Spirit of Texas Drag Hydro

[drwayne]

While this NEVER HAPPENED, at a SAW time trials that NEVER HAPPENED I (only imagined this since it NEVER HAPPENED) a 48" gas shovelnose hydro at full chat beheaded an IMAGINARY duck and it's IMAGINARY head shot straight up vertically about fifteen feet. The IMAGINARY headless duck paddled to shore (only in my imagination of course).

Didnt do it.... everyone saw nothing..... unable to prove anything

Over here its deemed ok as long as you take it home and barbecue it. Docs boat is actually classed as micro duck processing plant.... The messy tasks are mostly done for you. Not exactly sure how he got it passed by council tho... Hey...its gotta be more humane than duck shooting? One question.. how did you teach your duck to self retrieve? Still having problems with that...

Doc, I couldve made a cowl for you faster than that postmans bike is taking to deliver it... mabee hes got a puncture??

10 years back, our then club held the AustralianNationalTitles incorporating all clubs and states..... an eagle-eyed pedestrian on a bridge far to the East thought they saw a duck processed..... and reported it to a lead hungry paper reporter .. .Voila' the only news entry covering the event on page 3 between women's underwear and furniture sales.. ... go figure.

@Richie.. we can shoot 'em, trap 'em, run 'em down and strangle 'em .. but unable to process 'em on water. :shrug:

@srislash .... air, land, water .. Ive RC'd them all.. cross platforming is a technique I still work on .............. :)

@Cowl builder: hurry the far carp !!!

[Outkast]

Now this could prompt some interesting discussion..

Wayne your 430km/h reading may not be that far off the mark once you discount some basic assumptions!

There are a number of factors that influence GPS accuracy and a GPS that you can download data from normally records one or more of these:
Number of satellites in use
HDOP - Horizontal dilution of precision
VDOP - Vertical dilution of precision
TDOP - Time dilution of precision
PDOP - Position dilution of precision (essentially a 3d composite of the other DOP's)

Minor correction, (shouldn't try to go into in medium depth rants after a few bourbons late at night), the parameters above are recorded in hi end GPS receivers and available data for dumping and later analysis. The three items listed below probable errors that could influence any error seen, there are others but this isn't a GPS 101 thread...
RFI - Radio Frequency Interference
IDPE - Indirect path error
MPE - Multiple Path Error

Now most of these factors WILL have had an influence on the accuracy of the GPS in this instance to some extent, don't forget GPS is about capturing the two basic components of navigation, time and position, it calculates the distance between two points and the time taken to move between those points to establish speed and will do that at varying rates 10hz (10 times per second) or up to some high end units i know of at 100hz (100 times per second). Positional accuracy on some of the best units around short of DGPS still struggle to achieve a reliable + or - 5 metres. Given the speeds we're talking about that is a pretty huge potential for error every 1/10th or 1/100th of a second. Now if your crossing an ocean in a supertanker at 20 knots , not an issue.. They are pretty accurate if you consider them as a guide to navigation but as an accurate speed measurment tool leave a little to be desired outside of lots of data crunching by expert analysts.

I once was a resident of the area where Wayne did these runs and had an association with some of the technology businesses in the area. Given that the pond is in the midst of numerous buildings indirect path error is a high possibility, this is usually an issue where signals from only a low number of satellites, low on the horizon are being received and the signal is bouncing around off the buildings before and whilst being received by the GPS resulting in one or both of MPE or IDPE, now GPS programming will recognise MPE and filter out spurious data but not necessarily IDPE resulting in error. The local university and defence industry in the area is doing research and testing all the time that could result in all sorts of radio frequency noise that could easy interfere with the very weak GPS signals.
With a high end gps from which you could download and analyse recorded data it would be possible to calculate a probable percentage of error plus or minus given the full data set captures at least HDOP, VDOP and TDOP. There are a number of precedents here in australia where GPS data with expert analysis has held up over high end radar and speed cameras used by law enforcement in courts of law and saved people from some hefty speeding fines.

Now for some basic physics and the said assumptions. The basic fundamental flawed assumption is that all parts of the boat are moving at the same speed at the same time.

In reality allowing for pitch, roll and yaw different parts of the boat will be moving at different speeds in different planes dependent upong their distance from the rotational centre of the pitch, roll and yaw motions... Now consider if the boat as a whole was doing 197km/h at the time of the flip and add the rotational speed of the boat as it flipped. Just about every part of that boat was moving at a different speed at any given time, most pronounced during the flip, some faster than the speed of the boat as a whole, some slower. If the gps had some distance from the centre of that rotation in any plane the rotational speed component at some point would in part be added to the general forward speed of the whole boat at some time during it's journey.....In short in that specific position in the boat the GPS was placed, IT may have been recording reasonably accurate speeds of that magnitude during the flip...

Now taking the nerdy marine navigation trainer hat off, as everyone says, it don't count anyway, but IMHO it is a bloody impressive flip and worthy of recognition as one of the top ten i've seen for a while.

Can't wait to see it with the lid on Wayne, might settle down some of that battling between the aero and hydro dynamics that appears to be making it all a little wild.. Bloody good effort to date I reckon...

Steve

[drwayne]

Steve, thanks for the well written debrief.

I did note ... the assembled boat, stationary onshore awaiting collection and delivery to water.. would show a speed of 3.7ish kmh whenever the throttle was touched and the encased Rf bounced around inside the hull...
Additionally a steady 0.6kmh without Throttle.
Suggesting the RfSync from satellites had numerous reflections to confuse the 'toy' gps.

Some the larger RAN cans on who I served had multiple gps arrays for 'interpolated/interpreted' accuracy during rough passage ( no toilet jokes, please )

Thanks Steve.
Galilieo would turn in his grave .. using manmade celestial artefacts whilst playing with toys !

Now this could prompt some interesting discussion..

Wayne your 430km/h reading may not be that far off the mark once you discount some basic assumptions!

There are a number of factors that influence GPS accuracy and a GPS that you can download data from normally records one or more of these:
Number of satellites in use
HDOP - Horizontal dilution of precision
VDOP - Vertical dilution of precision
TDOP - Time dilution of precision
PDOP - Position dilution of precision (essentially a 3d composite of the other DOP's)
RFI - Radio Frequency Interference
IDPE - Indirect path error
MPE - Multiple Path Error

Now most of these factors WILL have had an influence on the accuracy of the GPS in this instance to some extent, don't forget GPS is about capturing the two basic components of navigation, time and position, it calculates the distance between two points and the time taken to move between those points to establish speed and will do that at varying rates 10hz (10 times per second) or up to some high end units i know of at 100hz (100 times per second). Positional accuracy on some of the best units around short of DGPS still struggle to achieve a reliable + or - 5 metres. Given the speeds we're talking about that is a pretty huge potential for error every 1/10th or 1/100th of a second. Now if your crossing an ocean in a supertanker at 20 knots , not an issue.. They are pretty accurate if you consider them as a guide to navigation but as an accurate speed measurment tool leave a little to be desired outside of lots of data crunching by expert analysts.

I once was a resident of the area where Wayne did these runs and had an association with some of the technology businesses in the area. Given that the pond is in the midst of numerous buildings indirect path error is a high possibility, this is usually an issue where signals from only a low number of satellites, low on the horizon are being received and the signal is bouncing around off the buildings before and whilst being received by the GPS resulting in one or both of MPE or IDPE, now GPS programming will recognise MPE and filter out spurious data but not necessarily IDPE resulting in error. The local university and defence industry in the area is doing research and testing all the time that could result in all sorts of radio frequency noise that could easy interfere with the very weak GPS signals.
With a high end gps from which you could download and analyse recorded data it would be possible to calculate a probable percentage of error plus or minus given the full data set captures at least HDOP, VDOP and TDOP. There are a number of precedents here in australia where GPS data with expert analysis has held up over high end radar and speed cameras used by law enforcement in courts of law and saved people from some hefty speeding fines.

Now for some basic physics and the said assumptions. The basic fundamental flawed assumption is that all parts of the boat are moving at the same speed at the same time.

In reality allowing for pitch, roll and yaw different parts of the boat will be moving at different speeds in different planes dependent upong their distance from the rotational centre of the pitch, roll and yaw motions... Now consider if the boat as a whole was doing 197km/h at the time of the flip and add the rotational speed of the boat as it flipped. Just about every part of that boat was moving at a different speed at any given time, most pronounced during the flip, some faster than the speed of the boat as a whole, some slower. If the gps had some distance from the centre of that rotation in any plane the rotational speed component at some point would in part be added to the general forward speed of the whole boat at some time during it's journey.....In short in that specific position in the boat the GPS was placed, IT may have been recording reasonably accurate speeds of that magnitude during the flip...

Now taking the nerdy marine navigation trainer hat off, as everyone says, it don't count anyway, but IMHO it is a bloody impressive flip and worthy of recognition as one of the top ten i've seen for a while.

Can't wait to see it with the lid on Wayne, might settle down some of that battling between the aero and hydro dynamics that appears to be making it all a little wild.. Bloody good effort to date I reckon...

Steve

[properchopper]

With apologies for interjecting an off-topic bit 'o info, I'd like to wish those who reside in this thread (as ones who stayed conscious through their math classes) a Happy Pi day (3/14) http://www.youtube.com/watch?v=uAsV5-Hv-7U

[drwayne]

Different hemisphere and all... .. we celebrate Pi ╥ around 22/7.

With apologies for interjecting an off-topic bit 'o info, I'd like to wish those who reside in this thread (as ones who stayed conscious through their math classes) a Happy Pi day (3/14) http://www.youtube.com/watch?v=uAsV5-Hv-7U

[Richie the shipwright]

Wow steve... what a brain!! Great read. I think my maths teacher gave up on me way before we got to this stuff... :-)
The gps was mounted in the rear of the boat, during the flip i figured it would have to have been travelling faster (pitch) than the actual boat speed. Triple backflip with a half twist normally wins a medal.....

I remember pie day used to be on mondays when i was a kid... :-)

[drwayne]

[drwayne]

added rc car airfoil on nose to add downforce.
big improvement
of vourse, the day was rough, but handled it well

[Outkast]

Wild. awesome video Wayne.
What sort of angle of planing angle on the sponsons?

[drwayne]

Thanks Steve.
This is first gut clenching drive at 100% ! .... previously it was 'uncontrollable" ..

2-3 on the ride pads, but it's progressive up to the nose.
cg at ~40% from rear, 3.9Kg on the props! ( they are behind the boat +90mm)
So much torque it's exhilarating... the launch and go is phenomenal !
Oh, NO turn fin either !!.
Will get some from shore video next runs.
W

[jcald2000]

That boat has a LOT of lift!
At least it appears to be flying more level now, where's that cowl?
Tunnel dam next?

[drwayne]

Water was blown into mild wavelets ~2→3" today.. the leaps between wave crests quite noticeable ! ..
without the airing out from wave top launches it should run props embedded at 100%.

where's the cowl ? I keep asking the cowl builder that same question .. he has posted the same one twice these last 6 weeks... !


I added an 1/10 car airfoil to add down force to nose.
That is the only change between runs #12 and #13 .. and woohoo the improvement is dramatic !

The elusive cowl should cater similar aerodynamics ...

[capnswanny]

Nice footage!
What camera do you use...and how do you keep it strapped to that rocket!!

[drwayne]

Aye Capn.
I use a Tachyon XC camera...a younger version of these. http://www.tachyoninc.com/
The xc waterproof to 15ft !
They are/wer around $100-ish

and I use lots and lots of gaffa tape to secure it down !

[capnswanny]

Daaaaargh...thanks, I'll check 'em out matey!