Building a 21' cruiser with inboard diesel and auto

[lucas12]

I've been trying for 3 months to find my ideal boat, but no luck.
So being a motorhome designer I've decided to make my own.
What I was thinking was using a glass hull 21' that is very ocean worthy but a planing hull, and converting it to inboard/shaft drive using a car diesel to be marinized 2.0 turbo diesel with the auto 3 speed.
The idea is to take on water ballast for rough seas that decreases volume (weight) at speed (calmer water) so in essence the boat would act as a semi displacement or a sport fisher (planing hull) all the interior panels would be alumium honeycomb which is 11kg per 8'x4'x 20mm board with incredible torsional stiffness, this would also do the bulkheads etc.
My question to anyone the wiser (which wouldn't be hard) is "What could be wrong with the concept if any ?
Oh the other factor is I want to spend $20,000 and so far looks achievable.

[lucas12]

I've read just about every thread involving "using auto running gear" and there is definately one side of the fence or the other, yet no examples of proof as to what works and what doesn't. I've also come across some examples of people using 2 speed autos in ski boats and they work fine, one comment was some people turn the auto upside down to enable servicability, even that seems drastic, as it's not hard to pull out an auto once every blue moon. As far as marinising and air flow and cooling, I can't believe marinised basicly means being able to pump cold salt water into any engine, that's insane engineering ! no wander boat motors are so unreliable ! No offence to any purists but you're all being ripped off buy the greatest consumer scam ever.
Fair enough when T model fords were around, but it's 2006 and we can almost catch a plane to the moon, and we're still pumping cold, corrosive water through an engine that generates heat and relies on heat soaking in order to run itself in, a piston is round so is the matched bore, if you pump cold water down one side and have hot on the other even a few deg it's going to last a very short while as they seem to. God help the poor engine if it ever ran dry even for 1/2 a second.
Another suposed down side to the Auto gear problem was the electrics, I went on the hunt looking at new boats over the weekend, the electrical design is the same as Toyota, I wouldn't use a petrol engine as the engine bay wouldn't have enough airflow but if I had a car that had the slightest hint of petrol smell I'de take it off the road, because it's illegal ! and dangerous, so why let a motor in a boat get to that stage ?
Anyway I'm sure I'll have some challenges getting the set up right, but for $2000 as aposed to about $20,000 or so for the same power theres no contest especially when actual thoughtful engineering has gone into it.

If you can't join em beat em !

[tom kane]

There are a lot of contradictory opinions about how a boat should be designed (especialy in boating forums)and like you I am not impressed with many boats that are supposed to be professionaly designed.That includes hull and propulsion.Like you say salt water running through any hot engine is silly,and of course there are alternatives.How you design your boat may be dictated by your local Boating Regulations and resale value,as your boat design may not impress others.I believe you have good ideas which are practical,but can you put them into practice,or more likely will you be allowed too.Automatic gearboxes from autos have been much used in boats, some with direct drive instead of torque converters,but correct ratios are a problem used in boats.Five speed automatics for boat have been used.If you do plenty of research about what others have done and study, you should have a lot of fun,but it will be expensive unless you can do the work yourself,as it will be difficult getting others to comply to your designs because it is not conventional and well understood.

[lucas12]

Thanx tom, someone who thinks latteraly is always worth listening to.
I will be doing all the work, I've done some pretty awesome conversions of cars and buses, my ideas are always based on budget and not losing money when I sell.
Since you mentioned "hull design and propulsion" that's my only grey area left, I've thought out the whole cooling and ventilation system as well as controls etc for the engine and the shaft. I even joked about using PARK on the auto to drop the anchor LOL. It's not that silly ??
I did ask around about putting a skeg on a planing hull, one theory was it won't want to turn, and if you did at high speed, it would lean out not in, but if it was shorter and curved would it follow the curve of the turn or is just a theory, because I can't remeber seeing a displacement hull leaning into a turn ???????

[tom kane]

I am sure you know that you can beef up auto boxes like the racers do by adding extras plates and redrilling the crutial holes ect.,to take big HP.The gear change is much better than clonky outboards or inboard/outboards and change at higher RPM,especially diving into reverse when you need it.There are some interesting books written by top American(must be top) power boat drivers if you have a look around,I have titles somewhere.A trimmable shaft drive that can be run as a surface piercing drive or as as a conventional shaft drive would be a good choice for an adverturous designer especially with say a modern five speed auto box,and tops in handling all sea conditions and docking and long service low maintenance.Changing down a gear or two in heavy seas gives better control.

[lucas12]

Hi tom, I had a guy in south Australia lined up to source the hull, but he's no longer got the moulds, so I'm looking for an appropriate hull in plan form, to form up to 28' x 8'.
Bruceroberts never returns emails so I've given up on that, Glen L has alot on offer all with 18deg deadrise. Would that hull design suit with prop below duck board, My main trips will be ocean up 5 km off shore on the east coast of Oz the idea is to travel to an area, launch and travel up or down the coast line for 2 weeks at a time, and camp ashore on rough nights with my 2 kids, the design criteria is to be able to manage 2 toddlers, a boat and everything else in reasonable comfort and safety. The worst case senario is big swell and being able to turn around and head back to shore in good time, as well as fish comfortably on chop. Don't worry people think I'm mad with what I get the kids involved in, but at their tender ages they absorb like sponges and adapt very smartly, each new challenge gets easier for them and they love it. No kid of mine will ever get a playstation. I looked at surface drives and the engineering seems fairly robust and simple, is that really the ideal drive ? And what are 'Trim Tabs' ?
Simon

[lucas12]

I know what trim tabs are now, how basic, it would be easy to make a set with air cylinders compressed off the engine and regulate the pressure (set and forget) Do you think they are an economical alternative to a surface drive with economy sacrifice ?
Cheers Simon

[lucas12]

I've been researching all night and just had to add one more thing before I get some sleep and get ready to solve other peoples problems tomorrow at work. On the motor homes I pressurise the chassis and containment and storage areas to keep dust out, just with a duct from the outside airflow, if I use a compressor like a modified auto aircon compressor to operate trim tabs I could also make the hold area leak proof to 1 or 2 bar, the seals would also be pressurised to seal airtight and the bulk heads would take less stress as the hull area would become structural against force as a whole. It might be overkill especialy if I spring a leaky seal and the thing farts !

Simon

[tom kane]

If you want to keep up to date in system controls,research interceptor plates (which react faster) instead of old trim tabs.

[lucas12]

Thanx tom, I'm going to take all the info I've collected and see how I can come up with a designed outdrive system that is ecconomical to produce without castings, solidedge is good as a design tool especially sheetmetal, which if it can't be folded the software won't flatten the model, during my research and modeling for Motorhome componentry I've established cheap ways of replicating injection moulding, instead of expensive dyes, I've come up with materials and mould designs formed on CNC that can be vacuum formed, I'm currently working with a fibreglasser to educate him on vacuum techniques and cheaper pattern making techniques to be able to quickly change mould sections with costs covered on the first unit sale and profitabilty there on. Hopefully in a year or so my boat will be on the water.
I guess my only hurdle will be acceptance of it's engineering, but saying "Hey we're not stupid enough to pump salt water into our engine" I might ruffle some feathers ? The intension is to create from the 'KISS' principle 'Keep It Simple Stupid' so that the hull design should be 'Basic' to pruduce the mechanical components will be cam type in function from standard sections and lazer cut components (raw but clever) and eventualy maybe even a steam engine (hey were surrounded by free fuel) and webasto make very efficient burners that could just about burn any fuel as a flame producing fuel perhaps fish oil ? I've been hooked on the issue of oil reserves lately and saw a show on SBS last night that pretty much confirmed what I keep preaching "Theyre not going to tell us when it will dry up, we'll just wake up one day and they'll be none left" No plastic, no rubber, no transport, no food, no medicine, .................. and so on. The world is 25% iron and I'm guessing 65% water, Iron burns well, and water expands 70,000 times on combustion.
Food for thought !

[Gilbert]

Most marine cooling systems do not have cold seawater going into the engine block. The raw seawater is normally pumped through one side of a heat exchanger and then into the water jacketed exhaust manifold and then, if it is a wet exhaust, out the exhaust pipe. Systems using raw water are most often intended for fresh water, and those intended for salt water use usually have heavy castings to give reasonable life with the corrosion that can be expected with salt water. Then there are closed systems with 'keel coolers' which transfer the heat to the water outside the hull. You could even use a closed system with a radiator but that would require getting rid of a lot of hot air.

[lucas12]

What I had intended to do was lay the aluminium radiator in a tank that the raw salt water is pumped into, which would then pass through a s/s jacket over the exhaust, basicly the same thing, as far as air cooling, diesels run colder than petrol engines, so I was going to keep the viscous fan with air being taken in through a grill on the engine cover (box) and duct out as much as possible to the stern. once I work out my weights of the boat I'll have to try to work out how much torque is needed to push at 1:1 in top gear at say 30 knotts at 2500 rpm, I think a 2.0 turbo diesel will have enough torque and hp to hold the prop against the water at 2500 rpm, It's alot easier to work out a cars requirements, with some experience, so I'm flying blind a bit. It's a new factor for me (calculculating power, drive ratios, and constant wheel spin)
I need to do prop research !
As far as hull design I've got the basis of ideal deadrise, for the length of the plane but what is the ideal length of the plane in % of the boat, in other words "When does the keel start to rise up to the bow" I would guess that would depend on the engine position, seeing that I'm centraly mounting the motor, does that mean my planings section (flat from the side profile) would start to finish just ahead of the centre of balance, or just behind to give a softer ride ??????
I still can't determine from other design plans what dictates inboard position centre, stern, or out board, when the hulls all look the same on the PDF's
But the designers state what the engine layout can only be one for the model. or does it purely depend on weight distribution of the whole vessel ??

[lucas12]

I've read a few threads on hull design, NUP ! I think I'll build my first boat hull from plans and look at it later when I've got kids who are independant and associated staff as well ! I've decided on Glen L's Monsoon 22' cruiser which should be do-able as a plug made from cheap ply and glass then pull a mould. Most of the mechanical components can be sourced from general suppliers for the surface drive, which at this time will be a porche CV joint and some other fabricated bits. Can't wait !
30 knotts is specified to req 180hp for the monsoon 22, hopefully a diesel with the right torque and 0.8:1 top gearing will reduce the hp required to about 100hp.

[tom kane]

It sound as though you are having a blast with this project,and using standard parts to build a good surface drive can be easy even if you use dynamic or passive steering.You do not realy need a lot of trimmability with surface drive but if you build a drive with 20 degrees of trim you can run the drive as a conventional drive if you do not like the surface drive option,and use standard design props,which are cheaper and you can access a bigger range of pitches without being held to ransom by a surface drive prop supplier.

[Willallison]

30 knotts is specified to req 180hp for the monsoon 22, hopefully a diesel with the right torque and 0.8:1 top gearing will reduce the hp required to about 100hp.


You can't simply change down gears, use less power, and still go the same speed. Sorry to pout cold (salty;) ) water on your plans, but that aspect of your plans simply won't work.
Propellors are optimized (generally) to give the highest speed at an engines max revs. At any other speed they are less efficient. There's a reason why you don't see boats running around with variable transmissions....
Sure there are 2-speed gearboxes available, but generally they are installed in one of two applications. Underpowered boats can benefit as it allows them to get onto plane with engines that would otherwise be overloaded. Also, high speed boats - particularly with surface drives that have huge blade area that is too much for the engine at slower speeds - can benfit as it allows then to fit higher pitch props.
It's not that the boat won't work with a multi-speed box, it's simply that it's complexity for complexity's sake. There's no real gain over a 2-speed system, which can be achieved in other ways - like a torque-shift prop for isntance.

Nonehtless - I admire your adventurous spirit!

[lucas12]

Sorry but I disagree ! The prop is held at it's rpm to achieve 30 knotts by the hp of an engine and it's torque. which is attatched by the shaft of what ever drive you use. Boat engines rely on hp not much torque gearing multiplies forces of torque or decreases the amount of torque to the driven item (prop) in a higher gear 0.8 : 1 to hold the props rpm the engine will need more torque to hold it before bogging down, diesels work purely on compression and have massive torque for their capacity compared to a petrol engine for eg a BMW 3.0 has 500 nm of torque a 3.0 petrol engine has about 275 nm of torque. Torque is real power to move resistance Hp is an engines ability to breathe and spin it's masses by throwing it self efficiently, Hp is far over rated and stated , it's torque that pushes mass hp is weaker and efficient only without load. A prop has little load a hull has great resistance, which requires torque to move it againt the water, so the torque of the diesel will hold against the waters opposing force.
If most drives are 2:1 this double the value of torque of the engine being transfered to the prop, a 150 hp outboard is basicly a motorcyle engine with buggerall torque about 80 nm, therfore 160 nm of torque is being used
A diesel with 350nm reduced to 0.8 :1 drive is reduced by 0.8 which is 280nm of torque I still have nearly double the power of a 150 outboard. which is the compensation for less hp, which to re itterate is useless in a boat because of it's constant resistance>>>>>>....!!!!!!!
To put it simply all I have to do is spin the prop at the right rpm for 30 knotts and it CAN BE DONE with TORQUE!!!!!
The point of my statement earlier in the post, is that the 'marinised world is old world thought and has little developement since it's coception. I know I work in robotics where every day I re invent the wheel 100 different ways and I'm always working with every force immaginable not by vectors and trojectories but with real life time and resistances, because all the calculations in world take far longer to input than a simple test (practical)
Gearing and resistance is very very basic. it's simply X or division by the ratio.
Now to educate you on why a marine engien has loads of hp and is driven through a reduction box.
Outboards need to be small and light, so a small engine can only produce so much torque and not enough to push a prop at 1:1 so it's run through a reduction box to increase it's torque value to the prop the hp gives it a higher rpm which equivilates to less load allowing the motor to use hp to spin more freely with less resistance. To get the same result with 1:1 drive you need twice the torque of the little outboard and half the hp (Diesel does that exactly!)
The reason not to use stanard marinised drive line is to get the same results at 10% of the price. The bonus of a gear box of at least 3 forward gears is to provide excellent prop speed control at lower speeds eg while docking.
The other benefit is to achieve fuel ecconomy at reduced rpm. I'm not saying I know exactly how the drive will behave but the fundamental equasion is correct. As far as complexity, compaired to standing a motor cylcle engine on it's end, stuffing all the plumbing into close fitting cover is complex, having more moving parts in modules is far less complex and far more reliable seeing Trust me I've built bikes with quad cams 4 carbs and gearboxes that are supurbly made but lack robustness, they have a life cycle of about 80,000 kms, A lexus V8 is the same i design but for sheer volume of internal parts they are robust, and good for 500,000 km's My lexus V8 in 900kg car sits on 8500 rpm for hours under the most strenuous conditions and speeds of 150 mph, my kawaski 900 breaks stuff every 5000kms at 11,000 rpm. The point is motorcar manufacturers design for reliability because the market demands it, noone rides their bike day in day out so they are built witha lesser duty cycle.
As with marine engines IT'S A BUSINESS AND DON'T BELIEVE WHAT THE SALES MAN TELLS YOU. because he does believe what the top guy says it's culturaly ingrained into the system.

[lucas12]

Sorry I've had 2 weeks of politics and trying to work out technical areas on a new system, and I'm tired of explaining METHOD, and how to get something right the first time.
Tom, I think that you're advice is without doubt "Valuble"
I agree about the surface drive options, because props are going to be my easiest variable to change in the drive, I was thinking of having the trimmable shaft drive able to nest up into the hull in a small cavity, with the prop able to surface just outside the stern. (under a fixed duck board) just to allow beaching etc as far as rudder, that would be mounted onto the duckboard, which could be unlocked to raise the rudder, or spring loaded and curved to lift automaticly on hitting something, Maybe cylinders ????
Actually seeing that all my cylinders are slow reacting I might look at the feasabilty of using the aircon compressor to pressurise soluble oil /water in conjunction with air cylinders 100psi is heaps then I can use standard airline and fittings, all over the place.
Hydrualics is too expensive and overdone for the forces required and electrical is too fragile in a corosive enviroment.
And at the end of the day I want the best and most versatile boat that is extremely reliable, cheap to service, and affordable.
My car with the lexus V8 cost $30,000 in parts and is as well engineered as any sports car in it's class and a hell of alot better looking and without doubt AWESOME.
And all made from wrecks, Mercedes, lexus, toyota, datsun, Nissan, and alot of fabricated stuff. Unfortunatley the Auto market is constrained to cultural ingraining of ideas, I'm hoping boats are a bit more liberal, seeing that there seems to be plenty of small manufacturers making a living.
The only market constraint seems to be hull design, wright or wrong it's what most boat buyers seem to judge on. so the rest is just something that won't get serviced or will be by someone else.
How do I tell a buyer that they should take the boat to Toyota for engine service, and Festo for anything else ???LOL
I think self service manual is mandetory, when I'll market to the budget conscious man, (or woman) with a passion for boating with only 50-60K not 110 or so.
And the other concideration is weight and keeping the tow vehicle affordable also. Thats where most of the aluminium honeycomb will take place. I'd like to keep it down to 1000kg fully dressed plus trailer.
Foam core hull and multi bulkheads in honeycomb as well as floor and cabin and furn. the transmission only need to be small, so front wheel drive is the key for the donor car, or an adapter plate for an other tranny of the same motor brand.
Once I get all this set in my mind I can start work on functional ideas such as driving by lcd screen and infra red for night driving, with all the forgiveness of space in the open water there's no reason a plc couldn't drive all the available technology to set course on true auto pilot. MAYBE.
I mean you can teach a plc to recognise wave height and conditions to alter pitch and speed and direction. But there goes the budget !
I'm ordering the plans after easter, so I don't think about it while I'm on holiday with the kids in Pambula, I m taking them out on a charter to see how they go in choppy seas, and then take the innevitable plunge into wee hours of the morning creating my dreams.
Simon.

[Willallison]

Lucas - just ask yourself this simple question. If it were simply a matter - regardless of speed, size, weight etc - of changing the gears and prop, then why aren't all boats powered by a little Honda 4-stroke and simply geared to the required speed?
Answer - because it wouldn't work.....
I suggest you buy a book called "The Proellor Handbook" by Dave Gerr. You will learn much

[lucas12]

Sorry mate learn some physics! I already explained it plain laymans terms.

[lucas12]

There is only force and resistance in moving an object, force is measured in Newton Meters, opposing forces are resistance to the force.
Torque moves against resistance.
Like I explained it an outboard needs to be small and lite to hang off the back of a boat therefore a small engine is used because of it's weight they are motor bike engines that have no torque to increase the torque value a reduction box is used 2:1 means doubling the torque effect.
to get exactly the same result with a 1:1 drive you need an engine with twice the torque the end result is exactly the same , the prop spins with the same force, the hull travels at the same speed, BUT your engine spins half as fast. like I said Horse power is using the engines innertia to mimick torque, simply by throwing mass, the result and physics is EXACTLY the same except at half the rpm.
Force,Mass,Resistance requires one value of force to move it, how you achieve it is called ENGINEERING I am a Mechanical engineer. It's what I do for a living and if I'm wrong you canhave everything I own, because it's what I get paid for, so every job out there must not be working and I'm just a conman selling boat motors. LOL

[tom kane]

www.stepdrive.co.uk is one of the many attempts to introduce multi gears to boats.Racing cars have many gear options for the days racing.Boats can make use of many gear optioins.especially with a trimmable shaft drive.See page three of Paul Kamens N.A. article Surface Piercing Propellers.www.well.com/user/pk/SPAprofboat.

[Willallison]

If you re-read my posts you will see that I've not once said that there's no value in variable-speed drives of one sort or another. I simply stated that you can't take a boat that normally requires 150hp to do 30 knots, stick a 100hp in it and still expect it to do 30 knots by changing down gears. When you get in this whiz-bang car you've built (love to see a pic...) and roar off in 1st gear, you don't do 100mph as you would if you were in 5th....
There WILL be some overlap - where the smaller motor, normally unable to get the boat onto the plane - can change down a 'gear'. Once on plane you can change up and attain a higher speed that you would otherwise have done with a non-variable system. Hence my recommendation that you look at the torque-shift props that are readily available.
But - since you're a mechanical engineer, you must already know everything about boats - cause that's what they train you about at uni - so as a lowly student of yacht design, I'll just butt out and look fwd to seeing your 30 footer come whizzing by, powered by a lawn-mower engine with a 300 speed gearbox....;)

[SamSam]

I've always heard auto transmissions aren't built to handle thrust as generated by a propeller. Austaralia? Sam

[lucas12]

Will, My intension if not clear is to source a motor with enough torque (turbo diesel). Please understand that horse power is not a usable force in equating power, it is some times and all too often used to state the overall power ability of a motor that is general terminology used to give the layman some idea of how much power an engine has.
I am assuming the quoted requirement of 180 hp for the 22 monsoon is an old engine designed around the time of the boat (about 20 years ago) in those days a 180 hp engine would have had about 275 Nm of torque, I need a modern engine with at least 375 Nm of torque, A modern turbo diesel with quoted Hp of 100 hp will have about 350 + Nm of torque.
So forgive me if I missed the step of quoting Hp in the beginning but I was relaying the info that is available for the design of boat hull I will use.
So for arguments sake or not to (preferably) Lets stick to torque figures not hp.

In regards to Sams comment, that could be a possibilty, I have already thought about, what it comes down to is what the shift was designed to react to, and what I can do to 'ideal' shift which will be a matter of ensuring shift is controlled off a TPS (throttle position sensor) and rpm point. The actual set up will take place in trial.
As far as (Thrust) spinning a prop will have less resistance to wheels on a road under full load, so that info is incorrect, what may be the case is how the trans behaves with less load and changing, it's hard to know without having run it. But there is a will and there is a way. It's just part of the challenge.
The other factor may be that the lesser but constant load may cause a problem and offer a shorter duty cycle compared to raod use, but given they are designed to handle load 50% of the time it might wear prematurley or need more regular servicing to avoid friction due to broken down oil etc.
And to both of you, keep in mind that this is a design process, and there will be problems , and that is the challenge to design with utmost thought and arrive close as possible to the concept upon completion.
And seeing that I know most people use hp as a way of describing an engines power, I used it to communicate, I hope now you understand that Hp is irrelevant for this or design process.

Regards Simon (Lucas is my son)

[lucas12]

Ok got my daughter off the computer.
I really wish to elaborate on the current discussion and principals so that anyone who has the question of whether auto running gear is usable in a boat that there is enough info to inform them correctly.

Another worthy note is hp is a relevant term for quoting a cars power, because the only resistance is air,tyre friction and the weight of the car.
Horse power can be used to a fuller advantage compared to a boat because the cars mass has innertia with minimal resistance to it's force.
So hp is relevant in a cars abilities.
However a boat is under heavy resistance until it gets on the plane and that dramaticly decreases the resistance, the engines torque gets it out of the water with and the hp power keeps it there.
Remembering max torque will take effect at lower rpm and the highest hp will come in at the end of the rev range.
A diesel engine has massive amounts of torque at low revs and hardly any hp at the top end.
Which is why the only time you will hear Torque being used in an advertisement for cars is when they are selling a diesel. because if the quoted that this massive 2 ton car had only 200 hp they wouldn't sell any to say it has 500Nm of torque is POWER to sell.
The two engines, petrol and deisel behave completely differently, and diesel in far more ecconomical, which is an important factor in my design.
Acceleration is not important to me, seeing that i intend to set to 2500rpm and coast up to 30 knotts through the auto.
Will, I think we got off on the wrong foot, I agree with you that I do need more power, but I assume that everybody understands what I naturaly know about power etc.
My appologies for missunderstanding your comments.
I will dig out my old PC and copy the build photos of the car, it's a 1962 ferrari gto replica, and I've had many enthusiasts of them look at it and told me it's the best they've seen, even questions of "I know about the replicas, but this is a real one right ?"
It weighs 950 kg and has 275 hp (relevant at 8500rpm) for aceleration it has 375 Nm of torque (lexus v8)
Now if I turbo charged it I might end up with 900hp (yes that's what they put out turbo charged) I will have about 500Nm of torque so the top end power would be nothing short of deadly. the accleration to the top end of the revs would be not that much greater as it currently accelerates to 100kmh in 4 seconds.
The 900hp would simply make accelerating in higher gears like 3 to 5 very bloody frightening.
So if everybody is satisfied with my statement of power please lets move on.
I'm getting the plans after easter and want to look at the hull design to see if I can improve on it's effeciancy to plane, be stable and be good all round and predictable and safe.
The info I have is it's a double curvature hull with bulbous keel, and 18 deg deadrise from stern.
I have looked at reverse hard chine info and strake info, but have not been able to determine their scientific use on their own. What effect do they have as a unit of whatever ?
I understand that all parts make a whole, but in order to understand any hull changes I need to understand the details of principals of the modifications effect.
Simon.

[lucas12]

Awesome link Tom, I need to digest it another time, but it gets me one step closer to the drive design. Thanx mate.

There's enough info there to really get the mind negotiating with the inner child and perhaps a feminine side LOL.
I wander if a model drive in 1/8 scale in something 1/8 density of salt water might be the way to go ?
It would be easy to make at least comparrisons and even fuel ecconomy etc.
I'm currently eyeing off my sons radio control speed boat.
Nup! dad use to do that to me, and I still get mad about it.
Ok looks like I'll be buying a radio control boat tomorrow and some glass for a big fish tank, YEAH !!!!!:D :o :idea:

[SamSam]

As far as (Thrust) spinning a prop will have less resistance to wheels on a road under full load, so that info is incorrect,
Regards Simon (Lucas is my son)
What I'm referring to is the fore and aft thrust. The propeller pushes the boat forward and has to transfer that thrust through the transmission. I don't believe auto transmissions are designed to withstand a lot of fore and aft thrust. Marine transmissions are. I'm not familiar with front wheel drive auto engines and transmissions but with a rear differential any fore and aft thrust is eliminated by the splines on the driveshaft. It would seem in a boat there would have to be a thrust bearing in the system able to handle all the HP or torque the engine was capable of developing. It would have to handle the thrust in both forward and reverse. Sam

[stevel]

Like Sam said, there does need to be a thrust bearing to transfer the foreward/reverse thrusts to the hull without it riding on the small thrust bearing(s) already in the transmission. Those are intended only to keep the internal parts in place, and to absorb a little friction from the splines on the driveshaft yoke. The thrust bearing does not have to be integrated into the transmision, however, so it would be reasonably straight-forward to put one in the driveline after the transmission.

[lucas12]

I have grappled with that part of the design briefly, just thinking out load. One of the main reasons to work out a way of displacing the thrust energy (force) to a wider area, but with minimal rotating mass, it to look at using a cars hub and assembly as the main thrust restriction as well as the possible trim for the surface drive , maybe even steering.
There are some very over engineered bearing setups on some hubs especialy on some earlier heavier japanese cars, one in mind is the datsun 260z, the other factor is cost, a car component is produced in much higher quantities than marine components, therefore a whole hub and bearing assembly will be around $200, the duty cylce will be less than intended, but the parts are designed to be ecconomicly (labour) replaced.
Theres nothing to stop me increasing the duty cycle by having a thrust bearing on the engine side as well, but that can be added in later.
So at this point my surface drive would have a prop, then shaft in a housing which attatches to the hub assembly, which is the trim. Then the Cv joint then a smaller thrust/seal, then transom, then another small thrust against drive shaft (opposite to first bearing) with seal. The actual drive shaft from the transmission would float on spline and universal joint inside a torque tube with basic externaly greasable bearings, supported by a mustache bar and bushed to the hulls support frames.
Although it may seem complex to work out and fit, most of the components could be donated from 1 or 2 cars, with all bearigs replaced.
It's actually better to use (used) housings etc because the stresses in the castings etc are already released from their previous lives.
The biggest and yet to be disvovered cost will be the prop.
Depending on what it might be worth, seeing that the process involved in making one would be bloody expensive as well as the cost of the material, will probably determine the rest of the driveline design.
I would prefer to go out and buy a standard mass produced prop, but with the price of fuel these days it's all a matter of balance.

[lucas12]

One other note, I looked at the Arneston designed surface drive last night, and to do away with stays (side load stability) he uses a pattented pivot housing over the universal joint, the thrust bearings are on the out shaft nested in the shaft housing. The only weakness is the pivoting housing that would not stand up to any side load, not that there would be much, but in conjunction with the small thrust bearings, the life expectancy of the bearings and eventual slop that would occur from general wear, would be reasonably short. Which is another design factor I'm trying to steer away from in that marine drive componentry seems to have shorter duty cycles than one would expect for the price.

[lucas12]

Finaly found the right surface piercing drive, the sea fury, it looks just how I wanted to design it except without trim variation, It's mostly sheet metal, and includes the rudder in the unit which mounts to the 45deg transom, under a duck board.
I've emailed for a quote, but seeing I found a 10 year old arneson drive on ebay for $8500 I doubt it will as cheap as it is simple.
What I really want is the right prop to use on my own design.

[tom kane]

Surfac Drives without trimability have driven many boaties to.....hell and back.
You also may be dissappointed,although your choice is probably a better one.Why would some one sell an Arnson for $8500 if it was a good drive,may be moving on through a bad experience.The right prop for your boat will have to be many comprises especially if using S/P drives as you cannot choose a prop just to suit your hull and motor,but you must take into account how S/P drives work.

[lucas12]

Tom, I was intending to make a similar surface/piercing drive to the seafury, (I had already visioned a similar concept,) but with a trim option It made sense use the seafury prop that they calculate to use on the hull. with their drive at 6 deg and the said clearances. As far as the props design, appart from what I've read up on in the principals of avoiding cavitation, I think if I'm 75% of the way to 100% of efficiency, I'll be happy for a first off boat.
I will learn alot in the processes of the whole design, and who to deal with, to get the right advice and the right price. So I guess I would be open to take any suggestions on who to get a prop from based on experience.
At least I'll have a good place to start, preferably someone who really understands the physics of their craft for propellers.
I also like to experiment with performance enhancing mods, making small incremantal mods to prop over time to get 100% efficiency is more than likely, with the final proven product the one I would on-sell.
I will also be building 2 boats at once with slight variations as a test as well, just to get instant comparisons on various mods, which will dramaticly speed up the development process.
Quite often in what I do, I take a process of a machine where there is more than one module the same and apply different theories to each, it's amazing what little intricate movements evolve within an action, to give subconsciously unforseen results.
The result is all the answers very quickly by crossing over the retrieved data
And the finshed and bullet proof product ahead of schedule and done right the first time !!!! Well third time, but who's counting
It's irrelevant when the overall time is shorter than doing it twice, which unfortunatley is how most engineering ops work.
It doesn't mean that I'll be spending twice as much, it means that one lucky mate will get a new 22' boat for $20,000.
Anyway ANY PROP CONTACTS PLEASE

[tom kane]

You are spoiled for prop selection and built to customers specs,investment casting the lot.There are very efficient and competitive South Korean (supplying some NZ businesses) Manufactures,and Turkey, India,and of course many others.The usual big names for props have much competition now.If you have the time to cover them all that will keep you very busy,and take a lot of checking on reliable supply,although that does not seem to be too great of problem to a competent modern business man.

[lucas12]

So far from the vast amounts of info I've bombarded myself with and the number of emails sent to have a prop size and pitch specified, I'm starting to think that given the step drive is 'new' that me stating I will have a final drive of 1:1 with a 3 speed auto, "so don't worry about acceleration" just the most efficient prop at 30 knotts seems to have them stumped, as I can't get reply.
I've found 2 local businesses that make and repair props, so I'll go and investigate to see if someone can actually give me the right 'oversized' prop.

On the engine side I've found some awesome new engines, one being the toyota avensis, with 2.2lt turbo diesel and 400Nm of torque, just released 2005, with fuel ecconomy that blows me away for the power. As I step back into importable engines from japan the power drops dramaticly as the technology decreases.
To get my 350Nm I might end up with a 3.0TD or higher. Which realy sucks out my fuel economy.
Funny enough I have a Mitsubishi Delica 2.8 TD which has 300Nm, which is the highest for it's age and size.
I often simulate while driving how it would push a boat, and considering it's a 2.5 ton car, it would work well, I guess then I should start with a bigger prop, and decrease it's size if the torque level doesn't hold the planing speed.
Does that sound logical ?

[lucas12]

Ok decided on an engine today The toyota hilux/prado engine and 4 speed auto
Displacement, cc 2982
Engine model 1KZ-TE
Max.power (Net), kw(PS)/rpm 145 ps (106.65 kw) / 3600 rpm
Max.torque(Net), N*m(kg*m)/rpm 35.0 kg*m (343.23 N*m) / 2000 rpm

The prop will be custom made about 20" bronze, when I get all the details, for about $1600
The surface drive I'm about to start modeling, the files in dxf, or any solid edge file format will be available to download if anyone wants to copy it, as well as parts list.
I think If anyone has the skills to assemble their own surface drive and doesn't have $11,500 +prop for the smallest unit available. Then I'm glad to share the design for free, keeping in mind the intellectual property rights and non commercial use of the design, as without this forum and the people on it It would not have been possible to concept the idea in the first place.
Please email if interested and I will forward files when available.
As well as file format you can read.dxf,dwg for cad drawings, psm or asm for model to make your own drawing files for cnc cut/fold etc.
Simon.

[fglass]

Hi Simon, you have hit the nail on the head with this project, the consept of what you are talking about sounds fantastic and I'm looking forward to working with you on this project.

Regards Jason.
JT Fibreglass Products.

[lucas12]

Hey Jason, I've been persuided by Neil (nigels brother) to dump the Glen L monsoon for the clark craft 26 crown cruiser, That will be another 3 foot of storage for kingy's;)
Go to Clarkcraft.com.
It takes more power to push it to 30 knots, quoted 250hp compared to 180 hp for the monsoon, but the write up's read well for ocean going
The Viking has the same hull design at 22' and one guy posted a 1.7 ltr diesel pushing 45mph
I think if the surface drive is set up right it should fly and be most importantly stable.
Don't have any other ideas on the hull, because I just ordered it.
And don't forget were adding another 3 - 4 feet for the duck board, that's 30 feet F&^%*%k !!

Should be good winding down through belgrave on the tight windy roads pushing tourists off the cliffs, hey now it has another good purpose.

See you soon, come on Muloways, I've been dreaming about hooking up giant 70kg mulloways.:D
Simon.

[lucas12]

This is exactly what I mean about "Marine" rip off

Re pricing our current Trade price for 1 x SF22 Unit complete is NZ$ 31,130.00 unfortunately this price will increase as the world metal price does as seems to be out of control at present.

Materials cost $300 + prop (where's the justification in that?)

[fglass]

Its called ripping off the little guy who knows nothing about the industury.
It realy is a shame that some people are so greedy.:confused: :mad:

[lucas12]

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Don't go around looking up peoples phone numbers with their profile information, with the sole purpose of harassment. It's Ilegal.
Courts don't see kindly to bully tactics.
The fact is your product is 10 x the price of one of your competitors

If you have a problem you also have my email address.

Simon:(