Boat handling characteristics

[Nomad Willy]

Power steering, bigger rudders and 2 turns L to L.

 

[Phyrcooler]

As others have iterated, the slewing caused by a quartering sea is common in squared off stern, SD trawlers, not just Mainships. I tend to run about 11 - 12 kts offshore to limit rolling and skewing and further alter course/speed as needed. That initial speed just gets me up on a reasonable plane and provides more comfort for those aboard. But then I have twin Yanmars. Though my rudders are not large, I've read anecdotally that I do have a bit more rudder authority than the single screw MS 350/390's have. What truly surprises me is your reported 8 turns lock to lock. Admittedly I've never clocked mine, but from experience, I'd have to guess I'm somewhere between 3 and 4 turns, lock to lock. I'd look into that first, then use the good advise otherwise provided here.

My 2 cents...

 

[markpierce]

My steering is a maximum of four revolutions from side to the other. Disturbing following waves are usually addressed with one-quarter to one-half turns.

One hasn't lived until having a spinnaker knock-down where one's shoved 90 degrees from one's course and the water washes over the leeward deck.

 

[AusCan]

Power steering, bigger rudders and 2 turns L to L.

That's pretty quick steering. You wouldn't need a rudder indicator, it would be fairly obvious with the helm wheel marked.


Mine's 3 turns lock to lock, a bit slower. The autopilot very small corrections to the wheel in most conditions and less than quarter turn very rough conditions. Any worse than that and its time to think about hand steering.

 

[FOG]

Don't know if your boat has a mast and boom, but hoisting a steadying sail could help.

I know that motor sailing at about 6 knots with my mainsail up helped to steady our boat tremendously.

 

[Art]

In Summary - Regarding most easily piloting through quartering of following seas.

What I believe to be best suggestions for handling same mentioned in this thread [with square stern boat]:

1. Eight turns L to L is something I've never experienced before. Get steering down to at least 1/2 that ratio

2. Make sure rudder sq. inch space is large enough - add to rudder if necessary

3. Alter course in zig zag pattern, i.e. tack boat with waves/wind to best advantage for handling helm while still following course as overall objective

4. Keep considerable weight aft rather than forward during travel in following seas

5. If ample power is available increase speed to more regularly stay in accordance with following wave speed... if at all possible

6. If your cruising pattern direction traveled are going to make you need to often encounter quartering following seas for long periods of piloting time then I suggest that you modify your swim step to fold up and hook securely on transom. See Mark's on Coot as example. Swim steps can become a menace in any angle/position of travel with following seas if sea conditions are aggressive enough


There are other items that could cost quite a few "boat bucks". Such as... steading sale, repower your boat to higher horse power, sell boat and get better power availability as well and/or better hull shape for travel while quartering following seas.

 

[Noahstvr]

Hi Benthic2,
in reply to Originally Posted by Noahstvr
.... They have a very square stern and a lot of buoyancy due to the foam (or after recall, hollow) swim platform hull extension. ....
This vintage 350/390 Mainships were built with the swimplatform/hull extension filled with foam. The sealing was poor and the foam became saturated. Maniship issued a recall that had the cap removed, the foam removed and the cap reinstalled with inspection ports added along with a drain valve to the main bilge to drain any water that may have leaked into the area. Mine was done in 2008. It was a big job, I am Glad that Mainship paid the bill!

 

[Shrew]

You folks are truly awesome and I greatly appreciate the time you've taken to provide feedback.

 

[Nomad Willy]

That's pretty quick steering. You wouldn't need a rudder indicator, it would be fairly obvious with the helm wheel marked.


Mine's 3 turns lock to lock, a bit slower. The autopilot very small corrections to the wheel in most conditions and less than quarter turn very rough conditions. Any worse than that and its time to think about hand steering.

Sorry Gaston,
But that was my offering for something to dream about. The ideal system. I should have said "my ideal system would be" .....

My boat has about 2.8 turns L to L. No power steering. I do have oversized hydraulic steering components like pump, hyd lines and slave cylinder. It's been a good system but is not typically one finger steering as the friction of the seals in/on the oversized components induces more friction. So that and the relatively fast steering dictates more steering effort at the helm. I was thinking my large dia hydraulic lines would result in very light steering. That was an experiment that failed in it's intended outcome. But as expected it's been very good otherwise.

 

[Art]

I've had hydraulic, cable, chain, rack and pinion steering in different boats.. not to mention tiller too and of course oars are a manner of steering - LOL


Rack and pinion is my favorite!

 

[RT Firefly]

Greetings,
Mr. S. ALL good comments thus far BUT one thing that has not been addressed, unless I missed it is loading and trim.

Do you normally cruise with full or near empty fluid tanks (water, fuel, waste)? Do you have all chain rode in the bow? When you load up for a vacation, do you pack everything in the v-berth, lazerette, one side or the other (is all your food/can storage on one side of the boat?) or on the fly bridge?

While one is not able to readily redesign transoms or rudders, I think some improvement in handling might be achieved by redistributing weight.

Just another slant on the situation...

 

[Codger2]

To echo what others have said, I find that changing heading can improve the ride. Yes, you'll look like a sailboat zig-zagging to your destination, but it helps to smooth out the roll.

I agree! I change course quite often to give the guests (and myself) a better ride, Just because it's a power boat does not marry you to all straight line courses.

 

[Shrew]

Greetings,
Mr. S. ALL good comments thus far BUT one thing that has not been addressed, unless I missed it is loading and trim.

Do you normally cruise with full or near empty fluid tanks (water, fuel, waste)? Do you have all chain rode in the bow? When you load up for a vacation, do you pack everything in the v-berth, lazerette, one side or the other (is all your food/can storage on one side of the boat?) or on the fly bridge?

While one is not able to readily redesign transoms or rudders, I think some improvement in handling might be achieved by redistributing weight.

Just another slant on the situation...

2 x 150 Gal. Fuel tanks: 3/4 (Located port and stbd outboard besides main engine.

2 x 65 gal. water tanks: Full (Located beneath cockpit in stern. Port and starboard, half way between keel and gunnels).

1 x 35 gal. holding: empty (Centered, slightly forward (inline with lower helm).

Large cooler in cockpit (located in Stbd quarter. balances trim as boat has a tendency to list slightly to port.

 

[Al]

I have several posted in the past speaking to adding weight to the boat in order to correct horrid balancing actions. The boat was constructed to the OP's desires resulting in too little overall weight. Between fuel, water capacity and a too light of weight engine, the resulting overall weight of the boat allowed the balance to be such that a slight movement external or internal would result in a 'Sudden' loss of balance by any unsuspected soul onboard.
With a following sea, the wandering action was a disaster with the boat leaning to the low side to an extent that one felt in danger for his or her safety.
My bad, sea trials were in flat calm conditions and my desire for the boat was in play.
After conversations on the forum where much advise was offered, the solution was found in lead ingots of 50# weight. We distributed a total of 1400# of these ingots in relation to the movement of the boat. Part of that determination was in following seas.
It was determined that a placement of weight below the engine running aft, approximately 800#, on a center line with about 200# of that weight set to each side of the engine bed stringers laying end to end outward towards the curve of the hull provided the most satisfactory placement. There is an approximate 3' space from the stern to the aft side of the twdship water tank which is a void as far as weight placement. We had placed 100# there and felt that it was too far aft so shifted it forward to the above mentioned area.
The end result has the boat rock solid with a very comfortable roll in a trough conditions (2-3 foot swell) that we travel in. In a following sea, the normal wandering 'Drunk Sailor' issue exist however with this weight placement, wheel anticipation is such that control is well within comfort levels where gentle movement of the wheel is sufficient to correct the sway.
Our turns from lock to lock are 6.5.
I am in the process of installing a auto pilot : Comnav autopilot from WMJ marine next week, Not so much for this stern sea issue as for the comfort of the longer straight streachs of our favorite routes. That it may assist in the following seas will be the subject of a report on our test period with the installation.

Al-Ketchikan

 

[Benthic2]

Thanks Noah

 

[Peter B]

Also worth noting. Rolling is something that we were not surprised at, but definitely notice. We're not worried about the rolling. What I'm referring too is more like 'yawwing' where the stern decides it's in a race with the bow and is deciding it wants to make a pass.

Call it serendipity or what, but owing to the way the PO dealt with the typical rust induced end of main tank life issue in our boat, my boat ended up with both water and fuel tanks in the after part of the hull, in the lazaret, in effect. Net effect is fair amount of weight aft, and the effect in the sort of seas you describe is amazing. I should also add, my steering is just 3 turns lock to lock = 1 & 1/2 to full lock each side from TDC. Is is chain and rod direct steering, not hydraulic or cable.

Our boat, also a 34 footer, just loves going down weather, be it stern quartering or dead astern, it just surfs along with a light feeling on the wheel, and almost no steering corrections needed, and no feeling that the stern is trying to race the bow you describe. I have seen our boat 'surf' at 11.5 kn in a quartering sea with absolutely no suggestion of any risk of a broach. Maybe you might find it possible to add in a couple of extra freshwater tanks in the lazaret to help in this way..? (I'd suggest the new plastic type) You can never have too much fresh water tankage when cruising, and it doesn't go off if left to sit. If you don't need it for more usual needs, they all say freshwater toilet flush is much more odour-free.

 

[BruceK]

I find in those conditions the boat movements follow a repeating pattern and after a little while the helm adjustment becomes easy,and near automatic. Of course there can be the exceptional larger sea, so keep your wits about you.
The IG seems ok in quartering seas, it`s the square stern on seas that call for a response. The added speed is amazing,were it a sailboat the rigging would develop that characteristic hum.

 

[AusCan]

Every boat has its limit. My boat is great in following seas up until a point.
I never really worried about it until we got caught in some 5-6 foot waves on the stern. At first the boat was handling it well, but as we proceeded closer to shore the waves started breaking and the size increased wherever the depth decreased. On a couple occasions I got worried as the boat got pushed around. I had to plot a careful course where there were no sudden depth changes to cause the waves to break.

 

[BandB]

Every boat has its limit. My boat is great in following seas up until a point.
I never really worried about it until we got caught in some 5-6 foot waves on the stern. At first the boat was handling it well, but as we proceeded closer to shore the waves started breaking and the size increased wherever the depth decreased. On a couple occasions I got worried as the boat got pushed around. I had to plot a careful course where there were no sudden depth changes to cause the waves to break.

Handling of boats goes down when you get to shallower water too, even without waves. You don't notice it much in most boats, but in some larger boats keeping a straight course on the ICW is extremely difficult.

Here's an interesting write up of the effect. While it's talking ships, it's true on all boats, just more noticeable on them. I'm sure we have some of our commercial boaters here who have experienced it often.

How Squat, Bank and Bank Cushion Effects Influence Ships in Restricted Waters?

 

[Art]

Just for S&G... about when the going gets rough...

There are semi rough following seas... then there are really rough following seas.

If a boat is designed and equipped correctly with strong enough build, ample steering response, engine that won't quit working and low enough cog... the boat will take as much or more than we can or will in following seas, or in any seas for that matter.

That said... really badd asssss following seas can make anyone aboard pucker-up for time it takes to get through it. The Captain can never blink and must trust that the boat will see the situation through.

In this video there were not square sterns, there was low cog and in general these working boats were equipped to handle items at hand. The captains were stellar!

 

[Brooksie]

To reduce my L to L, I'm need to replace the rudder cylinder with one with a smaller piston diameter. Or a helm with more displacement per rev. One or the other or both.

It surprises me a production boat has 8 turn L to L. Are you sure about that? Maybe you have air in your steering. That would be an easy fix!!!

That would do it but so would moving the cylinder pivot closer to the rudder stock. If your distance there is 6" now (for instance) and you want to change your 8 turn steering to 4 turns, then drill a new hole at 3" from the stock center and move the cylinder bolt. This assumes that 8 turns is giving you somewhere around 70 degrees total swing.
Autopilot nice for long passages in following seas but it won't correct your underlying problem and it may not work fast enough anyway. You need to at least halve your lock to lock turns. Maybe add power to your rudder by enlarge or otherwise redesigning it. Add balance to your rudder if steering becomes difficult after halving your number of turns, it will require twice the force when turns are halved. Adding height to your rudder is more effective than adding length. Adding a dam at the lower edge and raising it up nearly to the hull adds power w/o adding size to the rudder.

 

[Al]

Adding a dam at the lower edge and raising it up nearly to the hull adds power w/o adding size to the rudder.

Good Morning Brooksie- Could I ask for a bit more clarification on the above portion of your quote? What is a 'dam'? and could you discribe the 'raising it up---------? Thanks,

Al-Ketchikan

 

[Nomad Willy]

Brooksie,
That's about the first thing I did to Willy.
But one should be aware that that puts much heavier loads on the steering gear from the rudder horn up to the helm. On Willy drilling another hole wasn't necessary and since an optional hole was there I sortof assumed it was manufactured that way and engineered for the task (rudder size ect). But in my case I changed everything from the rudder horn to the helmsman's hand .....

Al,
Quite sure Brooksie's "dam" is a flange at upper or/and lower ends (top and/or bottom) of rudder. If the hull is close enough it can act as a dam to a degree. And for general shape a high aspect ratio rudder is best. As in tall and not wide as viewed from the side. attached to boat.

 

[Brooksie]

Brooksie,
Al,
Quite sure Brooksie's "dam" is a flange at upper or/and lower ends (top and/or bottom) of rudder. If the hull is close enough it can act as a dam to a degree. And for general shape a high aspect ratio rudder is best. As in tall and not wide as viewed from the side. attached to boat.

Exactly what I meant, thanks for that.

 

[Al]

Exactly what I meant, thanks for that.

Okay, let me respond. I have witnessed rudders with horizontal flange welded on the bottom of the rudder much as a stabilizer on a aircraft. I have witnessed angle iron welded to the tailing vertical edge of a rudder. I have witnessed 'wedges' that cover the full surface of one side, and both sides of an existing rudder. Do all of these then represent a form of 'Dam'?

Note: the horizontal flange application has more I think, to do with keeping fishing nets out of the wheel during the period the net is being gathered and it surrounds the stern of the craft.

Al-Ketchikan

 

[Art]

Exactly what I meant, thanks for that.

Brooksie / Eric... You guys have photo of rudder alterations you mention?

 

[Brooksie]

Brooksie / Eric... You guys have photo of rudder alterations you mention?

No, I am sorry I don't. But I will try to describe:
Increase the balance= adding to the area of the rudder ahead of the stock to make it "self powering" 15-18% is maximum normally.
Raising the top of the rudder close to the hull= within 1/2" forms a dam at the top and reduces spillover in a turn from the high to the low pressure side of the rudder. How this is done depends on the rudder's material. Mine is fiberglass.
Adding a plate (dam) on the bottom of the rudder does the same for spillover at the bottom and further increases the power of the rudder w/o increasing it's size. The proper plate width is open to some discussion but certainly 2-2.5" wider than the rudder each side would be a good start. Again the material used would depend on the rudders material. I used a fiberglass plate screwed and epoxied to the rudder.
Hope this helps.

 

[Al]

Brooksie / Eric... You guys have photo of rudder alterations you mention?

I'm with Art. Somebody will have a photo or two. somebody

 

[IntoTheBlue]

Owned a 390 with single 315 Yanmar back in 2002 and delivered a few around Long Island. Really loved the boat, but as others had said stern / aft seas made the boat stern will move quite a bit. Would also "surf" if conditions were strong enough. I used to run zig zag patterns heading east around Montauk to BI. Using Autopilot made it easier.

 

[jleonard]

Also remember that one of the design "shortcomings" of that model is a very small rudder.