Water creeping up hullsides

[Ad Hoc]

... we had some water blasts ...

Can you define what you mean by - water blasts.

....I noticed props were spinning out when we’d get water blasts. ....

In a following sea there will be times where the wave train will become coincident with the stern.
So, imagine the peak of the wave, sitting on the transom, and the length of the wave would mean the bows would be in the trough of the wave.
Having your new bulbous bows will prevent/help to reduce the propensity to bow dove, owing to more buoyancy up fwd.
However, depending upon the amplitude of the wave,, once the wave train passes the transom the attitude of the boat will still be in a bow down trim, so your props will then become close to the water surface profile, maybe even become exposed. Thus your props will spin/race.
So this is a function of how deep the props are relative to the static waterline and also the amplitude of the wave that lifts the stern, and how much of a bow down trim the boat experiences.

This is a common experience when running in a following sea.
Just change course/tack, and/or slow down, or if possible, increase speed.

Since the wave celerity (speed) will have a period of encounter at the stern, that promotes this behaviour, perhaps exacerbated by the wave length and amplitude you are encountering.

 

[fallguy]

Can you define what you mean by - water blasts.



In a following sea there will be times where the wave train will become coincident with the stern.
So, imagine the peak of the wave, sitting on the transom, and the length of the wave would mean the bows would be in the trough of the wave.
Having your new bulbous bows will prevent/help to reduce the propensity to bow dove, owing to more buoyancy up fwd.
However, depending upon the amplitude of the wave,, once the wave train passes the transom the attitude of the boat will still be in a bow down trim, so your props will then become close to the water surface profile, maybe even become exposed. Thus your props will spin/race.
So this is a function of how deep the props are relative to the static waterline and also the amplitude of the wave that lifts the stern, and how much of a bow down trim the boat experiences.

This is a common experience when running in a following sea.
Just change course/tack, and/or slow down, or if possible, increase speed.

Since the wave celerity (speed) will have a period of encounter at the stern, that promotes this behaviour, perhaps exacerbated by the wave length and amplitude you are encountering.

The wave ‘blasts’ are when so much water runs up the hull sides it blasts into the cockpit through the hull/bridgedeck gap. That water creates drag and also strikes the middle beam. And sometimes it can be gallons making it to the cockpit, like as in 10-20 gallons. Very chaotic and somewhat scary despite having me and my son on the raised helm and no passengers on deck.

So, your assessment of boat position in the wave state and the drag caused by water creeping up the hull causing loss of speed and props cavitating (and it was quite often) is correct,

I tried to speed up and the amount of water getting into the cockpit increased greatly a few times and was too chaotic, so we ran at a solid 19 kts. But we did have the props winding out rather often. We were trying to run 30 miles in mostly daylight and we had been running for 15 hours before that run, so we wanted to get in quicker than slower as well.

My engines are mounted at 14 degrees against a recommendation of 12. I tried to trim up a bit to help the bows stay up a tad, but this resulted in more slip/cav.

I think I will wait to change anything until after the rails are on.

I think I’m going to take a photo of the fixed trim tab Baeckmo designed versus the engine. Maybe that will also help affirm engine height as correct. Those tabs really improved the boat, but I did not adjust engine height after installing them.

From the helm, I can see the top pf the prop quite often in the gulf chop in following sea.

Seas were like 2’ maybe rolling up a bit higher now and then. Those waves or waves that hit the port hull insides were the worst.

 

[DogCavalry]

Have you considered steaming wooden spray rails? It has been 33 years since I steamed a frame, but it certainly made the oak flexible.

 

[Ad Hoc]

....I tried to speed up and the amount of water getting into the cockpit increased greatly a few times and was too chaotic, so we ran at a solid 19 kts. But we did have the props winding out rather often. We were trying to run 30 miles in mostly daylight and we had been running for 15 hours before that run, so we wanted to get in quicker than slower as well....

I think you are now understanding/exploring the limits of your boat.
So, it is basic seamanship knowing in what conditions your boat is safe in and what conditions it has issues with.
In other words, the boat is not really suited for such conditions, unless you run slower...ie 15 knots. It is merely a function of your vessel speed and the wave encounter period.

If, as an example, we assume a 1.0m wave, with a typical period of around 5-5.5s, we can construction the encounter periods v speed, like so:

The red band is a vessel natural period of motion, where it be, heave, pitch or roll. All conventional vessels under 40m, will exhibit their natural periods of motion in this band.
So in a head sea anything from 10 knots to around 22knots - where this red zone crosses the head seas - the vessel will encounter resonance, and thus become uncomfortable. Because the natural peirod of motion of the vessel is matching the wave encounter period.

If we look at a following sea, oddly this occurs around your 19 knots....periodically.

So, slowing down, to say around 15knots would be more prudent.

Watching the waves, their period and direction, and then match your course to avoid this red zone is the key....and face up to the fact that your vessel is not ideally suited for such conditions, as these encounter periods = accelerations based upon how much vertical displacement you experience over that time. Simply pout - seamanship.

Im not suggeting anything about your own, merely that, all vessel hit their "sweet spot" of being uncomfortable at some point. Knowing when it is, is then simply a matter of avoiding it, via mitigation.
Change speed or course or both.

 

[fallguy]

The boat feels ‘draggy’ at lower speeds. I suspect a couple of things. I watched the SOG and it varied a lot from 12-15 kts. Everytime I hit or was in the back of a wave and the hull water creep occured; it was excessive drag. So I did try to find a sort of sweet spot that didn’t feel draggy. I think the boat tends to slip into a hole, much like a normal planing hull, and at higher speeds the beaching keel and wear plate end up skiing more.

I am curious about the encounter period. If the wave period is 5 seconds in a following sea and the boat is running 17mph; the encounter rate Is near zero.

If I go half as fast of 8 knots or so, I am in the red band.

At say 12 knots speed in 4 -6 second waves about 2’ to 3’ max, I am out of the red, but in that draggy zone.

It is complex.

Baeckmo told me to modify the way the beaching keels meet the sea some. Has not been time and location is tricky.