Western red cedar question

[volkswagen50]

Could someone tell me what the maximum practical length is for a displacement hull built from WRC in strip fashion? i was planning on 25' with double planking (about 1.25" total thickness) set in epoxy, sheathed on both sides in glass.
Is this feasable for a coastal cruiser?

thanks, Greg

[peter radclyffe]

Originally Posted by volkswagen50

Could someone tell me what the maximum practical length is for a displacement hull built from WRC in strip fashion? i was planning on 25' with double planking (about 1.25" total thickness) set in epoxy, sheathed on both sides in glass.
Is this feasable for a coastal cruiser?

thanks, Greg

we built 2, 70 foot cruising yachts at SYS Craftmans Art, bill dixon, & Rocco, tony castro

[apex1]

In principle there is no maximum length, but its sensible to stay below 30 meter. Boats up to 40 meter have been done that way though.
At roughly 8 meter you have no problem.
Regards
Richard

[volkswagen50]

Thanks guys!

[alan white]

Originally Posted by volkswagen50

Could someone tell me what the maximum practical length is for a displacement hull built from WRC in strip fashion? i was planning on 25' with double planking (about 1.25" total thickness) set in epoxy, sheathed on both sides in glass.
Is this feasable for a coastal cruiser?

thanks, Greg

The Mount Desert Isle boat company built 25-26 ft Amphibicons and Amphibiettes as well as the larger thirty-something foot Controversy. All sailboats.
The boats were strip built in (I believe) cedar, resourcinol glued and edge fastened, but in any case a soft wood like pine or cedar, probably eastern white. No glass/resin at all.
I've examined a few and sailed at least one that was forty-some years old. The hulls stand up beautifully and the method is sound, perhaps more durable and trouble free than carvel. A friend built a 40 ft Chris White "Skyhook" tri with mostly 1/2" WRC, with epoxy/glass.

[PAR]

I have a 40' trawler with WRC planking, though it's carvel.

From a technical stand point there's really no limit, you can engineer a structure to work with WRC.

From a practical stand point, once you get past a certain size, other species and materials become more desirable.

Typically WRC is reserved for light weight smaller craft (under 30').

[volkswagen50]

Well, I had thought about building a frigate replica, but I've decided to build a 25' freighter instead, stern castle, two small hoists, a small diesel single screw. From what I see here, maybe single thickness will work fine. It will be for lake and some coastal cruising. The boat Little Leon really made me think.
I would rather use a heavy keel than water ballast, and a freigher like shape above the waterline with a softer shape below the waterline. I've got DelftShips free software in another window now to look at possible hull shapes to shrink for lines, but the basic hull will be laminated frames with wrc strip planking.

Going over some basic fomulas that I've seen on this site, a 25 on deck 22 or so WL, with a 7' beam won't be too ideal for fuel, but with a 8-10k speed, I should still be able to do well with small horse power.
I was thinking between 20 and 50, thoughts?

I think the key to making a freighter design work will be in getting enough ballast to keep initial stability good, paravanes on the hoists will help roll in moderate seas. Any input is helpfull, I was at the lumberyard today that specialises in WRC, any hints on selecting wood will help too. It's not bad stuff, reasonable with very small knots in the midgrade, a bit pricey in the A grade but if i have to I have to.
thanks!

[apex1]

Originally Posted by volkswagen50

I think the key to making a freighter design work will be in getting enough ballast to keep initial stability good, paravanes on the hoists will help roll in moderate seas
thanks!

Sorry NO,
not to dissappoint you, and please, no offense, but making a boat design has NOTHING to do with a nice program.
Knowledge makes a design! And even than it may be crap! Several thousands of floating devices in every western country can tell witness of that statement. Some bear big names.
Do not try to invent the wheel again, please. Lookup "Atkin boats" or boatplans.
You´ll find a hell of a good plans. Nothing suits you? ask for a "refined" design one or the other member here can offer you! Be shure you´ll get what you need.
Not from me!
I hate to abuse this forum for ad´s. I sell my crap where the people are aware of being robbed.
Regards
Richard

[PAR]

Freeship, Delftship and other free or low cost software packages are a wonderful tool for making pretty pictures and developing volumetric figures about them. Unfortunately, what these bits of software don't provide is the ability to see if one shape is better suited to your needs or more importantly if the shape is any good at all.

If you use the square sections typical of a freighter, you'll have very nice roll qualities and high initial stability. Of course these sections are the most efficient, they're intended to provide maximum internal volume and a side benefit is a low roll moment.




I found this model on line with free plans. Of course at the scale you want to build, the hull will need a larger beam/length ratio, but it's a starting point.

[volkswagen50]

Maybe I should clarify my statement about the key to making a freighter design work being ballast, as this seems to be taken out of context.
The key to making a freighter design work in this size and this hull material is going to be ballast. AND a softer bottom. The full lines of a real freighter are for capacity. I don't need to ship anything, but I do want the look and feel of the freighter. In wood and with a full squared bottom, it will float high and be like cork. It will roll on the surface of the waves because it will have low draft relative to size. SO, to fight this, I'm giving it some V in the hull, but below the waterline. Plus it will carry a good amount of fixed ballast, to get some draft. That will help stability as well.

To clarify a few things that I do know:

Squared chines will give high initial stability and will be slow to right once on the beam ends. Why? because stability works in BOTH directions. The heavy ballast will help in righting it should it roll far, while if it was a real freighter it would roll completely, capsize because of the weight of the load that would be higher.
Soft chines will roll more initialy but be harder to capsize because of higher stability on its sides. A smaller side in the wave, it will start to get lower in the water and right itself.The square edge won't be there to keep it from rolling back onto the keel again.
So we seek a compromise.
I'm not trying to reinvent the wheel here, and I do know that just sizing down an existing freighter plan won't work precisely because of the L/B ratio. So a compromise there will have to be made as well. I was thinking of a beam of around 7 feet and LWL of 22-23'. that sounds doable. On a lake the sive of Hartwell in GA/SC with no real heavy waves, this should be safe and work well at what I want.

PAR, that freighter model you show is the one that started me thinking. I found it a little bit ago and it looked EXACTLY like what I wanted.I'm glad you agree about that boat, it's nice looking.

What I expect from the programs are things that I can't do myself: where the waterline will be for a given length and beam and what weight will be needed to achieve it. Hull speed and figuring out a few other things should be within the scope as well. Were i designing a 100' boat I would definitely be looking at a naval architect, but to think that a 25' boat is beyond a home based non pro designer? I'll take all the free advice I can get but I've been around boats my whole life, I'm not going to build anything that doesn't LOOk right. I won't build anything I don't build a model of first.
That said, if anyone wants to help with critisism of my design, I welcome it. The more eyes the better! When I get something I like out of the software I'll post it here in a separate thread to get opinions. I really do appreciate everyones input, good, bad or indifferent.

[PAR]

Your beam length ratio is very workable, I just don't see the need to design a whole new hull, when all you need is a reasonable approximation. Learning enough to design a hull capable of offering the features and dynamics you want just seems a long way around a small problem.


This hull is the general dimensions you want, but needs topsides shaped to suit your needs. It's speed is limited to 18 knots or so, but that would be way out of scale for a freighter anyway, so why go faster. She has lots of hull volume so you can load her up with freighter looking stuff.

Plans are $50 from Atkins & Company.

[volkswagen50]

Thanks PAR. I did go and look at his designs after i saw what APEX was talking about. If I add what i want to the top of the hull, then add about the same in the form of a steel or lead shoe to the keel, (down the length)it will sit lower, sure, but should retain it's stability.
When i buy plans from a place like that, do the plans include something that tells me the design's weight carrying capacity? Not in people, but in pounds? Then I know what I can add. But it won't be a ton of wood, I'll tell you. Just enough to make it like a freighter and give it a small cuddy cabin.
I liked what they had in utility boats on his site. One of them may work out nice for me.
Thanks again, Greg

[apex1]

Jepp, I thought about the "Judge Hooker" that may attract you.

[PAR]

The basic dimensions and hull parameters will be covered in the plans. As long as you don't change the underwater configuration and most importantly keep the build light, you should be fine. In fact, most of their designs are good candidates for upgrading to modern building methods, which produce lighter, stronger structures. This requires some skill, but any reasonably experienced designer can preform the conversion. I did a conversion on one of Billy's "Sea Brights" this winter.

Adding weight before you know how much or where to add it, isn't a wise thing. Stability is derived through two paths, hull form (shape) and/or weight. The design I posted above is a quite stable shape as designed, without a chunk of metal hanging below anything. If a conversion is preformed, then you may gain some weight lose in the structure (very likely), which could be applied to the bottom of the keel if desired.