Panga 20 Build

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jacquesmm
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Re: Panga 20 Build

Post by jacquesmm »

I understand the question now. No need to calculate trim changes, just use the method described by TomW and try to keep your new LCG close to what it was. On that plan (as on most others), the LCG is just behind the console, under the feet of the tillerman.

The good news is that your coffin box is close to the existing LCG. I also see a larger seat that is not on the plans and that one is behind the LCG.
The resulting LCG looks close to what I designed.
That thing looks heavy BTW and the PG20 is a small boat for it's length.
Is the baitwell in there? Try to keep variable weights like fuel tank and baitwell as close as possible to the LCG.

Since you are an engineer, you can duplicate what I do in Orca:
- set a unit weight per material area (epoxy-ply), linear for tabbing, point for objects (steering, crew, fuel tank).
- calculate areas and length, apply weights, get moments for each and a total moment and weight
- do the same for the original parts and compare
The difference will tell you what to do: probably disregard the small difference.
Or take a short cut and trust me, it like it will be close.
-
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cape man
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Re: Panga 20 Build

Post by cape man »

To answer another question you raise about clearance, the 5 gallon bucket is a great way to do it easily. If a 5 gallon bucket will fit on the deck between the console, leaning post, casting deck, etc. you can walk through that area as well (without the bucket there 8) )
The world always seems brighter when you've just made something that wasn't there before - Neil Gaiman

FluidDynamic
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Re: Panga 20 Build

Post by FluidDynamic »

Fallguy, I think tones get lost in text sometimes. I didn't think anything of it. I think the tone got lost in my text as well. No big deal. You have been a major help with this project. Thank you.

FluidDynamic
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Re: Panga 20 Build

Post by FluidDynamic »

The baitwell was on front of coffin. I could switch the baitwell to be behind console if needed. I guess I need to sit down to figure out the weights of everything and calculate all the moments. The leaning post in the back can also be made smaller. Could also remove platform that leaning post was sitting on.

TomW1
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Re: Panga 20 Build

Post by TomW1 »

FD I have been away all day and Jacques is correct do the calculations as you want the boat. I think you will find with the water in the livewell forward that you will be pretty close depending on how many gallons your right. He and I have talked on this subject and both of us have taken courses from Westlawn me back in the 70's when I was bored sh**less while an officer in the Navy, he also after moving to the States, neither of us completed the full course load. :) But we can generally understand each other as we both got through power boat design.

HP for the PG20 is rated for 50-70, by Jacques and there are several companies that have motors in that range that weigh very close to within 10lbs of each other. Once you get to the 75-90 range you are adding 125-150lbs to the weight on the transom. Set the Longitudinal Center of Gravity as your fulcrum. Then move things fore and aft of it.. Remember it is at the waterline while you will be moving things at the deck level in most cases.

Well get out your old fashioned spread sheets :lol: and like Jacques and I previously said lay it out how you want. Once the deck is built how you do it as long as the LCOG is balanced the design is yours. :D :D 8) Remember we both said it is a long narrow boat when you make changes so keep them on the center line.

Tom

PS: Don't move the livewell back as it will just add more weight aft which you don't need. Do your calc's.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

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Re: Panga 20 Build

Post by TomTom »

FD - your build looks great - I think you are going to have a beautiful boat, beautiful boat.

At the risk of sounding presumptuous, but also as someone who has spent a lot of time putting way too much stuff into small boats, and learning that hard way that most often less is more... could I suggest that perhaps you consider a removable live well, and removable storage.

I have found that with small boats you have to think about what you will be doing on it for that particular day and pack accordingly. We all tend to start to imagine ourselves as the proud new owner of a 36 foot Sportfisherman and then imagine leaving that much stuff on board ... rod lockers, bait prep stations, fighting chairs get built with great enthusiasm - only for us to realize our boat is way heavier than designed.

The reality is that one day a small boat will be used for a day with mates and beers, another will be live bait fishing, another will be towing kids on a tube, or taking the relatives for a cruise.

You can never keep all that stuff, for all the different things you use your boat for on a small boat, so you end up taking it on and off the boat daily at the ramp. How do you get your stuff to the ramp ... probably in a storage box or cooler or something like that anyways. It then makes no real sense to unload this and put it into another storage locker.

Same goes for a live well... what about a live well that you put on the boat on the days you will use it. Have your plumbing in place and plug and play.

All of this means that you can adjust your weight and balance to suit the boat, the no of people on board etc.

Look around the forum and you will find post after post from people who say the boat sits deeper than planned, water comes in through the scuppers, its not as fast as it should be etc...

It isn't because Jacques got his maths wrong - its all because we love to overload our small boats. We've been brainwashed by the fact magazines and boat reviews to think that a 20 foot boat should have a fly-bridge!!

I think you are slightly in danger of doing this, and in so doing taking away all the advantages of having a small, light, fuel efficient Panga!

At the very least, I would suggest you build your boat to near completion and then launch it with the engine mounted, fuel tanks full etc. Have the console built or a mock up of it - but don't fix it anywhere - or bolt it temporarily where you want it.

Then move your other weights around and see how she sits in the water, how you feel about the spacing etc. Its much easier to take a little time and do this before your finish her beautifully inside and then realize its not how you want it.

Please don't take this as me being a harsh critic - it isn't - its 19 years of being on the bateau forum and 2 boats and one rebuild later suggesting how I would do it in your shoes. Best wishes Tom

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Re: Panga 20 Build

Post by FluidDynamic »

I don't take it as harsh at all. I usually dream big about something and bring it back to reality. I just quickly drew that concept up and really hadn't thought it through. To be honest with you, I'm probably going to just put a simple console and a simple leaning post on it and let it fly. I do realize that this is a small 20' boat. That was the intention. Just got a little out of control on things I wanted in the boat. I do think I'll end up just having a portable cooler that I can take out. May still put a livewell in, but it would be smaller.

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Re: Panga 20 Build

Post by TomTom »

I think u are making the right choice... you can always make a livewell that fits in place nicely later on ... or you can have one that is removable with straps or similar. But get to know your boat as it should be first. Many production boats use a cooler strapped in as a seat rather than a built in one. We fish a lot on Yamaha 23 foot Pangas ... there isn’t a lot of room and I have come to appreciate fwd planning for the day ahead over any amount of storage space in the boat.

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Re: Panga 20 Build

Post by jacquesmm »

FluidDynamic wrote: Wed May 08, 2019 12:00 am I. . . To be honest with you, I'm probably going to just put a simple console and a simple leaning post on it and let it fly. I do realize that this is a small 20' boat.
Wise decision.
The Pangas are small for their length, they have a small waterplane but they are very seaworthy.
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FluidDynamic
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Re: Panga 20 Build

Post by FluidDynamic »

Finally got the skeg and the spray rails on. Next step is to fiberglass them on. Hopefully they won't be hard to to fair them in.
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