Trimaran - Especially Searunner - Owners

[Roy M]

That's about what your boat and mine can achieve backwards or sideways.

[Cavalier MK2]

This is true.

[catsketcher]

I have done a little reading of this thread and that on boatdesign so I will put my two cents worth in.

Like everyone else here, I don't get the junk rig. You will be slower and not sail as well to windward. It certainly won't be a game changer and there is no conspiracy against them - just like there is not conspiracy against multis anymore. That being said, as a multihuller all I ever used to want was for people to respect my choice to sail a multi, so I will have to let you sail whatever you want. Dick Newick tried the Lungstrom, not many of us are in the same class as Dick - he was an iconoclast and a legend.

I have a friend who you may be corresponding with on the junk rig forum. He likes my cat, was thinking about buying my Twiggy years ago and has sailed lots of miles. Heaps on multis. He had a cute little steel cutter that he changed to a junk rig. I don't get it, he is slower than he used to be but he likes it. He has heaps of experience and sails up and down the coast - slowly. He loves his boat but to me I scratch my head. But he drifts up and down the coast at his own pace.

The Searunner would be a good donor boat. The cabin is very strong and tall. The offset mast would be fine. The beams would be up to the loading as the main load condition is flying a hull, which this loading would not change. I also like the idea of using a ply boat. Ply is wonderful at showing stress before failure. Look for tiny checks in the ply (around the mast) after sailing. I would also round off the corners off reinforcing timbers in the cabin with fillets and lots of uni glass splayed out.

Buy a pretty dead Searunner and give the idea a go. Then if it works you can change your rig to another boat. You should be able to pick one up on the West coast (an A frame would fit on a truck) for a few thousand. Build it and check it out. I have a friend who is busting to build a wing - I can't shake his conviction so he built a small version but still wants to do it.

No-one will mind you having a go - we are pretty sure what you will find out but I for one will be very interested to see how the Searunner goes with the junk rig.

[rossad]

Searunner with a junk rig ... not sure why!

[owly]

Originally Posted by catsketcher

I have done a little reading of this thread and that on boatdesign so I will put my two cents worth in.

Like everyone else here, I don't get the junk rig. You will be slower and not sail as well to windward. It certainly won't be a game changer and there is no conspiracy against them - just like there is not conspiracy against multis anymore. That being said, as a multihuller all I ever used to want was for people to respect my choice to sail a multi, so I will have to let you sail whatever you want. Dick Newick tried the Lungstrom, not many of us are in the same class as Dick - he was an iconoclast and a legend.

I have a friend who you may be corresponding with on the junk rig forum. He likes my cat, was thinking about buying my Twiggy years ago and has sailed lots of miles. Heaps on multis. He had a cute little steel cutter that he changed to a junk rig. I don't get it, he is slower than he used to be but he likes it. He has heaps of experience and sails up and down the coast - slowly. He loves his boat but to me I scratch my head. But he drifts up and down the coast at his own pace.

The Searunner would be a good donor boat. The cabin is very strong and tall. The offset mast would be fine. The beams would be up to the loading as the main load condition is flying a hull, which this loading would not change. I also like the idea of using a ply boat. Ply is wonderful at showing stress before failure. Look for tiny checks in the ply (around the mast) after sailing. I would also round off the corners off reinforcing timbers in the cabin with fillets and lots of uni glass splayed out.

Buy a pretty dead Searunner and give the idea a go. Then if it works you can change your rig to another boat. You should be able to pick one up on the West coast (an A frame would fit on a truck) for a few thousand. Build it and check it out. I have a friend who is busting to build a wing - I can't shake his conviction so he built a small version but still wants to do it.

No-one will mind you having a go - we are pretty sure what you will find out but I for one will be very interested to see how the Searunner goes with the junk rig.

] Nice to get something other than pure negativity, which is so often based on outdated information. The modern cambered and split junk rig is capable of pretty much competing head to head with a comparable Bermuda rig on an identical boat with the same sail area as has been demonstrated with two splinters, one with the Bermuda rig and one with as junk rig. The junk cambered and cambered/split junk rig will point just as high, and will outperform the Bermuda downwind. There seems to be a fairly universal assumption that the junk rig has not progressed beyond Blondie's flat junk rig, nor is the comparison of a primitive flat junk rig on a full keel 25 foot monohull, to a modern cambered / split junk rig on a trimaran even remotely valid, as some folks seem to suggest. The free standing mast is a completely different animal from the stayed mast. It imposes very little vertical loading compared to a stayed mast where the standing rigging is constantly trying to drive it through the bottom of the boat. The loading on the mast step and partners is primarily fore and aft and side to side, loads that are split between the standing rigging and the step on a stayed mast. The main structural bulkhead would of course be against the mast and the mast attached to it providing extremely strong support port to starboard at both the partners where the mast passes through the roof, and at the step. Fore and aft loads at the partners would need to be distributed out through the cabin roof, and might call for some "creative structural enhancement", possibly as simple as doubling the roof in the area adjacent to the mast. With a bit of imagination, a windscreen and hard dodger could incorporate some additional structural support using a couple of short struts. I don't see the mast support as being a huge challenge. More of a challenge is the fact that the mast passing down just forward of the doorway between the berth area and dressing room will be partially blocked by the mast even with it offset, and this may necessitate altering the opening. I need to obtain some drawings of this bulkhead, though I don't see this as a huge challenge. In any case it is not a simple conversion, but no conversion I've ever done has been "simple", and I've done a lot conversions to a lot of things. The last thing I want is to begin with a beauty, but on the other hand time spent on a junker (pun not intended) is time wasted. Boats built of 3 ply fir and glassed with polyester or vinyl ester need not apply. It's a fine line, but inevitably calls for confidence, courage of convictions, and judgment. I know what I want, and why I want it............ H.W.

[owly]

Originally Posted by rossad

Searunner with a junk rig ... not sure why!

Let me put it simply:

Searunner, for the same reasons many other people have chosen the Searunner 31. It's the right size, it has construction I'm comfortable with, a reasonable layout for a long distance cruiser, it's a multihull with minimal heel, which equates to far less fatigue on a long trip, they are relatively plentiful and affordable. Upkeep and maintenance costs quickly multiply with size, as does the rig needed to drive the boat.

Junk rig because it is simple, powerful, rugged, reliable, and the easiest rig to sail of anything out there. Because it involves only ONE sail, so I don't need to be changing out sails, and storing sail bags all over. Because the sail is extremely lightly loaded as the fabric loads are between the battens only, and a tear in one panel will not take the sail out of commission. The stresses are extremely low. Sheet loads are extremely light, meaning no winches needed. Balance area results in gentle tacks and jibes which don't require a bunch of antics, just put the tiller over, and readjust the sheet after the boom swings across. No traveler, no vang, no preventers. No standing rigging at all, no spreaders, no running backstays, no inner and outer forestays, no shrouds, nothing except a round mast. Reefing involves nothing more than releasing the halyard to drop one or more panels, something you can do without spilling your coffee. The battens hold the sail down when reefed so you don't need to tie in reefs, and you can reef without coming off the wind because there are no sail cars and track.

Junk rig because the modern cambered split junk rig has shown itself to be nearly the equal of the Bermuda rig, but encompasses the entire sail area in one sail.

Bermudan rig vs Junk rig - Practical Boat Owner

Junk rig because every component eliminated equals one less component to fail, one less component to inspect and maintain....... also weight removed. Failure of a winch, mid ocean on a Bermuda rig for example can be a crisis at worst, an inconvenience at best. A single cracked fitting or failed crimp connection (of many) in the standing rigging can bring the entire mast down.

The choice of boats came down to multihulls. Cats are not suitable for a single free standing mast, hence the only viable options are biplane rigs. Cruising cats in the size range I'm looking for are few and far between, and normally are something like a Warram with the accommodations split between two hulls. Large bridge decks equal lots of windage, or low tunnel clearance. Cats really are not for me. That leaves trimarans with the single main hull and two amas. Among the trimarans readily available, the selection inevitably came down to the Searunner series, and everything pointed to the SR31 or SR34. The 31 with it's typical open wing design being the choice for a number of reasons, minimum viable size being one of them. Smaller is better in this case. It means smaller rig, less maintenance costs, lighter weight, etc.

I'm aware of only about 4 junk rigged trimarans. A Dragonfly 25 being the largest and the only one of any size. It was quite successful.

My choices, and the process I've gone through to make them, and the reasoning behind them are specific to me. I don't expect others to reach the same conclusions or follow the same processes. If that were the case, we would all be sailing the same boats! It's pretty obvious that I am not interested in being talked out of this. None of this is the result of whim, but of serious long term consideration. Thus far I have heard not a single valid argument against this project providing concrete reasons NOT to do it.


H.W.

[Cavalier MK2]

Well Owly, the example is just using monos where speed is limited to hull speed and the junk rig is slower to windward and reaching where it is acting like a foil and faster just dead downwind where it is functioning as a unit of drag. Now a tri will be able to hit speeds about 3 times faster than this, rewarding the more efficient foil as the apparent wind is drawn dramatically forward. Off wind the difference is most dramatic as a slight change from dead down wind will have a large effect. Moving a few degrees from dead downwind and the junk can't keep up. It's drag superiority has a narrow window. Unlike the mono the tri has a wide sheeting base for wing and wing running which will give more drag with the larger area.

Cruising it is your boat and thankfully sailors can still explore alternatives to suit themselves regardless of the data. Going into a conversation with a chip on your shoulder is never efficient. Hard bitten Searunner sailors have a tradition of laughing into their beer and saying your nuts but go for it and do tell. If it sails good enough for you that is what counts but for most tri sailors the performance is part of the fun.

I like the junk variants where a 2 sided sail is used around the mast for a true foil, these skip the unsupported leading edge with a much more efficient rounded nose while retaining the control and reefing advantages. They also eliminate the mast turbulence.

As to mast location it does have to be further forward. I'd put it one bulkhead forward at the entrance to the head and beef up and alter the cabin front to act as part of the step. This is another reason I'd pick the wing deck boat because it would be easy to install a reinforcing beam in the wing to spread the loads out to the amas. This helps handle the hull twisting loads of the cantilevered mast in that location better than what would be possible with the A-frame.

As an alternative to moving the mast forward the center of lateral resistance has to come aft. The centerboard trunk could be converted to a daggerboard running in the aft half of the case. This would also be in the way of the aft cabin hatch when retracted for more fun!

[owly]

Originally Posted by Cavalier MK2

Well Owly, the example is just using monos where speed is limited to hull speed and the junk rig is slower to windward and reaching where it is acting like a foil and faster just dead downwind where it is functioning as a unit of drag. Now a tri will be able to hit speeds about 3 times faster than this, rewarding the more efficient foil as the apparent wind is drawn dramatically forward. Off wind the difference is most dramatic as a slight change from dead down wind will have a large effect. Moving a few degrees from dead downwind and the junk can't keep up. It's drag superiority has a narrow window. Unlike the mono the tri has a wide sheeting base for wing and wing running which will give more drag with the larger area.

Cruising it is your boat and thankfully sailors can still explore alternatives to suit themselves regardless of the data. Going into a conversation with a chip on your shoulder is never efficient. Hard bitten Searunner sailors have a tradition of laughing into their beer and saying your nuts but go for it and do tell. If it sails good enough for you that is what counts but for most tri sailors the performance is part of the fun.

I like the junk variants where a 2 sided sail is used around the mast for a true foil, these skip the unsupported leading edge with a much more efficient rounded nose while retaining the control and reefing advantages. They also eliminate the mast turbulence.

As to mast location it does have to be further forward. I'd put it one bulkhead forward at the entrance to the head and beef up and alter the cabin front to act as part of the step. This is another reason I'd pick the wing deck boat because it would be easy to install a reinforcing beam in the wing to spread the loads out to the amas. This helps handle the hull twisting loads of the cantilevered mast in that location better than what would be possible with the A-frame.

As an alternative to moving the mast forward the center of lateral resistance has to come aft. The centerboard trunk could be converted to a daggerboard running in the aft half of the case. This would also be in the way of the aft cabin hatch when retracted for more fun!

I've considered that alternative mast location, as well as dead in the middle of the dressing room. The latter alternative would function by distributing loads via the cabin roof to the two bulkheads, and of course would call for "creative reinforcing". There is very little vertical loading compared to a stayed mast, so loads radial to the mast are the ones of primary concern.
I'm apparently more familiar with modern junk rig variants than most folks seem to be. The split junk rig breaks the sail into a main and jib portion, sharing battens, everything being designed with suitable camber. With this rig, the sail balance can be much farther forward, as much as 30% forward of the mast, and this mitigates the mast location somewhat. The split junk, mentioned in the link I gave in my previous post is if not the equal of the Bermuda, still quite impressive compared to Blondie's flat junk rig, and this comparison is between a skilled race crew, and a single junk rig sailor, it's really nothing to sneeze at.
I do not expect to achieve the claimed 20 kts someone threw out there, but I don't consider that a realistic number for a cruising boat in a cruising situation. I'm not interested in top speed at all, but more in performance in light to moderate winds. That's where it really counts...... In my book.

I've looked at various ways of moving the CLR aft, and almost immediately scratched any notion of altering the centerboard on the Searunner. I consider that a "non-starter". I've looked at the idea of kick up fixed angle foil rudders on the transoms of each ama. A foil is extremely efficient in producing lift......... in horizontal or vertical directions. These would of course be designed for horizontal lift. They would be submerged based on angle of heel. The vertical change from one tack to the other is considerable, far more than most folks realize, and it is also progressive.
Someone suggested the innovative idea of twin rudders on the main hull, both foil type, and both kick up. One with a lot of balance area could be operated directly by the wind vane steering because of it's large balance area. The other would be for manual helming, and also to act as a trim rudder. Twin rudders would be a challenge to arrange on a Searunner, but quite possible. Again, the side force provided by a foil shaped surface is far more efficiently produced in terms of lift drag ratio than that of a centerboard or long keel.
I've given this project a lot of thought over a long period of time. I'm about a year out from even buying the boat because of local business obligations I have to deal with in wrapping up my business of 35 years. I've chosen to let someone else pay slip fees and maintenance until I'm ready to pull the trigger. My history is to "hit the ground running". I plan to have most of the details already worked out to the extent that is possible before I even begin the process. At the moment I'm working on a stitch and glue junk rig sailing dinghy so I will have a platform to experiment on.

H.W.

[Cavalier MK2]

I'm going to edit my post here...I'd put the mast just aft of the bulkhead at the entrance to the head which I'd consider making without openings and avoid all the foil gizmos. The layout I'd change to have the table/ seating area forward closest to the cockpit in the old bunk area so you can also see forward when keeping watch or hanging out. In the dressing room I'd put the galley.

Astern I'd put the bunks in the wing starting with the old galley area with the feet continuing forward under the cockpit. This keeps you from sliding head first into the bulkhead if you crash while asleep.
Astern in the old table area goes the head which will now be in a area of nicer motion and better at sea ventilation. Those bow hatches often have to be dogged down.

[rossad]

The problem with the junk rig for a tri is
1) Won't point as high (may on a mono bit not with a tri)
2) Won't deliver good boat speed
3) Centre of effort will have too much force structurally and need serious planning with a hit and miss situation.
Simple answer is get an expert like Jim or John the designers to evaluate.

[catsketcher]

CLR and tris

As part of the Searunner thread I think we should be talking about two CLRs, I say this because I was blown away when I found out about it.

I was testing the Jim Brown designed Windrider (I loved it by the way - still do) and found it had the same trait as my Twiggy, it had a dynamic and a stalled CLR. However the Windrider used this for good whereas the Twiggy used it for evil.

The large and low aspect fin under the seat had the silhouette CLR quite far aft. So far that when you stalled the boat, say coming out of a slow tack, it would bear away with no easing of sheet required and no helm needed. It is pretty much impossible to stall a Windrider and hang up into the wind after a tack, like many Hobie sailors have found themselves stuck within.

I was blown away by the trait as many multis, including the aforementioned Twiggy, act the other way. If you let the rudder stall, the lack of lift put the CLR forward and the boat rounds up (CE aft of CLR).

What I loved about the Windrider was that when the boat got going the floats dug in and they seemed to pull the CLR forward so the boat was balanced again when powering along. It was amazing for the ex sailing instructor in me to be able to push someone out into the water with a "push left to go left" instruction and nothing else required.

For most sloops we can position the CE effectively aft of the CLR. This is what gives us weather helm. On a una rig this can be difficult as you can't pull in a jib to bear away. The first part of an eased sail to come on with be the leech which will push the boat into the wind if stalled - you may need the motor to get going. Laser sailors with vangs on hard know this problem. Of course twist is one way of getting around it. My 38ft with its wishbone can tack with main only with its big rudders UNTIL I go too slowly (about 1-2 knots). Then as we come out of a tack the leech loads up and the rudders stall and she gets hung up into the wind. No way out unless I unroll the jib. A Laser sailor would ease the vang but I can't do that with the wishbone.

I would recommend Owly sails a Windrider and gets to know this dynamic. I would then be thinking of putting a larger rudder on the Searunner, to reduce loading and making it flow at slower speeds than the centreboard (maybe reduce the centreboards area), or even small foils up front of the amas. (stall at high load conditions after tacking etc. Just some extra forefoot perhaps 1.5 aft from the bow).

This dynamic is not much thought of in sloop rigs but I certainly would not want the "Hobie hang" to be part of a large boat's repertoire. Keep with the Jim Brown family and get the dynamic CLR working for you.

So for Owly I would recommend putting the silhouette CLR aft of the CE of the junk rig. He can do this by increasing rudder area and reducing board size. Then adding some forefoot (that is above the water when tacking), or even sharpening the forefoot, the sailed CLR can move forward again.

It would be fun to see it work large scale.

cheers

Phil

[Cavalier MK2]

Originally Posted by rossad

The problem with the junk rig for a tri is
1) Won't point as high (may on a mono bit not with a tri)
2) Won't deliver good boat speed
3) Centre of effort will have too much force structurally and need serious planning with a hit and miss situation.
Simple answer is get an expert like Jim or John the designers to evaluate.

We did tell him Rossad.

Interesting points Phil, this is much more important on a una rig without a jib to help you around. For sure the neat thing about conventional ama bows is the move the area forward as the boat heels.

A bigger skeg on the rudder would do what you suggest and be easy to implement. He also could do work on the stub keel to good effect.

[rossad]

The effect on a boat of a jib sail is actually to improve the efficiency of the mainsail. The gap between the two sails is a virtual slot in all the sail area present. That virtual slot is conveniently where the mast is when changing tack.
It is this foresail that is essentially required for the trimaran for any kind of of maneuver performance and safety

[owly]

Originally Posted by rossad

The problem with the junk rig for a tri is
1) Won't point as high (may on a mono bit not with a tri)
2) Won't deliver good boat speed
3) Centre of effort will have too much force structurally and need serious planning with a hit and miss situation.
Simple answer is get an expert like Jim or John the designers to evaluate.

How about some support for those statements. I frankly do not accept any of them.

For example why would a cambered split junk rig not point as high? Experience with monohulls shows that this is NOT true........ Please explain or provide as reference to support the contention that a tri is different. If you know of a junk rigged cruising trimaran on which you are basing this, please put me in contact with the owner.... it could save me a lot of grief.

Won't deliver good boat speed??? Based on what data? Derived from what boat and what rig exactly? That is a very broad brush statement.... With good drive you get good speed........... Again please point me to the boat and owner

The center of effort is located in one of the strongest parts of the boat.


I don't mean to be rude, but without some sort of support these statements, which you express as if they were facts, are merely opinion, and do not appear to have any foundation in reality.

I will not embark on this project lightly, but I'm also not inclined to be swayed by unsupported opinion. This is a project far out of the bounds of what is considered conventional by most people, and a project into which I expect to sink a considerable amount of money. I am VERY open to worthwhile input, and informed well thought out comments and suggestions............ Uninformed and poorly thought out opinions are worth exactly what they cost........ nothing.

Give me something meaningful, well informed and supported, and you will earn my respect, and perhaps influence the direction of this project.

To put this in context, I once had an extremely negative opinion of multihulls, and thought them dangerous and unstable......... In a relatively short time period as more information came into my hands, there was a complete turnaround to the point where I really don't want anything but a multihull. I'm open minded, and flexible where real and valid information is presented. Opinion........no.

H.W.

[Cavalier MK2]

Now Owly Rossad is a great guy who loves these fine boats and has been sailing them for a long time. You should not bite the hands of Searunners who are coming from a very understandable place you have apparently not been yet. I.E If it ain't broke, don't fix it. You owe it to yourself to sail on a stock Searunner so you have a legitimate base line.

That said Catsketcher offered some good ideas, he and I are used to hanging on Boatdesign where we do try different things from time to time.

You would get a lot farther with people if you laid back and said, "Hey maybe, let's find out." Call Jim and John tell them what you are into then be quiet and try to listen. really listen.

The main advantage of a conventional approach is being able to set lots of light air canvas all the way down to storm sails. There is no way a junk sized for all around winds will sail in the light stuff with a boat with more sail up. Or downwind with the guy flying a chute.

As to pointing it may, but it won't have the light performance range or power. As to speed you don't know yourself from firsthand experience how it will perform in the high apparent wind speeds a fast boat generates.

The structure is doing the math and engineering what you need.