Subject: [harryproa] Re: Estimating weight, revisited
From: "Robert" <cateran1949@yahoo.co.uk>
Date: 1/10/2009, 3:16 AM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

I am not sure if glass beams would have the stiffness to weight ratio
of the timber and carbon beams of Rare Bird

--- In harryproa@yahoogroups.com.au, carlos Solanilla
<carlosproacarlos@...> wrote:
>
> I always thought that if the parameters are know for the crossbeams
then you could take those requirments and shop for a
poltrudedfiberglass I Beam that fi these requirements. It should save
time and buy you piece of mind. One day while web surfing I stumble on
a small trimaran using pultruded I beam which made a lot of sense to me
>
> I used to have a link to a vendor who did custom work but when my
computer crashed it got lost
>
> Here are some of the sites in the web - does anybody know about the
parameters you will be looking for?
> http://www.sdplastics.com/frp.html
>
> this company here offers EXTREN I beams - if you click in their site
under Extren product guide, you can see a brochure of the products and
their engineering team - I just think that at the end you can get a
much lighter cross beam and probably a heck of a lot sturdier,
> http://www.professionalplastics.com/EXTRENSHEET
>
> http://www.strongwell.com/PDFfiles/Extren/EXTREN%20Brochure.pdf
>
> There is a guy in Mcgill who shed some light on pultruded tubes and
references for I beam testing
>
http://digitool.library.mcgill.ca:8881/R/?func=dbin-jump-full&object_id=27991&local_base=GEN01-MCG02
>
>  
>  
> Finally here is a site giving you a choice of manufacturers
> http://buy.ecplaza.net/search/1s1nf20sell/fiberglass_beams.html
>
>
> ________________________________
>
> From: Robert <cateran1949@...>
> To: harryproa@yahoogroups.com.au
> Sent: Thursday, January 8, 2009 9:57:08 PM
> Subject: [harryproa] Re: Estimating weight, revisited
>
> Strip planking can be done with using an expanding polyurethane glue
> to stick the strips together and then sanding smooth, bogging, sanding
> smooth again and putting on a fibreglass skin. Marginally heavier than
> foam plus glass as it is a denser core but needs less glass. The
> beauty of the table finish is the minimal use of bog which can
> significantly affect weight. The longitudinal stiffness is not needed
> so much in the ww hull so a little more weight can be saved there.
> Bulkheads are definitely needed at the mast position(s) and so is
> reinforcing of the hulls in that area. The beauty of sailing loads
> being so concentrated in the lw hull, is that the big openings for the
> main accommodation are well clear. It is amazing how much stress can
> be concentrated around a hatch opening. I calculated that there is
> much more weight in the extra support needed for a hatch than the
> equivalent skin without the hatch, and you still have the extra weight
> of the hatch. If a hatch area is subjected to sailing loads, then this
> is a nightmare. Consider the torque on the structure in a swell if one
> mast ws taking most of the load and the opposite ww bow was in the air
> on top of a wave. The unstayed rig means that the sailing loads are
> concentrated between the crossbeams, though there is some load on the
> lw bow as it supplies some of the leeway resistance.
> In my interpretation, a flare on the inside complicates things a
> little but is supported by bunks and shelving (adding at least a
> hundred pounds, but partly off set by increased bury for the
> crossbeams and ruddershafts) It is not just the surface area but also
> the extra weight of joining material ie hand layed glass with
> attendant bog.this can add 15-20% to the internal furniture
>
> Away from the main sailing loads, the need for bulkheads is less,
> depending on the skin structure. The thicker the skin, the less
> bulkheads needed. Much of the stiffening can be incorporated into the
> structure through the furnishings. Shelves, cupboards, tanks, bunks
> forward in the ww hull ends, ablution structures, steps, bouyancy
> compartments
> I can't give you accurately the weights of the crossbeams and rudders
> but they definitely weren't 'tuckable under the arm and walk of'
> weight. They have to support a cantilever of about a couple of tonnes
> at a distant of about 5m. This is a serious piece of engineering. The
> crossbeams would have to weigh at least in the order of a couple of
> hundred kg a piece plus at least another 40kg for the rudder supports,
> and the rudder blades from what I remember on Rare Bird were just
> possible for one person to lift, maybe in the order of 60-100kg.
> Transom hung rudders need to include the shaft which won't be light.
> In aluminium or stainless in the order of 50 to 100kg each.
>
> I think we have found about 2000lbs. Consider that Blind date came in
> at less than 2 tonnes before rig. Once you increase the accommodation
> weight, you need to increase the strength right through, hence the
> increase to Rare Bird
>
> --- In harryproa@yahoogrou ps.com.au, "Gardner Pomper" <gardner@ >
wrote:
> >
> > From what I understand of strip planking, you need to coat all 4
> sides of
> > each strip with resin. Isn't that alot heavier than just using a
> > foam/honeycomb core? Or do you reduce the weight of fiberglass to
> make up
> > for that?
> > Any idea what the weights of the crossbeams are for Rare Bird ?
> >
> > So, I might be fairly close on the structure, but just leaving out
> weights
> > of extra things like hatches, cleat backing plates, hardpoints and
> stuff?
> >
> > My feeling on bulkheads was that around the mast, the crosssection
> of the
> > lee hull is 8' h x 2' w. Two bulkheads on each side of the mast,
and the
> > equivalent of 1 more crosswise would be an extra 100 sq ft (or 100
lbs).
> > Needs to be accounted for, but does not take up the greater part
of the
> > 3-4000 pounds I suspect I am missing.
> >
> > - Gardner
> >
> > On Wed, Jan 7, 2009 at 9:14 PM, Robert <cateran1949@ ...> wrote:
> >
> > > There are a suprising amount of panels needed for interior
> separation,
> > > such as bulkheads, storage areas, bouyancy compartments, cupboards,
> > > shelving. Rare Bird was strip planked so would have to include a bit
> > > of bog. Rare Bird also has a dinghy ramp. The crossbeams and rudders
> > > need to be pretty substantial as do the reinforcing to transfer the
> > > loads between them and the rig There is also the weight of hatches.
> > > Rare Bird weight should be pretty close if you can keep the bogging
> > > down to a minimum.Blind date is a fair bit lighter.
> > > Your calculations of area seem just a little more than an extended
> > > Harry 15m/9m that I have been trying to design so we are making
> > > similar mistakes -- In
> harryproa@yahoogrou ps.com.au<harryproa%40yahoog roups.com. au>,
> > > "Gardner Pomper"
> > >
> > > <gardner@> wrote:
> > > >
> > > > Hi,
> > > > I have been spending way too much time researching materials
online,
> > > but the
> > > > end result is that I am again confused on how to estimate the
weight
> > > of a 50
> > > > ft cruising harryproa. I have gone through and added up the hull,
> > > bulkheads,
> > > > furniture, hardtop, cockpit, bunks, etc, etc and come up with 2100
> > > sq ft.
> > > > This does not include the rig, crossbeams or rudders, since I
don't
> > > know how
> > > > to calc that.
> > > >
> > > > Anyway, I then research the core material (pretty much all of
> them are
> > > > 80Kg/m3), which translates to 0.3 lbs/sq ft for 2/4" (20mm) core.
> > > Add in 2
> > > > layers of 18 oz/yd2 fiberglass (1 top and 1 bottom) and an equal
> > > weight of
> > > > resin and I get 0.8 lbs/sq ft total. Add 20% for fillets, bog,
etc,
> > > and it
> > > > comes out pretty much exactly 1 lb/sq ft.
> > > >
> > > > I add in my batteries, outboard engines, refrigeration, water
> and fuel
> > > > tanks, instrumentation, ground tackle, etc and get another
1500 lbs.
> > > >
> > > > With schooner rig, I would estimate each mast/sail/boom combo at
> > > about 500
> > > > lbs, so that is 1000 for the rig.
> > > >
> > > > I am now up to 2100 lbs for structure + 1500 lbs equipment + 1000
> > > lbs rig =
> > > > 4600 pounds.. supposedly only missing the crossbeams and rudders.
> > > >
> > > > I am happy with that. But then the urge to do a reality check
comes
> > > in and I
> > > > look at Rare Bird at 6,720 lbs, and it doesn't have a 10' x 12'
> > > bridgedeck.
> > > >
> > > > So, what am I doing wrong? At about 5000 lbs and 1000 sq ft of
sail,
> > > this
> > > > should be a screamer, but if it is 10,000 lbs with the same sail
> > > area, that
> > > > is a totally different boat!
> > > >
> > > > I would probably be safe by just taking Rare Bird and adding a
> couple
> > > > thousand pounds, but I actually want to be able to do this
> stuff. Help!
> > > >
> > > > Thanks,
> > > >
> > > > - Gardner Pomper
> > > > York, PA
> > > >
> > >
> > >
> > >
> >
>

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