Build methods

Questions about modifying a design

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Christer
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Build methods

Post by Christer » Sat Nov 03, 2018 10:03 am

Hi y'all,

I am sure this has been discussed in length before, but I am either useless at searching, or the topic has not been brought up in a separate thread. My money is on the former, but here goes anyway.

It seems to me that for amateur builders, there are two (three) main build methods: stitch & glue (plywood/epoxy/fibreglass), plywood on frame (timber frame, plywood sheeting, screws and epoxy to hold stuff down and fibreglass) (and aluminium/aluminum). I won't be discussing aluminium boat building as I can't weld and have absolutely no experience in that area.

So, S&G and PoF.

I am sure each method has its merits and that both lead to a safe, functional boat. I am also vaguely aware of how each method is carried out and as such my question may seem a little redundant, but, why is S&G favored some places, vs PoF over here at Glen-L? Tradition? Designer's preference and/or lack of familiarity with the other method?

Part of the reason I ask is that I built a S&G dinghy many, many years ago. Now I keep finding myself back at the pages for WildCat EXT Sport and BearCat Sport and I am curious if the PoF plans on offer are possible to convert to S&G, and if so, how much work it would be, if it's worth it, if I'll gain anything by doing so (lighter/stronger boat), etc.

I'm in no way bashing anyone's designs nor PoF or S&G as a build method - I built my 8' dinghy using S&G as a teenager and found it a very easy and satisfying way to build a boat, but if I'd found a plan using PoF, I'm not sure I would have felt differently. As I said above, both methods lead to a safe, functional boat, so I'm not entirely convinced either is better than the other, they're just different.

Comments welcome.

(Full disclosure: This question was also posted over at the Bateau2 forums, where S&G is the predominant build method. I've not bought any plans from either designer, I'm merely looking for opinions on the build methods. If the plans for the Cats are convertable to S&G I'll be very interested in help in doing so as well, but that's a secondary goal.)
8' dinghy built in 1992, BBV sufferer ever since.

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hoodman
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Re: Build methods

Post by hoodman » Sat Nov 03, 2018 7:07 pm

Hi, I took a look at the 22' Bateau cat which you might be comparing to one of the Glen-L cats. If I'm getting this right it appears that the Bateau is not only stitch-n-glue but also a fiberglass-plywood-fiberglass sandwich construction. It also appears that that design relies at least somewhat on the fiberglass for strength. What this tells me is that there is just oodles of epoxy required to build the Bateau. I'm thinking at least double the amount you would normally use to build a plywood on frame boat.

I really prefer the plywood on frame boats here at Glen-l. You get full-sized printed paper patterns for all the frames. The fiberglass covering is just a lightweight cloth so it's easy to wet out and doesn't take a ton of epoxy to fill the weave. It's not structural, it's only there to provide waterproofing and "armor" for the hull. I really can't imagine having to fiberglass the INSIDE of a hull. That truly sounds like a nightmare.

As to why Glen-L doesn't have as many stitch-n-glue designs is simply because it's a newer building method and most of the designs in the catalog predate it. Plywood on frame is an evolution of traditional boatbuilding methods. But you don't need as many frames as a "solid" wood planked hull. With epoxy used as the adhesive, the result is a super strong and stiff hull. Everything basically becomes one.

There are a lot of great looking designs over at Bateau. I'm sure they are great boats. However, I don't think stitch and glue is really fundamentally "easier" than plywood on frame.
Matt

Building a Geronimo......!
viewtopic.php?f=2&t=25139

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vupilot
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Re: Build methods

Post by vupilot » Sat Nov 03, 2018 8:14 pm

Having built both S&G and Framed up, in the final product I generally like the framed up builds better as the boat feels stronger/stiffer and more robust overall. However, S&G can be a much, much faster way to build. There are difficult tasks in both S&G and framed up builds but I think there are fewer difficult tasks with S&G. It depends what kind of boat your are building, how its designed and how it will be used. Some are perfect for S&G and some really need to be made of framed up construction. Either way stick to what the designer calls for and you'll probably have good results.

Christer
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Re: Build methods

Post by Christer » Sun Nov 04, 2018 3:38 pm

hoodman wrote:
Sat Nov 03, 2018 7:07 pm
Hi, I took a look at the 22' Bateau cat which you might be comparing to one of the Glen-L cats. If I'm getting this right it appears that the Bateau is not only stitch-n-glue but also a fiberglass-plywood-fiberglass sandwich construction. It also appears that that design relies at least somewhat on the fiberglass for strength. What this tells me is that there is just oodles of epoxy required to build the Bateau. I'm thinking at least double the amount you would normally use to build a plywood on frame boat.

I really prefer the plywood on frame boats here at Glen-l. You get full-sized printed paper patterns for all the frames. The fiberglass covering is just a lightweight cloth so it's easy to wet out and doesn't take a ton of epoxy to fill the weave. It's not structural, it's only there to provide waterproofing and "armor" for the hull. I really can't imagine having to fiberglass the INSIDE of a hull. That truly sounds like a nightmare.

As to why Glen-L doesn't have as many stitch-n-glue designs is simply because it's a newer building method and most of the designs in the catalog predate it. Plywood on frame is an evolution of traditional boatbuilding methods. But you don't need as many frames as a "solid" wood planked hull. With epoxy used as the adhesive, the result is a super strong and stiff hull. Everything basically becomes one.

There are a lot of great looking designs over at Bateau. I'm sure they are great boats. However, I don't think stitch and glue is really fundamentally "easier" than plywood on frame.
You're right, I have been comparing the Bateau CT22 to the WildCat, as they are more or less the same size. Most, if not all, Bateau designs are plywood cored fiberglass composite hulls, and yes, you need a lot of epoxy and fiberglass to build the boats. The hull gets its strength from the fiberglass and its stiffness from the plywood, from what I can tell. Regarding fiberglassing the inside of the boat - what is done with the Glen-L designs for the decks, gunwales, etc?

Ply on frame seems heavy to me; the builds I've seen use 2x4" lumber for framing, and while the lumber used in boats may be different/lighter than lumber used for constructing buildings, well... I don't know. Then again, 2-3 layers of fiberglass with lots of epoxy inside and out, plus lots of fairing compound on the outside also adds weight.

I didn't realize that the plans predated the S&G method.. I thought S&G was something that had been around for decades. But, then again I also thought that power catamarans was something new as well, until I learned they weren't. At all. That does explain quite a few things. Thanks :)

I'm not sure one method is principally "better" or "easier" than the other, either. Just different ways of getting a good-looking, functional, safe boat.
vupilot wrote:
Sat Nov 03, 2018 8:14 pm
Having built both S&G and Framed up, in the final product I generally like the framed up builds better as the boat feels stronger/stiffer and more robust overall. However, S&G can be a much, much faster way to build. There are difficult tasks in both S&G and framed up builds but I think there are fewer difficult tasks with S&G. It depends what kind of boat your are building, how its designed and how it will be used. Some are perfect for S&G and some really need to be made of framed up construction. Either way stick to what the designer calls for and you'll probably have good results.
I'm not sure if S&G is faster than PoF, really... the frames are cut according to plans in both cases. PoF frames are screwed together, and then are done. Add plywood sheeting, then one layer of fiberglass cloth, epoxy and wait until it cures. S&G hulls are stitched together, glued with epoxy putty, then taped. Then the epoxy has to cure. Then the hull is covered in fiberglass cloth, epoxied and again left to cure. Repeat for second layer. Then fairing and a million years of sanding. After the hull is flipped, the inside of the hull is glassed, and the frames are glued in with epoxy putty, which then has to set, then taped in with epoxy and fiberglass tape, which again has to cure. It seems to me that a PoF boat potentially cam come together and be finished faster than a S&G hull, since all the epoxy has to cure before the next step can be taken.

That said, I feel confident that a fiberglass-plywood-fiberglass S&G hull is as solid as a plywood on frame hull, given it is built as outlined in the plans.
8' dinghy built in 1992, BBV sufferer ever since.

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hoodman
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Re: Build methods

Post by hoodman » Sun Nov 04, 2018 7:01 pm

Christer wrote:
Sun Nov 04, 2018 3:38 pm
Regarding fiberglassing the inside of the boat - what is done with the Glen-L designs for the decks, gunwales, etc?
Generally, for hulls that are painted, the decks and gunwales will also get a layer of 6-7 oz fiberglass cloth. On my Geronimo I have 6 oz cloth on the hull and the decks including the motorwell. The interior of the hull just has 2 or three coats of epoxy.

Taking a look at the BOM for the Wildcat sport. There is some 2" lumber. But you need some husky framing to tie the two sides of the hull together. From what I can tell this is a seriously capable boat capable of high speeds. It's also big and decently heavy. Designed to take some serious punishment. But I bet it's similar in weight to an equivalent S&G design.

The S&G designs in the Glen-L catalog are all under 20'. They only have one layer of FG cloth on the outside (other than the FG taped seams on the inside of the hull). You are right that S&G has been around for decades. But consider that many of Glen's designs are close to 60 years old! I think he just preferred to design for the POF construction method. Also, the Wildcat is a Ken Hankinson design FYI. Ken worked for Glen for a while and then started his own business. Now all his designs are in the Glen-l catalog.

As I said before, glassing the inside of the hull sounds like a nightmare especially 2-3 layers. And then you have to do that on the exterior of the hull too.

However, like you say, either technique is valid and results in a great boat.

The boat you are proposing to build is a big complicated design (from either designer). Make sure it's what you really want and that you can afford it. And then go for it.
Matt

Building a Geronimo......!
viewtopic.php?f=2&t=25139

283
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Re: Build methods

Post by 283 » Mon Nov 05, 2018 5:19 am

Are stitch and glue boats really lighter in general?

A couple similar designs that I like that listed hull weights...

Double eagle... 1200lbs
Bateau NV23... 1500lbs


I personally don’t see a big deal fiberglassing the interior of a stitch and glue design. What’s so different then doing the outside? The fiberglass schedule bateau uses doesn’t seem too bad either. As a casual forum reader it seems most of their designs uses a layer of tape on the seems and then a layer of cloth on each side. The bigger designs may call for double layers of tape and or cloth?

And since they are not bright finishing the stitch and glue builders often do epoxy work wet on wet or green. So they don’t have wait for it to cure and then sand between every layer.

I like some of the stitch and glue designs and they definitely seem quicker to build. But it seems a lot more of the glen l boats are built to a higher standard. YMMV
Mike

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mrintense
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Re: Build methods

Post by mrintense » Mon Nov 05, 2018 6:01 am

Christer wrote:
Sun Nov 04, 2018 3:38 pm
the frames are cut according to plans in both cases. PoF frames are screwed together, and then are done. Add plywood sheeting, then one layer of fiberglass cloth, epoxy and wait until it cures.
This is not quite complete as there is one step of POF that S&G do not have and that is the fairing of the hull structure before applying the planking. In that sense, POF can take some additional time. And the frames are not just screwed together, they are also epoxied together.

I think the discussion of which is a faster build is as dependent upon the builder as anything. Given an equal amount of detail from the builder, I think the S&G hull would come together more quickly. I think it's popularity stems from that exact fact.

But the idea of a faster hull is not necessarily the only consideration. Most of the Glen L and Hankinson designs are classically styled from the generation they were originally drawn in. I made this point in a different thread, but some are functionally designed and some are designed with appearance as the primary consideration. Stitch and glue designs are from a different era and I think initially came about from experimentation to create a faster boat building process for the home builder. Later as the process proved itself more involved and larger designs came along. Devlin Boats has some quite large S & G boat plans available. There are now some quite nice S&G Boat designs available. This in no way detracts from the Glen L designs.

Ultimately, I think it is the builder's desires that are of the prime importance here. If you want one of Glen L woodies, then you'll do POF (either plywood sheet planking or cold molding). If you want a functional fishing boat, then Glen L has those in POF and S&G. Other designers have them as well and it's really your choice which you want. If you want a traditional built wooden boat, then you'll need to look at Atkins or any of many other older designs. If you want ease of construction or simple sailboats, the number of designs out there is nearly endless.

And one final point in this rather windy response. Fiberglassing the interior of a boat, or the interior of anything has one main difficulty that fiberglassing the exterior is less subject to. That is getting the fiberglass to confirm to the interior shapes and stay in place while applying the resin. It can be done but it is more difficult. However, S & G boats have less framing / bulkheads in the way than POF boats so it may not be as much trouble.
Carl
a.k.a. Clipper

Crafting a classically styled Vera Cruise named "Some Other Time"

Clipper's Vera Cruise Build

283
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Re: Build methods

Post by 283 » Mon Nov 05, 2018 6:28 am

mrintense wrote:
Mon Nov 05, 2018 6:01 am
And one final point in this rather windy response. Fiberglassing the interior of a boat, or the interior of anything has one main difficulty that fiberglassing the exterior is less subject to. That is getting the fiberglass to confirm to the interior shapes and stay in place while applying the resin. It can be done but it is more difficult. However, S & G boats have less framing / bulkheads in the way than POF boats so it may not be as much trouble.

With most if not all the bateau plans there is no interior sructure to work around. The bulkheads and stringers are first used as a jig while the hull is stitched and glue but they are not attached until after the hull is flipped and the interior glassed.
Mike

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Re: Build methods

Post by 283 » Tue Nov 06, 2018 4:59 am

@christer
Another forum to check out

https://messing-about.com/forums/

It’s the discussion board for several designers including B&B and bluejacket. Bluejackets are stitch and glue while most of the B&B are plank on frame or cold molded. Unlike glen l plans they are using a lot of plywood for the framing.

Members there have built some of the nicest diy ‘modern’ power boats I’ve seen.

An OC20 by lotus. Hard to believe it didn’t come out of a mold
BAA6BF5F-58F8-40D5-971F-E59CDA635700.jpeg
A5CC2801-1CFF-4E8C-8440-0DDAC5903137.jpeg
A5CC2801-1CFF-4E8C-8440-0DDAC5903137.jpeg (22.52 KiB) Viewed 957 times
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Last edited by 283 on Tue Nov 06, 2018 5:02 am, edited 1 time in total.
Mike

283
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Re: Build methods

Post by 283 » Tue Nov 06, 2018 5:01 am

And an OC24 that hightechmarine made out of foam core.
B71F6E14-4078-4595-B858-7E53968A4999.jpeg
Mike

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