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UK Zip Build

Posted: Tue Sep 26, 2017 3:01 am
by sproggy
I've changed my mind about what I build more times than I can remember myself but with the Ebihen 16, once I started I realised I'd bitten off more than I could chew (it's a BIG boat to build in a garage) so I'm back where I started with a Zip. And I'm just getting on with it, not worrying about it or about having to extend buildings to give me build space. Refreshing.

I'm in the very early stages, cutting out frame members from white oak. The boards are perfectly flat but having cut out sections for two of the frames (2 and 5.5) I've found that they've warped a bit - one of the deck beams and a couple of the side frames. The deflection is around 1/4" on the side frames and closer to 1/2" on the deck beam

I'm not hugely concerned about this having happened - I'm dealing with a natural product and this happens with timber. But how do I deal with its effect on the boat - try to straighten them out with weights/steam/boiling water before frame assembly or just deal with it once the frames are complete and mounted on the building form? The boards have sat in my garage for several months so have had plenty of time to settle - the cause is obviously stresses within the boards that I've now released by cutting.

I can't imagine I'm' the first to experience this issue but a search didn't bring up anything relevant. Is anyone able to offer some advice please?

Re: UK Zip Build

Posted: Tue Sep 26, 2017 3:46 am
by BarnacleMike
I experienced this to a degree with some of the frame parts on my Utility. I personally wouldn't worry about a 1/4" warp.

A 1/2" warp would push the boundaries of what I'd personally consider acceptable, though. For me, it would just depend on the specific piece. You may find that once the frame is assembled, the whole thing balances out within reasonable tolerances. A half-inch difference across a fully assembled frame probably wouldn't be worth worrying about.

Are you using vertically-grained wood? That should help with some of the warpage.

Re: UK Zip Build

Posted: Tue Sep 26, 2017 5:54 am
by JimmY
Looking at another Zip build, it looks like all the frames have a deck beam. So clamp them flat when gluing them together. If the assembled frame is slightly warped, when you put them on the frame you should be able to secure each frame to the sheer and chine to remove it. It will just take some measuring before mixing epoxy.

Re: UK Zip Build

Posted: Tue Sep 26, 2017 6:05 am
by BayouBengal
On my first build (a Squirt), I was all concerned about getting the frames perfect and had strongly considered using a CNC so that they would be cut perfectly. But after having completed a couple of boats, this type of extreme accuracy with the frames is quite unnecessary. While I certainly don't advocate careless sloppiness or inaccuracy in the frame construction, a bit of inaccuracy is not really a problem because it can be compensated for and adjusted during construction by appending or shaving off wood.

My personal opinion is that more important than dead on accurate frames is an extremely solid, square, and level building platform. Next, accurate alignment of the frames on the platform. Then, constant checking, rechecking, and checking again your alignment and positioning of the outer edges of the frames while fairing using long levels, water tube levels, string, and plumb-bob's (this is where any minor inaccuracy issues with the frames are alleviated). And lastly, ensuring that you have fair lines for your planking.

Re: UK Zip Build

Posted: Tue Sep 26, 2017 6:17 am
by BarnacleMike
BayouBengal wrote: this type of extreme accuracy with the frames is quite unnecessary. While I certainly don't advocate careless sloppiness or inaccuracy in the frame construction, a bit of inaccuracy is not really a problem because it can be compensated for and adjusted during construction by appending or shaving off wood.

My personal opinion is that more important than dead on accurate frames is an extremely solid, square, and level building platform. Next, accurate alignment of the frames on the platform. Then, constant checking, rechecking, and checking again your alignment and positioning of the outer edges of the frames while fairing using long levels, water tube levels, string, and plumb-bob's (this is where any minor inaccuracy issues with the frames are alleviated). And lastly, ensuring that you have fair lines for your planking.


Well-said! I couldn't agree more.

Re: UK Zip Build

Posted: Tue Sep 26, 2017 6:43 am
by sproggy
Mike, I'm not sure how the boards were sawn - I believe they're quarter sawn but don't have the experience to say for sure. Yes, I too think that 1/4" is probably OK but 1/2" probably isn't! But 1/2" on a deck beam can be dialled out when the deck supports are fitted between frames, I suppose.

JimmY, yes, all the frames have a deck beam. The beam is bow-shaped - the sheer points are OK (arguably - depends upon what you take as a datum!), just the centre that's 1/2" too far forward/back depending upon how I mount it. Easy enough to tweak later in the build.

Thanks to you all for putting my mind at rest. I'm not aiming for extreme accuracy, just trying to gauge what's considered acceptable deviation from true. It'll all be OK once assembled :-)

Re: UK Zip Build

Posted: Mon Feb 05, 2018 2:50 am
by sproggy
After 4 long months of my workshop acting as a furniture store while we had house alterations carried out I have at last reclaimed it as my personal domain and got back to work turning a small pile of large, regular-shaped boards into a large pile of small, irregular-shaped boards. And A LOT of wood dust.

Image

That's all the solid timber frame sections complete. Now I'm waiting for delivery next week of 18mm and 6mm ply for the stem/transom and frame gussets respectively. In the meantime I'm clearing space by demolishing a workbench - turns out my work space isn't as long as I thought (kidded myself) it was. So my plan to lengthen the Zip by a foot, adding frames at stations 1 and 3 in the process, isn't going to happen. Probably for the best.

My favourite tool up to this point is the oscillating belt sander - a real time-saver. Closely followed by the new Makita jigsaw that I bought to replace the 25 year old Black & Decker that probably wasn't up to the job when new, let alone now. Prize for biggest waste of space goes to the second hand Ryobi bandsaw - I used it once as an experiment only. Way too small for anything useful although it does give a nice, clean cut. Wish I hadn't bolted it to the counter as it makes it near impossible to use even if it was up to the job. Lesson learned there - buy only what you know you need, not what you think you might need.

Lurking in the corner - a flipover mitre/table saw. To be honest it scares me a bit. Well, quite a lot. I'll soon need to get to grips with it for ripping the keel, chines, battens, sheers etc. but I'm not looking forward to it. Plenty of practice needed on the debris from my workbench demolition before I gain the confidence to feed expensive oak through it.

Epoxy and silicone bronze fasteners at the ready - bring on the ply!

Re: UK Zip Build

Posted: Tue Feb 06, 2018 6:49 pm
by hoodman
Glad to see you making sawdust and getting on with your boat build. The zip is a really nice boat.

Re: UK Zip Build

Posted: Mon Feb 26, 2018 2:09 am
by sproggy
I made some progress this weekend - transom, stem, knee and breasthook are assembled. But they're assembled dry because it's only a couple of degrees above freezing in my shed and there's no way epoxy is going to cure properly in those temperatures. So I need to either carry on with assembling the other frames dry and hope that by the time I'm done with that the weather will have warmed up a bit or do the epoxy work in the cold and move the assemblies to a warmer environment to cure - any views on whether that's going to harm the epoxy's properties?

Here's the assembled transom:

Image

Re: UK Zip Build

Posted: Mon Feb 26, 2018 7:20 am
by hoodman
Epoxy is hard to mix up when it's cold (think molasses). If you keep it inside the house and bring it out when you're ready to use it you'll be better off. You can still use epoxy in cold temps. Once it's mixed up you've started an exothermic chemical reaction and it can't really be stopped (the reaction makes its own heat). It might take a day or two extra to fully cure but if you leave your parts undisturbed it shouldn't be a problem. You can bring the frames inside the house to help speed cure. Or point an electric space heater at them overnight on low. You'll get a feel for it after a while. The upside is you'll get plenty of working time after you're mixed up. The key is to mix THOROUGHLY! Scrape the sides of your mixing cup, scrape off the sides of your mixing stick. Mix until you get tired of it and them mix a little more. 2-3 minutes especially when it's cold. You'll fell the viscosity start to loosen up when it's mixed really well. Now when you get to encapsulate you'll want to do the first coat when temps are dropping. If temps are rising when you apply the first coat, the air in the wood will expand and create bubbles on the surface. Hope this helps!

Re: UK Zip Build

Posted: Mon Feb 26, 2018 7:36 am
by sproggy
Thanks Matt. I have the epoxy stored indoors but I'm aware that putting it on cold/damp timber may not help it any. I've never worked with epoxy before (plenty of experience with polyester resins, though) and I'm wary of ruining components with epoxy that'll never set. Also concerned about wasting expensive epoxy! Maybe I'm just worrying too much and I should try with the knee and breasthook which, at the end of the day, I could always start again from scratch if I had to. Then move onto the larger/more complex assemblies.

I'm a long way from encapsulating but good advice - sounds like a job for the evening rather than the morning.

Re: UK Zip Build

Posted: Mon Feb 26, 2018 9:23 am
by hoodman
The only way that it will never set is if you measure wrong or don't mix thoroughly. Once you take care of those two issues the chemical reaction will happen regardless of the temperature. You don't want to try to glue wet wood together obviously however, I don't see how timber stored in a shed is going to get damp enough to affect the epoxy bond. I would suggest doing as you say and glue up your transom knee. The worst that will happen is trashing a small amount of plywood and maybe 1.5 ounces of epoxy. I've worked all through the winter in an uninsulated barn using the methods I outlined in my last post including fiberglassing my hull. It was nice to have really long working time during that process especially.

I was really nervous the first time I tried epoxy too. After a few times, you'll have a process down and it will be old hat.

Re: UK Zip Build

Posted: Mon Feb 26, 2018 10:35 am
by Bill Edmundson
sproggy

I have often turned my glove inside out over a brush. I then put it in the freezer. I can use it the next day. But, after 2 or 3 days, they are hard as a rock. And, not from freezing. I think you'll like working with epoxy much more than polyester.

Bill

Re: UK Zip Build

Posted: Mon Feb 26, 2018 11:14 am
by sproggy
Bill, I think I have a natural tendency to over-think new things and get concerned about them when there is no need. Your anecdote has reassured me, as has Matt's information. Epoxy is perhaps more forgiving than I give it credit for. I just need to bite the bullet and get on with it. But right now it's too cold (23 degrees) outside for me, let alone for epoxy. I'll hold off until it our 'Siberian weather' passes and it rises above freezing at least!

Ian

Re: UK Zip Build

Posted: Mon Feb 26, 2018 5:43 pm
by BillW
That is a good looking transom. Just beautiful. Did you re-design the Zip to an inboard ?

What motor will that have ?

Bill