Multihull Structure Thoughts

John Passmore clung to the starboard keel of his capsized catamaran, breaking waves tried to tear him off the slippery upturned bridge deck. He’d read all the survival books and knew he must not even think he’d not make it. He shouted at the sky: ‘I’m not going to die,’ and he shouted at the waves: ‘I am going to stay here and hold onto this stub of keel. That is all I have to do and I can do that much.’ And he concentrated on seeing his wife Tamsin and their three young children again.

Let’s talk about why John got there on a Heavenly Twins Catamaran. The very spacious cruising cat is 27 x 13.75 foot with a minimum weight of 6000 lbs. The 32 foot aluminium mast carries 412 square foot in its rig. The length to beam is 6.5 to 1. The underwing clearance is 1 foot. The draft is 2.3 foot over the low aspect ratio keels. Mainly solid glass builds first made in 1971. There were 400 of these cats produced.

This is a cruising cat that peaks, repeat peaks, at 14 knots. It can average 7 knots but over long distances it averages about 5 knots. We are not talking about a racer. A Heavenly Twins has circumnavigated another has sailed from Britain to Australia. No problems in either case. The sailing qualities were OK but the cat pitched a bit.

Why the discussion, John Rivers asked about Wraps to minimise capsize on another thread. John Passmore can give some advice.

John was attempting to become the first solo sailor to circumnavigate the United Kingdom non-stop. “Lottie Warren” his 27ft Heavenly Twins catamaran, was enveloped in a north-westerly storm with sustained wind speeds of between 40 and 50 knots, with gusts much higher, off the top end of the Shetland Islands.

When the heavy weather arrived, John was ready for it with Heavenly Twins’ designer Pat Patterson’s ‘storm management manual.’ Stage one was to heave-to – not easy in a cat – stage-two was to drape a 100m (330ft) anchor warp, from the starboard bow to the starboard stern in the bight of which was a car tyre. For the next 24 hours Lottie Warren, bobbed over the waves, beam-to, like a duck. Gradually the wind speed increased until John reached the third and final stage of the ‘storm manual.’ This was when the impact from waves thumping the beam-to hull became ‘shock-like,’ making banging noises and hurling items across the cabin. John had to make his way on deck and slithering along on his belly, he transferred the bow line to the port stern and the catamaran swung stern to the seas, and suddenly was off: making six knots under bare poles.

Standing at the wheel, he watched the log hit 13 knots – then 16. Looking astern, two white wakes stretched out with the tyres kicking up plumes of spray, and then, behind them, the crest of the wave. It was high, of course, but it was a long way behind so it didn’t seem particularly threatening. Then the weather became worse.

The first he knew of the giant sea that would finish Lottie Warren, was an insistent hiss of rushing water as she began to broach. ‘I saw the bulkhead start a cartwheel and small items started cascading from cave lockers…I knew she was going over.’ Now upside down, John grabbed his EPIRB from its cockpit bracket. Next, he saw the aft cabin hatch was open and the life raft was missing. The boat began to settle and water came up to his chest as he squatted inside the hull. John climbed out and onto the upturned bridge deck. John’s ordeal fortunately lasted only three hours before the Coastguard helicopter arrived. The pilot had to switch to manual to get the helicopter the craft down to 50ft, negotiating between waves up to 100 ft high.

Small detail. The official largest open-water wave ever recorded measured 62.3 feet (19 m) and was detected by a buoy in the North Atlantic on Feb. 17, 2013, according to the World Meteorological Organization as at 9 April 2022. On October 29, 2020, Portuguese surfer António Laureano claimed to have ridden the biggest wave ever at European beach break at Praia do Norte. The University of Lisbon's Faculty of Human Kinetics (FMHUL) on the 4 Mar 2022, suggested the wave was 101.4-foot.

Summary. We have a very conservative cruising catamaran that was towing wraps to slow the boat and had no sail up. A very large wave arrived, the cat accelerated down the face then “capsized or pitch poled” and landed on its roof. John was picked up by a helicopter 3 hours after the capsize. The cat was later damaged and sunk or sold?? Depending on which version of Johns writings you read.

If you sail conservatively and are lucky you will never approach this situation. But even if you are well prepared in a good boat wave action can still get you. Learn about wraps, parachute anchors, drogues etc. All can assist but you can still can get into trouble if you hit a rouge sea.

The jpegs give the idea of the boat and the jpeg of the capsized cat is the pick up of John.

Finally for those who think modern designs can "just" run downwind etc, please look at this web site about the capsize of Anna, a Chris White Atlantic 57. Atlantic 57's are one of the best performance cruising catamarans available. They are superb, but Anna was still caught out. The site is: Capsize of Anna https://www.chriswhitedesigns.com/capsize-of-anna

 

The Eric Henseval designed M498 is a “cruising” day catamaran along the lines of the Slider 16 catamaran. Eric Henseval knows how to design and simplify the build of multihulls. His Sardine Run trimaran and Sardine Twins catamaran 18 footers are excellent examples of what can be done. The M498 was requested by a client for a fast “cruising” daysailor. The M498 is 16.3 x 8.3 foot with a weight of 805 lbs and a displacement of 1,470 lbs fully loaded with 3 crew, outboard etc. The 21 foot mast carries a 96 square foot mast, a 43 square foot jib and a 105 square foot gennaker. The length to beam on the hulls is about 10 to 1. The draft is 1.6 foot over the low aspect ratio keels. The rudders can be fixed as they are shallower than the keels. The outboard power can be from 2 to 10 HP.

The M498 has a large enough cockpit to sleep 2 people under a tent and there is storage in the rest of the cat for supplies, camp stove, the tent etc for a weekend cruise for 2. This cat is for those who want a nice day sailor to cruise on, without having to handle a large rig or be hiking out for “fun”. Also, it can be easily trailed and stored.

As I said, Eric knows how to design an easy to build multihull. This cat is mainly built from 9 mm marine plywood with glass taped seams and minimal amounts of timber stringers. Externally, all is covered with EG 200 gsm cloth and epoxy. You can hit something softly and not have to do a repair. The cross beam and wing structure are also wood. The only metal bits are the mast, boom sail tracks, rigging (if not Dyeema) and blocks etc. A relatively cheap boat to build that can be constructed in a double garage.

This cat could be a lot of fun. I do not know if the design was finished or if the cat was built. The person who asked for the design did build another small cat but that is tomorrows story. The jpegs are what we know.

 

When you own a sailing 13 foot monohull 2 berth cruising yacht, you occasionally need to get to or from shore to reach the moored cruiser. So, the owner who built the Eric Henseval Inseparable 398 asked Eric to design a dingy that was capable of being rowed, easy to sail, unsinkable and stable. The boat should also be able to carry 2 people, simple to build out of plywood with a easy to use rig and no centreboards. If it could be trailed or car topped it would be good. I now know why designers have less hair than the average person as they pull it out try and meet client requests.

So, Eric Henseval being a creative guy delivered the Turtle 198 catamaran. The Turtle 198 is 6.5 x 4.1 foot and weighs 74 lbs. The full load displacement is 480 lbs. The 2 part 11.3 foot freestanding carbon mast (or Aluminium) carries a 22 square foot furling sail around the mast. The near vertical battens allow the sail to wrap around the mast. The length to beam on the hulls is about 8 to 1. The draft over the mini keels is 240 mm (0.8 foot) and the draft over the centrally mounted rudder on the wingdeck is 410 mm. The power is oars or a 2.5 HP outboard.

The wingdeck provides a 4 x 4 foot seating space for a maximum of 2 people and some stuff. This is a smooth water cat capable of handling some small waves but it is not a coastal sailor. The cat has foam filled hulls to provide full buoyancy if there is a problem. The performance is unknown but any sailing jpeg I have seen show the cat moving well.

The construction is 4 or 5mm thick marine plywood, taped chines, glass fibre and epoxy resin. The hulls are simple flat bottom dory shape which can literally be put together in a day once the shapes are cut out of single sheets of plywood. This is simple! The main cross beams have timber top and bottom flanges with foam inserts between the flanges attached to the plywood webs. The underwing is plywood, foam, plywood sandwich. The mast step is a PVC tube glued and glassed to the main crossbeam. The Styrofoam foam provides some structural stiffening as well as buoyancy. The rudder is not a kickup but solid. The keels are solid timber which also acts as a stiffener. This is a simple well thought out structure with a minimum of parts. As a first build to act as a tender for a larger build, you would learn a lot and have fun while doing other things.

The jpegs give the idea. A very well designed cat that can do many functions and the kids will love it.

 

Part 2 Turtle 198 jpegs.

 

Help please.
Yesterday I was down at a marina here in St Augustin helping a friend with his powerboat. As I was walking down the dock this catamaran caught my attention. It appears to have an aft-mast rig something like that of a Prout, but much better stayed/rigged. Can someone help me ID it?

I went down to that marina today to see own I might contact the owner, but the office was closed for Fri. I took some photos, but my camera decided to give up on its battery power before I could get better photos.
Two nice size headsails, and a small mainsail with no traveler control.

Reminds me of how I might have rigged my aft-mast design had the client insisted on a straight standing mast.

 

Brian. I suspect this is a Escale 39 done by Prout. Try this site: Prout 39 Escale Review – CatamaranSite https://www.catamaransite.com/reference/prout-39-escale/

They were popular in the 90's and were the "luxury" extension of the Prout Snowgoose range. Like all later Prouts they could sail but were not great performers. After these cats Prout changed hands and then the EG 45 foot models had conventional sloop rigs.

 

That's it.
I guess I should have known that having been under the influence of Proud designs early on. Maybe its just my 80 year old memory....ha...ha

I'm going to pursue getting in touch with the owners, and see if I can learn some things from their experience. I also posted a comment of that site you referenced to see if I cold get in touch with the reviewer/owner Hunter Frey. I was particularly interested is this portion of his review,..

I did find his musings about sailing qualities interesting..

 

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Apologies for the delay in replying to this post - I sent a link to this post to an Aussie pal Jonathan on the YBW Forum (https://forums.ybw.com/index.php?members/neeves.76734/) who is an authority on anchors and anchoring, and he offered the following observations, and gave me permission to post them here.
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Thanks for the link.

I read through the specific post and ran through some of the earlier posts. I note 'oldmulti' is Australian, which explains the focus earlier on McConochie. The latter are top of he game for performance monohulls, recent entry to multihulls but decidedly expensive. They moved production to China...Vietnam ?? don't recall but previously were based 'just round the corner' - 5km away. They have built some very successful monohulls and if I had the money and inclination (I don't) they would be on my list. I'm discouraged by big cats as the ones I have crewed on are significant machines and I was only there because the owners simply could not handle such large vessels as a cruising couple. Seems daft to me - spend millions of dollars and then have the need to have friends on standby so that you can go sailing (and you cannot go out for an afternoon sail). It is good that we are not all the same.

Of the post on ground tackle

I was surprised with the detail and then the absence of any comment on the rode and bridles. To me the ground tackle is an integrated and matching package - and can only be considered as such. I make the same criticism of anchor makers and chandlers. I had the ambition to develop an integrated rode (which I did for myself) but the next step - offering the concept was a step too far (for me). I don't agree with bigger is better, waste of money - maybe underlined by the PBO results of different sizes of the same anchor - if you go up one size you will not actually notice the difference but if you want a difference you need to go 'much' bigger. Whilst having an anchor too small, smaller than the anchor maker recommends lacks logic I'm not aware that there is any evidence that stands scrutiny that a bigger anchor is actually needed or better. He mentions that a bigger, heavier, anchor sets better - absolute rubbish! If its physically bigger it will be more difficult to set. I detected a focus on performance, of the yacht, but reducing weight in the ground tackle was not covered and a 50' cat could save 100s of kgs with aluminium anchors and a lightweight rode.

There was an absence of mention that blue water yachts really need a clutch of anchors - no one anchor is perfect in all seabeds and all circumstances and ideally you also need a spare rode. If I understood he did mention he re-anchored with 2 anchors (having failed with one anchor) but did not elaborate on how he set the 2, nor why he had 2 and were they different - it would have been an interesting introduction to different methods of setting, why carry more than one anchor, catering for different seabeds etc.

However its easy to pick holes .... and maybe he has another post in the making covering other aspects.

The market place worships at the alter of anchor weight - its a difficult religion (like most) to offer an alternative. Fortress stood out and have made some success, after 30 years (long gestation period ). The strengths of Fortress simply underline the weakness of other anchors, good in sloppy mud and light. Horses for courses. Anchor right make an excellent aluminium version of the Excel - but its not really a commercial success and Viking are beating into the same headwind - you need to be in it for the long haul - and I admire their tenacity.

Thanks for thinking of me!
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Man, how that cat still capsized even with warps out is scary.

 

It's a deep dive to get comparisons, but this guy has taken anchor testing to a new level, with some surprising results.
https://www.youtube.com/channel/UCy1Fn_m9nfcf4asEG_bulHA

 

Russell, your link to SV Panope anchor tests is very good. The SV Panope guy has done some very realistic tests on a variety of anchors to help us all understand. The following was written yesterday before Russell’s contribution but I don’t think it needs any alteration. The Fortress anchor jpeg is not a recommendation for Fortress anchors just an indicator of rope chain and shackle sizes for a given boat size.

Anchoring number 2. To just reiterate anchoring is not simple. I have cruised where bottoms were sand, mud, rock, coral, heavy seaweed and indeterminate because it was too deep. The wind and wave conditions varied from calm to 40 knots and 6 foot waves (behind an island). There is no one anchoring answer to all situations.

The best solution I found for difficult, unpredictable situations, was to set a Danford type anchor connected by 30 foot of chain to a CQR type anchor that was connected to 80 foot of chain that was then connected to 100 foot of nylon rope which was connected to a VERY strong Sampson post or cleat in front of an anchor winch which would be required to lift the weight when raising anchor. On the 35 to 50 foots cats I was on, very rarely did they move far after those anchors were deployed. Alternative anchors would have worked just as well in that dual configuration. But please understand this is a lot of weight to carry around but it is needed if you are really going long range cruising.

A lot of people think 1 type of anchor can do it all, with a minimum of chain and rope. Great if you know what the bottom is in your area. But in cruising an indicated sandy bottom with seaweed is a very different thing from a sandy bottom. If there are occasional rocky or coral out crops you may find your anchor rope cut through or your anchor jams so hard it cannot be released. Travelling with 1 anchor is a risk, great for racing bad for cruising.

Anchoring is a totality. It starts with a lump of shaped metal at one end, a shackle, a swivel, some chain, some rope, a bridle, a rope guide, a deck cleat or Sampson post and finally if you are lucky an anchor winch. Last is an anchor locker to store all of this. Each component in this array must be strong enough to handle the loads but far more importantly the shock loads that are placed upon them. Each component must allow the free movement, without chafing, during deployment, use and recovery. The jpegs below will give an idea of the strength of chain and shackles etc. Remember that these charts are mainly for monos but one chart features a Lightwave 38 and PDQ 32. For a give size a mono and multi require similar gear but have differing characteristics. Mono’s are wave and tide controlled more than wind controlled when anchoring Multi are more wind influenced when anchoring Result, multi tend to wander around more and have higher shock loads on anchoring gear where as mono’s have more weight and more momentum when anchored.

When stored the anchor, chain and rope must be setup in a way they can be deployed immediately without foul-ups as the anchor is deployed. I have watched a 38 foot hit bottom because the anchor was thrown over the side but the chain got caught on a deck cleat, the anchor was hanging in the air. After they cleared the chain, the anchor rope got caught on the same cleat. Just bad design and layout resulting in hitting bottom.

Next, if possible, check the location you intend to anchor in. Off the coast of a little visited island with deep water we anchored at high tide. All was fine until 2 am when “bang”, torch light showed we had anchored within range of a rock outcrop just below the surface at low tide. The wind had shifted and the rudders had hit that rock outcrop. We moved the anchor 200 foot away after search for any other outcrops and went back to bed. Nothing should be taken for granted about anchoring.

Final comment, cruising anchoring is finding the combination for you that works with your design of multihull. If you have a high windage cruiser you will need a different configuration of anchoring gear to a low windage tri etc. Also do not underestimate the weight of all the chain and anchor(s) you deploy. A 40 lb anchor, 50 foot of 10 mm chain and 100 foot of rope can be 150 lbs of weight. Anchor winches are required in bigger boats. The jpegs give some further information.

To get another view on anchoring please read an article about tandem anchoring at: Two to Tandem: Maximizing Holding Power by Tandem Anchoring https://www.petersmith.net.nz/boat-anchors/tandem-anchoring.php

 

If you ever decide to get rid of the raka plans...please let me know. Depends on how much but that was always my fav wharram design. Not really practical to build now but...

 

Ha, it was my favorite too. I'm actually saving them for end of the world home store construction just in case..... They are pretty basic, pre Hanneke Boone art but fun. I even have a sail number...

The Nicol keeps me pretty busy, getting the stern cab redo now, miles more room than a Raka and probably faster but the thought of just wacking out those V hulls seems therapeutic at times..... I'd definitely go for the Tiki beams to get rid of those troughs, one of those things that is worth upgrading.

 

And here is another view - my pal Neeves on the YBW Forum sent it to me.
Doubling Up: Full-size Tandem Anchoring - Practical Sailor https://www.practical-sailor.com/sails-rigging-deckgear/doubling-up-full-size-tandem-anchoring

Neeves also offered this observation about tandem anchoring :

The problem is that under stress the rode straightens and simply lifts the anchor, nearest the mother ship, out of the seabed. Imagine the rode sitting on the seabed with one anchor at one end, the yacht at the other end and another anchor in the middle - as the rode tightens the middle anchor experiences an up lift, but no tension along the seabed (that is transferred to the anchor at the end) - the direction of that, upward, force was never designed into the anchor - it simply pops out.

 

Anchors are designed for correct scope, it might drag but the end anchor would bite. If the rode is too short to the first anchor then you could pop out.