Our thoughts recently turned to a Tender for our aluminum Explorer Yacht, Vanguard. What we first believed would be a simple process turned out to be anything, but we ultimately settled on a modified design that seemed to fit our needs.
Let me first explain the limitations we agreed upon:
A maximum length of 5.0m (16ft) and weight of 1000kg, all up (the limiting factor is the knuckle crane we are fitting).
Single fuel operation using the same diesel as the main engines
Capable of acting as a lifeboat of first recourse for a complement of 6.
Capable of working as a tug for a disabled Vanguard (>80bhp).
The first and most obvious choice would be a RIB. As we do not need to stow the boat below decks, we could consider fiberglass or an aluminum lower hull with hyperlon tubes. See the enclosed table for the range of RIBS considered (Bombard, Highfield, Vanguard!, Zodiac ...). All are great products. Our favorite
was the Highfield, which came with all the additional parts we needed. There are some compromises with a RIB; most notably, the internal volume is low due to the side tubes and limited weather protection. It can also be awkward to get back in from a swimming position. The killer for us was not the design but the limited power source. They typically do not take an inboard, and the only available diesel outboard in our size range is a D Torque from Neander. At 50 bhp,
it is a bit small for towing though the low-end torque is much better than an equivalent gasoline outboard.
For cost and performance, it is hard to beat a RIB. Even harder to make one single fuel in this size range. So we then started looking at other options.
Indestructible Polyprop Tenders
Pioneer makes a beautiful rotationally molded polypropylene product with a forward movable ramp. It would fit the available space and t
icked most boxes except for the outboard again, the same problem as the RIBS.
Other manufacturers that we found in this damage-resistant category of molded hulls include Whaly, Portland Pudgy, and Bullfrog.
We looked at a drop bow aluminum tender from Munson, which is also beautiful but too big for our application. We looked at Setsial.com for some inspiration.
Then on to the tender design fitted to our sister ship, Mobius (see opening illustration). Naval Yachts
made this with the owner providing a 110hp inboard Yanmar 4-cylinder diesel and Castoldi jet drive. An excellent implementation, though the aesthetics were not our preference. It is always easier the second time.
Our yard was quite busy, so we requested that we have it made elsewhere. Our partners, Artnautica, introduced us to Hebbeke Shipyard in the Netherlands. They specialize in custom small aluminum rescue craft and jet drives.
After a few rounds of discussion, we settled on a new rigid aluminum design that fitted our needs exactly, if at a cost! Taking the lessons from the tender on Mobius, XPM-001, we then reconfigured the build by adding:
Yanmar 4 Cylinder EPA Tier III compliant engine so we can import and operate in the USA. 110 bhp with 900kg all up weight, full fuel tanks.
Additional reversing gearbox before the Castoldi jet drive so that we can back flush the water intake and have an actual neutral position without balancing the bucket positions. The operating draft is now only about 9 inches, as there is no rudder or propeller to foul.
Repositioned jet drive forward slightly to reduce the overall length and remove the swim platform. Repositioned operating console aft over the jet drive for a drier ride.
A 3-point lifting system is both stable and makes a single-handed launch easier.
We beefed up the forefoot for beaching and impact from floating ice.
Drop down side panel that doubles as a swim ladder
Open stern to flush any water shipped in poor weather or surf.
We have a dedicated demountable instrument arch (GPS, AIS, FLIR, lights).
Estimated range >100NM, max speed 35 knots.
So there you have it, a rugged and versatile tender explicitly designed for the application. Delivery is for February 2023. Happy to share the design drawings if anyone is asking.