Designing a new type of fishing boat .

[helen07]

I'm thinking a steel hull designed to cut water from stem to prop then a flat bottom with fins at the outer edge starting above the prop to the transom stern (speed and stability) . A forward wheelhouse and accomadation and in a huge jump from the conventional placing a lifting gantry on the stern thus keeping all the net and dredge activity at the stern of the vessel and hopefully lowering the height needed to bring catch aboard .

What do those who know think of these dimensions for a displacement hull on a fishing trawler ?
Length 15 metres
Width 7.5 metres
Draft 2.5 metres
I'm assuming this will give for a very slow boat unless a very thirsty engine is used ?

It is common belief among fishermen that lifting poles should always be placed a half length of the boat , i find this difficult to believe as the width of a boat is usually approx one third of it's overall length so why can't poles be placed wherever , if it can lift that weight on it's side rail without capsizing then why would lifting the same weight say on the stern for example cause any problems as it would have 3 times the counter balance . Your thoughts on this please .

An earlier convo on here got me thinking about the so called rule beater fishing boats design and having brought myself up to date with the latest fishing rules i have been designing a hyperthetical fishing boat that is built to adhere to the rules while offering a level of safety and comfort only currently available from catamarans . Catamarans have no fish hold worth mentioning so are not appropriate .

Emptying nets inside the stern rail should in my mind prolong the life expectancy of a trawler considerably as several tons slamming into the midsection of a hull inevitable takes it's toll on any boat regardless of it's build .

I am without qualification and so i will be grateful for any criticism also , though it's very early days , my final drawings might one day end up at a shipyard as i have family still at sea .

[helen07]

has this posted ?

[apex1]

has this posted ?

Yeah has helen!
Now lets see what the NA community has to say.
Have some points for your effort and the unusual care you take for the improvement of your husbands and his collegues working conditions.

Regards
Richard

[gonzo]

My thoughts are that you haven't been around fishermen too much. The dimensions don't mean too much. Can you make a rough drawing? What are lifting poles. Trawlers normally bring the net up the stern ramp. What do you want to change?

[helen07]

I'm writing for my partner Gonzo who fished for many years and he say's your comment's are to be expected because he did not point out that his aim is scallop and queenie shellfish , dredge and net .
Did you ever see a UK trawler haul dredgers at the stern ? Americans do it and current rules mean the max spread of dregde gear allowed inside the 3 mile is 7.5metres , at present boats use 2 tow bars with 5 dredges each and haul them up each the side of the boat .
This means towing a long and short wire to stop gear fouling upon itself . The negative effect of this is that the long dredges cover the same ground as the short and so catch maybe 50% less . A ten dredge tow bar should improve catch by 25% but most boats small enough to fish inside the 3 mile limit could not possibly work a 10 dredge bar .
To bring the dredgers aboard on the stern it would be neccesary to lift from a point maybe 3.5 or 4 metres above the stern .
At present he is having difficulty working out exactly how to set up the net gear so it need not be removed while dredging and visa versa .

[Ad Hoc]

Helen

I don't design fishing boats, but other commercial vessels: passenger, crew, patrol etc. However, Your design will be driven by:

1) Regulations to satisfy
2) The max. distance you want to be from shore
3) The max payload you want
4) The max speed/range you want
5) Deck area/storage.
6) Method of retrieval of nets, just one, or more etc?
and of course
7) Cost

Once you have formulated those in your mind, then the design process can begin. Until then, one is just going around in hypothetical circles.

You shouldn't discount catamarans too. They are really becoming vogue now. SouthBoats in Cowes on the IoW produce some excellent examples of this.

[helen07]

An off the peg vessel can be bought new for between 250 - 350k , the changes i have in mind do not interfere with regs . A lower centre of gravity can only improve stability . Rigging is not a problem as such but ideally it would be a simple case of unshackling the dredge bar and hooking up a net , no shore time required . Cats are great but no storage below decks means a run ashore on a daily basis . Distance from shore is limited only by fair weather conditions and the need to land fish while it's still fresh .

P.S Gemini workboats are by far and away the UK's number one cat builders .

[baeckmo]

There is one point on towing operation that has a great influence on hull proportions: the "wet end" of the gear, be it a trawl, dredge or else, should move at constant speed. This means that the propeller must work as deeply as possible, where the orbiting velocities of the wave system are low, and the hull must be designed with low pitching and swaying in mind!

The classical "double-enders", designed with no (or little) regard of political catch rules, but to be good sea-boats and good working platforms, with smooth waterlines were good in these respects. Some of the newer rulecheaters that were designed for maximum displacement on a limited wl length were below expected catching capacity due to a combination of high pitching amplitudes and speed variations when the bluff stem was diving into a wave. In order to compensate for this, the vessels had to be operated with heavy ballast to increase weight.

The remaining loading capacity was thus reduced, and the result was increased fuel consumption and lower safety margins. In the end, the balance between catch value and costs turned out to be lower than expected!

This also means that the towing point should be placed as close to the vessels virtual center of movement as possible, in low speeds this is often close to the center of mass. When the heck gantry was introduced on some of the 100 - 130 foot vessels here, the increased movements of the towing point forced the introduction of load sensing hydraulics in the winch power systems.

My point here is that a fishing vessel has to be a balanced design. There are so many conflicting requirements. Every time you let one requirement dominate your design, all other qualities will suffer!!

[gonzo]

My experience working in trawlers with stern doors, is that when you haul in, the boat weather cocks and the stern sinks with the weight. They have to be designed with extra floatation aft. I think they are several advantages to a stern trawler, but in rough weather, they ship seas over the stern very often.

[Guillermo]

What do those who know think of these dimensions for a displacement hull on a fishing trawler ?
Length 15 metres
Width 7.5 metres
Draft 2.5 metres

Worrying for a monohull. Wide beam will induce very high accelerations to work safely on deck.

Cheers.

[baeckmo]

There were more of us sharing that experience Gonzo, and it was no pleasure!

Those trawlers in Sweden that were rebuilt from side trawling to aft gantry's (including side-to-side traverse for towing points), still take the catch onboard midships. The same goes for many of the newly designed boats here. Main reason beeing just the working conditions in the critical moments when you have a freely swinging load to control. It's easier to design a ships side to take the pounding than to avoid crew accidents on a violently heaving aft deck, green with water.

In this perspective, the British tradition of having the "poles" (as you call them, Helen) amidships, is simply clever engineering, regarding the circumstances. The heck towing arrangement, on the contrary, is depending on "brute force" and high fuel consumption/low fuel prices in order to be competitive.

Manual work must be placed where ship movements are the lowest in order to reduce accident risks and physical stress on the crew. There are studies showing the impact of ship layout in these respects. The difference for the crew can be quite dramatic; in one of the tests regarding catamarans for coastal fishing (nets and traps), the oxygen consumption (a direct measure of man's work load) was reduced by 20 %, at the same time as the guys had the "catch round" done in shorter time than with the original layout (same weather conditions, same amount of gear to haul)!

So, if you want your "quality time" together with your husband improved, you also have to care about his working conditions onboard when you are contemplating the vessel design! It's a bold undertaking and you have a long journey to go, but I really wish you good luck!!

BTW, the overall dimensions you mention are more suitable for a catamaran. I strongly agree with Guillermo's comment here. I think you must sit down with your ol'man and figure out what kind of storage capacity (volume and weight) you need for a "normal" catch, because it has a major impact on the hull design. Before you have figures on this, you are stuck with a lot of guesses, and any progress in the design spiral is impossible!

[helen07]

Gonzo it seem's to me that you are the only one here who knows that fishermen consider just being able to keep both feet planted firmly on the deck "comfort" . Hauling the cod end of a 20 fathom queenie net on a stern A frame seems to me of little consequence (dipping the rail is part of the job) . However i would appreciate your thoughts on lifting a 7.5 metre 10 dredge bar weighing maybe 2.5 ton (when full) on a 3 metre high stern A frame . Try to imagine the stern ramp being 7.5 metre wide with a stop each side to prevent the gear from swinging . My only concern is that without trying it there is no way to know how lively a 15m boat would become with 2.5 ton raised maybe 3m above the stern rail . If it can be lifted on the side rail without trouble then i can't see how this would be a problem but i am not a naval architect and was hoping someone might offer an educated opinion that might support or deny the unqualified theory .

Architects the world over completely ignore the customers wishes whenever possible in order to promote their own designs , in order to prevent this i would submit drawings as specific as possible to an architect so he could test the design for faults and it would prove an expensive mistake to submit a design that works only in theory .

Sorry beakmo you posted while i was writing this and thank you for your comments .

[Ad Hoc]

helen

Architects the world over completely ignore the customers wishes whenever possible in order to promote their own designs

That is a very broad brush you're using!

A professional naval architect only gives what the customer can afford. That is what the specification and general arrangement are for...it establishes the design intent and the cost, up front. If these are not fixed prior to placing a contract.....then you are at the mercy of everyone.

[baeckmo]

Connecting to notes on dimensions above, I would give two examples here, just to show that you cannot select main dimensions at random.

The first is a steel trawler, L 16.8 m, B 5.0 m, D 3.3 m. She has a fully laden displacement of 75 tons (metric) and engine power is 475 hp. This boat has been one of the most successful vessels for her size, fishing in very rough weather conditions. One of her real virtues is the constant speed towing performance, due to her deep draft. The propeller center is 2.7 m down and on one extreme occasion she was carrying a catch of 450 standard 40 kg boxes, including ice (but then she was full up to the coaming).

The second example was designed to "do the same job", but fit within the 15 m regulation, so she got a wider beam, close to 6 m, and a different (more boxlike) midsection and less draft. Her prop center is nearly one meter closer to the surface.

Looking at them at quayside there is not much difference, the deck layout very similar (I'll post pic's sooner, its too dark now to take any), shelterdecked with wheelhouse forward and fishing over the transom. But the second has far less trawling capacity due to the shoal operation of the prop and the shape of the hull making it much more sensitive to the wave forces. Her heaving motions aft at the towing points is much more violent than the first one. Both when using bottom trawl and pelagic trawl, the doors are jumping forwards, making the trawl mouth opening and collapsing all the time.

So, if this is aiming to something real i the future, my advice is that you first go back to Ad Hoc's list of the 7 items that "drive" the design. Your husband is the expert on how to handle the gear he is using, so the two of you should focus on how to use a deck area of ~15 x 5 meters for the handling/stowing of gear, crew and catch. When these things are condensating to some final idea, THEN it is time to seek qualified advice regarding hull shape. Any other strategy will result in backwards engineering and that is really wasting your time!

[helen07]

I have no basis on which to judge naval architects for or against , but i am an avid viewer of property tv programs and it seems to me every time an architect is given any leeway at all on the design say of a 3 bedroom house the customers ends up with a glass staircase or some other stupid feature that's worth more than the whole rest of the otherwise perfectly average house .

[Jenny Giles]

I have no basis on which to judge naval architects for or against , but i am an avid viewer of property tv programs and it seems to me every time an architect is given any leeway at all on the design say of a 3 bedroom house the customers ends up with a glass staircase or some other stupid feature that's worth more than the whole rest of the otherwise perfectly average house .

Using TV shows as a measure of what happens in reality is probably not the wisest course. It might come as a shock, but some of the actors on "Friends" don't actually like each other.

[helen07]

Thank you Jenny i don't know what i'd do without your unprecedented intelligence .

I would be very grateful for those pics baeckmo , I am aware the boat envisioned takes huge liberties with possibilities , not least of which is it's virtually being half as wide as it is long . This is obviously not the norm and so i am actually seeking reasonable probabilities that would deny the pursuit of this line of thought forthwith .

[JRM]

Hi Helen

There is nothing wrong with your basic assumption that if you can lift the gear at the ship side, it can also be lifted at the stern (as far as ship stability and motions are concerned). That is of course why stern trawlers can work.

I think the problem is that in this case it leads you to design a MONOhull (not a catamaran) with a WIDE stern. On a small boat, that means that the boat will be short and fat.

1) The wide beam will make the boat "stiff" so that the boat will roll a lot worse than a normal boat. For example google Ramform + Banff + FPSO. That was a ship with a very wide stern that was used in the North Sea and had to be removed from service for modifications because she rolled too much. She was a far larger vessel than any fishing boat (admittedly her crew were not as tough as fishermen).

2) the wide beam and short length are generally not a good idea. Ask your "other half" about the short "rule beater" fishing boats built in Scotland a few years ago. They were so short and fat (among other things) that they PITCHED when lying to a beam sea.

3) if you have a wide boat, it is going to take more power to drive through the water than a narrower boat of the same length. That will cost more fuel.

Some of the Dutch mussel dredgers are boats that are very shallow draft and wide (for working over shallow mussel beds), but I think even the Dutch will agree that they are not very good for open water work.

The old English sailing trawlers were up to 80ft long and used to drag a beam trawl. The beam would be at least half the length of the boat and they heaved that up to the side of the boat every time they hauled. And they did most of that hauling with a manual capstan. And they boarded the cod end (OK I know its not a scallop dredge) without any poles at the ship side. They had a block and tackle hanging from the mast on the centreline of the boat.

I think the basic problem with your idea is that it produces a monohull boat that is too wide - which has quite a few problems - as a few of the posters above also indicate.

[baeckmo]

......... I am aware the boat envisioned takes huge liberties with possibilities , not least of which is it's virtually being half as wide as it is long . This is obviously not the norm and so i am actually seeking reasonable probabilities that would deny the pursuit of this line of thought forthwith .

I touched upon the proportions issue in a thread on cat's before. It has been shown that when rolling and pitching periods come too close (by shortening and widening hull dimensions), the ship will exhibit a very uncomfortable "corkscrewing" motion in a seaway; it "jerks" in an unpredictable way that makes it difficult to keep on your feet. It seems that our sensor system for balance cannot cope effectively with motion in double directions unless there is a distinguishable difference in period between the two. This comes equally bad in a monohull as in a cat. In addition to that comes the obvious drawback of increasing the required propulsion power. JRM is correctly pointing to similar examples here.

Sorry, but you'll have to wait for pic's until the guys are back in harbour on thursday or friday now.

[peter radclyffe]

An off the peg vessel can be bought new for between 250 - 350k , the changes i have in mind do not interfere with regs . A lower centre of gravity can only improve stability . Rigging is not a problem as such but ideally it would be a simple case of unshackling the dredge bar and hooking up a net , no shore time required . Cats are great but no storage below decks means a run ashore on a daily basis . Distance from shore is limited only by fair weather conditions and the need to land fish while it's still fresh .

P.S Gemini workboats are by far and away the UK's number one cat builders .
this is interesting, i recently priced up a new 14 mt wooden fishing boat, without fishing gear & yes, 350 k
i guess you have looked at mcduffs site

[peter radclyffe]

you may like to ask napier co arbroath, to price a design

[Jenny Giles]

Thank you Jenny i don't know what i'd do without your unprecedented intelligence .


Sorry if you took my joke the the wrong way. I didn't mean to offend. It just seemed a bit odd to tar all architects, US or not, with the same brush.

If you have ever watch the UK show Grand Designs you will have seen that "architect-free" designs can be way overblown too.

[helen07]

Thanks everybody we are now getting to the crux of the matter and Jenny i appreciate what your saying but some go forward with their eyes wide shut and others put to much trust in architects , my Grand design would begin life as a doll's house and then be handed to an architect whom would be asked to use his profesional judgement and skill to turn it into a reality . Words can be misleading but solid matter is impossible to ignore . A few quid for a model boat is nothing if it ensures the real equivalent meets every expectation .

With regards to dimensions - unfortunately i'm in touch with my partner only trough txt at the mo but i asked what was the most comfortable boat he ever worked , it turns out it was a Dutch beamer 20m length - 6.5m beam - 2.5 draft , he said the test of a good boat is the Irish sea because being such a small stretch of water it gives a more violent motion , a boat doesn't so much rise and fall with the water like it does in the North sea , instead smaller waves slam into the boat .

I've ruined this now because he want's to know what i'm up to , i was hoping to impress him with my ideas .

Peter Radcliffe have you investigated the possibility of having your boat built in the Baltic states ? Latvia and the likes have huge shipyards and the average wage there is just £150 a month ! , I have discovered by accident while researching boats that many of the yards closer to the UK actually buy hulls built in the Baltic to increase their own profit margins . Of course steel and wood are very different and i would expect wood to cost considerably more in this day and age but i thought it might be worth mentioning ?

[Jenny Giles]

Thanks everybody we are now getting to the crux of the matter and Jenny i appreciate what your saying but some go forward with their eyes wide shut and others put to much trust in architects , my Grand design would begin life as a doll's house and then be handed to an architect whom would be asked to use his profesional judgement and skill to turn it into a reality .

My Grand Design is an underground house. If an architect dares to interfere, well, hey, I already have the hole dug, so watch it you bow-tied git! :)

[helen07]

Only the tow bar needs 7.5 metres deck space so dredgers can be emptied , so why not simply take a hull like the one pictured in the link below which is supposedly very fuel efficient (it's 15m L , 5m W ,and 2.7 draft) , then just create a 7.5 wide platform at deck height on the stern like a shelf ?

http://www.fiskeskibe.dk/upfiles.aspx/91/5F20CB10C8D44AFBB2EC11A490C59E9C.JPG

It seems viable to me but like i said i'm no expert so what do you all think of this ?

[JRM]

Now you are talking Helen

This way allows the underwater hull and most of the above water hull to be "normal" proportions, but wider higher up where you need to land the beam/dredges.

Main thing you need to be careful about is the "outriggers" or "overhang" at the stern are not
a) too close to the water
b) too flat
c) too flimsy

.....or the sea will slam under them and cause a lot of problems you dont want

However, it is an idea worth persisting with. Aircraft carriers have wide square bows (for launching aircraft) above a narrow fine bow, so the principle is used already (they manage to get their deck many metres above the sea and still have to be careful about wave slamming under their overhangs).

If you go on with suggesting hull proportions, listen to what baeckmo says - he seems to know a lot about fishing boats as well as ship/boat hull design.

By the way - in your previous post you referred to a Dutch BEAM trawler. Trust you know that (deep draft hull) is not the same as a Dutch MUSSEL dredger (shallow draft).

[helen07]

Thanks JRM , the dimensions of the Dutch beamer are given , apparently it was originally a mussel dredger , 2.5m seems pretty shallow for a 20m boat , a fluke design maybe ?
I would guess the deck on the boat pictured would only be maybe half a metre above waterline and so the extensions would definitely dip in poor conditions . Obviously this would cause drag but if designed correctly (by a pro) might it not act as a sort of stabiliser by increasing displacement when the boat rolls , if you get what i mean ?

[peter radclyffe]

thank you Helen, yes latvia is cheaper
but i dont want a boat built
i am an s. f. i .a builder

[helen07]

Peter i feel a little put out here because i can't offer any advice in return for the advice i get . I took a look at the boat you are building and was very impressed . It got me to thinking about a guy who many moons ago bought a similar looking boat and had another of his hair brained ideas for money making schemes .
He dug a hole , covered the boat in vaseline , dropped it in the hole and concreted around it . He then removed the boat and used the impression as a fibreglass mould . He was a long long way away from being a perfectionist but he did manage to sell 2 copied hulls before he moved on to his next adventure , selling ice to eskimoes or something similar (he was that type of guy)
I only mention this because it seems likely someone with your skills might very well make something of his idea if you were inclined to try .

[peter radclyffe]

thanks Helen, what a great idea, good luck to him, i am not qualified to advise you on your design even tho ive studied all i can about them, i prefer a boat with deep draught tho i know this is not possible in most of our harbours, thinking more about latvia, i could not trust them to build it without me overseeing it or a surveyor, the logistics can work for someone who knows the terrain , & for all i know they build good boats, however, i cant gaurantee an unknown build, & you know how hard it is to get any boat right let alone a fishing boat with all its various systems, there is also the wolfson tank testing unit at southampton which you may know of

[baeckmo]

I have been using one yard in Latvia for a couple of smaller (30´) al hulls, but it does take a lot of supervision. This was when the lat economy was on the way up, and after some time they became a bit "cocky" and arrogant, so I quit. It is not recommended unless you have a local connection you really can thrust.

On the other hand I have good experience from Russia, both with al hulls and with 15 m vessel "your" size. But again, it does take extra time for visa and travelling aso, plus the absolute need for professionalism and a thrustworthy local connection in all directions!!!!

[helen07]

Sorry to be persistant but can someone please explain to me why the dimensions of the boat in the link below cannot be increased to allow for a
7.5m beam ?
I can't do the math but if every measurement is expanded surely we would end up with a tried and tested design very similar in dimensions to the
15m L - 7.5 W - and 2.5 draft i originally suggested ?

http://www.findafishingboat.com/detail.php?aid=12200

[Ad Hoc]

As you can see from this MCA report
http://www.mcga.gov.uk/c4mca/research_report_484.pdf
Most boats of this type have an L/B ratio around 2.7, ie for a 7.5m beam => L=20.25m as a minimum..
Whereas using the beam as a guide, of 7.5m the length is around 25~35m in this report, for larger vessels.
http://www.mcga.gov.uk/c4mca/rp560_final_report.pdf

[apex1]

You can forget about Latvia for boatbuilding. The low wages are history, and the quality was hardly at the Russian or Polish level. And how would it be? They did not have much Capacity in The three Baltic states, during soviet times.

[helen07]

Thanks Ad Hoc for trying to help but i only read the small boat link and unfortunately it convinced me of nothing at all .

It seems to me a typical exercise in political hot air blowing . No consideration is given to ballast or weight carried above deck height - so should we assume both are unimportant factors ?

It seems to me that the software used would get very different results from identical hulls if one had nothing but a sail added and the other had maybe 10tons sat on its keel . Like laws there is a general acceptance of what is usual but every law is tested on a case by case basis as the variables deny unquestionable calculation .

Please except i am only trying to understand now and nothing on here or in all of what i've read on the internet seems to help , as far as i can tell boats have never been built half as wide as they are long because there was no need for them to be built this way .

[baeckmo]

........... as far as i can tell boats have never been built half as wide as they are long because there was no need for them to be built this way .

Naah, I would rather say that just any proportion, weird or not, has been tried somewhere, sometimes in mankind's fiddling with floating objects! It has been a development of shape like "the fittest will survive". You may rest completely assured that the request for deck space and stability is not unique for you! One example that comes to my mind is the disc-shaped "Popoffka", L/B=1. It was not exactly a roaring succes..... . If there were a successful variant, we would have seen it somewhere!

I'm quite certain that we could find both tank tests and de facto built boats with any extreme proportion you could think of. Please excuse me now if I become patronizing, but before you dig yourself deeper into that hole; listen to what experienced researchers, designers and sailors tell you here!! YOU CAN NOT SELECT BOAT PROPORTIONS AT RANDOM AND EXPECT TO ESCAPE BAD CONDITIONS ALIVE! Or are you in fact trying to get rid of the ol' man.........?

[helen07]

Hmmm ........ well he is insured !

So am i to accept that an RNLI lifeboat will only float if it is the size it is designed to be and if every dimension of the original design were increased at all it would sink ?

[baeckmo]

Nope, but it would not make a profit as a fishing boat either.......

Helen, for some reason you are not focussing on the issue where you and your husband are experts, namely what goes on on deck and in the loads departement, given a set of physically relevant restraints. If the restraint on beam is too sharp, the ONLY way to get around it is to go multihull!

Before you have settled with at least a rudimentary specification (Ad Hoc's seven points), a discussion on hull shape is simply a waste of time. Tomorrow I will send you the pictures I promised, then I will leave your thread before the trampomobile brigade and perpeetuum mobile inventors crowd in your short, wide and shoal hole!

Good Luck, and take care, it's mighty wet out there...

[apex1]

Tomorrow I will send you the pictures I promised, then I will leave your thread before the trampomobile brigade and perpeetuum mobile inventors crowd in your short, wide and shoal hole!

Good Luck, and take care, it's mighty wet out there...

Sorry,
I could not resist to save that (in case Bodo will edit his post) it´s just so good, and so sad either, `cos it´s true................:D

Richard

[helen07]

Who is designing anything ?
The boat for sale on findafishingboat is perfectly suitable for the job at hand , however it is ideally suited to a 6ft tall man . If say for the sake of discussion a 9ft tall man wanted the same boat , does it not stand to reason that he could order it in proportion to his size without altering the boats seaworthiness in any way ?

[Tad]

helen....

A search on the "Laws of Mechanical Similitude" will answer the question on scaling a given design.

Scaling from 6' to 9' is 150%.

If length, beam, and depth are increased by 50%......she'll have 3.4 times the displacement, 2.25 times the wetted surface, speed will increase by 22%, 3.4 times the resistance (at the higher speed), and 5 times the stability of the parent vessel.

What this all means is that her handling (seaworthiness) will be completely different.....good, bad, or indifferent remains to be seen.

[helen07]

Thank you very much Tad for an informative answer . This let's me know that it is worth looking at increasing the all over proportions of hulls already in use . A pro would have the software and whatever else was needed to test the the boat long before anyone fired up a welder .

[gonzo]

Helen07: There are harbor tugs built on a 2 to 1 ratio. They have a limited scope of use, and never offshore. A beamy boat like that would handle poorly. At 3 to 1 they are already pigs. I wish the legislators spent a couple of weeks at sea on the boats they are help create with their regulations.

[helen07]

Yes Gonzo and in an ideal world all judges should spend a month in prison .
I keep looking at tugs and wondering , put a deep v hull beneath it and drop all the weight below the water line with a much deeper prop , it would bob up and down like a yo-yo maybe but i just can't see why it would roll and worse than an old wooden trawler . I've got pics of my guy standing on the side rail up to his waist in water emptying dredgers , the boats rolled nearly 45 degrees and buried halfway up the deck in green water , and he couldn't even remember it happening a week later when i showed him the pic it was so run of the mill !

[gonzo]

He's a lucky guy to have someone like you worrying over him. :)

[baeckmo]

So, if pixels and electrones are with us today; here a few pic's of the "good" vessel I spoke about. It has an underwater shape resembling the red one you showed hanging in a crane. If you want to persue the search for short, wide fishing boats, you might look at Norway. They have a 15 m limit, forcing the design of rule cheaters. One of the most extreme I found has a L/B ratio of ~2.4:1.

[peter radclyffe]

http://i791.photobucket.com/albums/yy195/helpME7/img260.jpg
heres one of 2 we built in appledore for peterhead, tho standard ratios, 70ft x 23ft

[Tad]

Short, fat, monohulls are subject to capsize according to this paper.....

37101

Looking at a few wider monohull types, excessive and rapid motion seems to be a common complaint. Cousteau's Alcyone and the Ramform hull used by WHY are two examples.

Thinking out loud I would suggest investigation of a Trihull similar to that shown below. The form is a catamaran with a large storage hull added on centerline. The shape and volume of each hull could be tuned to obtain better motion characteristics......perhaps. The platform is 15m by 7.5m, as shown the underside of the platform is 1.2m above waterline. I suspect one would want it higher forward and perhaps lower aft. Probably the space between the hulls could be partially filled.

First though is that the center hull could be used to store your catch while the demi-hulls carry machinery. Fuel could be in the bottom of the center hull or in the demi's.....tuning again????

Displacement to DWL is approximately 84,000 pounds, PPI is about 3500 pounds. So 4.5" down will see her at 100,000 pounds (45 L tons). The sterns of the demi-hulls need modification for props and rudders, etc.

37102

[helen07]

Thanks all , i haven't been able to reply my laptops fried .
I have spoken to my guy about it over the weekend and it seems i am wasting my time . He said a trimaran would be the way to go but he'd have to rob the bank of england first , so thanks for the suggestion Tad .

He also said British fishermen are fast becoming extinct , it's a toss up who hates them most , the UK Gov or Europe . And as far as safety goes every single suggestion put forward by so called experts makes the job more dangerous . To explain he would , if he needed a boat , look for a wooden boat too big to meet the rules , he would then take a chainsaw and make it short enough to keep the pen pushers happy . The rules have made suitable boats ridiculously expensive so buy a wreck chop it up some more and hope it floats long enough to earn the cost of a replacement wreck before it sinks with you on it ! . If it doesn't well a few dead fishermen will justify another few million being wasted on expert reports .
Dipping a beam (beam trawlers) while leaving a tea boy at the wheel steaming home in heavy seas is the greatest cause of capsize in his opinion and no design of boat is built to withstand that kind of negative .

Personally i have learned through this exercise that the only way to know what will and won't work is to try it and see the results . I'm told i cannot just increase the scale of a boat for all sorts of reasons - yet millions are spent testing "scale models" in tanks before millions more are spent building the model in real life scale ?

It's been interesting though and i thank you all for your comments .

[peter radclyffe]

thanks Helen

[Tad]

I don't think anyone is wasting time talking about safety, economy, and the future of commercial fishing. These issues are just as important in every nation with a coastline. Here in Western Canada our fishermen are also endangered, due to mis-management, un-regulated fish farms, allocation of declining stocks to other parties....etc.

Almost no one on this coast can imagine building a new boat aimed solely at commercial fishing. But there are endless refits going on to better adapt to current conditions. In a lot of cases these include sponsons and deck extensions to carry more pots.

Helen....it's not that you cannot scale any hull up (or down) and not have a boat....you definitely will, but you cannot arbitrarily scale a hull equally in all three dimensions and expect to have the same performance...this will not happen.....as the testers of scale models will attest to!

[helen07]

As i said earlier Tad , the only way to know what works and what doesn't is to put theory into practice and gauge the results . I have read the reports some members were kind enough to offer and many others besides , and in every case the report focuses on maybe 2 aspects relevant to fishing boats , this is despite the fact that fishing boats are subject to maybe 10 different inevitably interwoven aspects . This makes all calculations given in the 2 aspect reports utterly worthless .

I can think of no other vehicle on land or sea that is exposed to the extremes of the average fishing boat , if the rule makers would just accept that fishermen , as hardy as they may be , do not want to die , fishing would be much safer . The current rules mean a skipper and 2 crew men can be hired at a decent wage for less than it cost to fuel a boat , this is without the constant maintenance , the cost of gear , depreciation , a fish market thats failing because fishermen are not allowed to deliver whats required , diseased shellfish caused by overpopulation of the grounds , and keeping the pen pushers happy .

If the powers that rule want safer fishing then let the men who risk thier lives daily earn enough to buy a newer safer boat maybe once a decade .

[JRM]

.

Personally i have learned through this exercise that the only way to know what will and won't work is to try it and see the results . .

Fortunately, that is not the way the real world works. Everybody would go bankrupt if they "tried things out" without designing them first. Fortunately, all ships and most boats are designed before they are built and largely do what they are meant to do. Some of these ships and boats have even been designed by people who have themselves worked on fishing boats.


.

I'm told i cannot just increase the scale of a boat for all sorts of reasons - yet millions are spent testing "scale models" in tanks before millions more are spent building the model in real life scale ?

.

I dont think anybody told you that. You are dead right, model tests are used to examine the performance of full size boats.

Finally, I agree with you that the UK fishing industry is being buried under a sea of bureacracy, with the UK MCA applying the full force of regulation to fishing vessels since they can no longer apply it to a huge UK merchant fleet. What they expect small 1 or 2 man businesses to do is unrealistic.

And at the end of the day, for your problem, I dont think anybody could justify the financial investment in a newbuild boat built specially to solve the problems you started out by describing.

The economic return would be too small. You would be better buying an old but large boat to do the job - however imperfectly. As you probably know, they can hardly give them away these days.

[helen07]

In the real world when profesionally designed equipment fails a jury rigged set up thrown together using whatever is available , shackles , nails , sleeping bags , fender tyres , cutlery , wellington boots , even underwear elastic has saved the day and perhaps the lives of just about every fisherman worth his salt . He says we buy what is supposed to work then hack it and chop it and weld it altogether again so it actually does work . The idea is then copied and sold back to us because we are considered to stupid to notice .

From me , the lack of suitable used boats is bad now and it is only set to increase and a new build might soon be the only option for those who want to stay at sea . I was investigating possibilities only a new build might allow , but i agree completely that nobody can afford to buy new just to remedy problems even if the problems might prove fatal , such is today's fishing industry here in Britain .

[waldoswhere]

your design is what iam looking at ,,,for years 52x18x9ft with jets full displacment...all steel with fly bridge aft for offshore shrimp fishing here in mexico...looking for some on e to help with the cad end of it can do scale drawings ...am a boat builder by trade..just helped build five yachts in tacoma washungton...two for uhaul...we are thinking about a ship yard in mexico...material is 700---800dlls per ton