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Weekly Update - Sea Trials Start!

Naval Yachts' Vanguard boat impresses in sea trials, exceeding estimated cruise speed and showcasing her wave-piercing design. A promising choice for boat enthusiasts and potential buyers.


We have spent the last 6 weeks visiting friends and family; Naval Yachts have had a free run at completing Vanguard. This week, they crossed a significant milestone and began initial sea trials. A three-hour run after a long day but sufficient time to demonstrate a future promise. This is how it went. 


Initial sea trial results

  • Sea state - calm

  • Wind - light

  • Load condition - Arrival but without permanent ballast.

  • Trim - even keel

  • Hull - 3 months in still seawater, probably mucky

Note: The trim and rudder position remain to be optimized. Both engines were running at a similar speed. Stabilizers folded and inoperative.


  • engines @1000 rpm @ 6,7 knots (also max speed for hybrid drive)

  • engines @1500 rpm @ 9,8 knots

  • engines @1680 rpm, and the speed was seen as 11.3 knots


The predictions from Bruntons were remarkably accurate and better than for an equivalent fixed pitch propeller. More on this when additional detailed data is available inc one engine operation.


The Vanguard's performance was impressive, aligning nicely with the predictions from Bruntons. However, it's worth noting that these predictions assumed a single engine running while we had two engines operating each at a lighter load. The Naval Architecture calculations indicated we should achieve this on a single engine, so that will be tested in the coming weeks. The typical direct correlation between shaft speed and load is removed as props are self-pitched. We still need to verify if the load display is calculated from engine speed or fuel rack position.



Regardless, Vanguard exceeded our estimated cruise speed by 1.3kN at about 60% installed power load factor, with plenty of additional power to spare. It's safe to say that it was a successful day. 


Does she make waves?


Wake at >11 knots. Swim platform remained dry, trim approximately even keel.


The next test was to look at how Vanguard slipped through the water. Her sister ship, Mobius, was remarkably hydrodynamic in that regard. Those big white bow waves you see in magazines may look dramatic, but to my eye, they represent wasted fuel. Nothing is for free in this world. So Vanguard was operated at three speeds, rising through the load range to just over 9 knots before they ran out of time. See the video below. The bow wave was virtually non-existent. This wave-piercing design is an arrow! Some stern wake at higher speeds, but again, not much. Also, the stern has little to no tendency to bog down at higher speeds, with the swim platform staying dry throughout. Many displacement hulls will try to climb their bow wave when pushed hard, but not so with Vanguard, at least not so far. 


Video showing wake performance at circa 4.5, 8.4 and 9 knots. Note very little bow and side waves. Make waves = burn fuel! More data on fuel consumption to come when available.


Ongoing Insurance Woes!

Lastly - Insurance is proving to be an issue right now. US Nationals with a US-owned yacht is a troublesome mixture. Our go-to of Pantaenius no longer insures in the USA. I will blog when we have made more positive progress.


Chris Leigh-Jones



A few other things transpired this week but the above is the major news. Wishing everyone reading a very happy 2024. The crew and builders of Vanguard.

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