Elco vs. Higgins PT-boats (was: Propellers)
DBSDESIGN
>DBSDESIGN wrote:
>>(Even though Elco 80s had better top speed with same engines).
>>and Speed differences were negligible. The notable differences
>>were in superior acceleration and turning of the Higgins and
>>the Higgins also manuevered better because of larger rudders
> I'm losing it somewhere??? Anyway, it seems they have different
> underwater shapes.
Definitely. I have several hours of footage showing Higgins and
Elco PTs underway at high speeds in the Pacific, the Med and the
English Channel. Some films are in color and very spectacular.
What I noticed most from watching these films is that in rough
water, the Elcos tend to ride on top of the waves because of the
flatter bottom. Whereas the Higgins Deep-V hull tends to dig in
to big waves, resulting in a massive bow splash that sometimes
obscures the entire boat from view. If you're riding on or near
the bow of a Higgins, you can bet, you're gonna get wet! :-)
> The pivot point on those PT boats was ahead of the vessel anyway,
> they skidded in a turn.
Yes. One of the tapes has some great footage taken from atop the
Brooklyn bridge, which demonstrates an excellent overhead view
of the turning/skidding ability of the Elco 80 at high speeds.
> The info on HP between Higgins and Elco is confusing, it seems
> the Higgins was 4500 normal, but the Elco was less, but upped
> for the trial? by using the same engines as a Higgins??
Jane's '56 is your source of confusion. They did not give the gross
HP rating for the W-14 engines fitted to Elco 600 boats. Which is
4500HP. The figure given by Janes's (4050HP) is either a misprint
or maybe the net power measured from the propeller shafts.
The only thing I could add is that on Elcos built up until PT 565,
the center engine was direct drive but the wing engines were not.
After that the engine room was redesigned so the wing engines
could turn the shafts directly without a gearbox. On the Higgins,
all three engines were always direct drive to the propeller.
I didn't mention this last time, but at the Miami Beach trials the
Navy had a set of boats with the old W-8 Packards for purposes
of comparison. Top speeds with the W-8 engine are listed below,
followed by the W-14 tests. Note that the Elcos used in the tests
still had the gear-driven wing engines.
W-8 Packards x 3 (3600HP gross)
PT 296, Higgins 78 ft:
106,500 lbs - 41.49 kts
PT 553, Elco 80 ft:
106,000 lbs - 40.99 kts
________________________________
W-14 Packards x 3 (4500HP gross)
PT 295, Higgins 78 ft:
105,100 lbs - 43.90 kts
PT 552, Elco 80 ft:
106,000 lbs - 45.14 kts
There are discrepancies here in top speeds and I think engine
tuning is probably the main factor. Looks to me like the Elco
W-8 engines may have been slightly out of tune.
> So where does that leave us with these PT boats??? On a car,
> they say it is torque that counts, not HP.
Engines without a lot of torque can still accelerate a vehicle
harder than a more torquey engine. My friend had a Boss 302
Mustang, and he (frequently) dusted big-block Chevy's in a drag
race. Ford 302 V-8 is not exactly the king of torque. Far from it.
However, maybe the gear-drive wing engines might cause a loss
of torque on Elco PTs, but you would think the US Navy would
note this if they felt it was a factor in acceleration tests.
> Eugene did emphasize draft as a big factor in effective HP in
> another thread.
I didn't catch that thread. When was this?
_____________________________________________________
D B S D E S I G N @ a o l. c o m
_____________________________________________________
...All I ask is a tall ship and a star to steer her by... - John Masefield
B F Lake
>> Eugene did emphasize draft as a big factor in effective HP in
another thread.<<
>I didn't catch that thread. When was this?<
trial was? Seems like apples and oranges to me.
This was a thread from the end of Feb "Italian Cruiser Propellers-1930" and
this was Eugene's post "DIDO vs ATLANTA" from 3 March:
> take things like SHP and speeds with a big grain of salt. These
things are meaningless in ships unless accompanied by graphs of
loading and hull bending. I have known a vessel get a higher speed on
the measured mile fully laden than it did with 1/3 fuel due to a
peculiar set of circumstances whereby the backside lifted when the aft
fuel tanks were empty moving the props into more dead water. IIRC she
got 25 knots at 1/3 fuel and 27 knots fully fuelled - it was a Brooke
Marine design too!
Before any measured mile the marks forrard, aft and midships, port
and starboard are carefully read and chiefy calculates a weird formula
- or consults a table of graphs to ascertain the "bend" in the hull
(hulls bend according to weight distribution). This has direct
bearing on the tonnage.
Some of a propellor almost inevitably runs in "dead water" - IOW it is
"masked" by the hull to some extent. This varies according to loading
and bending. A good designer tries to minimise this as much as he
can. One of the reasons that ships with four props often have a
higher pitch on the inner pair is to compensate for this.
So comparing two different hulls is often futile - hell comparing two
ostensibly same hulls is often futile with one getting 1/2 knot more
than the other for reasons that seem to defy logic. We had two type
twelve frigates like that. Both came from the same Clydeside yard and
were allegedly the same ships. One was always slightly faster at the
same revolutions than the other - a cause for much bitching among
station-keeping watch officers.
Eugene L Griessel eug...@dynagen.co.za <
Eugene Griessel
> >> Eugene did emphasize draft as a big factor in effective HP in
> another thread.<<
> >I didn't catch that thread.
I notice that this reply was also swallowed by the Usenet Message Eater. I
repost it here - begging forgivenes from those who have seen it:
"B F Lake" <bfl...@coastnet.com> wrote:
>DBSDESIGN wrote:
>> (Even though Elco 80s had better top speed with same engines). <
>and
>>Speed differences were negligible. The notable differences were in
>superior acceleration and turning of the Higgins <
>and
>> The Higgins also manuevered better because of larger rudders,
> which I guess might cause a bit more drag at certain speeds, <
> I'm losing it somewhere??? Anyway, it seems they have different
>underwater shapes. The larger rudders on the shorter boat ought to let
>her steer in as straight a line as a longer boat, and of course would have
>a larger effect when put over. The pivot point on those PT boats was
>ahead of the vessel anyway, they skidded in a turn.
> The info on HP between Higgins and Elco is confusing, it seems the
Higgins
>was 4500 normal, but the Elco was less, but upped for the trial? by using
>the same engines as a Higgins?? (this relates to prop design if they had
>props whose design points were for their own boats designed hp, so changing
>the engine and using the same prop is wrong??) Anyway the hp figures for
>a ship are a bit foggy too. It seems they figure out what hp you had After
>they figure your speed, and its not a question of what hp is "available"
>from the engine? Also they are waving around HP, BHP, and SHP. (with
>reciprocating engines, IHP seems fashionable- I remember the engineer in an
>old frigate going around the top of the engines getting a paper tape
>readout from the 4 cylinders-2 LP, 1-IP, and 1-HP I think it was, don't
>know if that's where the IHP comes from)
> eg the French DD LE TERRIBLE ~1934 on trials reached a record speed
of
>45.25 kts with about 100,000 HP average for one hour being 44.9 with 94,000
>Hp. On her 8 hr's trial she averaged 43 kts. Able to maintain 37 kts
>continuously at 74,000 SHP (from 42 Janes)
> So where does that leave us with these PT boats??? On a car, they say
it
>is torque that counts, not HP. (why my 68 Dodge 4-brl 381 used to try to
>turn upside down when gunned?<G>) Marine prop design has torque effective
>direction change along the blade to allow for the higher spin velocity as
>you go out from the hub-why it is twisted, so there are some choices you
>can make there. It is all too much for my non-engineer brain.
(In the following diatribe I use IP, SP and BP. These are the correct terms
but are synonymous with IHP, BHP and SHP.)
IP - indicated power is a calculation based on the Mean Effective Pressure
(the paper tape you alluded to earlier is a graphic representation thereof),
the length of the piston stroke, the area of the piston, the number of
effective power strokes per cycle and the revolutions the engine is running
at. The mnemonic for this is PLAN - PressureLengthAreaNumber of effective
RPM.
IP is largely the theoretical power an engine can deliver ignoring a whole lot
of pesky factors (such as friction etc.).
The figure offered by this calculation bears little resemblance to what a
brake calculation at the shaft offers. Mechanical efficiency is calculated
by dividing the IP by the BP. As an example let us look at a single acting
four stroke engine with a cylinder diameter of 180mm and a stroke of 350mm
running at 250 rpm with a calculated mean effective pressure of 426 kN/m^2.
The IP would be 7.21 kW
The same engine measured by rope brake or hydraulic dynamometer
gave a reading of 5.546 kW
Thus the mechanical efficiency of the engine is 76.93%. Now one has to take
losses in the shaft bearings, the p-brackets, the gearboxes, etc. into
consideration before finding out what eventually arrives at the propellor for
conversion into thrust. Thus the mechanical efficiency of the propulsive
system is usually calculated by a dynamometer affixed in place of the
propellor - which once again will show some losses over the BP. Overall
mechanical efficiency will be SP/IP.
Thus the only really significant power rating in the comparison should be the
SP and the thrust which would be a factor of propellor efficiency. In other
words how much power is it turning into useful pressure to move the boat
forward.
In the old days much effort went into hull shape and smoothness in an attempt
to keep as much of the water flow around the hull as laminar as possible.
(in fast boats). Turbulence = drag = lost power. However for vessels
running in the open sea the futility of extreme efforts in this direction
soon became apparent as waves, ripples, eddies and currents in the medium
being traversed negated a lot of the very "fine tuning".
Remember that Fred Cooper & Scott-Paine's "Miss England II" exceeded 100 mph
in 1930 already and before the end of 1931 notched 95.7 knots. The
propellor on Miss England II was a curious affair - I have a photograph of
it. It spun at 12 000 rpm and transmitted 3500 SHP. I mention these facts
to show that some knowledge of high speeds and the problems inherent did
exist quite early on.
Why the two PT boats did not perform equally well given all other factors
being seemingly equal? Very difficult to tell. We have no idea of the
respective water plane areas in either at the speeds achieved - which would
be indicative of the amount of friction on the hull. We have no idea of how
much of the propellor would have been "exposed" in each case. In other words
how much good decent water it had to "bite" into and how much deadwater it
ran in. This is very much dictated by hull shape too.
Ultimately we end up comparing apples and oranges to some degree. Even two
ostensibly similar boats would not have given exactly the same speeds. When
one starts pushing the edge of the envelope the tiniest factors can make a
difference. A screw exposed 1/16 inch more on one hull than on the other
can mean the loss of some speed.
Eugene L Griessel eug...@dynagen.co.za
www.dynagen.co.za/eugene
SAAF Crashboat Page - www.dynagen.co.za/eugene/eug3.htm
-----------== Posted via Deja News, The Discussion Network ==----------
http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
DBSDESIGN
> Interesting figures from the PT boats! I wonder what the intent
> of the trial was?
One reason for the trials was to determine whether the US Navy
should continue production of the Higgins PT-boat. Some earlier
complaints about the Higgins were legitimate but others were not.
This was discovered after the Miami Beach trials, and the end
result was that the Higgins PT was kept in production with a few
minor modifications to the conning station. Such as moving the
turrets back several feet to give the helmsman better visibility.
> Seems like apples and oranges to me.
Essentially the Miami Beach trials were designed to avoid apples
and oranges testing. There was an earlier comparison made, but
in that case, the tests were loaded (literally) to favor the Elco
80-footer. Both boats had the W-8 engines but for some reason
the Higgins was tested at 126,000 lbs. and the Elco was tested
at 106,000 lbs. Under those circumstances, the Elco obviously
performed better and the Higgins PT couldn't make 40 kts at that
weight with W-8 Packards. There was talk of discontinuing the
Higgins PT soon afterward.
Unfortunately the Higgins PT had also earned a bad rap because the
unit responsible for shaking them down was actually a subchaser
outfit! The SC boys apparently had some trouble tending to aircraft
style engines because they were only getting about 33 kts out of
new boats. Yet another good reason for conducting the Miami Beach
trials. To find out if any of the problems reported to date were in
some way self-generated. Which they were. :-)
The Miami Beach trials were in effect, an attempt to level the
playing field by loading the boats as comparably as possible and
conducting a more thorough and objective analysis. The US Navy
learned that the Higgins was actually better than the Elco in some
ways and without the trials, the Higgins PT probably would have
been cancelled. A classic bureaucratic mistake that was luckily
avoided by carrying out further tests.
> These things are meaningless in ships unless accompanied by
> graphs of loading and hull bending.
That would make it easier to compare one ship to another.
> I have known a vessel get a higher speed on the measured mile
> fully laden than it did with 1/3 fuel due to a peculiar set of
> circumstances whereby the backside lifted when the aft fuel
> tanks were empty moving the props into more dead water.
Good point. Planing hulls like PTs were sensitive to trim changes,
so it was important as to where additional weights were placed in
the hull or on the deck to maintain the best possible planing angle.
____________________________________________________
D B S D E S I G N @ a
o l. c o m
____________________________________________________
"Music we need... the Tipperary song if there are no objections!"
- Jurgen Prochnow from Das Boot -
DBSDESIGN
> Why the two PT boats did not perform equally well given all other
> factors being seemingly equal? Very difficult to tell. We have no idea
> of the respective water plane areas in either at the speeds achieved -
> which would be indicative of the amount of friction on the hull. We
> have no idea of how much of the propellor would have been "exposed"
> in each case. In other words how much good decent water it had to
> "bite" into and how much deadwater it ran in. This is very much
> dictated by hull shape too.
Well, Higgins PTs had greater draft forward and less drag aft than
the Elco if that possibly means anything about acceleration. Those
factors contributed to the Higgins ability to make tighter turns,
aided by the larger rudders of course. When you say "deadwater" do
you mean conditions caused by countering turbulence and bubbles?
Eugene Griessel
dbsd...@aol.com (DBSDESIGN) wrote:
> Eugene Griessel <eug...@dynagen.co.za> wrote:
>
> > Why the two PT boats did not perform equally well given all other
> > factors being seemingly equal? Very difficult to tell. We have no idea
> > of the respective water plane areas in either at the speeds achieved -
> > which would be indicative of the amount of friction on the hull. We
> > have no idea of how much of the propellor would have been "exposed"
> > in each case. In other words how much good decent water it had to
> > "bite" into and how much deadwater it ran in. This is very much
> > dictated by hull shape too.
>
> the Elco if that possibly means anything about acceleration. Those
> factors contributed to the Higgins ability to make tighter turns,
> aided by the larger rudders of course. When you say "deadwater" do
> you mean conditions caused by countering turbulence and bubbles?
A propellor is a positive displacement device that functions by adding
velocity to the medium in which it runs - much like an uncased centrifugal
pump. Assume you affix a propellor in the middle of a large flat plate and
stick this in the water - the propellor would spin merrily churning up the
water but adding no (or very little) forward motion to the plate. The
propellor is running in 100% deadwater - water where its actions cannot
complete a forward to aft displacement of the water. Virtually all
propellors run in some deadwater - every designer tries to minimise that as
much as possible, but has to fight with all sorts of other criteria (such as
having a suitable draft). "Deadwater" is that part of the water which occurs
behind "deadwood" or that part of the hull that effectively masks the
propellor. It aids in creating bubble or "burble" cavitation (as it is
sometimes called). Paradoxically planing hulls are notorious for creating
breakaway eddies at the rear as the laminar flow gets sluggish and starts to
break away from the hull, invariably incorporating air bubbles - due to the
aeration of the water by the very speed of the hull through it. Careful
design in this area is essential to avoid this. The Germans, in WW2, even
used a sort of primitive spoiler and a step astern of the props on their S
boat to re-energise the water flow and cause it to "stick" to the hull
better. I believe the Italians tried exhausting the engines into this area
in some experiments in an effort to defeat the hull-created "bubbling" on
fast boats. Marine propellors do not work well when running in air!
Needless to say the whole thing boils down to tradeoffs - if you want a hull
that does one thing better than another you pay for it somewhere along the way
in losses.
DBSDESIGN
>"Deadwater" is that part of the water which occurs behind "deadwood"
>or that part of the hull that effectively masks the propellor.
I see.
>It aids in creating bubble or "burble" cavitation.
I guess cavitation = serious bubble-trouble. I've often noticed that
when driving powerboats and cutting across someone else's wake,
I can hear the engine slow down noticeably when passing over. Is
that due mostly to turbulence in the water, or is it running into the
large trail of bubbles that reduces propeller efficiency even more?
>Paradoxically planing hulls are notorious for creating breakaway
>eddies at the rear as the laminar flow gets sluggish and starts to
>break away from the hull, invariably incorporating air bubbles -
>due to the aeration of the water by the very speed of the hull
>through it. Careful design in this area is essential to avoid this.
This is an interesting concept because the Elco and the Higgins
were very different in this way. The lines of the Higgins Deep-V
hull turned very abruptly into a totally flat bottom in the rear
section. While the Elco's Shallow-V tapered gently, retaining its
V-shape all the way to the stern.
>The Germans, in WW2, even used a sort of primitive spoiler and a
>step astern of the props on their S-boat to re-energise the water
>flow and cause it to "stick" to the hull better. I believe the Italians
>tried exhausting the engines into this area in some experiments in
>an effort to defeat the hull-created "bubbling" on fast boats. Marine
>propellors do not work well when running in air!
Redirecting exhaust is certainly a creative approach to dispersing
bubble formations under the hull.
Elco tried some experiments with their "slipper". An adjustable
platform mounted on the stern near the waterline to alter trim
angles. I guess a slipper could also re-energize waterflow by
changing the planing angle. Slippers eventually became common
on fast commercial pleasure boats although I haven't seen them
as much as I used to.
Modern planing boats usually have a series of shallow fins running
the length of the hull. I'm not sure if they are meant to keep water
moving more efficiently past the propellers, or just intended to
improve hull planing stability.
___________________________________________________
D B S D E S I G N @ a o l. c o m
___________________________________________________
All I ask is a tall ship and a star to steer her by. - John Masefield
Eugene Griessel
dbsd...@aol.com (DBSDESIGN) wrote:
> I guess cavitation = serious bubble-trouble. I've often noticed that
> when driving powerboats and cutting across someone else's wake,
> I can hear the engine slow down noticeably when passing over. Is
> that due mostly to turbulence in the water, or is it running into the
> large trail of bubbles that reduces propeller efficiency even more?
I would expect the engine to race if it were cavitating with a marked
reduction in speed.
> Modern planing boats usually have a series of shallow fins running
> the length of the hull. I'm not sure if they are meant to keep water
> moving more efficiently past the propellers, or just intended to
> improve hull planing stability.
I assume those shallow fins or strakes act much as fences do on aeroplane
wings. They deter crosswise flow and direct it aft. Which would help
reenergise the boundary layer and keep the flow more constant.
DBSDESIGN
dbsd...@aol.com (DBSDESIGN) wrote:
>> I guess cavitation = serious bubble-trouble. I've often noticed that
>> when driving powerboats and cutting across someone else's wake,
>> I can hear the engine slow down noticeably when passing over.
> I would expect the engine to race if it were cavitating with a marked
> reduction in speed.
You're right. I meant I could feel the boat slowing and the engine
changing speeds. I assumed that the engine raced because the prop
may have lifted partly out of the water as the boat leaped over a
wake at high speed. The engine seemed to slow down upon landing
but maybe I was making assumptions as to why the engine slows.
Maybe the propeller wasn't leaving the water after all. But I have
been airborne off of a wake for sure, at least a couple of times.
I didn't know that a trail of bubbles from a wake could also cause
a propeller to race like that. Interesting stuff.
> SAAF Crashboat Page - www.dynagen.co.za/eugene/eug3.htm
I checked out your crashboat page, it was very informative. Just
in case you didn't know, about 570 of the 63-ft. were ordered for
a variety of roles during WW2, according to reports by US Navy
Bureau of Ships and US Army Corps of Engineers. The 63-ft. was
produced until 1956, although there was no records given as to
how many were ordered in the postwar years. There's a reference
to eleven boats being transferred to South Africa in October 43.
The boat was designed by Dair N. Long of Miami Shipbuilding to
RAF requirements. They ordered 91 initially on what was called
the "1799 program" but 36 were commandeered by the US Navy.
Apparently the British signed their first contract for this boat
in May 1942 and the first ones were delivered without guns.
That changed after the Luftwaffe started attacking them in the
English Channel and at least one 63-footer was sunk at Dieppe.
One last tidbit is that the first inboard drawings of the 63-ft.
were dated December 15, 1940. I hope you've enjoyed all this
useless information about long-extinct machinery. :-)
___________________________________________________
D B S D E S I G N @ a o l. c o m
___________________________________________________
A man may build himself a throne of bayonets,
but he cannot sit on it. -
W.R. Inge
Eugene Griessel
dbsd...@aol.com (DBSDESIGN) wrote:
> > SAAF Crashboat Page - www.dynagen.co.za/eugene/eug3.htm
>
> I checked out your crashboat page, it was very informative. Just
> in case you didn't know, about 570 of the 63-ft. were ordered for
> a variety of roles during WW2, according to reports by US Navy
> Bureau of Ships and US Army Corps of Engineers. The 63-ft. was
> produced until 1956, although there was no records given as to
> how many were ordered in the postwar years. There's a reference
> to eleven boats being transferred to South Africa in October 43.
Fascinating - no I did not know this. South Africa bought two batches and
this must refer to the second batch. The first couple of boats had no
enclosed wheelhouse - which made them very difficult to use in our seas. The
second (and larger) batch did.
>
> The boat was designed by Dair N. Long of Miami Shipbuilding to
> RAF requirements. They ordered 91 initially on what was called
> the "1799 program" but 36 were commandeered by the US Navy.
> Apparently the British signed their first contract for this boat
> in May 1942 and the first ones were delivered without guns.
Once again - this is news. We were always told that the design was an ELCO
one which had been built by Miami. Strangely enough the men who manned these
boats knew very little about their origins. The history of SAR in the SAAF
is mostly lost. At the outbreak of WW2 a salesman/engineer from British
Powerboat was here in South Africa with a twin Merlin powered 72 footer
trying to interest the goverment in the thing. This was taken over at the
outbreak of war and became R0 - or better known as "Malmok". Further sales
from BP or Vosper became impossible as all their output was needed by the RAF
and RN. That's how we ended up with the Miamis. And excellent boats they
were too. I was present at the last official trial of the last boat before
it was sold to civilian interests and she still made over 40 knots in a state
4 sea. This was in 1972. But they chomped petrol like nobody's business. We
used to dash over to a nearby port - 8 nautical miles away - and that used to
cost 50 gallons of high octane. British gallons. Which would be around 70 US
gallons. They accelerated like a dream - and could stop on a sixpence as
well. Only hassle was doing the tappets - 288 per boat!
Another thing - we were always told that the Kermath engines were aero
engines. Nowhere have I ever managed to find evidence of a 550 hp Kermath
engine in an aeroplane. Each shaft had two Kermaths feeding into a "Joe's"
gearbox. Once again, Joe may be famous in the States for making this sort of
gearbox but all my attempts to track him down have failed.
> That changed after the Luftwaffe started attacking them in the
> English Channel and at least one 63-footer was sunk at Dieppe.
> One last tidbit is that the first inboard drawings of the 63-ft.
> were dated December 15, 1940. I hope you've enjoyed all this
> useless information about long-extinct machinery. :-)
>
Loved it - if you have any more I would really welcome it. My old man was the
base engineer for those boats. He served with the unit for 30 years and
sailed many thousand miles on the Miamis. They destroyed kidneys and wrecked
knees - but they were fun. We sometimes had to guardship racing motorboats -
and if the seas were slightly choppy we used to have no trouble pulling away
from the leaders. We used to speculate that "their knots" were a lot slower
than "our knots". Especially as they would all claim to be capable of
horrific speeds - approaching those of light - in the pub the night before
the race.
Eugene L Griessel eug...@dynagen.co.za
SAAF Crashboat Page - www.dynagen.co.za/eugene/eug3.htm
-----------== Posted via Deja News, The Discussion Network ==----------
DBSDESIGN
dbsd...@aol.com (DBSDESIGN) wrote:
>> The boat was designed by Dair N. Long of Miami Shipbuilding to
>> RAF requirements.
> Once again - this is news. We were always told that the design
> was an ELCO one which had been built by Miami.
I have a detailed table of construction dates and fates for the
boats that were built as PTCs and RPCs which represents about
104 of the 570 boats. Trumpy Yachtworks built about 30 PTCs
and the rest by Miami Shipbuilding between Jan-Sept 1943.
Elco built the first twelve PTCs, but those boats were modified
versions of their own 70-ft. PT-boat. That might be the reason
for confusion I think. There's no mention of Elco being contracted
to build Miami 63-footers, although it might be possible. They
had a lot of PTs to build and one reason the Higgins PT continued
is because Elco could not meet demands all by themselves.
> they chomped petrol like nobody's business. We used to dash over
> to a nearby port - 8 nautical miles away - and that used to cost 50
> gallons of high octane. Which would be around 70 US gallons
Good gas mileage just wasn't in the cards. PTs generally drank
about 292 US gallons per hour at 35 kts. At flank speed the rate
increased to about 474 gallons per hour.
> Another thing - we were always told that the Kermath engines
> were aero engines. Nowhere have I ever managed to find evidence
> of a 550 hp Kermath engine in an aeroplane.
US Navy versions of the 63-footer were originally supposed to
have Defender engines @630BHP x 2, for a top speed of 37 kts
at 52,000 lbs. Fuel complement was 1540 US gallons. I don't
know how many were built that way, and if the requirements
or specs changed at some point. The US Army designated the
standard 63-foot crashboat as "Design 416."
> Each shaft had two Kermaths feeding into a "Joe's" gearbox.
> Once again, Joe may be famous in the States for making this
> sort of gearbox but all my attempts to track him down have
> failed.
If Miami Shipbuilding is out of business, try John Trumpy.
There might be other subcontractors we don't know about.
You could try writing to the US National Archives to look
up this contractor. They could start with NAVSEA 941. It
has crashboat data from the Army and Navy and might have
some relevant info about the various subcontractors. Then
there's the US Navy BuShips Administrative History which
has the production tables. The US Archives should know if
there are other means to track down Mr. Joe's gearboxes.
> The history of SAR in the SAAF is mostly lost.
If that doesn't work, then maybe the RAF Air Ministry has
data, since they would have to order spare parts including
gearboxes for the propeller shafts. Files are maintained
at the Public Records Office in Kew.
> My old man was the base engineer for those boats. He served with
> the unit for 30 years and sailed many thousand miles on the Miamis.
> They destroyed kidneys and wrecked knees - but they were fun.
Destroyed kidneys? Ouch! :-)
___________________________________________________
D B S D E S I G N @ a o l. c o m
___________________________________________________
Ken Young
dbsd...@aol.com (DBSDESIGN) wrote:
> Definitely. I have several hours of footage showing Higgins and
> Elco PTs underway at high speeds in the Pacific, the Med and the
> English Channel. Some films are in color and very spectacular.
Something people might find interesting is that all the Elco boats
were derived from a British Power Boat 68ft craft. The original boat
entered service as PT09 and PT10 to 19 were pattern copies. The design
was later enlarged to 78 and then 80ft. The Higgins boat was a 78ft
modified version of the original British boat. The really interesting
thing about this was the BPB boat had been rejected by the British in
favour of the Vosper 70ft boat. See Battle of the Torpedo Boats and or
Fast Attack Craft.
Ken Young
ken...@cix.co.uk
Maternity is a matter of fact
Paternity is a matter of opinion
Ken Young
dbsd...@aol.com (DBSDESIGN) wrote:
> The US Navy
> learned that the Higgins was actually better than the Elco in some
> ways
As I said in another post both boats were derived from the BPB 68ft
craft which had been stretched to fit four tubes.
DBSDESIGN
dbsd...@aol.com (DBSDESIGN) wrote:
>> The US Navy learned that the Higgins was actually better
>> than the Elco in some ways
> As I said in another post both boats were derived from
> the BPB 68ft craft
As I mentioned earlier,
The Higgins PT was not derived from a BPB or any other British
design for that matter. 'Twas an all-American, apple-pie torpedo
boat designed and built by Higgins Industries.
DBSDESIGN
> Something people might find interesting is that all the Elco
> boats were derived from a British Power Boat 68ft craft.
> The original boat entered service as PT09 and PT10 to 19
> were pattern copies. The design was later enlarged to 78 and
> then 80ft.
If I was a nitpicking faultfinder, I would note that PT 9 was
actually a 70-footer. But I'm not, so I won't. :-)
Hubert Scott-Paine of British Power Boats designed a 60-foot
MTB in 1936. The lower hull lines were similar in shape to the
newer 70-footer. He also designed PT 9 and the first ten Elcos
were almost identical as you suggested. Beginning with PT 20,
Elco increased the length of the ship to 77-feet to accomodate
US torpedoes, and also to improve sea-keeping performance.
However, the Elco 80-footer was a radical departure from PT 9.
Both in hull lines and the deck arrangement.
> The Higgins boat was a 78ft modified version of the original
> British boat.
Actually, the Higgins PTs were not based on a British design.
> The really interesting thing about this was the BPB boat had
> been rejected by the British in favour of the Vosper 70ft boat.
True, but Elco rejected the Vosper when they went shopping
for existing boats to gain experience. Elco was more impressed
with Scott-Paines 70-footer because it was faster and more
manueverable at any given weight with the same engines.
That pretty much continued throughout the war, since US and
British boats were with few exceptions, fitted with the same
powerplants. Vospers were smaller and lighter than US boats,
yet consistently slower by several kts when fitted with the
same mark of Packard engines. Even late-war Elcos at 61 tons
could match speed with a Vosper that was 10 tons lighter.
I have no idea why the Admiralty chose the Vosper over the
BPB. But like Elco, the RAF didn't want Vospers either. They
went with BPB and Miami Shipbuilding for their crashboats.
Commander Peter Du Cane, an ex-Royal Navy officer worked
for Vosper, and may have had influence with the Admiralty.
If it wasn't politically influenced, then perhaps the Vosper
was more rugged, or rode better in rough water than BPBs.
But I seriously doubt that Vospers rode better than Elco 80s.
B F Lake
42 Janes that pre-war Vospers had 3 Isotta-Fraschini engines, but both
Vosper and BPB used Packards during the war.
On the rating scale, where would the RCAF's Montreal built Canadian Power
Boat rescue launches fit in? Look PTish, 70 X 20 X 4 1/2 ft, 2 shafts with
Packards, BHP 2,700=40kts?
The 1938 RN boats (Vosper 22 and Thornycroft 24 , 25) had" two auxiliary
cruising engines on wing shafts, which automatically turn over to maintain
engines at 9 kts. Below that these engines can be used for silent
approach." I think it was the Elco which had the wing shafts geared that
was mentioned before? Same idea? I remember in the book "White Plumes
Astern" by the RCN's Tony Law , that lurking and listening was the tactic,
then at the right moment opening up. Creeping around was important in
their work too!
Regards,
Barry
DBSDESIGN
>The 1938 RN boats (Vosper 22 and Thornycroft 24 , 25) had" two
>auxiliary cruising engines on wing shafts, which automatically
>turn over to maintain engines at 9 kts. Below that these engines
>can be used for silent approach."
Vosper went with that arrangement until the end of 1942. It was
discontinued because the speed attained from the V-8 auxiliaries
was considered to be inadequate by the Naval Staff, and thus did
not justify the additional weight added to the boat.
>I think it was the Elco which had the wing shafts geared that was
>mentioned before? Same idea?
Yes, and Vosper used the opposite configuration for the Packards.
The center shaft was geared and the wings were direct drive.
>I remember in the book "White Plumes Astern" by the RCN's
>Tony Law, that lurking and listening was the tactic, then at
>the right moment opening up. Creeping around was important
>in their work too!
Definitely. All the navies tried different ways to direct exhaust
underwater to quiet engines in the interest of stealth. Vosper
tried feeding exhaust under the hull with the intention to direct
exhaust flow towards the propellers and rudders to improve the
hydrodynamic efficiency. Unfortunately early trials created the
opposite effect with a loss of propeller efficiency instead. So
the idea was dropped, despite requests to continue experiments
with having the boats ride on a cushion of exhaust gases.
Eugene Griessel
> dbsd...@aol.com (DBSDESIGN) wrote:
>
> > The US Navy
> > learned that the Higgins was actually better than the Elco in some
> > ways
> As I said in another post both boats were derived from the BPB 68ft
It seems that the Higgins boat owed nothing to British Power boat's designs
but was based on a 1937 experimental shallow-water craft called "Eureka".
This was the brainchild of Andrew Higgins and had a fairly unique hull which
had a spoon bow designed to trap aerated water under the forefoot and reduce
friction. The V-shaped hull, as it ran aft, then changed to reverse curve.
The propellors ran in a semi-tunnel. The groove added stability and made the
Higgins boat very stable in high-speed turns.