Fast, Small, Boat Designed Around Mercuiser 140

Many US builders were smart if they had an outboard and sterndrive in the same model the hulls were different to carry the extra weight
Unfortunatley that never made it across the pacific to sterndrive boats out here so they never performed properly.
US sterndrive boats always amazed me how fast they went

 

There more to that boat than you might think !! tricks is where its at !!

though don't try to mimic the odd strakes and strippers, just use a couple of straight ones on each side

That's a typical boat designers answer!! you'd really have to twist his arm to get any more details about those 2 strakes but you are not seeing what's really there !!
Its those lovely little things that are possibly the most important things on the hull .
Have you actually had a really good close look at what they are there fore and actually doing ??
To start off with see what they do and can do .
Whats seemingly is unimportant could be the whole key to where those boats performance actually comes from . see the size and placement of the aft side stakes !! see also that small almost decretive protrusion along the length of the middle and how it actually curls almost flat to then form as it goes aft into a ski plank , that seemingly small and that insignificant raised decretive protrusion is in fact forming a step to deflect the main stream of water away from the hull skin .
In a older bigger picture I have with a little more detail that stream of water at high speed actually strikes that small strake and gets deflected downwards . What seemingly trivial and meaningless to some is actually quite important !!! . Have you also taken notice of the high-speed planning attitude of that boat at speed ?? how do you think it stays on that angle and what holds it there ?? how did it get there in the first place ???
Now have a very close look at the deck and front end of that particular hull , with the shape it has got wouldn't you say it could have a tendency to want to lift its nose with air pressure beneath and as the air pressure goes aft also lift the actual hull ??

I looked at this boat more than 4 years ago and saw what's there and wondered what it was all for !! so drew it out full sized and behold the hidden secrets unfolded !! . Size and placement is a big part but there's a couple of other tricks there as well that looking you never recognize but if you study the water flows along and from different parts of those bits for long enough you just might see what I saw .

 

This project makes about as much sense as building a new house around a second-hand stove, somewhere between very little, and none at all !

 

Tunnels, you have tried this on several threads, and you always get the same response. It's always the same with you - we designers don't know s**t, but hell you sure do - of course you can't explain anything, but you still insist we're nuts and you're the gifted child. Pleeease, your said story is way too easy to expose, with links to previous threads where your inability to understand is quite obvious. So, do us a favor and stick with what you know and leave the stuff that requires an education, to those that actually have it.

Simply put, you haven't any idea what those strakes or strippers do (proven time and time again in previous threads). I have a race boat design that is current doing very well and it, like all well designed high speed powerboats, holds it's 3 degree trim from the hump to near 100 MPH. I do know how to do this, but you wouldn't have the foggiest, though I suspect you could laminate the pieces, which doesn't require an understanding of their dynamics underway, you have absolutely no idea where, how big, what configuration, etc., etc., etc. for those strakes, and strippers, to get the performance of one of these pocket rockets.

Agreed, it's a bit like making a silk purse from a sow's ear, but if the engine/drive is new and reliable. The logical course, as previous mentioned is a hull swap. Though for the adventurous, making an 18', plywood monohedren, isn't such a costly thing. Certainly more so than a transplant, but not unreasonable, for the right person. I have a supply of 1/4" and 1/2" 6566 here and could easily have a hull shell in a week or so. Now, I'm not the average back yard hack and I sure wouldn't use a MR and 30 year old 181, but I can find mid and late 90's setups, for little investment, with drive you can still get parts for and an engine that has most of the features you want, plus has some cylinder liners left to them. I know of a '02 deck boat for $3k about 15 mile from here with a 5.7 Vortec on a Volvo. It's worth more to flip it, but a good candidate to highjack a reasonable engine/drive assembly.

 

You have done it again !! careful you dont stumble off your soap box and fall !!

Do I have the gift of being able to touch a raw nerve or some thing ??
why do you get so touchy ??
I have worked on and made a few race boats in my life time and have done fine tuning on all kinds of fast power boats over the years .
I don't need to have a head filled with theory and magic figures !
why do you always get so upset ?
Im not after you job but I do question some of you answers usually for good reason !!
I can look at something and see almost instantly what its for and how it works and in this case Know what the trick is that makes most of these things work , there are unwritten about tricks that are used .
The designer I worked very closely with was very clever also and we were friends !! but was guys like us on the floor that made his ideas a reality !!.
I don't have you gift of numbers and magic fingers to make computer designs !,but I still have the ability with a pencil ,ruler and a compass . I was always top of my engineering and industrial design classes at school way before the push button era . and I still have a very good eye for detail and imagination of the hidden things . there been a few times I have sent drawing back to a clever designer because of something he had missed and didn't have the foresight to see past his screen ! .
Im not trying to up set or tread on your toes and I am sorry if I piss you off so often but we are here to help people ! I am not going to move my chair just because I ruffled you feather yet again ,sorry !!

 

PAR Vs tunnels reminds me of The Bold and the Beautiful, even if you don't watch an episode for 6 months, the story won't have changed in the interim !

 

YEAH its happened a few time over the last couple of years . Like water off a ducks back ! people really don't want to part with hard learned knowledge unless there's a buck in it for them me , I will always tell what I see and know to anyone ,as long as it helps some one that's all that really matters at the end of the day .
That Allison boat is rather interesting all the same with all those little gimmicks along the bottom ! its got to be 4 years since I last saw those pictures .
Like I said I drew them out real size and saw what it was all about !!

 

Well that's a first Tunnels and I'll accept that. The only issue I have is, I've never met anyone that could just "see things" and know how they worked, without the fundamental and underlying understanding. It's one thing to take a watch apart, look at the gears and stuff and figure it out, but another to visualize the flow and dynamics, while a boat sits on some stands. In fact, your description sounds like the way I started out, under the wing of a "good one", while I was the shlep in the shop, trying to learn from the pros around me. Eventually, I finished school and tutelage from the builders and designers. I've never forgotten what I learned on the floor and still do it, but I also know I couldn't have designed a 100 MPH racer, without knowing the hydro end of it (the crazy math stuff you're so disfond of). To this point, I've seen old schoolers, much like you, try it and they all have longitudinal stability issues around 70 - 80 MPH and can't figure out why. Porpoising at 80 MPH isn't fun, can kill you and certainly will not win any races. The race boat I've mentioned is currently campaigning in a fleet of home schooled builds and everyone of these, has bad habits at speed, except the few that were designed by guys that know the hydro end of it. My design is the newest of the fleet and enjoying the benefits of this, still hasn't lost a heat or race, since it's launch last fall. This will end of course, but not by a design that some guy looked at and just figured it. Maybe at 50 MPH, but not 100. At these speeds you don't screw up or ask a crew to just trust you.

 

Sorry if all your training didnt come natural !!,

I understand what you are saying !
What I learned came from my father and he could turn his had to anything mechanical and fix it , a self taught mechanic !!.
Boats have been in me since I was still at primary school . I could see a picture in a magazine and go make a model that looked just the same . I designed my first ever real life sized boat while I was still at school and I asked my father to make all the bits for it including make a VEE drive because it had the motor in the back , the rudder I drew by eye and had lead and if you let the wheel go was like a car it went back to going in a straight line and one finger steering at speed !!,I hotted the motor up and by then I had learned to weld just watching my dad . he never actually stood over me I learned while he was away at work ,I made a tuned extractor exhaust system . and just reading from a old English car magazine I learned all about sizes of pipes and tuned lengths etc Plus to top that of ram tubes and porting and polishing etc etc . By the time I had the boat finished I had left school and started working in a ford Automotive spare department in a town close to where we lived . Mechanical thing just came natural because i'd been subjected to it since I could first walk . . My little 12 foot SK boat could go faster than I had hoped and handled like a dream .
was a long time till I eventually got into fibreglass work just as a laminator . glass work was me in two years I had companies ringing me up asking to come work for them , I never stayed at any place more than 4 months and went from shop to shop and always learning every where I went , once the marine glassing thing became same old same old I side tracked into industrial but Making pipes and all those kinds of thing didnt hold my interest for to long so television and scenery workshops was me . was there for over 5 years but missed boats so back there again and went to Tahiti for a while and Australia and onec back in nz again the race boat thing happened !! I became friends with the designer as he was right into tunnel boats , circuit racers F1 & F3 and also off shore power boats !! the biggest had triple mercs on the back . I tripped all over the country to every race meeting that I could get to . took hundreds of picture of all and any race boat including hydro's and specially tunnels . my wall was covered floor to ceiling all the time .
I raced cars for a while and always made all my own things did all my own porting and building manifolds intake and exhausts, modified my own heads and combustion chambers , made all my own road gear and suspensions and brake modifications etc etc and the list goes on and on !!
Then I got to building 8 match racing yachts for the south Korean first ever international boat show 2008 . after that the company designed and built a 23 foot fast fishing boat so went back 2009 to help with that project and iron out bugs they were having .a while later I came to china . I learned all the time every where I went , looking and knowing and ironing bugs of boats that don't go well has served me well and I find easy .
looking at things and knowing how they work is really quite simple and not hard at all
I always want to be a boat designer !! but the maths was so boring and didn't really make the boat go any faster at the end of the day so why bother !!
Just understand the principles involved and the rest simply falls into place !! .
Has any one actually answered when is a boat planning or is it still unsolved ?? see all the figures and formulas in the world and still no one knows !! how silly has that got to be !!

 

there was this ozzie that built a fast boat in his backyard in fact nobody has ever gone faster....

 

The question is did his underwater remain clean during those record runs ? I know mine would have been soiled long before the record speed was accomplished.

 

well when it wouldnt go fast enough he got the gas axe and cut a few inches off the rudder, dressed it with the angle grinder and off he went.

 

A "guts" man of the first order, and the boffin that designed it for him knew his hydro/aero dynamics.

 

Never read much about that, who was it?

 

I recall he had some help from a university academic at least in fine-tuning, but Warby may have designed it himself looking at the web. I vaguely recall the bloke helping him was a bit long in the tooth at that time, may have left us by now.