Rob, you should know by now that answering questions just creates more
questions <grin>. Mine are inline.
On Wed, Mar 25, 2009 at 11:08 PM, Rob Denney <harryproa@gmail.
>
> G'day,
>
> Me and my big mouth! Notice the "at this stage". ;-). Pretty easy
> design brief though. Faster than anything else out there, big and
> comfortable enough for a big guy to cruise solo, dead simple to build,
> trailerable and must not capsize.
>
> Crew weight and payload 700 lbs/320 kgs (I have to work weights in
> kgs or make some embarassing mistakes, 2.2 kgs/pound)
>
> Boat weight 900 lbs/410 kgs
Are you just restating what I said for specs, or do you actually think
the boat can weigh 410 kgs? I just made up numbers for rig and beams
and stuff.
>
> Sail area for BN of 2 = (assuming empty boat), SA= 370 sq'/34 sq m.
> Assume 5:1 aspect ratio, boom length is 2.6m, luff length is 13m.
> This assumes a una rig. It is not possible to (easily) telescope an
> easy rig. Thinking about it, it is not so complicated, but the loads
> will increase. Maybe have a 3/4 height jib, which is removed for the
> 1st reef, then telescope the top quarter of the rig for the second
> reef. Although for sailing in 5 knots of breeze, height is king, so
> the una rig is probably a better bet. Worth some more discussion, I
> think. Definitely a wing section, either way.
I was thinking to set it up as a "normal" easyrig, then be able to
raise just the main an extra 10' (guess) when in really light airs.
Have the jib forestay attached to the non-telescoping part.
I don't understand the unarig. On a monohull, a single sail is always
far forward, like a cat rigged boat. I don't understand how the
unarig, placed in the center of the boat works. I know it is in the
design plans for Rapscallion, but I never saw an explanation. Have you
tried this?
Oh, and did I forget to mention that I want to be able to pack the
boat in a container, so the mast should not be longer than 39'
collapsed, or it should be able to come apart the way I have shown in
the camper_mast.
>
> So far, so good, now the tricky part. No capsze. Not sure that I can
> guarantee this. That is a big rig on a little boat. I will pass
> responsibility for this requirement back to you and your sailing
> ability.
>
I think we can safely count on my being chicken to prevent capsize, so
long as I can reduce sail. I was taught the old adage that if you
think it might be time to reef, then it is time to reef.
> Files are now open again.
>
> Assuming the dimensions and calculations are correct (I rough checked
> a couple and they were), the drawings look good. I assume you have
> drawn it in the other view and 3d to be sure it all fits. If
> possible, I would extend the lee hull length to 35', and leave out the
> kink in the topsides.
I uploaded my 3D rendering to the files area. It looks ok to me.
Is there a specific reason to extend the lw hull to 35', or just the
"longer is better" idea? That hull already has a l/b ratio of 25:1.
Is the "kink" the part that raises up in the middle, like rapscallions
boat? Are you saying that I should raise the deck the whole way along,
or just slope it up from bows to the mast? I did it like this to give
me a convenient place to mount the crossbeams and because it was done
that way on Rapscallion. I am not disagreeing; I just am not sure I
follow what you are telling me.
>
> Righting moment is 300 kgs at 4.25m (not quite correct, but near
> enough) = 1.275 tonne metres, which will need a decent bury for the
> mast, or a stronger lee hull. You can either pay $aus1,000 to have
> this engineered, or go with my gut feeling, which I will post you off
> list with the usual cautions and conditions. I would advise the
> engineering.
>
> Easiest build is flat panels, partially or fully glassed with glassed
> polystyrene in the compound curve areas outside the beams, below the
> water. Either I can calculate the panel shapes, or you can and send
> it to me for comments. The deck can either have a deck edge radius,
> or you can use a timber stringer and glue the hull and decks to this,
> round the edge and apply a layer of external glass. Easier and
> quicker, but not as rounded or as neat as the der. You should be
> able to make the deck panel pretty accurately, but no big deal if it
> is a little bigger. Adding rebates to areas of the panel where there
> will be joins will make it neater/less fairing.
Why timber stringers? Would it be possible for me to just use glass
covered foam for stringers?
The simplest I can think of is to have the middle 50% of each hull
bent up, and use foam for the keel section of the end 25%. That would
require carving a 1'x8' solid foam block for the bow and stern of the
lw hull. Is that ok? Then I don't have to worry about the compound
curves in those areas.
What is a "rebate"? Is it just an overlapping flap of fiberglass?
>
> Telescoping beams are tricky. They need to be a tight fit when out
> and a loose fit for sliding. Plastic over pvc pipe will not release
> if the whole thing is laminated on it. Lay up your internal skin with
> a piece of plastic under the 2" overlap. When cured, remove the skin
> from the pipe, then glue the overlap so it is a loose fit on the pipe.
> Then layup the rest of the laminate. Build up the ends for the
> tight fit, the rest for a loose fit, fair it and use it as a mould for
> the other half beam, building it the same way.
>
> Telescoping beams are easier to build as square sections as you can
> work on the inside. Again, you have the choice of engineering the
> beams or going with my gut. More on this off list.
The beams can wait. Hopefully I can get these made in China, along
with the mast and rudders. I am mostly concerned with being able to
start the other parts of the boat. If I end up with some sort of
swinging crossbeam system, that might raise the deck, which will
cascade changes to all parts of the boat, so I probably need to
decide that before I start building it.
Do you think that telescoping is the best (simplest, most reliable)
way to do the reduction in beam? I know there have been alot of ideas
tossed around on the forum. Also, can you give me a figure for how
much overlap there needs to be in a telescoping beam? Roughly 10% of
length? 20%? I know this is someplace where engineering needs to be
done, but I just want to work out the approimate minimum and maximum
beams I can do.
>
> Anything else, let me know.
I can't believe you are still saying that <grin>
>
> regards,
>
> Rob
>
Thanks very, very much!
- Gardner
> On Wed, Mar 25, 2009 at 11:23 PM, Gardner Pomper <gardner@networknow.
> > Rob,
> >
> > Ok, you asked for it! <grin>. I haven't moved this to a new thread, but
> > maybe I should.
> > These questions are all based on the camper files I uploaded to
> > Files->Gardner'
> > moment, but hopefully that is a temporary problem.
> > First, the purpose of the boat is to be a long distance single person
> > cruiser. I want to do the same type of thing that Doug is doing with his,
> > but I probably weigh twice what he does and have a higher minimum comfort
> > level, I expect. Secondary purpose is as a fast, fun daysailor for the
> > family (2 adults, 1 child, total weight 550 lbs). But, I do *NOT* want to
> > capsize. I don't want to fly a hull. I want relaxation at speed, not
> > adrenaline rush.
> > As I have mentioned in prior posts, we live in an area of light winds.
> > Summers here often have winds light and variable, 5 kts or less. Over 10 kts
> > is uncommon. Over 15 and I don't go daysailing. Because of all this, I want
> > a large sail area that can be easily reduced to cope with higher winds. I
> > also want to be able to sail in 30+ kts, for those times I am cruising and
> > get caught.
> > The primary building characteristic of the boat must be simplicity. I have
> > no boatbuilding experience and want something forgiving. To this end, my
> > concept for this boat is that it can be built in 3 major sections, lw hull,
> > ww hull and deck. The idea is to build the deck first, as it is simplest and
> > least important to the structure, which will give me some experience before
> > I tackle the hulls.
> > One last thing; ignore the bicycle pedal idea for now. I may go with a
> > sculling oar and/or a portable electric outboard. That is all undecided and
> > I don't want it to hold up the rest of the boat.
> > Questions:
> > 1) I figure an empty weight (all up) of 200 lbs per hull, 200 lbs for the
> > deck, 100 lbs for rig (guess), 100 lbs for crossbeams (guess) and maybe 100
> > lbs misc, for about 900 lbs. Payload about 700 lbs (150 lbs equip + 550 lbs
> > crew for daysailing; 200 lbs equip, 300 lbs crew, 200 lbs stores for
> > cruising). Does all that seem reasonable, given the measurements in the
> > drawing?
> > 2) 3/8" core throughout, except for horizontal deck surfaces wehre I walk.
> > Use 1/2" there. 6oz fiberglass everwhere, except under the waterline, where
> > 18oz for grounding protection. All ok?
> > 3) Build telescoping beams by wrapping carbon fiber around PVC tubing
> > wrapped in plastic sheeting and vacuum bagged. Slide the PVC tubing out
> > after resin sets. What diameter tubing should I use? should I wrap carbon,
> > then wrap foam around, then another layer of carbon, or just 1 thick layer?
> > I seem to be able to get 12 oz carbon fiber twill reasonable cheap ($26/yd
> > in 47" width, so just over $2/sq ft).
> > 4) If I can still get it, there might be a few sheets of 3/8" airex
> > available at about the same price as corecell. If I just use it for the keel
> > sections, I figure I can cut 2'x8' pieces for teh keel and use 4 pieces for
> > the lw hull and 2 pieces for ww hull, so just 3 sheets of it. That should
> > allow me to make the 4" radius bend in the ww hull and 6" radius in the lw
> > hull.
> > 5) When I get to the rig, I want to look at your ideas for a telescoping
> > mast. That sounds appropriate for the light wind days, and I can just keep
> > it down on days with more wind and reef when it gets really windy. I have
> > not done the calcs yet for bruce number, but I would like to get close to a
> > 2 when loaded for sailing.
> > 6) I would like to start building the deck first. Given my idea of just
> > dropping it on top of the ww hull, I am assuming that we can make minor
> > changes in the hull specs without my having to redo the deck. I was not
> > planning on having the hull/deck vertical transition be seamless; I was just
> > going to make the deck rectangular and let the corners stick out, to
> > simplify building. Do you think I can get away with that?
> > 7) What would you change in the design, given my requirements?
> > Thanks,
> > - Gardner
> >
> > On Wed, Mar 25, 2009 at 6:13 AM, Rob Denney <harryproa@gmail.
> >>
> >> G'day,
> >>
> >> My Elementarry is 3mm foam with carbon each side. 10mm/3/8" will be
> >> heaps for yours. Flat floors on ww hulls hit with a bang after a
> >> capsize. Definitely 18 oz either side. Airex wil do, but it is very
> >> expensive. I'd persevere with the Core cell.
> >>
> >> No need for any money at this stage. Ask questions, I'll answer. I
> >> am away for 2 weeks from next week, so ask before Sunday, please.
> >>
> >> regards,
> >>
> >> Rob
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