R29S Dinghy / Davit Installation

[Kimberly Dawn]

I am shopping for a dinghy, motor and steering helm and a davit that will support the weight and accommodate a permanent motor mount throughout its deployment cycle.

I have zeroed in on a Achilles 280DX with Basic Console and a Tohatsu MFS9.9 EEPTS 15" for the dinghy. The combined weight is 463#.

I have tentatively selected the Olsson RS-5 / RS-8 (90# / 94#) davit system that will support the dinghy in an upright position off the swimstep just barely above the transom. This allows for excellent 4-to-8 visibility.

My concern is this: the whole system adds 555# +/- to the stern. Will this added weight merely slow the boat accelerating to cruising speed, or prevent it from reaching cruising speed. Are there any concerns for the exhaust system?

Any R29 / R31 owners out there with similar configurations? Any others with opinions or insight?

Thanks for your feedback!

Bob
Kimberly Dawn

 

[bluestreak]

Bob,
We have the Olsson Davit system on our 2016 R-27 classic.
Not sure of the model number but it has a very beefy stainless frame and supports an Achilles 7'10" RIB and a 5 HP Honda OB and external fuel tank.
The dinghy travels horizontally with OB mounted and minimally blocks the view to the rear.
Our boat is in charter service with Anacortes Yacht Charters so we added an electric winch to make it easier for charterers.
We did find the extra weight of the davit, dinghy and OB does put a hefty stress on the transom to the point the tramson door will not latch so we are having a bracket/brace added.
I am happy with the Olsson system and do not want to discourage you but just something to be aware of.
Bill
PM if you need more info.

 

[baz]

Bob:

Adding weight to the stern of the boat is the worst place to add weight. Now, having said that, of course installing a dinghy on the trailing edge of the swim step is what most people do and this of course adds weight some feet further aft of the transom.

The effect of adding weight to the stern affects the fuel burn as it causes more of the rear section of the hull to dig in and adds additional drag for the engine to overcome, along with added wind drag. The only way to really understand this and to get an estimate on the fuel burn is to run the boat on a calm day in zero current with and without the dinghy installed. I suspect if running the boat at a low speed, the fuel burn with and without the dinghy installed will not be that different.

Depending on the position of the dinghy (vertical vs. being horizontal) it will interfere with rear visibility and of course the overall length of the boat when docked and/or when finding a suitable slip size for permanent moorage.

If you get caught in a following sea with big swells the dinghy may get raised some with the seas overwhelming the swim step... something to keep an eye on.

IMO.... only have the dinghy installed when you know you will need it.

Adding a dinghy to small boats has no good solutions, and compromises will need to be made.

 

[Kimberly Dawn]

Thanks for the replies.

I'm hoping there are some 29/31 owners that have installed similarly loaded dinghy / davit configurations that can share their boat"s performance.

Other than the R43, RT's design of the 29/31 cabin lid does not offer full-size, readily deployable dinghies except on the swimstep. I see our dinghy as a permanent installation that's there for anticipated usage, as well as those unexpected times of convenience.

Added dinghy payload/ballast to the swimstep that impacts the fuel efficiency negatively is our "eyes wide-open" compromise we make as an integral part of our boating experience.

Bob
Kimberly Dawn