Reply
 
Thread Tools Search this Thread Display Modes
 
Old 02-16-2021, 07:27 PM   #41
TF Site Team
 
Insequent's Avatar
 
City: Brisbane
Vessel Name: Insequent
Vessel Model: Ocean Alexander 50 Mk I
Join Date: Mar 2012
Posts: 3,217
Alan
I later realised that while I was describing vents on a 'normal' Mk 1, you have a flushdeck. We have the same hulls with vents on the hulls in the sme places But you can see your vents from the ER when standing, at about head height. For me, the bulwarks are hollow at least in that location and are higher than my ER ceiling.

First pic is starboard side rear exterior hull. I have Vetus vents, and we built a dorade internally for them, hence the 1/2" black spacer. The second pic is the port side, interior of the hull bulwark with a cover in place. The covers are not watertight, but if in open ocean I could have them on all 4 external hull vents and block most of the water from entering. But I would still have the same vent intake capacity as I originally had using the new vents added inside the bulwark.

If you are contemplating crossing oceans then I think you would be better to engineer some intake vents from much higher, perhaps on the boat deck. It will steal interior room, and be a lot of work. Good luck with your investigations - keep us posted!
Attached Thumbnails
Stbd vent rear outside copy.jpg   Port vent rear inside.jpg  
__________________
Advertisement

__________________
Brian
Insequent is offline   Reply With Quote
Old 02-18-2021, 06:51 AM   #42
Member
 
City: Sydney
Join Date: Jun 2017
Posts: 18
Thx Brian. We inherited Pasha of Hamble.
__________________

Almad is offline   Reply With Quote
Old 02-18-2021, 07:04 AM   #43
Member
 
City: Sydney
Join Date: Jun 2017
Posts: 18
Thx Brian. It really helps seeing where others have gone before.
Appreciate the logic you’ve used, and yes, even though a flush deck, will be applying the same.
Some thing for thought. Looking at the nordhavns, the weight of comparable sized boats are around double ours. I assume this has got a lot to do with underwater ballast, so am trying to get my head around this logic.
Coming back from 60deg would have to have something to do with this.
Do I add more weight to the keel
It’s worth taking the time to look at Cruising Sea Venture on YouTube.
They r up where you bought your boat from and they have just added a bulbous bow.
So many opinions on this, but they do it really well.
Rgds,
Alan
Almad is offline   Reply With Quote
Old 02-18-2021, 05:42 PM   #44
TF Site Team
 
Insequent's Avatar
 
City: Brisbane
Vessel Name: Insequent
Vessel Model: Ocean Alexander 50 Mk I
Join Date: Mar 2012
Posts: 3,217
Well, very nice inheritance I must say!

You may already know all this (if so forgive me!), but in case you don't:

Nordhavn's are displacement hull designs, whereas the OA Mk 1 is a semi-displacement hull design. Nordy's have deeper draft & heavier construction in addition to some ballast. That gives them great static stability, but those factors and their hull shape makes them slow. They can't get over hull speed. But they will have better fuel efficiency and for some purposes, such as crossing oceans, they excel.

The Mk 1's, like other semi-displacement hull forms, can exceed hull speed given enough HP. Even modest use of the installed HP will be 1 or 2 kn faster than a displacement hull form without consuming prodigious quantities of fuel. They are less fuel efficient than both displacement hulls and fast planing hulls, but the compromises give a boat that is great for coastal cruising and typically has a lot of home comforts. Hence their popularity despite some shortcomings compared to the more specialised hull forms.

It won't be feasible to add ballast to a Mk 1 to mimic a Nordhavn. It would be like taking a sports sedan and converting it to a camper van. You might well succeed to some degree, but the cost in time and money won't make sense. And at the end of it you definitely would not have a sports sedan anymore, and likely will have poor camper as well.

In terms of cost to make a Mk 1 seaworthy for an ocean crossing, plus fuel etc for the crossing, it will likely be cheaper to ship it most of the way, or at least past long stretches of ocean or places prone to piracy. In your case some of the work has been done already, but doors and windows are huge vulnerabilities in addition to the ER vents. Sorting out those issues, in a way that does not butcher the boat, wont be cheap. Yes, you could though-bolt 12-15mm perspex over the windows and it might be enough, but then there is some repair work to do once it is removed at the end of the crossing which could be challenging to look decent. Of course by using Pilot Charts and travelling at the right time of the year, and with a bit of luck, you may very well be able to get the boat ready with relatively minor modification and cross without drama. I was intending to do that back in 2012 and started refitting the boat to be fit for purpose. But then shipping rates halved and it became the prudent option to ship.

These days I regard my boat as an outstanding vessel for long distance coastal cruising. It can handle more in terms of sea state than I am comfortable with. Crew sea sickness and fatigue can lead to adverse consequences from poor decisions, even if the vessel is fine. At this point I don't think I would ever cross an ocean in a semi-displacement hull because I don't have the tolerance for extended periods of being uncomfortable and just not enjoying it.

Having said all that, I hope you keep us posted on your research and plans. You might prove me wrong, and If so I'd be delighted to welcome you ashore at the end of a crossing!
__________________
Brian
Insequent is offline   Reply With Quote
Old 02-23-2021, 07:24 AM   #45
Member
 
City: Sydney
Join Date: Jun 2017
Posts: 18
Thx Brian.
Appreciate the feedback.
It all helps on the homework.
Can only dream of shipping rates halving.
$100kaud back to Aus and half the trip gets a 10% discount!
__________________

Almad is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 06:24 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012
×