Gyro and paravane stabilizer

So I’ve got a 42 foot semi displacement boat with massive range Rough guess is at 7.5 kts I should have 4000+ no range. She also has paravane stabilizers built in from factory, now it being a semi displacement hull without running the stabilizers anything over 3-4 feet starts getting uncomfortable, and they are also a hassle for short hops or shallow water like the Bahamas. I’d say she is actually a relatively tender boat when compared to any full displacement hull. So even with the range to easily cross oceans I would be very hesitant to even consider it with only having one type of stabilization. So I was thinking of adding a Seakeeper 5 stabilizer and keeping the paravane stabilizers as well. Has anyone run these two stabilization systems together? If so did the two of them running together improve upon the overall comfort? And having an inherently tender hull would anyone consider crossing oceans with both systems since you would have a completely separate system for back up?

I can't comment on vanes + gyros. Ive run fins + vanes and they work fine. Would suggest run one or the other. Not so easy with gyro that takes 30 mins to spool up.

Per you comment on your boat being tender. David Gerr has done a ton of research on stability. In short, he states that stabilizers do not make a boat more stabile, just more comfortable.

You may want to peruse some of these articles to help you determine the nature of your boats tenderness. Could be initial stability but ultimate stability is fine.

https://www.gerrmarine.com/Articles.html

Peter

While I have had neither system, if I had a gyro I think that it would be the go to system due to how easy it is to use compared to the paravanes. It has to be easier to use than deploying the vanes. However you will have to run the genset so that is a consideration. Intriguing question though, I will be interested in seeing what answers you get from more knowledgeable people.

The gyro means you run a generator all the time. That changes your range. And it means you're wearing out 2 pieces of equipment. If either fail, you have no roll control.

I ran commercial fishing flopper stoppers for years. I had big ones that allowed me to turn around in huge waves, 50' close together. Some people added hydraulics to put the floppers in and out, making it easier.

Hmmm so it’s sounding like it would be a run either or thing, at least If that’s what I decided to do. And I would be able to run the gyro stabilizer off of my alternators and inverter or have a 12 or 24v gyro so while underway I wouldn’t need to run a generator unless Im at anchor, so that would be a plus. I Don’t see the power requirement from the alternators for gyro being any worse than the speed reduction and or power increase needed to maintain a certain speed for the paravane stabilizers, in fact I bet if we really did the math I bet it would be almost the same. Pretty much any way you are cutting it you are converting diesel fuel Into comfort. Kinda figured paravane stabilizers would be used when on the hook for long periods of time with flopper stoppers or when the weather gets to rough for the gyro to be safe, I was hoping using the paravane stabilizers in conjunction with the gyro would make it more comfortable, and safer by the gyro taking some of the load off the rigging for the paravane and give it an extra safety factor so to speak. Hmmmm yes I have read a bunch of his work, but I do have to disagree with some of what he said at least to some extent. And keep in mind I do like a lot of his work but in that statement I believe he is wrong.. Any reduction degree wise in roll is making the boat safer by making it that much harder to get to the point of vanishing stability, now the statement he should have said was all stabilizing systems do not change the boats inherent stability(a boat that will capsize at 65 degrees will always tip over at 65 degrees no matter the stabilizing system) but when The stabilization system is in service it will make the boat more stable by reducing roll and thereby making it harder for the boat to reach the point of vanishing stability.... at least that’s what I get from all the research I’ve read on the subject and I’ve read a lot, not saying I’m right but this is where the research has taken me. Now as for what I’m truly worried about would be heavy weather stuff where if my paravane system failed if it got rough enough I’d probably have to turn off my gyro as well since they don’t do so well in the extremes from the research I’ve done. And with knowing that my boat would not survive what a full displacement boat would and more than likely would not right itself if nocked down or rolled, would that be an acceptable risk? Now I do have options like speed that a full displacement boat would not have, and even to the pins on my boat I still should have over a 1000 mile range so other than for small fast moving storm systems I should be able to outrun most of the bigger systems.

Btw I’d also have alternator large enough to run all my systems on both engines so even if one went down I’d have a backup. I’m thinking I’d go 12 or 24V gyro system btw for just that reason.

Alternators*

Do they make gyros big enough to do the stabilization that run on DC? I know they make DC units for small boats.

Seakeeper 3 can be dc, and I believe they are working on a Seakeeper 5 in dc. Size wise I need the 5 but Not sure which would be optimal for me because of my weight. I’m 42 long but unloaded weight it only 17,000lbs I figure fully loaded with fuel and stuff I should be around 25,000lbs. So the Seakeeper 3 may work for my boat. Not sure yet and not at the point where I’m needing any quotes

It would be an interesting setup.

Yea, Gyro stabilizers are fairly common on planing, and semi displacement hulls. But the paravanes are uncommon enough on that style boat I’ve never seen it before, I’m sure it’s been done but I have no clue on the results of it. I’ve also never heard of both on the same boat, let alone both on a semi displacement. It’s prob been tried on a full displacement hull maybe a nordhaven or something similar at some point but again I’ve never seen, nor heard about it so again I’m at a loss on how it will turn out or how effective it would be.

Correction I’m sure it’s been done on another boat other than mine. But I’ve only traveled 600 miles in mostly protected waters and my entire experience with them lasted 20 min, to good effect btw but hardly a definitive answer on how good they work for that style boat.

Sometimes I’m just not sure what they were thinking when the designed and built my boat. It’s a lot of contradictions, as well as a lot of downsides to it.

Lol well obviously it wasn’t the best thing since sliced bread, because the company failed and there wasn’t much of a market for cramped, over priced, super long range, semi displacement boats

Jmarsh203 said:

Seakeeper 3 can be dc, and I believe they are working on a Seakeeper 5 in dc. Size wise I need the 5 but Not sure which would be optimal for me because of my weight. I’m 42 long but unloaded weight it only 17,000lbs I figure fully loaded with fuel and stuff I should be around 25,000lbs. So the Seakeeper 3 may work for my boat. Not sure yet and not at the point where I’m needing any quotes

Click to expand...

You're gonna have to pick a weight to design against. If she's 17k# dry and carries enough fuel for 4000 nms at 7.5 kts, I'd guess she has 1200 gals tankage. Or over 9000# - and that does not include stores, spares, and provisions necessary to trek that type of distance. Hard to imagine she'd sit on her lines properly let alone remain semi-planing. Are you sure you have room to retrofit a Seakeeper with all that tankage?

The only people I've heard who have been unhappy with gyros have undersized them to cut cost. Those who install correct size seem to love them. This is the first I've heard of running from an inverter off engine alternators. Seems feasible, though they take more energy at startup than in sustain/run mode.

Pictures of your boat would be interesting if you care to share

Peter

Got it exactly right, 1200 in fuel, twin ford Leighmans for now, she is semi planing with full load right now but is definitly a little anemicat full load, she does about 11.5 full load no wind or current to the pins. Half load is 12.8 ish That’s why if she doesn’t have too many bad habits and I keep it long term after I start cruising her she may get twin Cummins 6b’s or maybe 6bt and I will do the Seakeeper mod then. I should have some room amidship for the Seakeeper in front of the v drives and right behind the fuel tanks. Sorry don’t have any pics of the space where the Seakeeper would fit but between that spot is about a 6 foot dead space with nothing but the sea strainers which would be easy enough to move a bit. All the cooling water is run through a sea chest about 4 feet to the port off centerline so think it should fit and be fairly easy to move the hoses. Half tempted to turn her into single screw. Her two sister ships were single screw boats. One Had a 300hp Cummins v8 and the other 200hp Perkins turbo. Have no other info on the other boats other than they existed and what they were powered with. but it looks like a 300hp Cummins c series would fit pretty easily, may actually be able to fit an 855 big cam 400hp after some measurements which to my calculations should do something like 17kts with full load. . Idk yet most boats that have done conversions never really turn out well but since I know that it was designed for it on the same hull I feel a bit more warm and fuzzy about it. I’ll say this I really don’t like how much room is in the engine compartment with the twins, a single centerline with a generator on one side and Seakeeper on the other would be really nice to work in that engine compartment. But that’s just me bouncing ideas around at this point.

Both of those pics are full load of diesel btw

Thanks for letting me know about how the people that are happy with the conversions are the ones that size properly and the ones that are not went undersized, that pretty much cemented me in for the Seakeeper 5. If your spending that type of money it’s definitely better to be happy about it afterworlds.

I know She looks a little rough btw, but when I am done with her she will look as good as new. Just waiting for the economy to stabilize before I start dumping all my money into her for the refit lol I’m going bare aluminum above waterline, paint only on the hull below waterline and the decks.

Window ac unit is definitly coming out btw, gotta love PO’s.

We don't have any stabilisers.
We do have time to pick favourable conditions.
And if it gets wobbly en route, we change course or RPM to make it more comfortable
The cost of stabilisers buys a hell of a lot of tacking miles.

But, what we have noticed is the only time we have thought stabilisers (paravanes) would help is usually at the beginning or end of passage when heading on a course that is not the main direction (hooking it around to enter or leave an anchorage)
During these miles, for us, water is usually not deep enough to have fish in anyway

JMarsh, sounds to me like you haven't decided what you want your boat to be: is it a displacement long range cruiser or is it a semi-D with a good turn of speed?

You're all over the placing talking about twin small Lehmans, then 6b, then 6bt, then 6C fire breathing dragons, then a single 400hp 855NT. Your boat only displaces 25,000lbs fully loaded, so you'll run your powering models at 2/3 liquids, so probably about 21,000lbs.

Personally I think a single is a fantastic idea. Might not be as expensive as most will think since aluminum is weldable and you can sell your twins and save the money of buying two new engines/gear/props. Perhaps keep one Lehmans and rebuild it. Even 120-135hp is alot for a 20k lb boat cruising at 7 knots.

However if you install 600hp worth of engines then perhaps you don't need stabilizers - you have hull form and dynamic stability when running at 14 knots. Anyway, first clarify your requirements then find a solution second. IMO

For what it’s worth we only have paravanes. On our trip from Alaska to Florida they were in the water probably 80% of the time. We had a couple of failures. Once a swivel broke and I’ve had two fish hit objects. Repairs took less than 30 minutes. We also carry additional rigging for any line failures which we haven’t had in 13 plus years. We are full displacement and with the paravanes in the water we loose about 1/2 to 3/4 of knot based on conditions.

If your looking for reliability the paravanes should win out.

It’s definitly not a displacement long range cruiser, as much as I’d like it to be. Just doesn’t weigh enough, Nor does it have a suitable hull design. It’s pretty much an old gb42 with over twice the tankage and paravane stabilizers and weighs 10,000 lbs less even fully loaded with fuel. So it will be faster than that with any similar power, and with the paravanes prob a more comfortable ride at sub 10kts Figured even if I put a bigger engine or engines in it I can always pull back on the power if I’m trying to go some distance. And even with the 400hp of engine in her I should still have close to a 1000 mile range to the pins if I ever needed the power. And pulling back I will have virtually the same if not better efficiently. I know one thing if I end up keeping the boat the old leighmans are coming out. I know a lot of guys love them and they are reliable engines if taken care of but there is no arguing that they are comparatively high maintenance fragile motors. Should be able to do an easy steady cruise at 14 kts with 400 hp, and according to the math still get better than 1nm per gallon. Now that would be quite interesting to see in practice but that’s whet the math is saying at least so should be ballpark at least

Sure. Sounds like you’re developing a plan now. But I’d recommend the 6C8.3 over the NT855 for your application.

Other than the weight thing any reason to go for the c series over the big cam Not that the 1000 lb difference isn’t enough lol hmmm weight wise if I went with the c series the weight reduction from the twin leighmans is almost enough to cover the addition of the Seakeeper I’d probobly be over like 200lbs after the Seakeeper install. I’ve messed with both on the road and have a preference for the big cam at the 400hp mark. I do have a c series in my rv and I do have to admit that thing is super smooth. But marine application I have 0 interaction with.

Have you ever actually weighed the boat? 17K in a twin engine 42' hull smacks of manufacturer optimism. Not impossible, but pretty hard to do.

No I haven’t weighed it, but I would like too. Where would I be able to weigh it?

DDW said:

Have you ever actually weighed the boat? 17K in a twin engine 42' hull smacks of manufacturer optimism. Not impossible, but pretty hard to do.

Click to expand...

I agree. Our single engine, 42’ Krogen with 37’ water line at 1/2 load displaces 37,500 lbs. In cruising mode with full fuel, water and provisions we’re right around 44,000 lbs

Jmarsh203 said:

No I haven’t weighed it, but I would like too. Where would I be able to weigh it?

Click to expand...

Most travel lifts have the ability if they are maintained.

Larry M said:

I agree. Our single engine, 42’ Krogen with 37’ water line at 1/2 load displaces 37,500 lbs. In cruising mode with full fuel, water and provisions we’re right around 44,000 lbs

Most travel lifts have the ability if they are maintained.

Click to expand...

Our boat was weighed when it was lifted on to the ship for transport a couple years ago. The dry weight and wet weights are very similar to those numbers.