Long - Skinny Power Boats

[Boston]

Im actually kicking its ass day trading
I posted my day in real time over on the global economic conditions for live aboard yachties thread
if your curious go check it out
my final post in the series Ill quote here as it was a good synopses of the day
it was a series rather than one after close post because I wanted the times on the posts to correspond with actual market positions thus corroborating my buys and sells
I figured people might want to actually see for themselves I was in fact keeping step with the market motions with my positions on the day

I ended up having a great day but obviously could not have known that at the start
I just wanted to honestly represent the uncertainties in real time

my last post in the series was an effort to explain my reasoning and its results

this morning is a great example
the open was high
well above the close of the previous day
above the 7 day trend but not above the anomalous high on the fifth ( which resulted in a drop from that opening high back to within trend )
so I was thinking it was not so far off to be fully outside of trend and given that, I bet it would drop like a rock ( as it had before ) back to average at least for the 7 day period which was down around 940.0
I got in early at 954.2 with a strong conviction it was going to drop
it did
but bounced a little more than I wanted to see and so I got out missing some additional gains but still
taking a tidy profit
then it fell some more, I could have flipped my trade and gone sds but by that time it was in average territory and predicting its next move was not so easy, so I waited, it bounced off the average trend line as it had a few times before over the previous 7 sessions
so I got back in on the bounce and then out again when the bounce fizzled out ( that was my smallest gain on the day )
at which point there were no clear indicators as to where to go from there, so I waited again
it fell
and fell
and fell ( lots of missed profit there but hey I was not sure which way it was going to go so I just watched and waited )
it crashed all the way to my predicted low from a few days ago
at which point I expected a bounce so I got back in with sso funds
it shot upwards and landed me another nice profit
I got out a few minutes before close with all indicators favoring a continued upward movement right up till the end

day trading is about the only way Ive managed to survive since the contracting biz fell flat on its face over the last few
surprisingly, when so many people told me not to even think about it
turns out Im good at it
I think it just might pay for the yacht cause contracting sure isn't

cheers
B

[Tad]

Boston...

What the ........ does your day trading bs have to do with long skinny powerboats?

Thread drift I understand....intentionally adding posts with no bearing at all on the subject makes no sense!

[Boston]

Rick had mentioned something about financing the project with day trading
so I threw him some bs about day trading
which turns out will likely finance a long skinny hull just fine

sorry if it didnt make any sense
cheers
B

pertinant question then
Im working on my math skills
submerged area, 60' hull 6' beam 2.75' draft
when I crunch the numbers I get 2500 lbs of thrust to reach 20 knots
or 100 hp
Im sure you have a hull efficiency calculator in there somewhere
whats it say when you input those numbers
Im curious if Im close
thanks
B

[Guest625101138]

Boston
Here is a test on one of my slender boats with a small motor operating at 200W. The motor is rated at 600W. It went to 10kph (5.4kts).
http://www.boatdesign.net/gallery/da...11JE_10kph.wmv

I intend to use this motor on the 1/5th scale model faux-tri but it will be minus the big gear ratio.

One of the sailors looking on could not imagine that a tiny motor could move me at that speed. The motor weighs 149 grams and is 40mm diameter I have a 12:1 overall gear reduction.

Anyhow it demonstrates how little power a long slender hull needs.

Rick W

[eponodyne]

no can view on a Mac, sorry.

[Guest625101138]

Originally Posted by eponodyne

no can view on a Mac, sorry.

Can you view YouTube:
http://www.youtube.com/watch?v=GJedBprmSkk

There is nothing particularly great about the video. The impressive bit is the little 140 gram motor pushing a person on a boat it 10kph.

There is a little program called Flip4Mac that enable Quicktime to view wmv files.

I use Mac for email and web viewing so it is handy to have.

Rick W

[eponodyne]

oh holy crap that sounds like a dentist drill moving the gates of doom into place. Sure, that's a dandy little powerful motor. Annoying as f*ck.

Better you than me, buddy. I'm glad you're wiling to do the research and put up with it, because it would drive me to world domination or some **** like that.

[Guest625101138]

Originally Posted by eponodyne

oh holy crap that sounds like a dentist drill moving the gates of doom into place. Sure, that's a dandy little powerful motor. Annoying as f*ck.

Better you than me, buddy. I'm glad you're wiling to do the research and put up with it, because it would drive me to world domination or some **** like that.

The camera seems to amplify the sound quite a lot. It is not anywhere as noticeable on the boat. My son also found it very annoying when I first viewed the video at home.

My main issue during the test was lack of a third hand and fear of losing the remote control while filming. I was trying to run directly with the waves so it would stop the jerky roll before I tried full power. I later found I had collected some weed in that run and was able to nudge just over 10kph with a clean prop.

When you compare noise with the equivalent ICE used for model planes it is silent.

Rick W

[Boston]

ya as a kid we used to play with those RC planes a lot and dam
they scream
ok well then I guess my numbers may be at least close then cause I took a big guess at the wave resistance and assumed it was half at 20 knots
basically I only figured for the fluid resistance and doubled it to get to 20 kts at 160 hp for a 32000 trihull with one 60x6x2.75 and two 40x1.5x2 sponsons
the sponsons work out to 30 hp each at 4000 lbs disp and the primary hull works out to 100 hp at 32000 lb displacement
or 160 hp to hit 20 kts
so the 250 hp Im planing on should be more than enough to keep me ahead of weather

funny part is at 8 knots
it seems to work out to about 16 hp
cant be right
which Is why I was hoping some one would check my numbers

[Boston]

oh
video played fine on my mac
but I already have flip for mac installed

[Tad]

Rick....

What is the length, beam, and weight(total with you aboard), of the boat in the video?

Thanks...that's interesting work.

[Guest625101138]

Boston
The lowest drag hull for 15kts with max length of 18m, max beam of 4m and max draft of 1.4m is a mono. The beam of the hull is 0.8m. The wetted surface area is 62sq.m.

It requires 66kW for 15kts and 115kW for 20kts.

A catamaran requires 80kW and 153kW.

A trimaran with a 1t minimum displacement amas requires 71kw and 132kW.

So the best option from a powering perspective for these constraints is still the faux-tri.

Rick W

[Guest625101138]

Originally Posted by Tad

Rick....

What is the length, beam, and weight(total with you aboard), of the boat in the video?

Thanks...that's interesting work.

Tad

Around 110kg total. LWL = 7.2m, BWL = 225mm, draft a little over 100mm.

The two little VRLA batteries are 12Ah and weigh 7kg combined. I have done full discharge test on these and they give about 1 hour operation at 7A. The 12Ah is based on 20h discharge rate. These batteries die if you try to pull 12A. That is where the lithium batteries win out. With a 5Ah lithium battery you can pull 70A and they still hold voltage. A 1kg battery will allow me to get full power from the motor - not for very long though.

I know it was cold so there has to be some motivation. I am truly impressed with these modern motors and controllers. They are very well engineered and do not cost much.

Rick W

[Willallison]

Rick,
What I want to know, is what on earth posessed you to go out in a pair of shorts on a cold Melbourne winter's day !?!

[Guest625101138]

Originally Posted by Willallison

Rick,
What I want to know, is what on earth posessed you to go out in a pair of shorts on a cold Melbourne winter's day !?!

That is my normal attire for pedalling when it is not sunny. Once I start pedalling I enjoy the fresh air. No pedalling was very cold. I was shivering it was so cold. All for the sake of scientific enquiry.

With hindsight I should have set up the pedals so I could have got warmed up.

Rick