Subject: Re: [harryproa] Build trailerable as a test?
From: "Gardner Pomper" <>
Date: 5/28/2008, 10:49 AM

Rob, great reply, as usual. Now the onslaught of questions.

Prismatic coefficient (I have been embarrased to ask, but since you mention it), I must be using it wrong.

15' * 1.5' * (8.5/12)' = 15.93 cubic feet * 0.77 = 12.27 cubic feet * 62.4 lbs/cubic foot = 765 lbs displacement. Where did I go wrong?

What is your guideline on relative sizes of the hulls. This looks like you are building the shortest ww hull that can handle the weight, then you put on a lw hull that is as long as possible. Extrapolating from your numbers, I guess you want at least 10:1 length to beam for ww and a draft of 1/2 beam (so the underwater cross section is roughly semi-circular?). lw skinnie-ness (wrong word?) is based on full-up whole vessel weight, with a ratio of 20:1 or better??? Is there a rule of thumb relating the lengths of the ww and lw hull? In Visionarry and the charter, it seems to be ww length + 10 feet. In this it is 15' ww and 40' lw.

My biggest concern with the trailering is stepping the mast; particularly by myself. I had a 25' trailerable tri, which I never used because it took 4-8 hours to set up or tear down. But raising the mast was the easiest part, using the hinge at the mast step and all the rigging to hoist it up. I picture myself standing on top of the trailer trying to pick up a 175lb mast that is 40' long and wave it around until I can stick it in a hole. I am sure that is not what you have in mind, since you mentioned some sort of a pole, but I am not understanding how it can be done. I was thinking maybe a hinged sleeve at the mast hole opening that I slid the mast into, with a lip on the other side of the hole? Then  stand on top of the trailering vehicle with a long stick to push the mast upright? Sounds difficult.

I had a question about the telescoping. You mentioned that the boat could trailer at 8'6", fit in a slip at 12' and sail at 20', all with a single telescoping beam. I would think that for an 8'6" width, the theoretical max beam would be 2*8'6" = 17', which would leave no overlap for strength. How are you doing that?

On the layout for my version, you say "Yours will have the cockpit in this area." I don't know which area you mean. From "front" to "back" is the layout: galley, bunk, cockpit, bunk, toilet? Deck hatches between galley and bunk and between head and bunk? Refering to questions in the first paragraph, if the lw hull has to be 40', is there any real downside to making the ww hull 20' or even 25? If the hulls are to be made from 2 flat panels each, it would seem to be a minimal increase in cost and labor and would make things easier to fit.

I really appreciate the resin infusion tips. I am unfamiliar with some of your terms. What do you mean by "shade cloth"? Something you would make an awning out of? Sunbrella, or similar (dense weave, heavy, almost like canvas)? Is "window sealant" like caulk?

when you say "cut the cloth and peel ply", do you mean the fiberglass cloth? or the shade cloth? The order of stacking is glass, peel ply, foam, glass, peel ply?

The plastic conduit (with holes drilled) is layed on top of the glass? or on top of the stack of foam/fiberglass? If on top of the glass, how does the layer of fiberglass on top of the foam ever get infused?

I'll start gathering materials this weekend. I have some West System epoxy resin already. I guess I can experiment with that, but it is high viscosity.

As always, your help is appreciated.

- Gardner

On Wed, May 28, 2008 at 1:19 AM, Rob Denney <> wrote:


Preliminary numbers

ww hull 5m/15' long, waterline 450mm/18", draft 220mm/8.5",
displacement 640 lbs, prismatic .77. (Use this to allow for the hull
shape when you multiply the cross sectional area in the middle of the
boat by the length). I would probably go a little longer to cope
with your other requirements.
lw hull, as long as you can build, trail, afford and handle. The
longer it is, the higher the top speed and the drier and more
comfortable the motion.

The single sail works well on boats with light windward hulls, as the
rudder is aft, which makes it balanced. With 600 kgs on a shortish ww
hull, the ballestron may be a better bet, although once you know how
to shunt, it won't be a problem. With a lot of people on board, and
not much boom clearance the ballestron needs to be watched while

There will be trampolines, which will be on side pieces with a hinge
in the middle so it can be folded when the boat telescopes. A
walkway can do the same.

Sail is loose footed (attached only to the outboard end of the boom).
On Elementarry, the boom is attached to the mast. It has a sock luff,
so this is not a problem. Yours would have slides, so the boom needs
to rotate relative to the mast, but not move vertically. Not a big
deal. Your boom will indeed be too long to attach permanently. It
will be strapped to the bearing on the mast, again, not a big deal.

The hours on the charter boat are for the shell. This one could take
anywhere from 500-1,000+ hours depending on all the usual stuff, but
mostly on the standard of finish required. There are some alignment
details to make it telescope smoothly, which could add some time.
They are all done before the beams are closed up permanently, so are
not difficult, just might take a while.

Materials cost? Same as the other trailer sailor, give or take a bit.
It is cheaper to import the materials from here. Let me or Raps
know if you want to share the shipping costs.

Could be a single bunk, or the galley and stowage. The double is
6'x5', the single is 5x3. Yours will have the cockpit in this area.
The toilet at one end of the hull and the galley at the other end.
Access will be through deck hatches.

Re infusion. Derek's workshops are fantastic, Henny at has a lot of info and a cd, as does Steve in
Houston, but I don't have his web address. By far the best way to
learn about it is:

Get a vacuum pump from ebay, (old milking pumps, fridge compressors,
air con evacuators all work) and a sheet of window glass about 30"
square. Buy some clear builders plastic, some window sealant, glass,
foam, peel ply and resin, some shade cloth and some 10mm plastic
conduit. Drill the smallest holes you can every 4" in the foam and a
1/4" hole every 4" in the middle 18" of 2 pieces of 4' lengths of
conduit, cut the cloth and peel ply and lay it on the glass with a 2"
border all the way round. Put the shade cloth on the glass and wrap
it around the perforated section of the lengths of conduit such that
one piece is on one side of the job, the other is on the opposite
side. Cut a piece of plastic the same size as the glass and seal it
to the glass and around the conduit. Block one end of one piece of
conduit and hook the other end up to the vac pump. Block both ends
of the other piece. Check for leaks (listening) is the best way.
When it is leak free, unseal the ends of the non vacuum conduit and
put them in buckets of resin. Prepare to be amazed. When the
infusion is complete (look under the glass aswell as on top), seal off
the resin conduit and leave it to cure. You now know more about
infusion than 95% of the world's boatbuilders. Study and weigh the
sample, and let me know what it looks like and what went wrong and I
will start lesson 2.

Elementarry as a tender? Could do, but without seats, it is not very
comfortable. It is also a bit fragile for hauling up beaches and over
rocks. The Torqueedo would work, but rowing wouldn't. No sweat on
the payload, but it would all be on the trampoline. You would be
better off with a conventional dinghy. Loading El on the cabin top
for blasting around when you get there has more merit, but the mother
ship really should be bigger for this.

Let me know what the next step is, or if I have forgotten to reply to anything.


On Tue, May 27, 2008 at 11:57 PM, Gardner Pomper <> wrote:
> Hi,
> Ok, I can tell by the responses that it won't be a small boat :( I was
> hoping for something smaller than the design that is taking shape. Since
> that looks to be not true, let me fall back to that one, and drop the weight
> requirements and the 6 passenger (we will only invite people on a nice day
> for a few hours. They can sit on the trampolines (there can be trampolines,
> right?) Then we can design for crew weight of 600lbs, and seating for 3-4.
> I notice that you are not using the ballestron right. I am flouting my
> ingorance here, but how can you go upwind with a mast centered for and aft
> and no headsail?
> I was also thinking of a 3-4' flat panel, hinged at the floor, to give some
> sort of walkway outside the cockpit. Fold it down once the beam is expanded.
> Is the sail loose footed? The charter proa talks about the boom and mast
> being one piece, but it would seem to make it too wide for trailering.
> Since you have basics worked out on that trailer sailor, do you have an
> estimate of work hours for an "average" finish? I know you have mentioned
> 1400 for the charter proa hull (by professionals, I am sure).
> There looks to be a single bunk "forward" also. Is that true, or is that the
> galley? What are the bunk dimensions?
> On Tue, May 27, 2008 at 11:38 AM, Rob Denney <> wrote:
>> G'day,
>> On Tue, May 27, 2008 at 11:00 PM, gardnerpomper <>
>> wrote:
>> > Hi,
>> >
>> > Some sort of liveaboard harryproa seems like my next cruising boat. I
>> > am interested in both sampling the experience, and finding out if I
>> > have the fortitude to build one. I have seen messages about a
>> > trailerable design and I have some questions specific to using it to
>> > "try out" the home build/proa idea.
>> >
>> > Requirements:
>> > 1) trailerable as other specs (8'6" trailer width,
>> easy
>> ><1000lbs with trailer (negotiable))
>> Difficult, negotiations can start when i have done some drawings.
>> > 2) build method as similar to proposed charter boat as possible, since
>> > that is identified as simplest for larger boats
>> > fast and easy on/off the trailer. this would be a daysailer, driving 2
>> > hours to the water, set it up, sail for a few hours, break it down,
>> > trailer it 2 hours home.
>> Easy
>> > 3) I am heavy (300lbs), so the crew weight (3 of us) would be about
>> > 550lbs. We would like to be able to invite another 2 adults and a
>> > child and still sail it well, so total crew weight could be 900 lbs.
>> Difficult, I will see what the minimum size is to do this. How much
>> extra for food and safety gear?
>> > 4) Enclosed head
>> easy
>> > 5) sail without getting wet
>> easy
>> > 6) camping propane stove
>> > 7) comfy seats and table to eat at
>> Can this be outside, under a removable bimini with roll down sides?
>> Otherwise, it is a bit ticky for 6 people.
>> > 8) standing headroom (fold down bimini ok)
>> easy
>> > 9) rain protected
>> easy
>> > 10) will never be INTENTIONALLY sailed in > 20 kts
>> Yeah, right!
>> > 11) ballestron rig
>> easy
>> >
>> > I won't be racing, but I will want performance comparable to what we
>> > have heard from Rare Bird and the charter proa design (i.e. windspeed
>> > up to 15 knots). I *don't* want to fly a hull!! (I'm timid)
>> Timid is good, but it will be a sizableboat to do this with 6 people on
>> board.
>> >
>> > Questions:
>> > 1) What would plan cost be?
>> TBA when i see what is involved. Probably $Aus3,000, as it is going
>> to be a one off. You get 10% off any future plans sold to the
>> design until the next one is sailing. After that it is as per the
>> Goodwill Fee on Part of the plans
>> price wil be deducted from the big boat fee.
>> 2) would plans include info on resin infusion and building a table,
>> > etc, etc? Or at least point me to such info?
>> yes. As much information as you need on anything in the plans.
>> > 2) Estimated build time (novice.. experienced with epoxy/fiberglass,
>> > even some with carbon mat as reinforement, but never built a boat). If
>> > you prefer, you can supply "average estimated build" and I will put in
>> > my own "idiot factor" multiplier
>> TBA, but mostly it will depend on the level of finish inside and
>> outside that you require.
>> > 3) Would it be close to the "trailer sailer" layout jpg I see posted
>> > in the forums?
>> Not if you want a cockpit for 6, which will replace the bunks
>> >What are hull lengths?
>> Long! What is the longest you can build, trailer and handle on the ramp?
>> > 4) When could I start? I have a building available this summer/fall,
>> > but it is not heated
>> Tomorrow, building the table. You won't get all the plans
>> immediately, but i will keep ahead of your progress. Pay for half the
>> plans up front, the rest before the last drawings arrive.
>> > 5) material cost? availablity?
>> Not a huge amount, probably less than the resale value of the boat.
>> Can get it from your local supplier, apart from the carbon for the
>> mast, boom, rudders and beams which I will supply from Texas.
>> >
>> > BTW, I live in Pennsylvania (US).
>> No problem ;-)
>> > Thanks,
>> > - Gardner
>> My pleasure,
>> Rob
>> >
>> >

Y!7 Toolbar

Get it Free!

easy 1-click access

to your groups.

Yahoo!7 Groups

Start a group

in 3 easy steps.

Connect with others.