Jump to content

Proa talk


rob denney

Recommended Posts

I have an image of Rob Denny on a ridge somewhere cocking his AK47 with 8x 'scope sight and methodically picking off one by one a gang of ranting mouth frothers who are throwing clumps of horse defecation at him. But he is aiming not to kill but to shoot their big Texas-like hats off, and slowly they start to see reason -while the few hard core diehards require a second hole through their big hats for them to finally retain their senses.

 

thats a pretty vivid and possibly correct picture!

 

:D

 

bit like you against the 'world' i mean '8.5s' :lol:

 

Some people like to talk, others like to go racing :evil:

Link to post
Share on other sites

G'day,

 

Lots of interesting stuff. Hopefully this (on proas) and the following 2 posts (one on W one on unstayed masts) will answer most of it. Anything I have missed, please let me know and I will go into more detail. If any of this gets hived off into a new thread, please let me know.

 

Tim C, Thanks for the nice words.

 

I may well have problems in the light, but am hoping that the very tall mast will help overcome these. If light air downwind is the only challenge with this boat, I will be a very happy boy!

 

Is there any data on the boats which pulled out of the last Coastal? What broke, why they pulled out, etc?

 

I don't really care if this boat sells or not. It is my boat, to go as fast as I can, as cheaply as I can. If people want to buy one and bling it up, they will have to live with the weight and cost increase and the performance decrease.

 

Samin, Whatever. You said you wanted a bet, I made you one. If you want to change your mind, no problem.

 

You tell me. Do you think a 15m proa weighing less than a ton with 50 sq m of sail will be faster than a 15m race cat? If not, why not?

 

ScottiE, Spot on. Thanks.

 

RyanT, Engineer is Peter Eagles, Etamax. Very competent, with no connections to material suppliers. Safety factors are funny things. They are more fudge factors to handle unexpected and unknown loads. The more complex the item, the higher the analysis or safety factor required. Proa loads are simpler than cat loads, so the Sf can be lower. The build technique is very reliable, which lowers it further. No, I am not going to start another pissing match by stating a number, particularly as it appears to be required for Cat 3. (see below).

Not sure what you mean by what happens in a side on seaway? The ww hull lifts, then the lw hull does, same as a cat. If it is a breaking wave it pushes the whole boat sideways. In the first, the beams are in bending/twisting, in the second, compression. Load case studies have been done for both scenarios. The laminate at the tip of Rare Bird's mast is 1.9mm thick. Not a big deal in carbon as long as you don't use it as an anvil. The 1.6mm part of the beams is inside the hull, supported by a bulkhead.

 

 

MrWolf,

I have had a paint sample in the Perth sun (hotter and more regular than Auckland's) for the last 4 years. On the horizontal surfaces, the raw epoxy resin is only now starting to break down. The high build undercoat is chalky, but still doing it's job. I prefer to put on a light coat of paint in high exposure areas every year or so and save the weight, the money and the sanding.

The boat will be sailed dry, but even if it wasn't, many antifoulings do not need primer.

 

The porosity of unpainted panels is non existant on all the boats I have built and all the panels I have tested in normal conditions. Please let me know some proof of this. You might want to tell the Volvo guys (unpainted interiors) and the Gougeons as well. Could we also have some proof that 700 gsm of paint will be more waterproof than half a millimetre of epoxy/glass coating, please.

 

My panels are not infused. Infusion takes longer, wastes more resin and almost always weighs more (it can never weigh less) than hand laid, vac bagged panels.

 

You put 60 kgs of paint on Timberwolf, 40 of which were for show. How much money did you spend on carbon bits and pieces on the boat to remove 40 kgs? How much did the paint and preparation cost? Different strokes, different folks.

 

I appreciate your view that 40 kgs is "a little optimistic" but all your reasons for this view have been discounted . Core bonding and the coves are included in the numbers, although with edge radii, there are very few coves. I did not include the edge joining of the core. Please add 12m of edge x 12mm thickness of core x 400gsm = 40 grammes to the total lee hull weight.

 

I am sure that the Coastal does not have more stringent safety requirements than the Solo Transpac. If it does, then I guess I will have to carry more weight and you can be the first to say "I told you so".

 

Also appreciate your beam input, but where does your safety factor of 4 come from? I have never seen this in any racing regs. If I do a Coastal Classic it will be on a boat I have sailed across from Aus. I think this will outweigh your calculations and fears.

 

re W and cat 3. Can't let it go, can you? See my previous 3 posts on the subject.

 

The 12m cruising Harry left Coffs for Lord Howe last Wednesday.

 

GregW,

Apologies if you didn't post the beam question.

Two medium hulls may well be more pitchpole resistant than a long and a short, if the boat weight and the prismatic are the same and they are going straight down a wave. More often one hull digs in and over you go. I base my premise on the harry being lighter, with lower centre of gravity and nothing froward to trip on. As you said, all are secondary compared to the skipper. Bit like laminate weight. Any skipper determined to ding or pitchpole his boat probably will, regardless of laminate weight or boat design.

 

Shunting downwind is slow compared to gybing. Safer and less likely to be a stuff up, but way slower. Crew movement and aggressive steering will speed it up, but this is one area where the proa is definitely worse off.

 

Proa righting moment:

A beach proa has less rm for it's weight than a beach cat as the mast helps the cat. On a proa with accommodation, the accommodation is always on the windward side. As long as this (and the food, water, safety etc) is heavier than the rig weight, the proa will have more rm than a cat of equivalent weight. On harrys it is around 65/35 windward hull/leeward hull, so the proa has near enough the same rm as a cat of similar beam, but twice the weight. See the Wilderness example in the next post.

 

rob

Link to post
Share on other sites

Unstayed masts. Following from another forum. Prices are aussie dollars.

 

Originally Posted by Fard (a Brisbane mast builder)

The shell weight of a Wilderness 1230 (Schionning cat) rig is 140KG. The all up weight is approx 260kg including furler, rigging (standing and running) boom, light package TV aerial, VHF and cable (12mm) and provision for a radar on lower spreader.

The cost of a rig for this boat is $29500.00 approx including furler and mast RCB cars and striker wire.

Deck hardware and winches extra.

Mast rigging should be checked by the owner constantly and by a rigger every year or so.

Wires should be replaced depending on mileage every 7 or 8 years.

The mast should last for the life of the boat.

 

The 1230 Wilderness has rm of 17,500 kg m. The 50' harryproa in the video

has rm of 18,000 kgm.

 

The mast for the harryproa cost $AUS25,000 including paint, all fittings for the ballestron boom and jib and very light carbon rcb track. The bare tube was about half of this cost. It weighed, when finished about 130 kgs.

 

The Wilderness rig did not include the traveller, deck gear, forebeam and seagull striker.

 

An unstayed carbon mast is appreciably cheaper and lighter to put on a boat designed for it than an alloy stayed rig. This assumes the unstayed rig is built by professionals using sensible technology rather than aircraft technology. You could also (easily) build it yourself and it would cost about one third as much.

 

Unstayed rig benefits:

1) They work on multihulls, as the boat in the video, Team Phillips (2nd highest righting moment of any performance cat, ever), Jimmy (60' Irens cat) and others have shown. TP broke due to faultu workmanship, the unstayed rigs were a huge success.

2) There is almost nothing (total standing and running rigging is one halyard, 2 reefs, one mainsheet) to go wrong, particularly on a jibless rig.

3) There is no maintenance.

4) They are safer. The knowledge that releasing the mainsheet, on any point of sail, in any breeze will stop the boat is extremely reassuring.

5) They are less effort to sail. The first reef is automatic. The mast flexes, the sail depowers. The sail can be easily raised and lowered on any point of sail, in any wind. The savings on ball bearing cars and tracks and on your nerves, are appreciable. There are no flogging headsails, winches or deck tracks and gybes are safe as the boom does not hit the shrouds.

6) The boom can be self vanging, so no traveller is required. This is a cost and safety consideration.

7) The loads on the deck and heel bearings are high, but the load on the rest of the boat from the rig is non existent. Much lighter scantlings, no forebeam, no massive main beam, no traveller beam, no chainplates or bulkheads to attach them to.

8) They can be wing section, which uses less carbon, and has much less drag, and more lift than a stayed rig.

9) They can be much taller than stayed masts, with very little weight added.

 

There is no need for dinghy analogies. Compare the boat in the video with any cat with similar accommodation and the proa will be half the weight.

 

Dynamic loads include shock loads. These are tiny for an unstayed rig compared to a stayed one. This is one reason why stayed mast (and the beams on these boats) safety factors have to be so high.

 

rob

Link to post
Share on other sites

W

Rod Boy,

I wish someone would buy W and have a go. Any offer above a couple of months marina fees would probably score it. The hulls are very light (3 kgs per sq m from memory), stiff and strong (fell off the truck on the first corner on the way to Westhaven) and the mast is a lamp post compared to what we are doing now, but you could add 4-5m on the top of it and it would be very quick. Chop off everything above the deck, get it back to how it was before the cat 3 mods and it would be a lot of fun. W

 

It would not prove anything about proas though as although the mast is in one hull, the hulls are not double ended.

 

W has one beam which is free to rotate in pitch, can telescope from 4-7m long and is attached to the hulls by an elbow which goes vertically into the hulls. The hulls can rotate around this, in yaw. The string that kept the two hulls pointing in the same direction was 12mm vectran. They were doing some adjustments, tied it and went sailing in a decent breeze. The knot came undone at speed, the bows came together and it all fell over. The unstayed mast was not tied in, came out and did some superficial damage. They got towed to Cheltenham, went home, got the trailer and took it back to the ramp, reassembled it and relaunched it, then fixed the damage. I was not on board, did not get the story for a few weeks and cannot find the email now, so take this story with a grain of salt.

 

The owner is one of the nicest and most innovative guys I know. He was not keen on racing it, the builder and I were. When Jason said no, he prevailed.

 

W is possibly the most radical boat launched in NZ since Fiery Cross. It was built across the road from Playstation, whatever year that was. '97?'98? The build shed was an open house (open brewery would be more correct) and lots of people came through. There was plenty of talk about how light it was and how potentially fast. The designer (me) and the shed owner who helped me build it probably shot their mouths off occasionally about it's potential performance, the owner never would.

 

rob

Link to post
Share on other sites

I've sailed on W once, and it is certainly an innovative concept and boat. It is not slow as it is so light and low windage. It is a little disconcerting when sailing to leeward, with the rig to windward of you, and with the hulls responding to waves independently. From memory it wasn't the easiest to tack.

 

Yes the owner is a wonderful free thinker who put his money where his mouth is for the project. The boat needs further development, and the concept certainly warrants it.

 

I understand it was refused a Cat 3 certificate simply because of the lack of headroom in the cabin. Hence the construction you see now, which is surprisingly roomy inside. But lacks sailing shelter on deck.

 

The owner and I took the concept, bi-maran further to enter it into a RINA design competition a few years ago, which it won. See http://www.tcdesign.co.nz/bt_9bi.htm

http://www.bimaran.com/

 

Rob has moved onto a different path which is great.

 

However it has not enjoyed any commercial success. I would suggest that buyers have struggled with multihulls (beyond the 12m+ charter cats), so presenting them with an asymmetric boat, despite all its potential advantages, is just too hard to understand. (See thread on 101 reasons...)

Link to post
Share on other sites
Guest Robertcateran

About seaworthiness due to length, and whether a 15m/9m is better than a 12m even length hulls.

What are the reasons for the improvement in seaworthiness due to length? Is it the reduced tendency to pitchpole down a wave, or the extra momentum in the case of a wave hitting them, or the better chance of gaining ground against a sea?

If some of these are held against a long hulled Harrproa with high prismatic coefficient, no flare on the bows and no rocker, then the lack of pitching moment makes the boat eminently seaworthy for its length. Having two different length hulls reduces hobbyhorsing and contributes to being able to make way against chop. If momentum is important, then the Harry dips out

Link to post
Share on other sites
About seaworthiness due to length, and whether a 15m/9m is better than a 12m even length hulls.

What are the reasons for the improvement in seaworthiness due to length? Is it the reduced tendency to pitchpole down a wave, or the extra momentum in the case of a wave hitting them, or the better chance of gaining ground against a sea?

If some of these are held against a long hulled Harrproa with high prismatic coefficient, no flare on the bows and no rocker, then the lack of pitching moment makes the boat eminently seaworthy for its length. Having two different length hulls reduces hobbyhorsing and contributes to being able to make way against chop. If momentum is important, then the Harry dips out

 

Sideways stability is a function of width and weight. Longwise it is length and weight. The longer, wider and heavier the better in a storm. However we are not about to make boats heavier for storm conditions. (water ballast when on a sea anchor may have benefits. Perhaps a different discussion...)

 

Nothing wrong with long skinny bows on a light multihull, entering the waves gently and reducing the pitching. The smaller and further aft the fore beam the better.

 

Flare in bow areas is so Eighties. There is a wave out there higher than the bow of your boat. No matter how big the boat. Get over it. So a wide flat foredeck is simply going to be driven down by the wave breaking on it, compared to a well radiused deck that sheds the water.

 

None of the above about Proa's really, just multi's in general...

Link to post
Share on other sites
Guest Robertcateran

I hear Bain on the Harryproa 'Aroha' is due in Whangerai sometime towards the end of the week from OZ. It would be nice if anyone is around their if they could get some pics of the arrival,

regards,

Robert

Link to post
Share on other sites

Hi,

 

I was sailing sidecar up the coast one day and he waves were getting uncomfortabley steep. With the short sharp hull the digging into the trough at the bottom as I went sliding down in the following seas.

I would steer off across the face when it looked like a steeper one coming - this gets tiring after a while - but thought matbe I was being a bit GAY so went straight on one and felt the bow dig in and pop up again slightly, losing a little speed.

 

Doug

Link to post
Share on other sites

For those who don't know Doug built and cruises one of Rob's designs a 25ft?harry.He's done a few miles in it now and is ready to build a larger version.

Link to post
Share on other sites

squid,

i have to pass comment on that avatar - it freaks me out a bit.

i swa my first shark ever only recently on the trip up the coast.

thankfully it was quite a friendly little fellow swimming along on its own.

time for a change squid.

doug

Link to post
Share on other sites

It's a friendly little pussycat.

 

When I was in the process of introducing my beloved to sailing I talked her into a charter holiday on a Seawind cat out of Hinchinbrook.

One of her objections I had to overcome was that there would be sharks. I po-poo ed the notion.

!5 mins out I look over and there's a shark shadowing the boat (a very big shark). The bugger stayed with us all the way to our first anchorage. I said nothing and only told her about it years later.

Link to post
Share on other sites
squid,

i have to pass comment on that avatar - it freaks me out a bit.

i swa my first shark ever only recently on the trip up the coast.

thankfully it was quite a friendly little fellow swimming along on its own.

time for a change squid.

doug

 

Welcome to Crew.org Doug. Can you post a photo of your Proa? have you ever raced it?

Link to post
Share on other sites

hello Sam,

 

it may be an easier race for you than racing against Rob.

My top speed is only 14 knots to date.

new work underway may try racing after completed, august time.

 

doug

post-10260-141887153876.jpg

post-10260-141887153878.jpg

Link to post
Share on other sites
Guest sassarassa
I hear Bain on the Harryproa 'Aroha' is due in Whangerai sometime towards the end of the week from OZ. It would be nice if anyone is around their if they could get some pics of the arrival,

regards,

Robert

 

It would be great to hear how this trip went ... I dont have any NZ contacts for Bain or I would have given him a call already. Is this the first blue water crossing for a harryproa?

 

cheers

 

Jon J

Link to post
Share on other sites

G'day,

 

Nothing heard from Bain, despite many people looking for him. We know he arrived, no idea where he has gone since, but he is an ex fisherman from the northern part of the North Island, so he could be tucked away somewhere up there. If anyone hears anything about him, I would love to be informed. Thanks.

 

regards,

rob

Link to post
Share on other sites

This from another forum, posted by Mark Stephens, who helped build Aroha.

 

The12m had some weather 8hrs east of Lord Howe and broke some gear, put

out parachute for 36 hrs till it calmed down enough to do repairs. 250

miles out from Lord Howe leeward hull started flexing a lot in a beam

sea, solved the problem temporarly by using the jib halyard as shroud

and tightened it with the winch and did the rest of the trip with the

main with 1 and 2 reefs in, had to baby it. He's going to try solid

bulkheads at beams and same at mast. end quote

 

Before they left, Bain asked me about reinforcing the lee hull. I

advised him to fit full bulkheads, which should have been in from the

start for stiffness and watertightness reasons. As far as I know, he

decided to just add more laminate to the hull. I have asked Mark for

more details of the weather and the gear that broke, will let you know

what I hear.

 

regards,

 

Rob

Link to post
Share on other sites

Archived

This topic is now archived and is closed to further replies.


×
×
  • Create New...