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  1. #31
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    Feb 2008
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    Morgan SA
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    Try this link, although it looks ridiculously long.
    Otherwise google 'The Bending Of Timber'. Hopefully you will find a pdf from NSW Primary Industries which has some excellent info including a list of species and their suitability for bending.
    https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB0QFjAAahUKEwjour_PxvvHAhXH2qYKHc5bA7c&url=http%3A%2F%2Fwww.dpi.nsw.gov.au%2F__data%2Fassets%2Fpdf_file%2F0008%2F390293%2FThe-Bending-of-Timber.pdf&usg=AFQjCNF19knlk6gnYkepToIEoDXp5ClWfg&sig2=2uxNN2ovVUroTKO0q1YvwQ



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  3. #32
    Join Date
    Feb 2008
    Location
    Eustis, FL, USA
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    One hour is the usual time, per inch of thickness, though this can vary wildly between species. I've bent a lot of wood over the years and now I'm not using steam boxes as much as applied steam and/or just heat.

    I stole the tile grout steam cleaner from the other half, for a quick job on a combing repair and have been using it and similar devices ever since. The one I have now isn't the steam mob looking thing, but a wand, with a cooker attached by a hose. It generates steam in about 5 minutes and it can be applied very locally or over a fairly broad area. Because it's pressurized, it blows deep into the wood and the job gets done quickly. This coupled with a regular heat gun, used in concert or just heat gun alone, I've managed to avoid dragging out the old, big steam box I made from large diameter pipe years ago.

    If the moisture content can be raised or the wood is good and green, it'll bend faster and more reliability (less breakage). Most bending success depends on species, moisture content, grain orientation and runout. Some species just don't like to bend, while with others, all you have to do is breath hard on it.

    Once wood has been "cooked" it generally doesn't like to be recooked, unless you can dramatically raise the moisture content and hope there's enough goo still left in the wood cells. If the surface has seen some glue or other type of sealant, this also presents issues. The worst that will happen is it'll break. Some breakage should be expected, especially with some species, so give it shot and see. Soak a towel with boiling water and drape it over the piece for a half hour before you apply the heat and/or steam, to increase it's pliability.

  4. #33
    Join Date
    Jun 2007
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    Aberfoyle Park SA
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    63
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    Well, I googled Tas Oak & it came up as good steam bending.
    Picked up 4 lengths of 20x8 because it will be more stable than 20x12 on edge, and bend easier than 20x16.
    Popped it into the steampipe, along with the 2 x bent Meranti.
    Started the clock from when the pipe was hot & steam spurting out all holes.
    at 30mins, whacked them onto the formers.
    WP_20150917_001.jpg

    Felt totally different. The meranti fought all the way to the stops.
    The eucalypt was initially stiff then suddenly 'gave'.
    Still had about 30% spring-back, so my insurance policy kicked in... laminating the two staves for each side.
    WP_20150917_002.jpg

    Overestimated the springback after laminating, so they're a little too curved now, but that's easier to manage.
    WP_20150918_006.jpg

    Oh, and the meranti lengths... they sprung back to nearly straight in the steamer.

    Thanks Mark & PAR
    Alan J

    Nothing says "Unprofessional Job" so loudly as wrinkles in the duct tape. - B.Spencer

  5. #34
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    Feb 2008
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    Eustis, FL, USA
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    Spring back is the real butt kicker of this process and each species is different, but a 10% - 15% tighter radius, is the norm for most woods.

  6. #35
    Join Date
    Jun 2007
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    Aberfoyle Park SA
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    They're on.
    Only problem encountered was a #10 screw which snuck into the #8 tin.
    Of course it was the screw I drove into the very end of one rail...
    Eucalypt is very hard, so it caused a slight splitting.
    Easy fixed.
    WP_20150919_003.jpg

    Splash some varnish on the rails, sand & paint the rest of the deck then reassemble. )
    Should be getting her bum wet again in Oct. Nov at the worst.
    Alan J

    Nothing says "Unprofessional Job" so loudly as wrinkles in the duct tape. - B.Spencer

  7. #36
    Join Date
    Feb 2009
    Location
    Adelaide - outer south
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    67
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    935

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    So tell us AJ, has there been any wetting of Ethel's nether regions? Or is there any imminent?
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  8. #37
    Join Date
    Jun 2007
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    Eth'l not finished, but reassembled over two evenings hard labour, for a day on the water out of Clayton Bay with my sister last Saturday. Worth every minute of the work. Couldn't have asked for a nicer day really. Mix of light & 'healthy" wind to test her out in. 10 - 25km/h approx. Wonderful.
    My sister took some pics at the jetty before we set off (and the wind kicked up).
    DSCN1495.jpg DSCN1498.jpg DSCN1499 -10%.jpg DSCN1501.jpg DSCN1502.jpg DSCN1505.jpg DSCN1508.jpg

    The day also gave me a new list of things I need to do, as well as reinforcing the ones already identified, and highlighted some handling issues that I need to figure out.

    Firstly, anything I do has to take into account that she WANTS to move forward, even in the faintest of breezes. Very hard convincing her to go backwards, even with the jib backed. No danger of planing in any wind less than mast-breaking. In 25km/h or so wind on a broad reach we dug a deep hole with an impressive following wave set. But still very relaxed & light on the sheets. Heavy on the tiller though, considering its length and the small rudder.

    So, new priorities (after I strip all the fittings off the deck again and paint it)...

    In stronger wind, some weather helm present, even under jib & main alone. More or less balanced under jib & mizzen alone, possibly a little lee helm. Changing to the smaller area of OzRacer sail should improve this. I may even need to go taller & narrower in a balanced lug.

    Perhaps more pressing is that she has a turning circle comparable to the QE2.
    Due to the tiller being looped around the mizzen, the rudder can only be swung about 12deg either side of centre. One needs to plan a -lot- further ahead than is customary in a 15' dinghy! Confined space manoevering and emergency turning at any speed are utterly impossible unless already head to wind AND nearly stationary. Also, at low speed, the rudder lacks authority beyond negating whatever steering I try to do with the mizzen. So, a bigger rudder blade, and a push-rod tiller linkage required. I'll probably make the existing blade the core of a Pollock foil about 300mm longer than existing.

    Somehow need to fit this around first learning, then training the rest of the brigade in the new fire tanker - hopefully arrives next Thursday https://www.youtube.com/watch?v=6cokZNwvrWI
    Alan J

    Nothing says "Unprofessional Job" so loudly as wrinkles in the duct tape. - B.Spencer

  9. #38
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    Feb 2008
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    Eustis, FL, USA
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    A lovely beast, good to see her bottom wet. It does a heart good, to see those lines intermingled with the element she was intended to grace.

    Well done . . .

  10. #39
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    Feb 2009
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    Adelaide - outer south
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    Yep, totally agree with what Par said.

    Plus, I know you were keen to be on the water in time for your sister's visit so it's good to see that you managed a great day on the water.

    It will be interesting to see what therapy succeeds in dealing with Ethel's behavioural problems.
    Cheers, Bob the labrat

    Measure once and.... the phone rings!

  11. #40
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    Feb 2008
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    Eustis, FL, USA
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    One of the biggest changes I've found from "antique designs" to modern ones is a better set of appendages. We've got much better sectional shapes and plan forms comparatively and these can make huge handling differences on an old boat or old design. I recently removed a barndoor, transom hung rudder from an old classic, replacing it with an under slung, kickup spade on a small skeg. The previous rudder was just a straight sided, hunk of mahogany, with rounded leading and trailing edges. The new spade was NACA 00 sectioned, with a modest amount of balance below the skeg and nearly 3 times the aspect ratio of the barndoor. The result was remarkable. The helm was no longer heavy, sensitivity was dramatically improved, she came about with authority and tracked much better too. She did lose the look of the elegantly shaped barndoor, but the advantages of this upgrade where remarkable to her handling manners.

  12. #41
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    Jun 2007
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    Aberfoyle Park SA
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    Got started on a larger rudder. The easiest job first.
    Using the original blade as the core (roughly outlined) & adding about 250mm to the bottom.
    Will be 24mm thick Pollock section, 550 x 350.
    Given the combination of short, thick, wide & aluminium core, plywood should be strong enough.
    If it is too big & does something disturbing like causing lee helm, I can progressively shorten it to re-balance.
    If it is too wide & makes steering too heavy, I have Teal's old (and too small) NACA CB and rudder blade in the shed somewhere.

    WP_20151026_003 outlined.jpg

    I can work on this late at night without disturbing family or neighbours, while I ponder how to install a near-cockpit tiller fulcrum, and how to connect that to the rudder stock. Push-rod on a side arm is perhaps the "obvious way, but not the only one. No point in sanding the deck until this is installed.
    Alan J

    Nothing says "Unprofessional Job" so loudly as wrinkles in the duct tape. - B.Spencer

  13. #42
    Join Date
    Jan 2009
    Location
    Blaxland, Australia
    Age
    65
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    Looking fantastic in the drink! what they all said. Nice to see Clayton Bay again, too. I recently unloaded the shipping container which had the plywood and chipboard for the CB 144 - into another lockup...

    Hopefully the new tweaks will get her handling a lot better, and you might take me for a sail next time we are over (around Christmas? - although I guess you will be off over to Brissy then, oh well).

    REALLY jealous of your New Foam Spouting Toy (and I liked the early-Cure-like sound track, too :). We wouldn't have the room in our tiny shed, however. The video made me quite a bit homesick, though <sniffle>...

    Cheers,
    Alex.

  14. #43
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    Feb 2008
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    Odds are you'll be fine with the new rudder. If it was me, I'd reduce the length of the chord a bit and possibly make the leading and trailing edges parallel, which makes making them foil shaped, a lot easier. These two plan form changes will improve aspect ratio and building ease. With the chord narrowed a bit, you can use a reasonable section shape too (wide chords require fat sections). The shape of your boat and her rig type will be quite forgiving in regard to helm reaction to these changes. If the helm was very light, maybe almost lee on 'ya, it might go a touch lee in these same winds, if the chord is the same as it was, but if the chord is reduced and just the span (depth) increased, you'll likely have the same if not slightly better helm "reply" in light air. Of course in heavy air, the deeper blade will be much better and less heavy, comparatively.

    In fact the way I do it, is measure the blade thickness, then multiply this by 12 or 14 (NACA 0012 or 0014). This multiplied figure is what I use for the chord length, so if you have a 25 mm blade, the chord would be 300 (at 12) or 350 mm (14) long. To refine this a little more, I add enough chord length to the foil I elect to use, so I can chop off the trailing edge square (not razor edged). This amounts to about 5% of the chord length, but makes maintaining the trailing edge a whole lot easier. Razor edges are nice, but only a racer needs them and they're impossible to keep at a razor edge, so I usually make a 1/4" (6 mm) flat along the after edge, which is easier to care for.

    I'm not sure which Pollock section you'll use, but Pollock himself suggested at the Reynolds numbers most small sailboats go (displacement speeds), the 4 digit NACA section (0008 through 0012) are the best across the criteria used to judge them. I've found that 0012 is the most common employed by the manufactures on rudders, with few exceptions, except on blades than carry a lot of lateral area (like some of Bolgers designs) or on full plane mode sailing. The high speed shapes usually require less drag, per lift unit, while the higher load blades often need thicker sections, to tolerate the cantilever loads, they be subjected to underway.

    Okay, probably more information than you needed, but hey, there it is.

  15. #44
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    Jun 2007
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    Aberfoyle Park SA
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    Thanks Paul
    Trying to re-use / adapt existing hardware while retaining a simple back-out option.
    Were I starting from scratch, I'd do exactly as you suggest.
    Already have a suitable foil in the shed, but it seems more work to adapt that than to tweak existing.
    It is still my Plan B.
    Alan J

    Nothing says "Unprofessional Job" so loudly as wrinkles in the duct tape. - B.Spencer

  16. #45
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    Feb 2008
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    Eustis, FL, USA
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    Your existing centerboard seems like a good option, certainly a quicker and probably easier one too. I'll be curious to see how it works out.

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