J I Thornycroft Coastal Motor Boat


J I Thornycroft Coastal Motor Boat
photo ex Peter Loughlin ex Historic NZ Photos

Today’s mystery motorboat could be a real challenge – what I can tell you is  (1) its obviously the inner Waitemata with the Devonport Naval Base in the background (2) the launch is fast, very fast (3) the Historic NZ listing says c.1930 but I’d say its earlier than that (4) the seagull above the boat almost definitely had a bowel movement when the boat went by 🙂

All Is Revealed Thanks To Harold Kidd

Harold says that the solution was to identify the cruiser first (REPULSE) and with a little help from Papers Past the rest fell into place. The news clip from the Auckland Star 13 May 1924 below explain all.

 

19-09-2015 Further reading below (ex Peter Loughlan). The first link is for CMB9 which is under restoration, the second link some specs for the entire series.

http://www.nationalhistoricships.org.uk/register/2430/dcb1

http://www.navypedia.org/ships/uk/brit_c_f_cmb40.htm

17 thoughts on “J I Thornycroft Coastal Motor Boat

  1. Peter Loughlin has drawn my attention to 2 sites which deal with CMBs in some detail. From that it’s clear that CMB123 was originally fitted with a V12 Green aero engine which, in aircraft use, was rated at 275bhp. That would have been detuned for marine use, almost certainly as were the Napiers in W1.
    Greens were pretty old hat in design by 1916 and I can’t find any other application so they were probably pressed into service to get these wonderful craft out on the water.

    http://www.nationalhistoricships.org.uk/register/2430/dcb1

    http://www.navypedia.org/ships/uk/brit_c_f_cmb40.htm

    Both are well worth looking at.

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  2. Absolutely fascinating stuff!!! — A field I know absolutely nothing about, — wish I did. All totally exciting & absorbing, — wonderful!! — KEN R

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  3. 1375 rpm. Excellant. High horsepower at low revs turning a decent size screw. Just like it should be.
    Back then real engines “rotated”, now days engines just “vibrate”.

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  4. I’ve been researching an article on the New Zealand RNVR contingent in WW1, most of whom were in the crew of the ML’s assembled in Canada from components built in the US for the RN by Elco with Standard petrol engines.
    These 40ft high speed Coastal Motor Boats were designed by Thornycrofts and were extremely hush hush until the Zeebrugge Raid of April 1917. They were based on a prewar racing hydroplane MIRANDA built by Thornycrofts and used Sunbeam or Napier aero engines marinised by Thornycroft. From the sound of it, CMB123 had a V12 Sunbeam Arab or Manitou engine c350bhp. Wallace McNair’s Sunbeam Special in Hamilton runs one of these beasts. I can vouch for its torque and low-end power.
    The CMBs were precursors to the Vosper and British Power Boat Scott-Paine-designed craft of the 1930s exemplified by the RNZAF’s W1 which used Napiers.

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  5. Would love to put her up against My Girl in the Kawau Race , though I imagine would need a sponsor to fuel her!

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  6. Hubert Scott-Paine was just founding Supermarine when this beauty was designed by other people. She’s a single-step hydroplane with an aircraft engine (Sunbeam or Napier) if that helps?

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  7. The warship in the background is either HMS Renown or HMS Repulse. Renown visited in 1920 with the Prince of Wales and berthed alongside. The Repulse visited in 1924 in company with HMS Hood. In this visit Hood went alongside whereas Repulse remained in the stream. I am assuming that this photo was taken during the visit of the Repulse in May 1924.

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  8. She sure has a large crew. I can count 8 to 10 in the back cockpit. Are they going snapper fishing? Anyone identify the warship in the background – could be a ships power boat?

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  9. !: Yes.
    2: Ooh yes! Look at that roostertail!
    3. I’d say earlier too.
    4: Yes, but seagulls do that without provocation.
    A small dark thing gibbering at the back of my mind says; ” Early motor torpedo boat”, but I can’t get any more than that. There’s something vaguely military about the boat.
    Can’t wait to hear from someone who actually knows about her.

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