Some ideas

[yipster]

Strange encounters in trust vectoring dynamic bodies.

When steering a (stern mounted) OB on a monohull the boat actually goes another direction as oposite to the prop’s trust because the hull works as a rudder up front. The prop also try’s to encircle the beam vertically when cornering, thereby creating inward heeling.

On fast catamarans 2 canted OB’s (i want those!) can do the same job on heeling, but that may be too much for a mono hull. Making it more complex by putting the OB on the bow -for the sake of the argument- the boot will simply follow the OB but give NEGATIVE, OUTWARDS heeling! Ok, it might take the bow wave away but that’s another story.

I started wondering what will happen with the water bike design having the ob behind the front leg, wasn’t so sure if it would encircle its front leg or -due to the rear legs drag- follow the engine. That means wasnt sure it go left or right, heel in or out.

So I made another model, fairly accurate this time. Got a small RC outboard on the back of the front leg and guess what happened? From stationary it follows the OB and heels a little out, not good! But when getting only a little on speed it starts encircling the front leg going the other way (without steering) and give the rite inward heeling!

Must be strange going slow steering opposite! I wont be the last shooting my own balloons down and guess I’ll better finish the real thing and call it “test model”. Making the new waterbike model I again realised how precise a swath concept must be. Strange encounters in trust vectoring may turn out the smallest of problems / challenges…

[yipster]

in my search for a swath VPP i came acros lockheed martin marine systems its popular reading on swath / slice but no real WSA VPP or 3D units in the drawing above, witch looks like fun tho

[yipster]

ok, seriously, i'm back on the (water) bike, could not help my eye fell on this 14 page .pdf paper:
Optimal Design of Thruster System for Superconducting Electromagnetic Propulsion by: Shinsuke AKAGI, Kikuo FUJITA and Kazuo SOGA who investigated this superconducting truster on swath pods, propulsive efficiency is still to be improved, (sea water has a low conductivity) but i just wanted to let ya guy's know, i got to hurry or i am getting old... "time" the rabbit said asking for half a cup...

[yipster]

Wow, a one legged HYSWATH eek eek who dreamed that one up, great! (see demonstration at http://www.mapcorp.com/page4.html with thanks to Steve) Have -bla bla- that leg “somehow” retractable? Feel a bit yesterday’s paper now with my trike. Got the legs about done, making the ailerons now. Would it be allowable to have a cable only for the ailerons upward motion that pulls the leg down or is it going to swivel wildly?

Getting technical reactions (with or without sending my drawing) for a quote from the scaffolding, aluminum, stainless and steel trade here is almost hopeless. Yes they like the drawing but I had thought they could give the necessary strength estimates (like at http://www.efunda.com/formulae/solid...imple_2symload with thanks to MDV for the address), confirm steel ads 40% weight on ali, diameter to wall thickness advice, pipe weight, advice locking systems, at least get the concrete sizes to figger the sleeves and a price. Not so! the few pipes I need are probably financially not interesting to them anyway.

On the net –and here on boatdesign- is more info! It made me think of some 80-page manuals for building a 2-sheeter rowing boat is no joke! Now I see that in reality it actually does make a lot of sense to calculate and detail in advance! That design spiral counts to the very last part!

Got a calendar but got too many open questions left that wiser be answered before pushing ahead to fast and goofing it up. So I’ll keep checking the piping industry here (and maybe reply’s on this mail?) because “ready in 2 months” should -without delay- be feasable! looking at the date, time fly's! yipster

but today i'm off to the beach, why not spy around a few cats

[yipster]

Hello all,
September now and must admit I’m slightly of scheme. It’s been a while since I updated this thread but last month my trike building came to a stop. Our sundancer had to return from France and now it’s missing its props. Otherwise the trike could have been in the water but propulsion needs an extra long shaft (and actually 15 to 20 instead of my 7.5 Hp OB). An extra long tail on a new OB cost 100 bucks more but having that conversion bought separate comes to 700. Pictured an electric drive but needs an external power source and only checking on these alternative’s recently. Anyone with fresh simpler ideas?

yipster

[Nomad]

Can't wait to see some finished Pictures and specs!!!

[yipster]

i can only second that and thanks for the interest.
the sundancer is in the water and hope doing some tow testing with the trike soon. propulsion i'm searching for. ah, and dont forget to make a seat, wheel, cables etc. what looks so easy is still work and money, havent given up tho!

yipster

[yipster]

hi all, broke but now getting some insight in the mercruiser EFI setup. so the trike has to wait a little longer. was reading the tunnel boat news letter and it had a rather interesting article on OB torpedo drag. you all probably allready read but if not, here the article "How does a tunnel hull work? (Part 4)". for more info contact jimboat below or here on the forum.

We have had many requests to explain each of the many factors that can influence the performance of a tunnel boat. There are literally dozens of factors that have an impact of performance, and most all of them influence the other factors. This makes the prediction of tunnel hull performance a tricky business - to maintain the inter-relationships of all of these factors throughout the operating velocity range of the boat. The good news is that most of these factors are controllable (by design and setup). We usually rely on computers, and the advanced "Tunnel Boat Design Program" (Version 7 now released) to do the hard work for us.

In the last three TBPNews letters, we looked at the factors that influence performance resulting from lift & drag relationships, thrust relationships and the location of weights & measures influences on performance.

This week we will look at lower unit design and the influences on performance. The optimum setup of your gearcase can create a gain of 13 hp at 100 mph! Read on to see how!

Much can be done to optimize the balance of all the forces acting on the tunnel boat in motion. This balance can be achieved for a range of speeds at the design stage, by optimizing the location of the forces involved. By selective designing of all the aerodynamic and hydrodynamic surfaces that become critical at high speeds, each tunnel hull can be tuned at the design stage. It is important to do this "dynamic balance" at all speeds through the boat's operating range - since balance at one speed just is not enough! (So balancing your boat on the trailer, by moving weight around is only going to help if you boat never leaves the trailer).


"Appendage" or motor drag. This component is not easy to calculate in a simple manner, since there are so many different designs of outboard lower units in use today, and since every boat will have the loser unit set up with respect to the hull just a little bit differently. The chore of analyzing such a 'beast' can be split into the parts of the lower unit, that is - the skeg, the torpedo and the propeller. Here's some of the design measures that we have control over:

* Lower Unit Height - Height of lower unit "bullet" above/below sponson running pad. (+) is above, (-) is below. Most high performance setups start with as little of the lower unit bullet in the water as possible, thus reducing drag significantly. Surface piercing propellers and low-level water pick-ups make this feasible. Normally, values of +0.5" to +1" (above sponson running surfaces) are possible in very high performance applications. Without low water pickup, or when low-end torque is a requirement, then LwrUnitHeight values of -0.5 to -2" (below sponson running surfaces) is applied.
* Lower Unit Drives Quantity - The number of lower unit drives (no. of engines) will impact the hydrodynamic drag generated at all speeds. It is a design trade-off as additional propeller thrust of multiple drives can reduce propeller slip, increasing overall efficiency.
* Skeg Width - average width of motor lower unit/outdrive skeg (leading edge of skeg to back of skeg). The Skeg is really just a kind of wing, flying through the water - sideways. It can be analyzed as such, using traditional aerodynamic approaches. It affects the friction and induced drag generated by the lower unit.
* Skeg Length - length of motor lower unit/outdrive skeg (top of skeg to bottom of skeg). Also affects the friction and induced drag generated by the lower unit; but on the positive side, longer skeg can provide better stability and handling under high load conditions such as cornering.
* Skeg Thickness - Thickness of motor lower unit/outdrive skeg (thickness of the skeg plate). It affects the form, friction and induced drags generated by the lower unit. Only reason for "thick" skeg design is a structural or reliability one - thinner is better.
* Torpedo Length - length of motor lower unit/outdrive torpedo housing (leading edge of torpedo to aft edge of torpedo, at prop shaft). The 'Torpedo', or the part of the lower unit that houses the transmission, etc., is really very well described by it's colloquially used term - torpedo. This part is actually just a projectile moving through the water, usually generating 'zero-lift' - just drag. The longer torpedo is better, as it will have a higher "aspect ratio" thus generating less induced drag. After-market nosecones are used for exactly this purpose, presenting a more stable water flow over the torpedo length, reducing drag and reducing propeller burning or blow-out.
* Torpedo diameter - diameter of motor lower unit/outdrive torpedo housing (in cross-section). Affects the form, friction and induced drags generated by the lower unit. Only reason for larger diameter design is a structural or reliability one - smaller is definitely better.
* The Propeller of course, is a multi-aerofoil component generating lift and drag in all different directions. (One of these directions we call thrust, and we use it to 'propel' our tunnel boat). As far as additional drag on the hull however, the propeller contributes very, very little and so we can ignore it!

The total drag of the motor then, will be determined in a very general way, based on the velocity of the hull, and the 'type' of outboard motor lower unit used (i.e. size of engine, stock/racing unit, etc.)

Height of gearcase makes a difference. A typical Mercury Sportmaster gearcase at 60 mph velocity, with the torpedo positioned exactly at the trailing edge of the running surface (height = 0) can have about 34 pounds of drag. If the gearcase was 1" lower in position (1" below the trailing edge of the running surface, or height = -1") then we would generate 43 pounds drag - that's over 6 HP worth of drag! The same gearcase at 1" above the trailing edge of the running surface (or height = +1") would however, have only 25 pounds of drag at 60 mph. And think of that gearcase setup at 100 mph - it will create 112 pounds (30 hp) of drag at height = -1"; and only 64 pounds drag (17 hp) at height = +1"!

As we explained earlier, the motor drag can be a very long and tedious contribution to calculate in detail. This drag is made up of the drag on the 'skeg' on the lower unit, and of the drag on the 'torpedo' itself. Naturally, the size, shape and length dimensions of both the skeg and torpedo, as well as the velocity of the hull, will influence their relative contributions to total drag.

The actual details for calculating such contributions are complicated, and really outside the scope of 'hand-calculations'. With the use of Computer-Aided-Design programs, we have reduced this calculation process considerably. To save a lot of time, we will try to 'standardize' the characteristic hydrodynamic drags of the popular outboard engine lower units available and currently in use on tunnel hulls.

The smaller stock outboard engines can be categorized into one group of say less than 50 Cubic inch displacement (cid) to establish a group of similar lower unit characteristics. The engines larger than about this size, even up to the engines with displacements greater than 125 cid, can be categorized into another group of stock engine sizes. Two additional groups are represented by the Racing versions of these engine sizes, since the dimensions, shape and size of these lower units are substantially different again.

At AeroMarine Research, we use the "Tunnel Boat Design Program(c) " software to make the analysis easy. The TBDP calculates all hydrodynamic and aerodynamic lift forces by all lifting surfaces, all drag contributors, and does a dynamic balance of the hull at every speed defined in the performance specification. Doing this all in seconds makes it very easy to make small changes to the hull design, power or setup, and to determine the effect on performance and stability. We use the "PropWorks2(c) " software for propeller selection and speed prediction. Whether done manually (as shown in the "Secrets of Tunnel Boat Design" book, or by computer with TBDP, designing a tunnel boat that will optimize performance and ensure stability is possible when we understand how these factors influence performance and stability.

Well, that's enough for this issue - and this is the end of this series of articles. I hope that we have seen the major areas of design control that we can concentrate our design efforts.

See you next time!

/Jimboat

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>> Tunnel Boat Performance News >>>>>>>>>>>>>>

Let us know any ideas you have, requests for articles, questions or comments on our TBPNews. Send your comments to TBPNews@aeromarineresearch.com
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Get your full, illustrated, NEW 12th edition copy of the world known "Secrets of Tunnel Boat Design" book. GO TO: http://www.aeromarineresearch.com

in time i'll get the books, software etc!
yipster

Did you ever find any one who used a gas engine in a keel bulb?

[yipster]

Guest,
i belive MAPC has its (diesel?) engine in the bulb? and i've seen a few other, it's interesting and can be done but is certainly not the easyest setup...

Yipster:
I am toying with the idea of making a remote control torpedo sub. the smaller the engine the better.

Do you have a rough idea of how fast 100 hp would be able to push a 16" wide wave piercing torpedo.

[yipster]

you want to do that remote? not with a warhead i hope! and why a fast wave piercing torpedo that will hit wavemaking resistance, going fast the idea is to get out of that i belive?
see http://www.users.globalnet.co.uk/~fs...ds/fred.htmand you can also use the search button here and check for "froude" or "resistance" for much more on this.
i did check submerged torpedo speeds versus HP and found a high curve diagram. here some not so easy to find info.

from another forum:
>yipster:
>>how much power / hp is needed to proppel a torpedo? who can help?
>I. Yes. Need dimensional info not here. 300kg not important unless vehicle "planes" (under/over water).
>It depends. Need info. Cyl Diameter, Length
>Drag Force = Cd.. * SomeArea * 0.5RhoV^2
>Wetsurf + Form + Wave + Lift-induced(not here - planing only)
> wsa; profileareas; L^2, shape factor; Liftarea
> consts consts consts consts
>Appropriate references for Cd....

A typical 21” (533mm) steam torpedo produced upwards of 300hp to achieve its maximum speed, usually around 45 knots. Many also had lower power settings available to achieve longer range. The Japanese Type 93 had what was probably the most powerful engine in a WW2 production torpedo, producing over 500hp. Aerial torpedoes usually produced about 150hp, good for about 40 knots. exception was the USN Mark 13, which produced only 98hp, good for about 33 knots.

http://uboat.net/allies/technical/fido.htm shows 12 kts on 5 hp for 680 lbs (=approximately 45? squered ft / close to the displacement of the waterbike design

Torpedo MK 24 - "FIDO" The First American ASW Acoustic Homing Torpedo
Size: 19" dia. x 84" long
Weight: 680 lbs.
Propulsion: Single propeller driven by a 5 HP electric motor-48 volt lead acid battery
Speed and Endurance: 12 kts for approx. 15 min.

at http://uboat.net/types/schwertw.htm another WSA sample going 30 knots but don’t say how much WSA or on how much hp/kw

The US Mark 14 ran at 46 knots -- some current models are reported to do as fast a 60 knots

here some hard to find links i collected, not sure if they are all still active.
http://www/warships1.com/Weapons/WTBR_WWII.htm
http://www.warships1.com/Weapons/WTJAP_WWII.htm
http://www.warships1.com/Weapons/WTRussian_WWII.htm
http://www.warships1.comWeaponsWTGER_notes.htm
http://www.diodon349.com/torpedoman/....torpedoes.htm
http://www.militarism.navy.ru/torpedoes.htm
http://www.geocities.com/Pentagon/1592/ustorp1.htm
http://www.geocities.com/Pentagon/1592/ustorp2.htm
http://www.geocities.com/Pentagon/1592/ustorp3.htm
http://www.regiamarina.net/index_it.htm
http://www.geocities.com/Pentagon/1592/ustorp3.htm
http://www.geocities.com/ssvong/subm...ch/torpedo.htm
http://www.dataphone.se/~ms/ubootw/torpedoes.htm
http://www.weymouthdiving.co.uk/torpedoes.htm
http://www.weymouthdiving.co.uk/torpjist.htm
Japanese Torpedoes: http://www.skypoint.com/members/jpb.torps.htm
Russian Torpedo Armament: http://www.militarism.navy.ru/torpedoes.htm
http://64.124.221.191/torps.htm) has a good primer on IJN torpedoes www.warships1.com.
http://www.j-aircraft.org/bbs/jship_....pl?read=11800

[yipster]

from the "a question on drag" thread:

Apparently "boundary area bleeding" would have been a better terminology for what I was trying to express above. Could this also be referred to as "induced cavitation"?

ref:
http://www.usc.edu/CSSF/History/2003/Projects/S0101.pdf
http://www.curj.caltech.edu/archives/vol1/1004005.pdf

Doug Carlson

Doug, thats very high speed! 230 mile hr torp's and supercavitating passenger submarines that could cross the atlantic in less than an hour! from caltech! makes me wonder where they plan that crossing. reading edmund pope's story i wonder if i dear mentioning a new water repelant boat paint that couses cavitation and should reduce resistance dramaticly?
yipster

its a pitty the http://www.curj.caltech.edu/archives/vol1/1004005.pdf paper went ofline, hope it gets back without the wargames talk? very fast torpedos i heard of before but its sort of hush hush top secret. on whatever propulsion it still must be amazing friction reduction tho, perhaps start a new thread on it as Doug suggested?

yipster

[Doug Carlson]

Yipster,

Here in the US they have been running a TV commercial for a luxury sedan, Mercedes I think, that has its underside sheathed in dimpled material to reduce wind resistance (read surface friction) and noise.

Doug Carlson

[yipster]

Doug,
thanks for that info. i've been watching all european tv commercials for a while now but havent seen such dimpled surface materials other than on golfball's here yet... the tv spot is remarkable!
it was a thought and in boating is probably subject to other conditions, who knows?
meanwhile i learned that state of the art CFD programs wont input / handle this anyway yet but sure are interesting as well.
real high (submerged) speeds -and there is enough reason to belive- i can only wonder about and guess your thoughts are as good as mine; air ventilation and boundary area bleeding and?
dont expect getting the answers soon though.

keep me updated
yipster