Semi Displacement advice

[Failcon]

We are looking to change our 8 metre fast fisher for something that would be more comfortable in less than ideal conditions. Our present boat is fine in flattish sea conditions but is easily stopped by head seas and needs to be given a good bit of throttle to stop rolling in beam seas. The resulting water coming over the bow makes it difficult to see and steer. All in all we are not using the boat as much as planned because its very noisy (at 15-18 kts) and uncomfortable in moderate seas.

We are now planning something larger and heavier that would increase the weather envelope for comfortable cruising. Boats that come to mind so far are an Aquastar 33, Hardy Commander 32 or a Halmatic/Humber 34. All have the same general concept, but with significant differences. The Humber and Aquastar tend to be boats from the late 70s/early 80s with engines that may not be very fuel efficient judged by todays standards (??) and uncertain parts availability (??). Also the Aquastar has a fairly rounded hull profile aft and is said to roll a lot at displacement speeds and be very wet. Increasing speeds to (say) 16 kts is said to stop the roll but is it still too wet to see? The Hardy is more recent and a bit different as it is more of a planing hull with quite flat sections aft that should help rolling (??) while still being OK at displacement speeds due to the keel. However, do the flat aft sections limit the legendary Hardy seekeeping? I have searched for a photo of a Humber 34 out of the water or a review but drawn a blank so the characteristics are a bit of an unknown.

There are few examples of these boats for sale so at the moment so its a case of trying to get a better idea through internet research and personal advice. I would be glad of any input from people who have owned any of the above. There is a school of thought that says all SD hull are wet, roll like a pig and are very thirsty so maybe I am looking in the wrong direction. If you have this view what else do you think we should be looking at in this size range? We are looking for reasonable comfort in moderate conditions rather than heroic survivability in really bad weather.

Thanks

 

[oldgit]

Have recently changed from a semi displacement Broom 37 with a keel hull to a planing Olineski hull.
The difference was obvious within half a dozen trips, especially if in any wind over tide chop and especially when encountering wash from large fast commercial traffic.
The planing hull was more steady, comfortable and predictable.
Noticeably reduced was the uncomfortable rolling and swinging of the semi displacement hull even though that hull was longer and probably far heavier.

 

[Bouba]

I have a short (34 foot) semi displacement and I don’t recognize those problems. 17 knots is usually top speed at semi D so the fuel consumption is horrific, so I don’t do that except for an Italian tune up. The conditions you describe aren’t those I would go out in, but a cheaper alternative to changing boats would be to invest in better windscreen wipers.

 

[Portofino]

Welcome to the forum .
Sounds like you know your onions boat hull wise :encouragement:

Picking up on “ looking in the wrong direction “

We started with a Sunseeker Portofino ( hence my name here ) it got to the stage because of the seakeeping combined with a fragile wife sailor that our envelope just kept decreasing ,
Same reasons , wet ride up wind ,slamming , having to slow down so waves lift it and exaggerate roll etc etc .
One day out in unexpected afternoon conditions a Rivarama 44 cruised past dead flat and dry seemingly just slicing through while we had a torrid time by comparison.Same direction for comparison.

Next morning We were at the Riva dealer in Monaco and they had one lifted on the quay .Sales person laid it all out for me - hull form .It s blatantly obvious when you look under the waterline why some hulls perform better than others .Size for Size .
We ended up getting one of these - better accommodation and I fact arguably better boat all round in the seakeeping .Its not rocket science a smoth dry ride dead flat .

We often outperform far bigger stuff in rough seas .

Counterintuitively we actual speed up in a head sea ( while others slow ) .If you go fast the splash / impact part moves back to the behind or very near the windscreen .This means combined with the speed the boat stays bone dry as when the water curls back the boats gone so it falls in the propwash .Our boat has no wipers btw .

Huge compromises but well worth it ride / seakeeping wise ,Wife ( and guests ) have absolutely total confidence in the boat in rough weather .Its opened up a huge cruising conditions envelope. hardly ever look at the Met these days cos it down,t matter - much .

Here you can see the spray point - on the subject and the boat filming .
https://m.youtube.com/watch?v=bHRxWnk7yT4

Here it’s the 38 , easy to truck back to the U.K. and they do a canopy as well .Straight shafts as well I,am assuming you’ve done homework about outdrives to the same due diligence you have about hull form and ride .
So it’s deadrise over 20 degrees , mid not stern engines , low centre of gravity , solid grp hulls and shafts with low prop shaft angle ——centre of lift and CoG the same point ,not miles apart like modern stuff, put all those ingredients together and hey presto .

https://m.youtube.com/watch?v=mpNV2XPMC5U

 

[Keith-i]

I have a Channel Island 32 which is very similar to an Aquastar. There is no comparison between an 8m fast fisher and a 10m SD. The SD will roll much more and seem tediously slow when the sea is flat but of course it’ll weigh 2 or 3 times as much. We get spray on the front windows but not enough to make driving difficult and only when the bow drops off the crest of a wave or some swell and ploughs into the next wave. I don’t think engine vintage has as much an effect on economy as you might like to believe. All SD boats will be very inefficient beyond SD speed and will load up the engine.

 

[benjenbav]

I owned an Aquastar 33 for quite a few years. It was wet, rolled like a pig and thirsty,

As to each of the above:

Wet - wipers and radar help.

Rolly - you get used to it and it doesn’t make a difference if you slow down, and speeding up isn’t much of an option, so you plough on. The boat will go through just about anything.

Thirsty - it depends what engines are fitted. There was a wide variety as many hulls were sold to be fitted out by owners. Mine had 2x bulletproof Cummins B6Ts rated at 210hp.

 

[burgundyben]

I owned an Aquastar 33 for quite a few years. It was wet, rolled like a pig and thirsty,

As to each of the above:

Wet - wipers and radar help.

Rolly - you get used to it and it doesn’t make a difference if you slow down, and speeding up isn’t much of an option, so you plough on. The boat will go through just about anything.

Thirsty - it depends what engines are fitted. There was a wide variety as many hulls were sold to be fitted out by owners. Mine had 2x bulletproof Cummins B6Ts rated at 210hp.

What was max speed? and how heavy was she?

Bit smaller, but what about a Mitchell 31?

 

[BruceK]

I have a friend who is a diehard fisherman and will go out in most weather in his Mitchell 31. A very good sea boat unquestionably but he keeps a video cam on the back of the pilot house to record the catch and post up to FB. I can say unequivocally that his boat rolls like a drunk and is very wet by comparison to my 34 foot sports cruiser and I will go out in far worse weather than him as a consequence. This surprised me somewhat as I was given the impression that SD hulls were far more sea kindly by which I took for comfort. This does not seem to be the case. I take it then that sea kindly means they can weather worse weather and sea conditions? Either way I am comfortable going out in a head sea up to F6 gusting 7 in the coastal Irish sea at cruise which will typically create 1.5 to 1.6 m steep faced waves but with a 4 -6 second period in my locale and happy to return with a following sea pushing F8 which will produce a 2m rounded swell with a 8 second period provided the waves are not breaking. Those wave heights and periods I consider to be within the boat's safe envelope if I maintain ~16knts in a head sea and 19 in a following sea timing the swells to maximise comfort.

 

[BruceK]

Comparative vids in the same conditions

Mitchell 31

Sports Cruiser

 

[BruceK]

Mitchell 31 roll

Sports cruiser roll at Moelfre Lifeboat day after Shannon Class created wakes for jetski's to play in. (Not same condition as it was a wake set up by a circling LB)

 

[omega2]

wHAT YOU MEAN IS YOU HAVE BEEN CAUGHT OUT IN THOSE CONDITIONS, and very happy to have got back !!

 

[BruceK]

wHAT YOU MEAN IS YOU HAVE BEEN CAUGHT OUT IN THOSE CONDITIONS, and very happy to have got back !!

Not at all. I go out in those conditions. I'm not bigging up here, it's fact and can be confirmed by any of my peers from Conwy on this board.
Edit
Here is Seastoke in front. We are off for some grub in Caernarfon. My very first trip out in a cruiser mind, trial by fire. We have never looked back.

 

[vas]

Not at all. I go out in those conditions. I'm not bigging up here, it's fact and can be confirmed by any of my peers from Conwy on this board.
Edit
Here is Seastoke in front. We are off for some grub in Caernarfon. My very first trip out in a cruiser mind, trial by fire. We have never looked back.

no disrespect Bruce, but that's NOT my idea of pleasure boating...

cheers

V.

PS. you should edit the title of the last video to: nutters go for a beer and natter

 

[BruceK]

no disrespect Bruce, but that's NOT my idea of pleasure boating...

cheers

V.

PS. you should edit the title of the last video to: nutters go for a beer and natter

None taken Vas, my children are with you 100% on that score..... "Why do you do this? I am going to die!"

But if you have a look at my youtube channel you will see that comprises 80% plus of the conditions I'm out in. What we do have though is Anglesey and the Menai and you can always find shelter for a comfortable anchorage.

 

[julians]

no disrespect Bruce, but that's NOT my idea of pleasure boating...

cheers

V.

You could extend that sentiment to most 'pleasure' boating in the uk

 

[MapisM]

no disrespect Bruce, but that's NOT my idea of pleasure boating...

+1.
'Course a decent boat can withstand those conditions - been there, done that (and then some).
But going out there intentionally? Possibly, it depends on how much I get paid!
In fact, children aside, also the helmsman face at 1:03 doesn't look exactly relaxed to me...

 

[BruceK]

You could extend that sentiment to most 'pleasure' boating in the uk

That entirely depends on what you want to get out of boating. We are out every weekend of the season bar but a few. The point I am trying to make to the OP is that he needn't go SD as a cruiser will perform as well if not better in the conditions he is most likely to go out in and I am not just spouting that because of a bias but showing the evidence as proof of my conviction.

 

[gordmac]

Very impressed with my friend's recently acquired BT 35. Nowhere near the roll or pitch of his previous similarly sized heavy displacement boat. And you can actually get somewhere in a few hours.

 

[BruceK]

+1.
......also the helmsman face at 1:03 doesn't look exactly relaxed to me...

No the helmsman is seriously concerned the idiot up front is leading him to his doom. As I said it was my first outing and proved a non-event and a valuable lesson on what the boat can take vs it's crew. How about this then in a following sea? Following seas are much more relaxing and you get time to smile for the camera

 

[MapisM]

The point I am trying to make to the OP is that he needn't go SD as a cruiser will perform as well if not better in the conditions he is most likely to go out in and I am not just spouting that because of a bias but showing the evidence as proof of my conviction.

By and large, I agree. Truth is, nobody really "need" SD boats (let alone full D) for pleasure boating, if by that we mean in conditions which, albeit uncomfortable as they can be in the video which you posted, are still cruise-able at P speed.
It's when you cruise at D speed, not because you choose to do so but because the sea conditions don't allow you to go faster, that I don't agree anymore.
Of course, by "sea conditions", I mean combined with your route.
This summer I crossed the Adriatic in a situation similar to the one of your last video in a following sea, and all considered it was a rather pleasant passage, at 20+ kts (see below, and consider that the camera was hand held, to have an idea of the boat stability).
But when we saw an AZ 78 passing alongside us, on the opposite route, crashing and slamming into every other wave at less than half of our speed, well, I couldn't help thinking that a Fleming 55 or similar (let alone Nordies etc.), even if smaller, would have been MUCH better...

PS: I'm afraid I neither took pics nor videos of that AZ78, but since I suppose it could sound unrealistic that those conditions could make life hard to such big boat, below is a couple of pics of a large fishing vessel (100' or so, I would guess) which we also met in that occasion, steaming just about in the opposite direction...