On Fri, Mar 27, 2009 at 9:01 AM, Rob Denney <harryproa@gmail.
> On Thu, Mar 26, 2009 at 9:47 PM, Gardner Pomper <gardner@networknow.
> wrote:
>> Rob, you should know by now that answering questions just creates more
>> questions <grin>. Mine are inline.
>
> Keep them coming, this is the enjoyable part of boat design, for me.
Well, then, I must just be your FAVORITE person <grin>
>
>>
>> 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.
>
> Suspect it will be more than this as your laminate is a bit light for
> a knock around boat with foam core. Cedar or kiri are much more ding
> resistant.
>>
>
>> 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.
>
> The forestay has to be on the telescoping part, as this slides down
> over the lower mast. Having the top mast as the internal is "normal"
> but much harder to organise.
Someday when you are not so rushed, it would be great to start a
thread on your telescoping mast idea. I was thinking that an internal
top mast would be smaller and lighter. The sail track for the main
seems to be a problem either way. You do need to have a dam inside the
mast to let the water out before it gets down to the deck.
>>
>> 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?
>
> On El and Harriette and on my Easy rigged boats with the jib down. I
> think it works because the clr is a long way aft with only one beam
> mounted rudder.
Well, I planned on having the rudders on the ww side, so I am still
pretty nervous about that unarig. At one point you were gong to try
this on your harriette, but I imagine it has not worked its way up to
top priority yet. Plus, I am a bit nervous about the boat weight going
up and not having the extra sail area from the jib.
>>
>> 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.
>
> Should be pretty easy, if the ww hull is less than 8' wide. Joining
> masts at the deck is not a good solution as it is the highest stressed
> area.
>>
Not sure how to get an easyrig into a container unless there is a
short (< 8') mast stub or if the booms come off, which would also be a
stress issue, at least with the jib, I would think. But, if I end up
with a unarig with a boom < 8' long, I guess that is a moot point.
>
>>>
>>> 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.
>
> The bow of the lee hull can be lower, but otherwise fine.
The bows are 2' above the waterline, as that is where the crossbeam
sits. I could lower the hulls outside of the crossbeams. What do you
suggest for a height?
>>
>> 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.
>
> Longer is better, faster, safer and more comfortable. Not that much
> trickier on the trailer.
I may have to bite the bullet and learn to trailer properly.
Trailering my 25' trimaran made me pretty nervous, so I only did it
rarely, which meant I never got used it it.
>>
>> 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.
>
> No, the kink is in the section view. The hull sides can be straight
> from the bottom radius to the deck.
So, you are saying that the overall beam of the lw hull can be just 1
foot? I did not think that would give enough support for the mast. If
1 foot is enough beam, then I am fine with that.
>>
>>
>> Why timber stringers? Would it be possible for me to just use glass
>> covered foam for stringers?
> Timber for ease and longitudinal strength. Could be foam/glass with
> some uni added.
>>
>
>>
>> What is a "rebate"? Is it just an overlapping flap of fiberglass?
>
> An area of the panel where the surface is lower than the rest, such as
> where the glass over the polystyrene overlaps onto the hull panel.
> The overlap sits in the rebate, so fairing is minimal.
>>>
How wide should the rebate be? 3" on each side of the seam? 6" ?
>
>>
>> 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.
>
> Swinging beams are also fraught.
>>
>> 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.
>
> I have a single swinging beam system which is easier, but telescoping
> is tried and tested so you know what you are getting into.
> Overlapping sliding beams (like a horizontal gunter rig) are easier to
> build and use, but not very attractive. Overlap should be 10-15% of
> the unsupported length, but this always looks too short on beams, so
> 2' is minimum.
>>
>>>
>>> Anything else, let me know.
>>
>> I can't believe you are still saying that <grin>
> Like I said, this is the enjoyable bit.
That's it for now! Have fun in Brisbane!
>
> regards,
>
> Rob
>>
>>>
>>> regards,
>>>
>>> Rob
>>>
>>
>> Thanks very, very much!
>>
>> - Gardner
>>
>>> On Wed, Mar 25, 2009 at 11:23 PM, Gardner Pomper <gardner@networknow.
>>> wrote:
>>> > 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.
>>> > wrote:
>>> >>
>>> >> 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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