Mk 13 Air Dropped Torpedo

[Kyle Boatright]

I just finished the book "The Last Stand of the Tin Can Sailors" and it
raised some questions about the air dropped torpedoes (the Mk 13) in use by
the US Navy in WWII.

What drove the range/speed trade-offs for the Mk 13? According to the
spec's I've found, it had a range of ~6,000 yards and a speed of 33 knots.
With a likely launch range of 1,000 yards or less, wouldn't it have made
sense to sacrifice the 6,000 yard range to get an increase in speed?
Wouldn't a 45 or 50 knot torpedo with a 1,500 or 2,000 yard range have been
a better compromise? I'd certainly think the higher speed would have
increased the probability of a hit, because it would have reduced the
deflection at launch by 1/3 or so. Also, it would have given the target 1/3
less time to maneuver to avoid the torpedo.

A second question addresses launch speed. Early in the war, drop speed and
altitude were in the 110 knot, 150' range. Later, a couple of plywood
fairings were added to increase drag, lift, and stability, and these add-ons
improved the drop parameters for the torpedo. The sources I've found have
contradictions about the launch envelope after these fairings were added.
Can someone point me to a reputable source for this information?

Thanks,

KB

[Dave Deep]

Ahh but the closer you get to the target the longer you are exposed to enemy
fire & the higher the chances of losing an expensively trained crew plus the
aircraft; Far better to waste multiple torpedoes saving the crews & AC for
further missions.

DD


"Kyle Boatright" > wrote in message
...
>I just finished the book "The Last Stand of the Tin Can Sailors" and it
>raised some questions about the air dropped torpedoes (the Mk 13) in use by
>the US Navy in WWII.
>
> What drove the range/speed trade-offs for the Mk 13? According to the
> spec's I've found, it had a range of ~6,000 yards and a speed of 33 knots.
> With a likely launch range of 1,000 yards or less, wouldn't it have made
> sense to sacrifice the 6,000 yard range to get an increase in speed?
> Wouldn't a 45 or 50 knot torpedo with a 1,500 or 2,000 yard range have
> been a better compromise? I'd certainly think the higher speed would have
> increased the probability of a hit, because it would have reduced the
> deflection at launch by 1/3 or so. Also, it would have given the target
> 1/3 less time to maneuver to avoid the torpedo.
>
> A second question addresses launch speed. Early in the war, drop speed
> and altitude were in the 110 knot, 150' range. Later, a couple of plywood
> fairings were added to increase drag, lift, and stability, and these
> add-ons improved the drop parameters for the torpedo. The sources I've
> found have contradictions about the launch envelope after these fairings
> were added. Can someone point me to a reputable source for this
> information?
>
> Thanks,
>
> KB
>
>
>

[Al]

You might drop it 1000 yds out, but it still has to run down the target.
This can be a long chase if the target is even semi quick.

Al


"Kyle Boatright" > wrote in message
...
>I just finished the book "The Last Stand of the Tin Can Sailors" and it
>raised some questions about the air dropped torpedoes (the Mk 13) in use by
>the US Navy in WWII.
>
> What drove the range/speed trade-offs for the Mk 13? According to the
> spec's I've found, it had a range of ~6,000 yards and a speed of 33 knots.
> With a likely launch range of 1,000 yards or less, wouldn't it have made
> sense to sacrifice the 6,000 yard range to get an increase in speed?
> Wouldn't a 45 or 50 knot torpedo with a 1,500 or 2,000 yard range have
> been a better compromise? I'd certainly think the higher speed would have
> increased the probability of a hit, because it would have reduced the
> deflection at launch by 1/3 or so. Also, it would have given the target
> 1/3 less time to maneuver to avoid the torpedo.
>
> A second question addresses launch speed. Early in the war, drop speed
> and altitude were in the 110 knot, 150' range. Later, a couple of plywood
> fairings were added to increase drag, lift, and stability, and these
> add-ons improved the drop parameters for the torpedo. The sources I've
> found have contradictions about the launch envelope after these fairings
> were added. Can someone point me to a reputable source for this
> information?
>
> Thanks,
>
> KB
>
>
>

[W. D. Allen Sr.]

For a good WWII torpedo check out the Japanese Long Lance torpedo.

WDA

end

"Kyle Boatright" > wrote in message
...
>I just finished the book "The Last Stand of the Tin Can Sailors" and it
>raised some questions about the air dropped torpedoes (the Mk 13) in use
by
>the US Navy in WWII.
>
> What drove the range/speed trade-offs for the Mk 13? According to the
> spec's I've found, it had a range of ~6,000 yards and a speed of 33
knots.
> With a likely launch range of 1,000 yards or less, wouldn't it have made
> sense to sacrifice the 6,000 yard range to get an increase in speed?
> Wouldn't a 45 or 50 knot torpedo with a 1,500 or 2,000 yard range have
> been a better compromise? I'd certainly think the higher speed would
have
> increased the probability of a hit, because it would have reduced the
> deflection at launch by 1/3 or so. Also, it would have given the target
> 1/3 less time to maneuver to avoid the torpedo.
>
> A second question addresses launch speed. Early in the war, drop speed
> and altitude were in the 110 knot, 150' range. Later, a couple of
plywood
> fairings were added to increase drag, lift, and stability, and these
> add-ons improved the drop parameters for the torpedo. The sources I've
> found have contradictions about the launch envelope after these fairings
> were added. Can someone point me to a reputable source for this
> information?
>
> Thanks,
>
> KB
>
>
>


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[Kyle Boatright]

"Al" > wrote in message
. ..
> You might drop it 1000 yds out, but it still has to run down the target.
> This can be a long chase if the target is even semi quick.
>
> Al

You're right and in a sideways way you bring up another problem with a 33
knot torpedo. If it gets in a chase situation, the torpedo can't catch the
enemy, regardless of the torpedo's range. Destroyers, some cruisers, some
carriers, and some battleships are as fast or faster than 33 knots. A
faster torpedo gives the enemy less time to avoid the attack in the first
place.

[Kyle Boatright]

"Dave Deep" > wrote in message
...
> Ahh but the closer you get to the target the longer you are exposed to
> enemy fire & the higher the chances of losing an expensively trained crew
> plus the aircraft; Far better to waste multiple torpedoes saving the crews
> & AC for further missions.
>
> DD

Agreed, but as I stated earlier, air dropped torpedoes were launched at
1,000 yards or less. I'm not advocating launching closer, I'm simply asking
why the torpedo's speed and range wasn't better matched to how the actual
launch range...

KB

[Keith Willshaw]

"W. D. Allen Sr." > wrote in message
...
> For a good WWII torpedo check out the Japanese Long Lance torpedo.
>
> WDA
>
> end
>

Which wasnt an air dropped weapon

Keith

[Eric Joiner]

Keith Willshaw wrote:
> "W. D. Allen Sr." > wrote in message
> ...
>
>>For a good WWII torpedo check out the Japanese Long Lance torpedo.
>>
>>WDA
>>
>>end
>>
>
>
> Which wasnt an air dropped weapon
>
> Keith
>
>

I seem to recall the long lance was too an air dropped weapon. Kates
used it in Pearl Harbor...I think.

Eric

[Larry Cauble]

The Japanese long lance type 93 was a 24-inch monster weighing almost 6000 lbs. The air-dropped weapon was the type 91, 450mm (17.7in) in diameter with a weight in the 1700-2300 lb range depending upon mod. There were Japanese torpedoes developed using the long lance's oxygen propulsion system, but I'm not aware of any air-dropped models in service.

www.combinedfleet.com



I seem to recall the long lance was too an air dropped weapon. Kates
used it in Pearl Harbor...I think.

Eric

[Kyle Boatright]

"Eric Joiner" > wrote in message
...
> Keith Willshaw wrote:
>> "W. D. Allen Sr." > wrote in message
>> ...
>>
>>>For a good WWII torpedo check out the Japanese Long Lance torpedo.
>>>
>>>WDA
>>>
>>>end
>>>
>>
>>
>> Which wasnt an air dropped weapon
>>
>> Keith
>
> I seem to recall the long lance was too an air dropped weapon. Kates used
> it in Pearl Harbor...I think.
>
> Eric

Nope. The Long Lance was a shipboard weapon only. It weighed something like
6,000 lbs, and was almost 30' long - a real monster. It had a range of
20,000 meters at 48 knots. On the slow setting, it had a range of 40,000
meters at 36 knots. A downsized version was used aboard submarines. It
weighed 4,000 lbs and had a 9,000 meter range at 49 knots.

The air dropped torpedoes used by the Japanese during WWII were 17.7"
torpedoes and weighed approximately 2,000 lbs depending on variant. Very
comparable to US airborne torpedos. EXCEPT for their dynamic performance,
which gave a drop speed of 260-350 knots (variant dependant), a speed of 41
knots, and a 2000 meter range.

[Larry Cauble]

The Long Lance was a shipboard weapon only. It weighed something like
6,000 lbs, and was almost 30' long - a real monster. It had a range of
20,000 meters at 48 knots. On the slow setting, it had a range of 40,000
meters at 36 knots. A downsized version was used aboard submarines. It
weighed 4,000 lbs and had a 9,000 meter range at 49 knots.

The air dropped torpedoes used by the Japanese during WWII were 17.7"
torpedoes and weighed approximately 2,000 lbs depending on variant. Very
comparable to US airborne torpedos. EXCEPT for their dynamic performance,
which gave a drop speed of 260-350 knots (variant dependant), a speed of 41
knots, and a 2000 meter range.

A couple of sources, Kyle:

(1) A history of US torpedoes of all types, originally published in the Submarine Review, and I would say pretty authoritative:
www.geocities.com/Pentagon/1592/torpedoes.html
but which does not much address the subject of Mk 13 limitations. It does
mention the successor weapon, the Mk 25, which apparently was produced in very limited numbers due to the huge number of Mk 13s still in stock late in the war. Sounds like the Mk 25 would be the ultimate USN air-dropped anti-ship torpedo and the specs on it would be interesting.

(2) www.microworks.net/Pacific/armament/
which states that, by early 1944, the Mk 13 could be launched at high speed at 1000 ft altitude and that later variants were good to 410 knots/2400 ft. In this case, however, I have no feel for the validity of these numbers.

[Keith W]

"Eric Joiner" > wrote in message
...
> Keith Willshaw wrote:

>> Which wasnt an air dropped weapon
>>
>> Keith
>
> I seem to recall the long lance was too an air dropped weapon. Kates used
> it in Pearl Harbor...I think.
>
> Eric

As others have pointed out the Long Lance was 30ft long and
was around 3 times heavier than the max weight a Kate could carry

Keith

[Merlin Dorfman]

Larry Cauble > wrote:

....

> A couple of sources, Kyle:

> (1) A history of US torpedoes of all types, originally published in the
> Submarine Review, and I would say pretty authoritative:
> www.geocities.com/Pentagon/1592/torpedoes.html

This "404s." Has it moved to a new URL?

[Eric Joiner]

Kyle Boatright wrote:
> "Eric Joiner" > wrote in message
> ...
>
>>Keith Willshaw wrote:
>>
>>>"W. D. Allen Sr." > wrote in message
...
>>>
>>>
>>>>For a good WWII torpedo check out the Japanese Long Lance torpedo.
>>>>
>>>>WDA
>>>>
>>>>end
>>>>
>>>
>>>
>>>Which wasnt an air dropped weapon
>>>
>>>Keith
>>
>>I seem to recall the long lance was too an air dropped weapon. Kates used
>>it in Pearl Harbor...I think.
>>
>>Eric
>
>
> Nope. The Long Lance was a shipboard weapon only. It weighed something like
> 6,000 lbs, and was almost 30' long - a real monster. It had a range of
> 20,000 meters at 48 knots. On the slow setting, it had a range of 40,000
> meters at 36 knots. A downsized version was used aboard submarines. It
> weighed 4,000 lbs and had a 9,000 meter range at 49 knots.
>
> The air dropped torpedoes used by the Japanese during WWII were 17.7"
> torpedoes and weighed approximately 2,000 lbs depending on variant. Very
> comparable to US airborne torpedos. EXCEPT for their dynamic performance,
> which gave a drop speed of 260-350 knots (variant dependant), a speed of 41
> knots, and a 2000 meter range.
>
>
>
Thanks for the education!

Eric

[Larry Cauble]

Larry Cauble wrote:

....

A couple of sources, Kyle:

(1) A history of US torpedoes of all types, originally published in the
Submarine Review, and I would say pretty authoritative:
www.geocities.com/Pentagon/1592/torpedoes.html

This "404s." Has it moved to a new URL?

Odd...I guess it just won't allow linking. You can also go to:
www.geocities.com/Pentagon/1592
and then click on the "torpedoes" button. That one does not appear to 404.

Once you're at torpedoes, you see five pdf-format parts that you must click on it turn to get the whole thing.

By the way, I think I indicated that the Mk 13 replacement (Mk 25) was fielded in small numbers near the end of WWII. I now see that is incorrect; it was only a prototype/test weapon and the Mk 13 was the last straight-running/non-homing air-dropped torpedo.

[Keith W]

"Larry Cauble" > wrote in
message .. .
>
> Merlin Dorfman Wrote:
>> Larry Cauble wrote:
>>
>> ....
>>
>> A couple of sources, Kyle:
>>
>> (1) A history of US torpedoes of all types, originally published in
>> the
>> Submarine Review, and I would say pretty authoritative:
>> www.geocities.com/Pentagon/1592/torpedoes.html
>>
>> This "404s." Has it moved to a new URL?
>
> Odd...I guess it just won't allow linking. You can also go to:
> www.geocities.com/Pentagon/1592
> and then click on the "torpedoes" button. That one does not appear to
> 404.
>

Your post had a spelling error the URL is actually

http://www.geocities.com/Pentagon/1592/torpedos.html

Another useful resource is

http://www.navweaps.com/Weapons/index_weapons.htm


The Mk 13 was markedly improved throughout the war and
by 1945 was a very effective weapon indeed.

Keith