Trimaran - Especially Searunner - Owners

[Roy M]

Boatguy, are you attempting to be funny, or do you realize that what you just said is pretty rude? Are you questioning my facts? I'm confused by your comments, which appear to be steadily become a bit strident and somewhat hostile. Please clarify whether I am misinterpreting what you are saying. My old Volvo MD2B averaged 8 knots at 2250 RPM, and the Yanmar is pretty close to those figures.

[Boatguy30]

Can't comment on the Volvo, but the Yanmars in 34 and 37s won't perform anything like that. I think on honey wind we got about 5.5 knots at around 2700 and of course would never get close to 8 knots in the 34 with the 3YM30. That was a 2gm but I'd guess no more than say 6 or 6.5 with a 3 turning lower rpms.

Must be the perfect combo of drag, prop selection, and waterline length.

[Roy M]

I think I've got an idea of what is on your mind. I would have expected a greater appreciation on your part for the technical side of boat design, but apparently, I'm mistaken. I think you had better have a conversation with someone who has better credentials than I regarding the dynamics of boats moving through the water. Perhaps John Marples can explain this stuff to you, because it's not probably going to appear reasonable or believable. Still, it's all about math and physics, so other folks can verify your objections with a simple calculator. And you're right about it being a perfect combination of drag, prop and waterline length.

Have John explain to you about displacement speed. It's a simple enough calculation to determine what the theoretical top speed that our small engines can achieve. The formula is 1.34 times the square root of the waterline length of the boat. There are other factors, but that's the primary guideline. For a Searunner 40, that's a waterline of about 38 feet, The square root of 38 is about 6.2. Multiply that with 1.34 and the result is 8.3 knots. That, of course is affected by a number of factors such as a crappy bottom, overloading of the boat, or not having the prop diameter and pitch capable of effectively delivering the rated horsepower of these engines (all of which come with the necessary tables and graphs showing performance). The 34 and 37, that you use for your statement, all have design hull speeds that exceed your observations. Those of us who have Searunners have had the opportunities to actually test our craft. Let's see, fellow Searunners, have your boats been able to achieve, under motor power alone, the following calculated hull speeds?

SR34: waterline 32, square root being 5.7, times 1.34 equals about 7 1/2 knots
SR 37: waterline 35, square root being 5.9, times 1.34 equals just under 8 knots

If your boat is not doing that, when on its lines in flat water, then you have a pretty good factual indication that something is wrong with the prop. To claim that a boat can't achieve calculated hull speed is just wrong and misguided. You just have to get the combination of pitch and diameter, and keep the boat at its proper weight.

You can, by using considerable additional horsepower, get a Searunner, or other multihull, to exceed the displacement speed, but it takes a real boost. I know, I was a member of the crew of YANMAR ENDEAVOR, a trimaran designed by Gino Morelli to be powered by twin 25 HP diesel outboards. We established the world record from San Francisco to Honolulu, exclusively under outboard power, in 1989, at an average that exceeded 11 knots, for a forty foot multihull. The difference is because the extra power got us onto a plane, and since we had a planing hull design, like Searunners, we kicked butt.

So, check your facts before making claims that these boats, with lightweight, efficient engines, properly matched with the correct prop, can't make the speeds we claim. We can prove it.

[Boatguy30]

Huh, still not seeing no 8 knots at 2300 from a 3GM30. Maybe if you have it proped to only turn 2800 or so but if you get anywhere near that .6 gal/hr you'd have to be lightly proped.

Anyway, original point was no way you get 10 knots with an OB burning any less than tons of gas. My original comment to you was how much hp needed to push a 40 to 10 knots.

[Cavalier MK2]

I get over 7 knots on the Nicol, which is between the SR 34 and 37 in size, with a Yamaha 9.9 with an average bottom. The prop runs with virtually no slip which surprised me. We cruise around 5 - 5 1/2 knots for a large boost in economy, getting from 12 - 16 mpg depending on wind, load etc....Skene's Elements of Yacht design has a good section on prop selection, it makes a huge difference.

[Mark Johnson]

Roy,
As usual, your points are quite valid, and your motoring speed numbers (regarding the 34 I know), are spot on.

Bear in mind: We seldom go out without my gently wiping down the hull and cleaning the prop the day before, which I suggest to anyone who hasn't been out of their slip for a couple of weeks or longer. There is actually a .5 to 1 knot penalty, from even a thin layer of slime!

Using our boat as real world example:

We have a 20 year old Yanmar 2 GM20-F, which is actually just rated at 18 HP,
(@ our max "cruising" rpm of 3,400). Our max "short term" RPM for this engine is 3,600 RPM, and as should ALWAYS be the case, our prop "just" allows us to hit that Max short term RPM.

At our 3,400 max "cruising" RPM, on a calm day and flat water, with our perfectly sized "FlexOFold" prop and a clean bottom... Our "fully loaded for cruising" SR 34, will motor at from 7.2 to 7.4 knots. This is while consuming about .5 gallons of diesel per hour.

Having said that, our engine's "sweet spot" regarding fuel consumption to power output optimization, is 2,850 RPM. At that RPM, (Which is where small Yanmars prefer to run long term), we motor at about 6.2 - 6.5 knots, with a bit less fuel consumption.

Now... a 20+ knot headwind with a chop, will knock another knot off of that, but unless we're putzing up a canal on the ICW, we would usually be purely "sailing" instead, at 8 - 9 knots. (Our "best" crossing from the Bahamas btw, was at a steady 13+ knots, while surfing 15' waves). We left at dawn, and had the hook down in Biscayne Bay for lunch!

These motoring numbers are referring to FULL TIME liveaboards that were way over payload at the time... So I would say:
Searunners that do not match these descriptions of motoring and sailing speeds, have something wrong with them.
I.E. (a foul bottom or prop, a GROSSLY overweight boat, a poorly matched prop size, an inefficient prop design, too small an engine, or they have a malfunctioning engine).

As an aside Roy:
Regarding those on this thread who aren't learning OR teaching, who have neither a Searunner nor even a trimaran... who are often ill informed naysayers and lacking in common respect for others points of view as well... It is best to ignore them. I do.

YOUR comments on the other hand, are pertinent, almost always accurate, useful, well written, and above all else... civil! No one knows better than I do how much effort it takes to try to pass on our decades of experience, to those who can benefit from it.
YOUR CONTINUED EFFORTS IN THIS REGARD ARE APPRECIATED!

Mark

[Cavalier MK2]

Couple points that seem pretty silly lately. First the listing of a trimaran for not being a official Searunner. These boats are 3rd to 4th hand probably by now and this thread would seem a good resource for them. Yes Jim and John should have got a design fee but if Marples was more savvy he'd realize that by making consulting available to those boats he'd at least get something. So the forum should welcome those owners, maybe there are some interesting variations official SRs can check out. Maybe a fellow boater can be helped out with something that may not have been done right....

2 While people should attempt to behave while posting, like the classroom all kinds wind up there. Someone may not have a tri yet but if they like them it should be enough.....Ostracizing those with different points of view or experiences is childish at best. Teachers should realize some kids try to get answers by baiting, for sure there is a lot of chum in this thread at times.

3 Hey Rossad, I think all that wire is pretty silly. I'm trying to go as "wireless" as possible. During our renovation everything was yanked and I don't want it back. I've been taking a page from the old kerosene lantern approach and using LED cabin lights and things that have their own rechargeable batteries. Then I can use a battery charger near the 12 volt set up for the "refueling station". Like wise I prefer the hand held electronics approach, GPS, laptop, radio etc....the batteries can go to the refueling station which has an inverter and the stuff can be carried off the boat when not used and used hiking, in the car etc.....not for everyone but a good way to go light, 40 years of wire and add ons weighed quite a bit......

[Boatguy30]

You and me CAV we gotta stick together.

On the subject of the modified boats: I understand this guy built several boats on spec. Now, in someways if he was able to build a 40' trimaran and sell it for a profit, that is something.

On the other hand, it does seem respectful to send Jim and John the modest fee to keep things legit. It's relative because one of the last boats he built was recently for sale as "new" "custom trimaran". Not third or fourth hand.

good for people or have the proper info.

[Cavalier MK2]

Right Boatguy, we'll sit in the back of the bus and laugh at the front pew sitters

Does John have a legal recourse? Piver had the same problem but if enough is changed there isn't much to do. Lines could be copyrighted separately from layout maybe? The only good place to save on a boat is leaving off the gizmos and by having good basic gear that can be expanded later. Compromising on design and building materials is never a good mix with the sea.

[rossad]

I got Yanmar 30hp in my 37 foot Searunner. max rev's is 3600. i cruise at 2000 rev's dong 5.5 knots. So economical. I will hit 9 knots if i am clean and if the water not moving at 3600 revs.

I have noted that this Thread is "trimaran and especially searunners" meaning its not just about Searunners but trimarans and that is fair enough. All trimaraners should be welcome to these threads even if they have different points of view. But to challenge somebody's word might be offensive so we all got to tread with some care and respect.

[blewett_john]

Mark,
I noted in your recent picture of your prop that your strut and shaft is painted. Is that the best way to keep them clean? My locals seem to think no paint, just polish and let the copper in the bronze do its job.

John B.

[Boatguy30]

CAV-

I'm certainly in no position to poke fun, but do hope to have a mostly waterproof main cabin by the end of the year and maybe do a bit of sailing early next summer.

Most of the discussion here tends towards maintenance and construction so it is a good thread for anyone with a boat of this TYPE of construction in my opinion. Clearly there are some diehard Searunnerers out there, but also lots of guys that have owned one and moved on to other designs for various reasons.

Cheers,
Jeff

[Mark Johnson]

Originally Posted by blewett_john

Mark,
I noted in your recent picture of your prop that your strut and shaft is painted. Is that the best way to keep them clean? My locals seem to think no paint, just polish and let the copper in the bronze do its job.

John B.

Hi John,
No, the copper content in Bronze props (or any other underwater fittings), will not help to repel barnacles at all.

First off, corrosion PROTECTION:
These fittings need to be protected with a Zinc anode, like the one on my shaft. In my case, this one shaft zinc also protects my prop AND bronze strut. The shaft makes the electrical connection to the prop directly, and the strut gets protection from the shaft zinc because of a shaft "brush" at the engine to CV joint area. This is wired into the upper end of the bonded in strut, internally. Otherwise, although it is very close to the shaft, the strut would not be electrically connected to it, due to the strut's rubber bearing. The shaft brush with internal bonding wire, gets around this.

The "internal" Zinc seen on the photo btw, HAS NOTHING TO DO WITH METAL PROTECTION AT ALL! It is there as a fail-safe, preventing the PSS shaft seal's rotor, from ever sliding up the shaft... AGAIN!

If not properly protected, (assuming it's in SALT water)... the Zinc IN the bronze alloys gets eaten away, making the pinker metal that is left behind, porous and weak. AVOID IT!

Copper in sheet form does not repel barnacles. Sure, "some" ships in the past had copper sheathing, but it "mostly" only repelled boring worms, not barnacles. They careened their ship regularly, laid her over, and scraped them off!
Bottom paint that has "Cupperous Oxide powder" in it, (among other things), is a very different animal from sheet copper. That's why none of the sheet copper barnacle growth solutions of the past, have stood the test of time.

My copper "lightning protection ground plate", which I keep isolated (but no longer Zinc protected), does get growth on it. The rest of my underwater metal, (both SS & bronze), must be bottom painted OR it gets the worst barnacle growth on the boat. The parts that are zinc protected seem even worse.

The critters love the small battery that is created here, and the protective electrical action sometimes causes paint to eventually fail too.

By using a proper metal etch and 2 part metal primers... I have had 5 year success with painting, (between bottom jobs), on the shaft, strut, and rudder hardware. (95% remained intact). When I have painted the entire prop, it quickly failed due to erosion I suppose. There are some REALLY high dollar specialized prop coatings now, (like PropSpeed), but even those are only good for a year or two. Thing is... If a product "sort of works", but you still have a few barnacles on your blades, you remove paint/coating as well, when you scrape them off.
Roy recently used PropSpeed on his drivetrain, so in a couple of years, we should get some good feedback about it from him... IT IS EXPENSIVE, like I said!

This last bottom paint job has not been great, (regarding my success in painting underwater metal). This was due to a batch of faulty primer that I got last time around. I normally paint the shaft, strut, and gudgeons/pintles, but painting the prop's hub as well was an experiment this time and not a successful one, for that reason. Otherwise, I think it would've worked. The other parts are a year and a half old now, and "mostly" still painted.

Stopping short of the REALLY high dollar underwater potions,
(Like "PropSpeed")... You should have success painting these parts IF you do it exactly right and get lucky, but NOT likely on the prop's blades. For these, it is best to jump over the side and scrape the critters off, every time you go out. Anything over 10 days, is too long to take the risk, because a dozen pea sized barnacles can cut your thrust CONSIDERABLY, and when they get in the gears or hinges, they can prevent the prop from folding.

Btw... I too make random experiments when a failure can do no harm. What will NOT help in my experience, is black MagicMarker (as I had been informed), NOR PropGlop wax, which "they" claim works great).

Hope this helps,
Mark

[Cavalier MK2]

Originally Posted by Boatguy30

CAV-

I'm certainly in no position to poke fun, but do hope to have a mostly waterproof main cabin by the end of the year and maybe do a bit of sailing early next summer.

Most of the discussion here tends towards maintenance and construction so it is a good thread for anyone with a boat of this TYPE of construction in my opinion. Clearly there are some diehard Searunnerers out there, but also lots of guys that have owned one and moved on to other designs for various reasons.

Cheers,
Jeff

If you own a boat chances are you're never in a position to poke fun in the maintenance stakes. Laughing does help ease the load though. Currently I'm sanding up every thing installed over the summer to be ready to epoxy coat when it warms up again. On our summer "rough, who cares about ready" cruise my boat friends told me for the second year it wasn't girl proof yet so it was off to Bear instead of bare country! Can't believe the fog here now. It isn't raining but everything is still wet, cruel weather for boat guys in the PNW....

Cheers, Cav

[Mark Johnson]

USEFUL INFORMATION, TROLLS, and CIVILITY:

INFORMATION, really useful/accurate information, is the key to my success, and the key to the success or failure of anyone else's boat project and cruising agenda. We must all, "Know What You Don't Know".

Now that boatbuilding and cruising has been my passion, as well as both vocation and avocation for over 45 years, I think I have a valid opinion. Sometimes I give it, yet more often than not, I am just passing on hard learned FACTS. These comments are not like Tweets, or random thoughts on Face Book, they represent a lot of research and experience, WAY over 100,000 hours of it! Still, anyone's "personal life experience", no matter how much, is a VERY small amount of information compared to the worlds collective boatbuilding/cruising experience. I spent decades gathering that as best I could, to minimize the "error" half of my life of "trial & error". It has served me well, yet so much was "error" and I had to try it over again anyway...

I worked on boats (mostly my dad's) all through my childhood, then... As a young teen I left home and apprenticed professionally for 5 years, (while also getting as far as 1 year of mechanical Engineering and later being a draftsman.) Over the decades since, I have helped build dozens of large/complex boat projects, built more than a dozen small boats myself, then I built three personal cruising boats and my own house, (twice). To finance my habit, I have also worked on or repaired thousands of other boats. During the 21 years I was in a "personal" cruising boat project, I read hundreds of boatbuilding/equipping or cruising books, thousands of magazines, tens of thousands of articles, and sought advice from NUMEROUS experts in the field, even internationally. (People like Stan Honey, Kern Hendrix, Jim Watson, Jan Gougeon, Chris White, John Marples, Jim Brown, and the "engineers" behind designing half of the items that ended up on my boat).

This was all pre Internet years mind you, and coming from "vetted" sources, the information was about 95% accurate, or at least VERY useful in making up my own mind, before I leap. Gathering information was a substantial part of my boatbuilding year's budget. The information available on the internet, however, is often useful, but 75% of it is just wrong! You'd need a crystal ball to tell the **** from the shinola! They let "just anybody" write on the internet...

Since John Marples co-designed two of my three boats, and I was a client (so he was graciously willing), he was my most useful source of information "back in the day". I have known him now for over 36 years, and we are friends as well. Our chats surely were in the hundreds of hours I'd guess. I didn't always take his advise, but DID always appreciate and consider it. I NEVER argued with him, but might ask him to "convince me"... He usually could! He suggested my over sized rig, sailing it as a sloop, the engine location mod, the CV joint, vastly upgraded glass schedule in critical places, paint options, deck hardware, bias cut glass tape, modern material options, best winch locations, etc... He also kept me from making many many HUGE mistakes! With his already being the recipient of thousands of client's feedback over decades, his information was "the collective knowledge" of ALL of them, plus his own considerable experience. I have integrated this vast amount of collective information as best one can, with my own tens of thousands of hours spent in research, and well over 100,000 hours of hands on experience. My life has therefore been mostly spent in learning about and mastering my craft, livingaboard my creations, and cruising extensively.

SO... WHAT AM I DOING HERE?
It is true that due to CF I have gotten a number of consultation clients I might not have otherwise met, and this is how I make a meager living these days, (along with the stuff on OutRig Media)... But I have made 1,447 posts here, passing on this VAST amount of really useful information to those who are interested. It may have a mistake here and there, but I hazard to guess that it is 98% accurate. There is a LOT that I don't know, but that is when I DON'T post at all, but wait for someone with similar experience to pipe in. (It is my opportunity to learn something)... I AM ONLY TRYING TO LEARN, OR HELP YOU GUYS OUT, not tell anyone what to do!

For this, I only expect to be spoken to with respect, and not be "argued with", about petty details, or the veracity of my posts. I frequently "disagree" with someone who has a valid point of view nonetheless, and I try to keep my disagreement to myself. IF it is soo important that the group as a whole needs to know the facts, however, I do state them respectfully, without making reference to the person who put out the inaccurate information. I TRY not to hurt anyone's feelings. For my failures in that regard, Mea Culpa, Mea Culpa...

TROLL ALERT!!!
We now have a couple of "TROLLS" on this thread that just continue to linger on here without taking the hint... They inanely argue for the superiority of their boats, for putting keels on Searunners, that polyester resin is better than epoxy and WEST system built boats are NOT better, that digital cameras are no good, that the Searunner hull shape is the same as a Cross, that latex house paint is better than LP paint in every way, that John Marples did not win the TransPac in '72, that my accounts of my refer's efficiency are made up, same with Roy's Searunner motoring speed numbers, Etc. It's all nonsense... They have as much as called us handful of really experienced Searunner old-timers, and John Marples, and Jim Brown, a bunch of liars.

You two guys know who you are! I quit responding to your posts a long time ago, as most of them are not worthy of it. Your comments are a bit weird or just "wrong" more often than not, and many are disrespectful, confrontatory, and down right rude. You have been asked to "lighten up" in the past, yet you persist. So, "Peace and good luck", but PLEASE, PLEASE go away... This behavior is not welcome here. I miss the way this thread used to be...

The only reason I have put so much energy into this thread, was to help those receptive to the idea of minimizing the "error", in their "trial & error". I wish I could've done better in that respect decades ago, and that "this volume" of good information had been available to me all along, and all at one source.

Like I said guys, I have only been trying to help.

Kindest regards to all,
Mark