General S&G question

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bsgman
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General S&G question

Post by bsgman » Fri Jun 25, 2010 7:14 pm

I've not built a boat yet (As I mentioned in another post) and have a simple question. With the stich&glue technique, do the panels get chamfered/beveled at all so that the wire holds them together flush? Or do they form imperfect joinings that need sanded/planed?

This seems like a question I could answer myself with a little reading but I've not come across it yet!

Thanks!



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lncc63
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Re: General S&G question

Post by lncc63 » Fri Jun 25, 2010 7:47 pm

In our group, we often tell those starting out: "Don't worry epoxy will save you". Once they get over the initial confidence barrier, they hear about precise curves, constant gaps, and what I like to call stitch-tuning.

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Re: General S&G question

Post by gstanfield » Fri Jun 25, 2010 10:18 pm

I think Steve was just going with the concept sold here by the guy who owns and operates this forum and sells the plans for all the boats we're building on here :? An excert from the FAQ page:
What is the precision required when cutting panels?

Not much.
There are two factors to consider.
1. Epoxy does not require tight fits, quite the opposite. Some gap between parts is required for the epoxy glue to work.
2. We want to avoid hard spots between panels. The strength comes from the fiberglass and a gap is preferred.
For those reasons, 1/4" precision (5 mm) is more than sufficient. Our plans are very precise but the dimensions use a 1/8" (3 mm) tolerance.
Do not try to be more precise, instead focus on fairness and symmetry when scribing and cutting parts.
I'm not a designer nor do I claim to be, I'm just posting a direct quote from Mr. JM himself here. I can see where a CNC cut panel would allow you to have a consistent gap all along which would be better than pressure points here and there. Again, I'm not claiming to know, nor am I trying to argue with you as a designer, but I'd never accuse JM of being wrong about his building style either. :wink: FWIW, I've seen some of your designs and I'm really impressed, if I had use for it I'd strongly consider the Floom (I think that's the name) as it's a really nice looking craft.

George

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Re: General S&G question

Post by gstanfield » Fri Jun 25, 2010 11:20 pm

Just to be clear, I wasn't saying you were wrong before, I was just stating that I can see how "needs a gap" can get translated into "leave the panels far apart" :D Since most of us build with square cut edges that oftentimes leaves a small gap as we're not chamfering (machinest term, sorry) the edges like in your picture with the "backcut" joint. I guess that's one of the reasons I like working with epoxy is that while it's good to get thigns right, it also doesn't hurt at times to get things "good enough" as epoxy will fill anything but the crack of dawn and repair anything but a broken heart :D

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Re: General S&G question

Post by ks8 » Sat Jun 26, 2010 1:20 am

It's best Jacques address this himself. I don't want to get it wrong. Until he jumps in, I'll take a shot at it. This topic has cycled a few times and can be searched for in the forums with quite a few hits, including responses from Jacques. You could search for *hard spot*. If I've got this right, on high stress planing designs and larger hulls, Jacques prefers a gap to the extent that the panels do not touch, thus ensuring a fully *plastic flange* on which the loads are transmitted/absorbed/distributed, along with the glass skins, with no wood contact *hard spots*. It is the goal he recommends on the higher load planing hulls or larger hulls, and is not as critical on the smaller hulls of dinghies, row or sail. Some builders have accomplished this complete gap by placing some small nails in and along the seam to force a complete gap all along the seam, nails pulled later and holes filled, just like the stitch holes get filled, panels now completely bedded in fillet blend. Some have used plastic straws as periodic *spacers* to ensure a gap into which the goo is googed. Personally, I made mostly proper fit panels, but also made sure that they were bedded well in goo when panels were installed and seams made.

Image0789

Simply, I didn't want to use more epoxy than needed just because of real sloppy fit cuts. In retrospect, looking at how much epoxy I used, that's pretty funny! All that glass to cover the cheaper checky panels. But I would have used even more without getting the panels fairly close. Just made sure they were thoroughly bedded, and didn't even actually have to on this smallish displacement speed sailboat. :)

Image0808

Squished into a complete bed of goo...

Image0853

Yes, the next build intended to last will be with much better wood. I have no further motivation to *prove* a good boat can be made with ACX and BCX, and last very long when fully glassed. :wink:

But back to subject, I believe on the high load planing hulls and larger hulls, Jacques prefers a complete goo filled gap, panels completely *floating* in the composite seams, with little if any panel contact at all (no hard spots). He is the one best to re-state his preference for these designs. So I'm backing out to see how this goes, thinking the design in question is also going to be an important part of the issue. :)

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Re: General S&G question

Post by jacquesmm » Sat Jun 26, 2010 9:15 am

bsgman wrote:I've not built a boat yet (As I mentioned in another post) and have a simple question. With the stich&glue technique, do the panels get chamfered/beveled at all so that the wire holds them together flush? Or do they form imperfect joinings that need sanded/planed?
Absolutely no chamfer or bevel required in our designs. Never, no exceptions.
Jacques Mertens - Designer
http://bateau.com

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Re: General S&G question

Post by jacquesmm » Sat Jun 26, 2010 9:22 am

ks8 wrote:It's best Jacques address this himself. I don't want to get it wrong. Until he jumps in, I'll take a shot at it. This topic has cycled a few times and can be searched for in the forums with quite a few hits, including responses from Jacques. You could search for *hard spot*. If I've got this right, on high stress planing designs and larger hulls, Jacques prefers a gap to the extent that the panels do not touch, thus ensuring a fully *plastic flange* on which the loads are transmitted/absorbed/distributed, along with the glass skins, with no wood contact *hard spots*. It is the goal he recommends on the higher load planing hulls or larger hulls, and is not as critical on the smaller hulls of dinghies, row or sail.
Thank you, that is correct.

I have deleted a number of responses with which I disagree. Our method is extremely simple: no chamfer or bevels.
Plus, especially in large boats or planing hulls, we want a small gap between panels to avoid hard spots.
It is the fiberglass that transmit the loads, not the plywood.
It is simple and produces very strong hulls.
I do not want new builders to be confused by other methods.
Jacques Mertens - Designer
http://bateau.com

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Re: General S&G question

Post by ks8 » Sat Jun 26, 2010 11:58 am

PAR,

I want to thank you for what you had posted, even though another method. I also understand and respect Jacques doing his best to ensure no confusion with the method under which he designed these scantlings for these boats. Please do continue contributing the same sort of detail and let Jacques determine when a different method might lead to more confusion than we would prefer with the builders he takes much time to support. :)

I truly appreciate your point of view and experiences, and I don't think I'm alone in that at all. there can also be value in no bevel at all, since the panel then has a nice flat *foot* sitting in what you called the *plastic flange*. Even though the glass bears most of the load, the flat foot probably presents any panel load that goes that route, more securely and evenly to the entire fillet structure (no hard spots). Your method seemed to be a sort of hybrid development between Devlin and Jacques. Interesting to see documented, but again respecting what Jacques is spec'ing for these designs. :) I also appreciated your input on the abrasion resistance thread. I'm adding a comment there now also. Thank you again for your posts and please continue PAR. :)

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Re: General S&G question

Post by jacquesmm » Sat Jun 26, 2010 2:46 pm

It looks like something is happening behind the scenes . . . I don't know what but let's keep in mind that, except for repairs, this forum is about the bateau designs. The bateau designs all use the same material and are all built the same way.
There are other valid ways to build boats but on this forum, I want to give support for our well proven method.
The posts I deleted conflicted with our tutorials.

I am open to different opinions but do not want to confuse builders.
If someone wants to debate methods or compare their merits, please do it on the wooden boat forum or at amateurboatbuilding.com.
Those who are new to our material should read our tutorials.

If someone wants to compare methods, please read this:
http://www.bateau2.com/howto/material_difference.php
Jacques Mertens - Designer
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