Comparing Vanguard vs FPB-70

Vanguard was recently featured in a friend's Video following his trip to NavalYachts. It was a popular video attracting many comments, including a few comparing Vanguard to the successful series for FPB designed by Steve and Linda Dashew and built Circa Marine. Rather than becoming anecdotal at this point, what are the factual similarities and differences?

FPB 70 - acknowledgement to Circa Marine

Firstly though, there is a confession to make, the owners of Vanguard (us!) initially wanted an FPB 70 (think Buffalo Nickel). A competent and rugged explorer yacht design capable of being handled by a minimum owner/crew of 2. The only problem is that they will never make another to that design. So rather than roll belly up and opt for the typical US "Down East", we decided to build our own.


XPM-78 under construction at Naval Yachts

Enter designers like Nigel Irens or Dennis Harjama, proponents of high "Length to Bean" ratio, efficient ocean-going yacht designs. Of these, Dennis of Artnautica is the most active in the space having plans from 58, 65, 68, and, latterly, 85 feet LOA. Comprehensive data on FPB-70 is sparse. With some digging, these are the comparisons that we can find and the differences we have highlighted.


The Hulls

To look firstly at the hull itself. FPB-70 is the same length (LOA) but slightly wider and has a 20% deeper draft. XPM-78 design uses electrical and hybrid power, and that concept demands the lowest hydrodynamic resistance to achieve any practical range. Vanguard sacrifices internal volume to satisfy this, and the seakeeping is yet to be proven. Suffice it to say; Vanguard is a slightly skinnier hull for the same length. Her forefoot is slightly more pronounced to facilitate mounting the bow thruster forward in the narrower beam. Additionally a small bulwark has been fitted for aesthetics and to help keep the foredeck dry(er). She will carry the same crew and has approximately the same internal configuration, just a little less space in comparison but still large by most standards. Notable, though, is that both designs target MCA Category (0) operating envelope; they will both run in the arctic and antarctic regions in the summer months. Stability is perhaps more a marketing figure than something of practical importance. In theory Vanguard has no angle of vanishing stability and FPB-70 has 140 deg in its specification. Both angles are well past a knock-flat and if you ever find the vessel in that position then rollback may be the least of your worries. Let us agree they are both unusually stable and resistant to flooding. Let us also hope the motions are not too stiff then leave it at that. (I remember once carrying a bulk cargo of finished steel and unable to ballast the wing tanks, horrible motion that went on for weeks.)

Unit

XPM-78

FPB-70

UK MCA Category

(0)

(0)

LOA

m

23.8

23.8

LWL

m

23.8

23

Official length

m

22.4

21.3

Beam (deck)

m

5.13

5.66

Draft (50% load)

m

1.3

1.55

​Draft (max @ skeg)

m

1.3

1.55

Air Draft

m

6.4

6.4

Displacement

kg

41,000

50,000

Fuel

litres

14,000

15,100

Water

litres

7,000

10,000

Cabins (double)

3

3

Performance

I am wary of quoting exact figures for performance as it is not, in truth, an exact science. It is tempting to simplify this to say that the performance and range are similar. The only notable difference is the maximum speed of Vanguard being somewhat over the theoretical hull speed. She has duplicated diesel with an additional twin hybrid drive to boost performance. Not a practical long-term option, but if you want instantaneous speed, then she has the edge.

Unit

XPM-78

FPB-70

Range (20% fuel reserve)

NM

7000 @ 9 KN

5000 @ 10.5 KN

Max angle positive stability

degrees

180

140

Cruising speed

KN

10.5

11

Top Speed

KN

15

12.75

Min Crew

2

2

Structure

Moving on to the structure, they are again similar. Both have relatively massive scantlings compared to acceptable construction codes; both are marine-grade aluminum and have identical plate thicknesses. The design is equivalent, with five water-tight compartments and extensive use of double-skin tank construction.


Propulsion

On the topic of propulsion, there are some notable differences. Vanguard uses twin Brunton's Autoprops. These are similar to sail drives meaning she can voyage on a single engine without windmilling or incurring much drag. Thus engine operating hours are considerably reduced. She also has a modern diesel electric hybrid drive as the owner's indulgence. Great for in-port maneuvering (with full Dynamic Positioning) and even better for those huge 120kW.H power storage batteries meaning no generator running in port or at anchor, ever! It also means she can charge batteries by running the hybrid drive de-clutched from the propeller resulting in over 90kW charging capacity. Similarly, the solar arrays are larger, further increasing her power independence.


Summary

Other differences noted boil down to personal choice, the tender design, and the type of stabilizers, painted or bare aluminum, interior facades. These are not fundamental differences and could fit either design with no notable modifications.


So, in essence, to answer the initial question? Yes, very similar, with the XPM-78 reflecting more recently available technology.


However, differences aside, the XPM-78 gives us all that we were looking for in the FPB-70. We also gain a Yard that will indulge our personal biases in a new build.


To conclude, if any reader has considered an FPB as their dream yacht, now consider an XPM a viable, attainable alternative in this size range.


Useful Links

- Berthon International FPB-70 details - HERE

- FPB-70, Buffalo Nickel Blog Site - HERE

- Steve and Linda Dashew FPB Blog Site, FPB-70 details - HERE

- Artnautica LRC/XPM yacht designs - HERE

- XPM-78-02 specification - HERE


Dincer Dinc/Chris Leigh-Jones


221 views0 comments

Recent Posts

See All