Q: How is my propeller and estimated
performance calculated?
A: All the data that you provide on our
Henleys specification sheet is entered into either
two or four separate propulsion packages. The
resulting size is then designed with CAD to American
Bureau of Shipping standards and pitched to ISO484/2
Class 1 or 2 standard.
Q: Will these design packages give a
defined result in performance and engine load?
A: NO! This is not possible as the
number of endless combinations of vessel design;
applied BHP and reductions make it impossible for a
design programme to quantify.
Q: Will tank testing the design help
with defining performance?
A: Yes - this is the best method known
to closely define performance at the DESIGN STAGE!
The next problem is that the vessel must be built
exactly to the design specification, as again all
predictions will fall wide of the mark if say the
vessel is overweight or does not achieve correct
designed trim when in use.
Q: Are all propellers the same?
A: No – different configurations
from various suppliers will give varying performance
results – hence in most cases our own designs
have given outstanding results on the majority of
applications BUT there have been instances where
other makes / designs have suited a particular style
of craft better. The unfortunate part of this is that
"discovery" is made through trial and error
and one cannot purchase a “custom built”
propeller from Henleys on a trial and buy situation!
Q: Should I have my vessel weighed
while under construction?
A: Yes – vessel displacement is
critical to vessel performance and engine load. Most
engine makes now require that maximum loaded RPM is
set within a 20 to 50 margin on engine RPM which
equals a target of approximately 1.5%, yet a lot of
vessels do not achieve the correct trial weight
specified - being as much as 10 to 30% out!
Note:
Engine suppliers can have a 3 to 5% variance on power
supplied including latest electronic motors! This will affect
achieved performance and rpm. This can only be discovered on sea
trial with the engines being fully tested. Please follow this
link to print a sea trial result
form.
Q: Will I get any form of performance
guarantee with the purchase of my propeller?
A: No – due to above stated
variables it is not possible for us to guarantee
something that we cannot truly define. A vessel's
performance is locked into the vessel's design and
final form – A PROPELLER IS NOT A MAGIC WAND! We
use our past experiences to provide as accurate as
possible performance estimates!
Q: What form of warranty do I get?
A: Henleys will warrant the products
supplied for 12 months from date of purchase, to be of merchantable quality and that they
meet the international pitching standard of ISO484/2 Class 1
for the Propeller Range designs except for the "Skip Jack" and
"Groper" – which are pitched to ISO484/2 Class 2 standard.
Q: What happens if on trial the
engine loaded maximum RPM is not to the manufacturers
specifications?
A: The propellers will need to be
adjusted (if possible) – generally in the order
of pitch, cup, diameter or blade area.
Q: Who pays for this work?
A: Henleys will pay up to 50% of one repitch only for a
new propeller based on the current Henleys Propellers and Marine list price, and must be
claimed within eight months from date of purchase. This
offer only applies to New Zealand. In
the majority of cases one repitch is sufficient, but as the
programmes used to calculate the adjustment are generic only, in
some cases the client may need to repeat the process. ALL relating
extra costs i.e. loss of chargeable hours, haulage, removal, freight
and re-installation are the owners responsibility.
Q: What causes a vibration?
A: In most cases it is bent shafts,
engine alignment to drive train when the vessel is in
service or the machinery supplied has not been fitted
correctly as per instructions supplied.
Q: What about vibration in relation
to my propeller.
A: Henleys will guarantee that their
propellers achieve a static balance at time of
manufacture. This is a universally accepted tolerance
and is sufficient for 99% of product supplied. However some vessels are more susceptible to panel
vibration. This becomes apparent after a sea trial
and the first best option that we have found is to
have the propeller dynamic balanced which 99% of the
time improves or rectifies the situation. Any costs
involved in dynamic balancing are the owner's responsibility.
Q: What happens if there is a vibration?
A: Henleys do not accept any
responsibility for vibration levels on sea trial as
the resulting combinations of machinery and vessel
make it impossible to pre-define a level of tolerance
unless an in-depth design study and TVA is undertaken
by the client before any equipment is fitted to the
vessel.
Q: Can galvanic reaction affect my
propeller and sterngear?
A: YES - all propellers (including Stainless
Steel) and sterngear are
susceptible. It is the owner's total responsibility to ensure his
bonding system is adequate for total protection at all times.
Henleys certificate, supplied with every new propeller, includes a
full material specification and batch number. There are well known
EXPERTS in this field - please ask for their contact details if you
are not sure. To view some photos of metal galvanic reactions please
click this link.
Q: How important is the installation of
the sterngear?
A: The correct installation of your drive
train equipment is CRITICAL to the final result. Henleys experience
is that over 98% of problems realised on sea trial are the direct
result of incorrectly installed engines, gearboxes, drive shafts,
sterngear, and propellers. Henleys have taken this area very seriously
and provide full installation instructions with every new propeller
purchased. We also supply full installation instructions of drive train
equipment, available on request to suit each individual
situation.
Q: How can we ensure the propeller will fit
the shaft and key?
A: If Henleys supply the propeller and shaft, then in
approximately 90% of cases the two are fitted (lapped and blued) in
our workshop to ensure an 85% to 100% fit is achieved. For
approximately 10% of our work the shaft is not in our shop at time
of propeller completion - it the becomes the responsibility of the
vessel's engineer to lap and blue on site (at owners cost). Please
see propeller fitting instructions. If the shaft is machined by
another company Henleys do not accept any responsibility for fit
based on given dimensions or a drawing. However, Henleys will ensure
an 85% to 100% fit is achieved to a supplied and tapered mandrel
that is an exact copy of the finished shaft taper. The above also
applies to the forward end of the shaft taper and coupling.
Q: Why is an anti – singing edge required on some propellers?
A: In our experience a “singing” prop occurs approx 4 in every 100
propellers. It can affect any craft from small cruisers to large
ships in new or recently refurbished existing propellers or drive
train equipment. In twin installations it can be one or both of a
matched pair.
Ever run your finger around the edge of a wine glass? Depending on
the amount of fluid in the glass and on your finger one can get
varying degrees of harmonics. The same can apply with a propeller
and drive train when rotating at any RPM
through
the range. In most
cases the rpm bands are only small say 50 rpm but they can go as far
as 400 before it is outside a certain frequency that we can hear.
The same propeller, which meets all industry design parameters, can
be placed on another vessel without the same problem occurring.
Q: Why can’t anti singing edges be applied to all propellers from
new?
A: They can but it would not prevent harmonic’s occurring as a
propeller manufacturer has no way of defining if there will be a
problem or at what rpm band it may become audible – the anti singing
edge is only applied after a sea trial uncovers the problem - in an
effort to change the frequency. In most cases the problem is sorted
out first time but in some vessels the anti singing edge simply
moves the band up or down – shorter or wider.
Q: Who pays for this work?
A: This is a matter of trial and error to custom match the prop
(easiest item to alter in the drive train) to a particular vessel –
there is no other way of defining a result so the costs fall on the
owner.
Q:
Will the noise experienced damage my propeller?
A: NO – it is just annoying if one cannot drive
through
the band quickly.
Please follow this link to learn some
basic technical terms associated
with marine propellers. Relatively, please follow this link to
read the Henleys Terms and
Conditions of Sale.
To find out what is the best propeller
that will suit your vessel, email us at
Henleys
Propellers and Marine for a copy of the
Propeller Calculation Sheet to be sent to you or you
can click here to
fill out a form
online.
As above, to view a drive
train specification sheet please click
here or
email
us for a copy that will suit your requirement.
Relatively, you can click
this link to view a complete drivetrain assembly installed
in a vessel.
|
