question about mast rotation offset

[M Van Hoy]

Hi Northwest Multihull Association,

I watched the YouTube video about mast rotation.

I am curious if 2 steadycast sensors could replace 1 steadycast and 1 B&G compass for doing mast rotation corrections. I have a ShipModul.

Are there Pros/Cons of one v. the other?

Thanks,

Mike Van Hoy, Chapel Hill, NC

aka Elfego Baca (WaterTribe)

aka Snowflakes (R2AK26 Tornado)

[William Quigley]

Hi Mike,
There's no reason why you couldn't plug in 2 Steadycast sensors, but
it depends on what you're trying to accomplish. The Steadycast is
accurate to +/-3 degrees. I feel like an average sailor like me can
sense wind direction within 10 degrees by just looking at a windex and
telltales, so getting to within 6 degrees doesn't feel like enough of
an improvement to be worthwhile. I tried using two BNO08X IMUs on my
boat (and on Ceratops), and the results were decent but not great. At
the same time, the crew of Mojo use a Steadycast + B&G + Shipmodul,
which technically is about as good as two BNO08X, and they are happy
with the accuracy.
I recently found a rotation sensor that's around $200 and we're going
to try it on Ceratops sometime soon. Email me if you're interested and
I will keep you updated about how well it works.
If you don't already have a masthead wind transducer, I would consider
going with one of the Calypso models mounted on your bowsprit. It will
read slightly lower wind speed than the masthead, but wind direction
will be extremely accurate, and you will have fewer moving parts.
Regarding the Maptatoo, in my opinion it's fairly expensive for what
you're getting, which is a GPS and (proprietary) chart display. I
don't think it can connect to the rest of your instruments (or the
Shipmodul).

Bill

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[M Van Hoy]

Hi Bill,

Thank you very much for the very quick response. Yes, please keep me up to date on your experience with the rotation sensor. It really seems like the best option if it can be made to be 'snagless.' I already have the Garmin Wind indicator on my mast. I will definitely keep a bow sprit indicator in mind. makes sense.

Wondering out loud, I wonder if the steadycast error is independent or if there is a component of the error that would be identical in 2 different steadycasts, therefore making it less than +/-6% accurate?

I already have the MapTattoo for R2AK26. I am just trying to figure out if it could act as an NMEA2000 GPS in the short term. If not, I have other options.

Much appreciative,

MikeV

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[Andy Inglis]

Re: MapTattoo

Pros: 

Readable in direct sunlight. 

Very long battery life, even with display “always on”. 

Usable when wet. 

Durable. (So far, knock wood)

Cons:

Expensive. 

B&W display. 

Scrolling and panning somewhat “laggy”.

I view this as a niche product that is awesome for ambitious small and/or open-boat sailors who need to run their navigation device in a totally exposed location and were frustrated by devices (I’m looking at you, iPhone) that can’t be used in sun or rain and chew up batteries if you leave it on. 

On Feb 2, 2026, at 11:15 AM, M Van Hoy <nuros...@gmail.com> wrote:



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[philip styne]

I have questions about MapTattoo

It seems to me because of the black and white and proprietary charts that details maybe hard to see or not there.

 I have some current where I sail but not nearly what I assume you get in R2AK. Did the tide and current information work adequately 

Are you going to use it this year in R2AK. What watercraft are going to use

Philip Styne

C750 mkii

Tiburon CA

On Feb 2, 2026, at 15:54, Andy Inglis <andyin...@gmail.com> wrote:



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