight of that much of it plus the fiberglass and epoxy concerns me. You mentioned earlier the plans mentioned "a light pilot house defined by the tower dimensions." This would be nothing like you are planning. This is what Jacques considers a Pilot House. Though you can make yours much larger to encompass the tower. https://www.boatbuildercentral.com/wp-c ... 07/PH3.pdf You can put a head in it, heat it. Seats for passengers to get out of the wind and whatever. The main thing is that it is centered over the CG unlike your idea. You will still have your sleeping bunks up front, and it will cost less.

Well my thoughts for today. Tom

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

Posted: Thu Sep 15, 2022 8:32 pm
by rick berrey
One option might be to build the pilot house with sitting head room , put a sliding hatch over the steering position if you want to stand . Cutting down height might let you build the pilot house a foot or so longer .

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

Posted: Thu Sep 15, 2022 10:58 pm
by Matt Gent
A foam and glass pilot house structure doesn’t weigh much at all. The bigger impact is the space you create to haul more crap along.

I’d be surprised if mine were much more than 200lb. The windows are the heaviest bit.

I’d build the house you want. I think the GS28 would be a great long distance platform for rougher water at moderate speeds.

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

Posted: Thu Sep 15, 2022 11:13 pm
by TomTom
Having re-read your initial requirements for power, I think that the GS 28 would fit the bill well and also surprise you with its efficiency. I suspect you would meet those cruise speeds with a single 150 HP so 200 would be fine.

I also agree with Matt that you could build a light enough structure and not affect performance too badly so long as you didn’t start using the cabin as a dumping ground for gadgets and fishing accessories!

And I also agree with your point that a superstructure with a tower etc vs a light cabin there is probably not that much difference.

I think you could balance the extra weight fwds by moving console area slightly back if needed - but I wouldn’t go with a bracket option.

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

Posted: Fri Sep 16, 2022 7:40 am
by barrelroll
I've got a pilot house roughly mocked up on the GS. Frame spacing makes for a 6' long pilot house floor. The back of the pilot house falls where the back of the console is in the study plans. Drop the sole to the bottom of the stringers in the middle of the pilot house and the peak of the roof is roughly 32" above the gunnels with a 6' walking height. Instead of a large console just a small dash would bump out from the cuddy bulkhead, 2 seats on pedestals and everything modular/ removable. Around 6-7 sheets of foam with a lot of waste, large lexan windows for anything besides the windshields and 36" long marine sliders for the helm seats to drop weight even more.

How much weight if any does going with honeycomb floors/ soles save over the speced 1/2" plywood?

The plans call for 2" aluminum pipe for the tower, rough guess 150-200' of pipe @1.24 lbs per foot with weight up much higher. Dropping the sole to between the stringers helps get it a fair amount lower than the tower as well.

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

Posted: Fri Sep 16, 2022 11:08 am
by fallguy1000
All about flex.

1/2" ply is okay on spans under 20", but needs topside laminate of about 1208 minimum for wear

1" honeycomb can span 50", but requires a mega glass layup for that., so its apples to donuts

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

Posted: Fri Sep 16, 2022 3:32 pm
by rick berrey
If you do not plan on a foam build using infusion then I would consider that for weight savings over all . Replacing heaver layups of 1708 that are not in structural areas where mat is used only for puncture resistance with 1700 , and maybe Kevlar might save a pound here or there . I think Evan used some carbon fiber in his catamaran rebuild in non structural areas of the interior , he might advise on weight savings .

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

Posted: Fri Sep 16, 2022 3:53 pm
by TomW1
Jacques has pointed out time after time that building in foam for small boats or structurers do not save weight. The extra fiberglass and epoxy make up for the weight of the wood. Building the pilot house forward is definitely going to affect the LCG by a couple of 100lbs. So, he will also need to move the helm back 6"-1'. I would have to do the calculations to say how much exactly.

Barrelroll one thing you will want to do is install the skeg since you're in the Gulf of Alaska.

I am not sure why he wants the extended front end on his sketch but if he cut it off as it came down from the front that would be great, or even a couple of feet for a toilet. Maybe he can explain what it is going to be used for?

If he only wants to do the white section on his sketch, I think that would be fine.

Tom

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

Posted: Fri Sep 16, 2022 5:35 pm
by rick berrey
If you go back and read past post on use of foam and weight savings on the forum , I think you will find around 25' is the rule of thumb where weight savings start . If foam would not give a weight savings to a narrow beam boat designed to be light like the GS28 , I don't think it would be a design option , but I'm not the designer . The Designer gives the options , if they were not safe or feasible he would not give them as options , so if someone ask if they can build in a pilot house , and it is listed as an option , the answer should be sure you can , and it is safe and feasible or the Designer would't have given you that option . Foam will save weight on larger boats if the work ( method and means ) is done correctly and as per design . Weight for E-glass is 159 lbs per cubic foot , Kevlar is 89.9 lbs , so about half the weight , carbon 108.9 , Kevlar cost factor will be around 4x E- glass , but if you can replace some epoxy sucking mat or E-glass with Kevlar or Carbon infused on foam then you have some major weight savings at a cost .

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

Posted: Fri Sep 16, 2022 7:32 pm
by fallguy1000
Any boat CAN be made lighter in foam. Fact.

Will it be as good as a ply boat? Maybe better, maybe worse.

I can't wait for winter to show you guys a short, ultralight foam boat.

The reason foam in almost ANY pilothouse is a good choice is that lower weights up high keep the boat more stable. And, fortunately, a great layup for foam pilothouses can be done with 12mm cores and db1700 glass each side. Using vac, you can reduce the weight by about one pound per yard if you want to work that hard.

But.

Many a pilothouse has been built in 6mm plywood with lighter skins. And the weight tradeoff is not great. I can calc it, but not now. Dinner bell..

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

Posted: Fri Sep 16, 2022 7:49 pm
by Matt Gent
The foam payoff comes at smaller structures when you don't need the skin thickness for puncture resistance.

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

Posted: Fri Sep 16, 2022 9:34 pm
by fallguy1000
Matt Gent wrote: Fri Sep 16, 2022 7:49 pm The foam payoff comes at smaller structures when you don't need the skin thickness for puncture resistance.
Bingo

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

Posted: Sat Sep 17, 2022 11:37 pm
by OneWayTraffic
Having another read of the OP and further information he provided I think that the PG25 should be given another look. The C and P series perform very close to the Tolman that he already has, and it seems like one main factor for the second build is to change things that he is not satisfied with for his first. Ride in a formed sea being one of the main reasons. I have the pilothouse console plans, and I am sure that they could be built very light, using foam or 6mm ply. The cuddy could be redone as a jump cabin with fishing platform on top, lowering windage somewhat. A fuel tank in the bottom of the boat would help a deal as well.

When it comes to ride in chop the PG25 is one of the best options out there.

There's a good discussion on this thread where TomTom and the designer have a chat about the two boats.

viewtopic.php?t=60954

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

Posted: Sun Sep 18, 2022 10:24 am
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 .

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

Posted: Thu Sep 29, 2022 1:57 am
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.

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

Posted: Thu Sep 29, 2022 9:59 am
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

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

Posted: Thu Sep 29, 2022 11:57 am
by TomW1
Duplicate, sorry. Tom

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

Posted: Thu Sep 29, 2022 12:40 pm
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

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

Posted: Thu Sep 29, 2022 1:12 pm
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 .

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

Posted: Thu Sep 29, 2022 2:52 pm
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

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

Posted: Thu Sep 29, 2022 4:54 pm
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 .