Author Topic: Ed's boat in Perth  (Read 57401 times)

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Ed Snyder

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Re: Ed's boat in Perth
« Reply #180 on: April 25, 2016, 08:19:59 AM »
Actually Brian, the keel as drawn isn't correct, when I extended the width, I thought I may have an issue with it, as the forward dead-rise is what it is, as you designed, to have the extension fair in, the keel is deeper at the forefoot, by aboat 3".
You seen those launches with there forefoot deeper than the after dead-rise? it's to get the dead-rise wanted at the forefoot, otherwise we end up with 13 deg dead-rise throughout right?  ???
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Brian.Dixon

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Re: Ed's boat in Perth
« Reply #181 on: April 26, 2016, 05:36:18 AM »
Actually Brian, the keel as drawn isn't correct, when I extended the width, I thought I may have an issue with it, as the forward dead-rise is what it is, as you designed, to have the extension fair in, the keel is deeper at the forefoot, by aboat 3".
You seen those launches with there forefoot deeper than the after dead-rise? it's to get the dead-rise wanted at the forefoot, otherwise we end up with 13 deg dead-rise throughout right?  ???

Interesting side effect of slicing the boat in two from end to end and then making it wider!  I'm sure it'll work fine, although I'd prefer you adjust the center of gravity far enough aft to raise the f'w'd keel to be the same depth as the aft keel, or even an inch or two higher.  In a perfectly balanced, as-designed, 26-foot GA, the bow trims 1-1/2 inches higher than the stern, FYI.  With the forefoot running deeper, I would wonder about digging in when coming off a following swell, creating a slight tendency to broach ...but maybe on a 33' long boat, the  3" isn't enough to worry about?

Brian
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Ed Snyder

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Re: Ed's boat in Perth
« Reply #182 on: April 27, 2016, 05:39:10 AM »
Yep always a concern the broaching issue going downhill on a down wind run, usually the waters going the same way, so, perhaps the skeg build isn't such a bad idea......
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Brian.Dixon

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Re: Ed's boat in Perth
« Reply #183 on: April 27, 2016, 01:52:46 PM »
Yep always a concern the broaching issue going downhill on a down wind run, usually the waters going the same way, so, perhaps the skeg build isn't such a bad idea......

The rules for avoiding broaching are:

1. Try for balanced ends.  A stern that is narrower than amidships, down to about 70-75% of the max waterline beam combined with a forefoot entry that is neither too fine (digs in) or too bluff (puts the brakes on when you hit a swell).  Most of the lift for a planing hull is developed amidships (along the 'line of stagnation' ...the 'V' shape of water cut by the hull - this means that narrowing the stern doesn't lose much planing capacity.  You do however, lose stern flotation.  For an inboard like yours, this is not an issue.  For those that like big heavy outboards on 'offshore brackets', this IS an issue.  The GA is 3" narrower at the stern than at amidships... not much of a change, but better than nothing.

2. You want the center of lateral resistance to be aft of the longitudinal center of gravity.  Thinking of a boat being pushed sideways through the water (like by a tug or barge), what type of 'sail' does it make versus the water?  Having an aft skeg, like your inboard, guarantees that your lateral center of resistance is indeed aft of the LCG.  For planing hulls that have a fairly prismatic (monohedron) hull form. the lateral resistance is fairly evenly distributed along the hull, and if the hull is a warped hull (amidships deadrise more significantly higher than the stern deadrise), then the center of lateral resistance may actually be forward of the LCG when not on plane.  The best way to fix the issue then, is to add a skeg or keel aft of amidships ...just make sure it tapers up to meet the hull far enough short of the transom so it doesn't cause prop cavitation on hard turns (especially when accelerating ...like to head into a wave to prevent capsize).

The bottom line:  Your boat will be fine.  The GA could use a little skeg aft of amidships, but then again, I'd like the boat to be beachable ...let the builder be aware and build and use appropriately.

Brian

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Ed Snyder

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Re: Ed's boat in Perth
« Reply #184 on: April 29, 2016, 11:33:15 AM »
Yea....
That's what I said....  :o
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Brian.Dixon

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Re: Ed's boat in Perth
« Reply #185 on: April 29, 2016, 01:07:03 PM »
Yea....
That's what I said....  :o

I re-read what I wrote, and it sounds like one big confusing run-on sentence to me.  I'm no literary giant.  :(  Hopefully, I got the right points across?

Brian
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Ed Snyder

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Re: Ed's boat in Perth
« Reply #186 on: April 29, 2016, 01:17:20 PM »
yes an excelant answer I did understand Brian.
Been a loooong time since I read up those issues in design.
So very much appreciated.
Skeg it is to be then.
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Ed Snyder

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Re: Ed's boat in Perth
« Reply #187 on: April 29, 2016, 01:30:24 PM »
I had planed on turning the hull over last weekend. The forcast was rain all week and indeed it rained!
While shes bum up I'll weld up a solid steel cradle, coat of paint, strap it onto the hull for a turn over.
This weekend is now welding and lotsa head scratching for easiest way to turn her.
Tyres, jacks, endless chain & coffee.
Yep that'll do it.
A full size mockup of the extended topsides forward and interior with 6 mm MDF and hot glue.
Be good to tweak the interior before mixing glue.....
Not waving....... Drowning!

Brian.Dixon

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Re: Ed's boat in Perth
« Reply #188 on: April 29, 2016, 01:40:16 PM »
Weld up a round frame around the boat so you can just roll it over.  Or get about 30 friends over, 30 bottles of Irish Whiskey, and that boat'll turn over at some point during the night...  :o ::) ;D

bd
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Murray in N.Z.

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Re: Ed's boat in Perth
« Reply #189 on: October 05, 2016, 06:13:35 AM »
C,mon Ed.
Get R Dun !!!  If you get the commercial block with a shed on it I can give you a few good ideas on how to set one up for sleeping in. Got my head in a far better space after a few years of hell. So good to see you making some progress, and gee hasn't Phelix grown a heap. Can just see him launching down the road at the boat club and rowing round the basin. Bet old Gramps has a big smile on.  Hows the 'coon, still humming along?
Muzza.

Ed Snyder

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Re: Ed's boat in Perth
« Reply #190 on: November 03, 2016, 06:13:10 AM »
Gidday cuz!
Chit waddaya up to uther than fishin?
Gotta flip the hull 12 Nov. Making steel cradle this weekend, er, need help flipping here over though, she's 3.2m wide now....
Havin a beer & BBq day too, so, thinking on that note, figer we will have the beers first, flip the hull then BBQ.
Just gunna make the whole lot easier on all I recon.....




Repair the damage later....
Not waving....... Drowning!

Brian.Dixon

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Re: Ed's boat in Perth
« Reply #191 on: November 03, 2016, 09:07:08 AM »
... More pix!  (Especially of said turnover....)
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Ed Snyder

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Re: Ed's boat in Perth
« Reply #192 on: November 03, 2016, 09:38:22 AM »
Dream boat.......
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Brian.Dixon

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Re: Ed's boat in Perth
« Reply #193 on: November 03, 2016, 12:58:40 PM »
That's beautiful... And if you buy it, you don't need a house anymore (and no more lawn mowing in that summer heat!)
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Ed Snyder

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Re: Ed's boat in Perth
« Reply #194 on: November 28, 2016, 01:00:41 AM »
Ur right, no bloody brown lawns, I never have had luck keeping ANY lawn green!

Pix of the flip few wks ago, thought few of you may enjoy, sayswho visited us here in Perth fortnight ago helping flip the 3.4M wide hull, it was fun lol, wait for the vid I will post on photobucket soon, called "62 yr old man gets airborne filpping his boat" !
Mad rush after Monday week to get the 4M high shed roof up - the heat & rain here is tropical to say the least.
Next will be a 1/4" MDF mock up of the hull topside extension forward of the aft bulkhead, to get a boat to look more in proportion to it's new size, cockpit topsides to stay the same as will the floor for better fishing, decks I'll build 12" wide as Lamont has 12" feet, the saloon floor will be raised about 8" to get the Cummins donk under and that'll sit below it, from there it's all up to getting the cabin & cuddy shape as up drew it - love the design here Brian. If I got me pencil & rule out on paper as I was taught 100 yrs ago then all this mock up wouldn't be needed.....
Not waving....... Drowning!