Side to Side motion on a powerboat

[jbinbi]

I am just wondering as a sailboat owner with a wife who gets seasick what the motion on a powerboat is.

I would think that a trawler would have roughly motion, it going the same speed (6-10 kts).

I am wondering about the 30 to 40' cabin cruisers/fishing boats/searays, etc. that go 20+ kts.

In 2-4' chop or swells both abeam and on, does it not affect the boat as it is on a plane? Sorry to be a newbie on this, I have actually never been on one of these boats. Thanks.

[hobopacket]

Up at speed on plane, very little rocking motion as you would get going slow.

Trade off? Of course! With a little seas you can get a beating from pounding waves at speed.

[skipmac]

As Hobopacket said, a powerboat at speed on a plane or semi-planing for a larger boats, the motion is almost all pitching (the bow bouncing up and down) and very little yaw and roll (twisting/turning and side to side rolling). The yaw and roll are generally considered the most uncomfortable and most likely to cause sea sickness.

If the seas are rough the boat could pitch a lot and even bang as it comes down from a wave top (called pounding) and you could have to slow down then the yaw and roll are back.

How much a 2-4' chop on the beam would effect the boat would depend on the boat. The difference from 30-40' can be significant. Also would depend on the hull design; deep v, shallow v, beam of the boat and how steep and choppy the waves. I ride on a friends 33' power boat and at 20-35 kts 2' chop is like nothing. 4' it will pound a little going into the waves and a little roll if the seas are beam on.

[jbinbi]

Appreciate the input. At 20 to 35 kts on a 33' boat, I am assuming you are using 10-20 gph?

[spearfish3]

In the 40'+ trawler range, you can have active or passive stabilization, or both. Both options can be very effective. Also, some smaller boats are even adding in a gyro stabilizer. They are even being placed on larger center console fishing boats.

[skipmac]

Originally Posted by jbinbi

Appreciate the input. At 20 to 35 kts on a 33' boat, I am assuming you are using 10-20 gph?

Boat is a 33' Grady White with twin 300 hp outboards. I think it burns a lot less than that but have to ask.

Boat is heavy, solid deep v and a very comfortable ride.

[Cheechako]

At planing speed no rocking/rolling, but the problem is the banging. It's bone jarring if you try to go thru heavy chop. So you end up slowing down and rolling anyway. The only answer I have to your problem is: catamaran or tri.

[Cheechako]

Originally Posted by jbinbi

Appreciate the input. At 20 to 35 kts on a 33' boat, I am assuming you are using 10-20 gph?

Yeah, on say 26-29 ft with two 250 HP outboards cruising at say 3.5k-4k rpm/35 knots speed you are going to burn 14+ gph. But you are going to get 35 miles too.
In a trawler at 8 knots you are burning 1.5-2gph So maybe 8 gallons for the 35 miles trip... more or less.

[Zven]

As others have said, it will depend on the boat and the waves what a certain speed feels like. But the great thing is, at any given situation, you can just pull the throttle a little bit back or forth in order to find the most comfortable speed :-)

[skipmac]

Originally Posted by Cheechako

Yeah, on say 26-29 ft with two 250 HP outboards cruising at say 3.5k-4k rpm/35 knots speed you are going to burn 14+ gph. But you are going to get 35 miles too.
In a trawler at 8 knots you are burning 1.5-2gph So maybe 8 gallons for the 35 miles trip... more or less.

Just heard back from my son-in-law with the 33 Grady. With twin 300 hp 4 strokes he's burning 28 gph at 30 mph. Burns about 25% less at 25 mph.

The Grady White is a very heavy boat. Burns more than I thought. Would burn a little less in a lighter boat but probably wouldn't handle the seas like the Grady.

Went with him to gas up on Monday. He was down about half. Cost $650.00 to top off the tanks.

[Kenomac]

Have your wife take some Bonine over the counter sicksick medication.

[Simi 60]

We simply wait for calm days before doing long passages.
If doing shorter trips in rougher weather we tack.
Head up or down not doing the optimal course, but doing the comfortable one, then tack across when the angles are right until reaching the destination.

Bigger boat but it is our home and we do use glassware so try and keep her on the level.

[DeepFrz]

There are a number of videos on youtube that show trawlers in heavy seas. You can see the difference with and without stabilizers. Makes a huge difference in comfort and ability to ward off sea sickness.

[Simi 60]

Originally Posted by DeepFrz

There are a number of videos on youtube that show trawlers in heavy seas. You can see the difference with and without stabilizers. Makes a huge difference in comfort and ability to ward off sea sickness.

Huge difference in cost and maintenance for actives as well, especially if in a remote location.

[daysgoneby]

Buzzards Bay 33 displacement cat

https://www.youtube.com/watch?v=nq_i9b7FvXo

2006 Buzzards Bay 33 Power Boat For Sale - www.yachtworld.com