View Full Version : Boat Impacts - Thanks for the responses

William K. Prusaczyk
03-12-1996, 01:43 AM
I would like to thank all those who responded to my post. It generated
a much greater response than I had anticipated. The following is a
summary of the of the information provided in response to:

From: VAX309::PRUSACZYK 6-MAR-1996 15:14:29.99
To: DDN%"biomch-l@hearn.nic.surfnet.nl"
Subj: impact forces during high-speed boat operation

I have recently begun a line of research examining injury during
high speed boat operations. The craft are of multiple designs.
One class is rigid hull with an inflatable above-water rim (rigid
hull inflatables[RIBS]). Others are rigid hull craft of various
lengths. All of these craft are capable of speeds in excess of 35

We have data on the impact forces on the craft in various sea
states (wave/swell heights), some in excess of 10 g. We are
interested in the long term effects of shock and vibration on the
lower limbs and the lower back. We would like to instrument boat
operators and riders to obtain data on the forces imposed on them.

I would appreciate any information on:
1. Appropriate accelerometers (brand/name) or other
equipment that could record impact profiles,
2. Where the accelerometers should be attached to obtain a
'meaningful' force profile, and
3. Mathematical/Computer models that might be used in
predicting the forces.

Not being a biomechanist by training (physiology is my area), I
would appreciate any information that this group could provide on
these questions. Responses could be by post or personal E-mail,
if that's preferred.
Thanks in advance,

================================================== ==========

You may wish to look up some of Malcolm Pope and Dave Wilder's
work on vibration and lower back injury.

Doug Adams
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Dear Keith,

The two accelerometer manufacturers of note are Endevco and Entran.
My experience is that both make a good product. Endevco has a flatter
response at higher frequencies but that is typically outside the
bandwidth you are likely to encounter so the difference is minimal. I
think a more important problem is obtaining a good data acquisition
capability. Robert A. Denton in Detroit is a good source for this sort
of expertise.

My opinion is that your biggest headache will be in attaching the
sensors to obtain good reproduction of the accelerations.
Accelerometers work best when directly attached to bone either with
cement or by threaded rods (we use steinman pins which are common in
orthopaedic surgery). As a rule, most volunteers will not consent to
this so you will have to work out some sort of strap or skin surface
mounting. This will suffer from movement of the superficial tissues
relative to the bones. If you are really careful, you can minimize this
problem. Good luck on this one.

I don't know what level of detail you need out of a numerical
(computer) model but if you have a special problem, you are probably
better off building your own model in a good general purpose package.
Two good packages are Dyna and Pam Crash. All numerical models have to
be tweaked to your data (other words are benchmarked or fudged) and
someone else's model was likely tweaked to their special circumstances.
Trying to work all this out can be a real nightmare for a reasonably
complex model. If you're looking for quick and slightly dirty results,
Dynaman is a good coupled dynamics program. The public domain version
is called ATB and you could probably get it from us or from
Wright-Patterson AFB which supports it.

/ Gregg Klopp
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Have you considered using foot pressure sensors used often in gait
studies. We are presently using Tekscan (Fscan) Pressure Sensor System.
The total cost of the system is approximately $22,000 (?). With this
software the foot pressure is recorded and the total force an output.
With the force output any biomechanical model can be used to calculate
lumbar compression loads. A time synch video camera would give you the
ability the digitize the persons position and then use the model. The
calibration routine for the software is extremely easly. The only draw
back would be to find a computer system "strong enough" to take the
motion of the boat. They are available. We are in the process of
deciding on a laptop system to use in a portable field unit.

Steve MacNeil

Ps: I believe the company is located in Boston, but I am not sure. If
you require the address I can locate it.
================================================== ==========

It may well be worth your while contacting Professor Mike Griffin at the
Human Factors Research Unit, Institute of Sound and Vibration Research,
University of Southampton, U.K.

His group has tremendous experience in using accelerometers and I
believe they did do some work a couple of years back either for the
Royal Navy (Marines and Special Forces) or for the RNLI (Lifeboats)
measuring accelerations on the seats of RIBS. The UK's Institute of
Naval Medicine may also have some knowledge of this area although I
think they may simply have funded the work HFRU did.

Good Luck

Mike Llewellyn
================================================== ==========
I was forwarded your posting and thought I'd respond and offer some
help. I've been working in a related field for a couple of years,
specifically on a shock mitigation system for just such a vehicle. To
help our work I instrumented a suitable boat and took it out on the open
sea, in sea state 4&5. My interests are a little different, so my
measurements were designed a little differently from what you might be
interested in.
My focus was on the input to the operators & passengers, rather than
the shock affect on them. Of course they're related and I am ultimately
interested in what the long term effects are, but at the time I wanted
data from the boat itself.
To get the data I needed I used a couple sets of accelerometers
located in a few places in the boat. I did some research and found a
company called Instrumented Sensor Technology in Okemos, MI
(517-349-8487). They sell a device which is designed to be used to
monitor shock loading on a payload during shipment. The devices I
selected are stand alone units that had triaxial peizoresistive
accelerometers, built in anti-aliasing filters, and on board storage of
about 1Meg. You can select a bunch of data acquisition options to suit
your needs.
I mounted 3 of these devices at a couple of location on the boat; on
the centerline at approximately the center of gravity of the boat, on
the centerline forward in the boat, and on the gunnel of the boat
opposite the center of gravity. The strategy allowed me to get, in
theory, pitch, roll and yaw of the boat, as well as the vertical and
lateral acceleration levels.
As you can tell, I'm very interested in this field. I've got some
data records which I can send to you and I might be able to help you out
with some of your instrumentation problems. Let me know if this would
be of any help to you, and feel free to call and chat.
Good luck,
Dave Frommer
================================================== ==========
I am currently investigating shock wave transmission during locomotion.
Each foot contact creates a shock which travels through the body to the
head. Various factors can influence the attenuation of this shockwave.
To measure this we monitor ground reaction forces with a force platform,
and use lightweight accelerometers fixed to the tibia and on a bite bar
held in the teeth. The biggest problem for surface mounted
accelerometers is the high frequency motion of the skin and soft tissue.
This can contaminate one's data. The bite bar avoids this problem, but
other body sites are problematic. We are using Entran accelerometers
which are small, lightweight and have good response characteristics.
The force plate we use if a Kistler Biomobile plate. There is an
excellent book by Griffin (1990/1991?) called "Handbook of Human
Vibration" which contains a huge amount of very useful information.
Also look at the Engineering Data Compendium by Boff & Lincoln (from
Armstrong Lab at WPAFB). Then the following literature may also help
you with this topic (not exhaustive). I would be happy to discuss this
further with you.

Vernon McDonald

Corbridge C, Griffin MJ (1991) Effects of vertical vibration on
passenger activities - writing and drinking. Ergonomics 34:
Griffin MJ (1975) Vertical vibration of seated subjects: Effects of
posture, vibration level and frequency. Aviat Space Environ Med
46: 269-276
Griffin MJ, Lewis CH (1978) A review of the effects of vibration
on visual acuity and continuous manual control, Part I: Visual
acuity. Journal of Sound and Vibration 56: 383-413
Griffin MJ, Lewis CH (1978) A review of the effects of vibration on
visual acuity and continuous manual control, Part II: Manual
control. Journal of Sound and Vibration 56: 415-457
Kitazaki S, Griffin MJ (1995) A data correction method for surface
measurement of vibration on the human body. J Biomech 28:
Lewis CH, Griffin MJ (1978) A review of the effects of vibration on
visual acuity and continuous manual control, Part I: visual
acuity. Journal of Sound and Vibration 56: 383-413
Lewis CH, Griffin MJ (1978) A review of the effects of vibration on
visual acuity and continuous manual control, Part II: continuous
manual control. Journal of Sound and Vibration 56: 415-457
Moseley MJ, Griffin MJ (1986) Effects of display vibration and whole
body vibration on visual performance. Ergonomics 29: 977-983
Paddan GS, Griffin MJ (1993) Transmission of vibration through the
human body to the head: a summary of experimental data.
Institute of Sound & Vibration Research, University of
Southampton, ISVR Technical Report, 218
Paddan GS, Griffin MJ (1994) Transmission of roll and pitch seat
vibration to the head. Ergonomics 37: 1513-1531
Bhattacharya A, McCutcheon EP, Shvartz E, Greenleaf JE (1980) Body
acceleration distribution and O2 uptake in humans during running
and jumping. J Appl Physiol 49: 881-887
Lafortune MA, Henning E, Valiant G (1995) Tibial shock measured with
bone and skin mounted transducers. J Biomech 28: 989-993
Lafortune MA, Lake MJ, Hennig E (1995) Transfer function between tibial
acceleration and ground reaction force. J Biomech 28: 113-117
Lafortune MA, Lake MJ, Wilson R (1994) Shock transmissibility of the
human body. Eigth Biennial Conference, Canadian Society for
Biomechanics. Calgary, Canada
Luo ZP, Goldsmith W (1991) Reaction of a human head neck torso system
to shock. J Biomech 24: 499-510
Pratt DJ (1989) Mechanisms of shock attenutation via the lower
extremity during running. Clinical Biomechanics 4: 51-57
Salathe EPJ, Arangio GA, Salathe EP (1990) The foot as a shock absorber.
J Biomech 23: 655-659
Shorten MR, Winslow DS (1992) Spectral analysis of impact shock during
running. International Journal of Sport Biomechanics 8: 288-304
Smith SD, Kazarian LE (1994) The Effects Of Acceleration On the
Mechanical Impedance Response Of a Primate Model Exposed to
Sinusoidal Vibration. Annals Of Biomedical Engineering 22: 78-87
Tong A, Hill R, Tripp L, Webb J (1994) The Effect Of Head And Body
Position On +G(Z), Acceleration Tolerance. Aviat Space Environ Med
65: A90
Valiant GA (1990) Transmission and Attenuation of Heelstrike
Accelerations. In: Cavanagh PR (ed) Biomechanics of Distance
Running. Human Kinetics Books, Champaign, Ill, pp 225-247
Voloshin A, Loy DJ (1994) Biomechanical evaluation and management
of the shock waves resulting from the high heel gait: I - temporal
domain study. Gait & Posture 2: 117-122
Voloshin AS (1988) Shock absorption during running and walking.
Journal of the American Podiatric Medical Association 78: 295-299
Voloshin AS, Wosk J (1982) An in vivo study of low back pain and shock
absorption in the human locomotor system. J Biomech 15: 21-27
================================================== ==========
Hi Keith!

Regarding your questions on the net.

We are working in the very field you are describing and we measure
impact up to 7 g on the crew of modern nay boats.

We have a number of articles ready for publication and you are welcome
to get over here an se what we have done.

We have a new method of applying measureing devices on the crew.

We have also designed a new helmsmans workstation that takes out much of

The work is being done in the departement of occupational orthopaedics
at Sahlgrenksa University Hospital Gotheburg Sweden in cooperation with
Dept. of Injury Prevention, Chalmers University of Technology same town.



Johan Ullman M.D.
================================================== ==========
Dear Dr. Prusaczyk,

We have begun looking into the effects of hull slap and the
resulting response of the occupant. In fact, we had submitted
a proposal some time ago to a group wihtin the military (I
can't recall what branch but probably navy). We have developed
some test equipment to simulate the shock loading and were
proposing to conduct tests using instrumented dummies,
cadavers, and human volunteers. Base don our literature
search, we found that the flexion of the knees and the action
of muscular bracing could be dominant effects in tdetermining
the risk of injury. We have been studying shock loading of the
lower limbs in the automotive environment for the last 3 years
and feel that a lot of this research could be applied to the
boat occupant.

Jeff R. Crandall
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I received a copy of your note dated 6 March 1996 on the above topic
sent out through the biomechanics list. Our company is conducting a
major research project for the US Army involving repeated impact in
tactical ground vehicles. We have put together a team of specialists,
led by Dr. Jim Morrison of Shearwater Human Engineering, including a
Biomechanical Engineer, Kinesiologists, a Mathematical Physicist and
Physiologists to deal with the complex issues. The team also includes 3
delegates of the International Standards Organization committee on human
response to vibration.

We have already encountered and solved most of the issues that you
mentioned in your note (i.e., selection and placement of accelerometers,
correction for skin movement, signal conditioning and processing, and
interpetation of data). We have also completed an extensive series of
data collection involving human exposure to repeated impact exposures
from 3.5 minutes to 7 hours, with shock waveforms of different
magnitudes and frequencies.

Currently, we are developing and testing a series of models to predict
probability of injury. We have also examined the performance of
existing models using our human response data and found them to be
inadequate in representing human response to impact.

We have discussed the application of our work to modelling of injury
risk in high speed boats, and would be very interested in discussing it
further with you.

Barbara Cameron
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Try Jack Sandover for details of accelerometers: he and I succesfully
meeasured similar forces in Grand Prix racing cars a few years back.
Contact: Dr Jack Sandover.
Kim Burton
================================================== ==========

I suggest you to compute the jerk of the boat, together
with its acceleration (Jerk is the derivative of the acceleration).
In fact, human tissues are not rigid, and the damage produced by
a given acceleration greatly depends on the history of the accel
curve and on the jerk as well.

Paolo de Leva

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