Your most frequently asked questions… answered.
Editor’s notes (2019)
The FAQ and discussion below has been mildly edited to eliminate typos, make it clearer who the authors are and which boats they themselves have (by hull number and boat name if known). Wherever possible alternative (i.e. current) references to products & suppliers are provided.
The bulk of this FAQ was originally generated as a Q&A in the period 2005 – 2015. In this period Lester Helmus acted as a clearing house for questions and responses, but some respondents would also write direct to each other, hence some of the overlapping answers you see in the FAQ. In places there are 2019 and subsequent comments, drawing either on my own experiences, or from other Corbin 39 owners and sources, including our Corbin 39 Group on Facebook. More comments are most welcome and this FAQ will inevitably grow.
We have attempted to contact all contributors to the 2015 version of the FAQ. All responses have been most supportive, thank you. If you are a contributor who has yet to respond please contact us.
As will be apparent there are multiple viewpoints on some topics. Sometimes, but not always, this can be traced to differences in arrangement between the boats of the various authors. Some of the topics raised are not so much a Q&A, as simply being a statement of why a particular owner thought something was a good idea, which of course it may not have been at all. Make your own mind up.
If you have further comments or suggestions on any of these questions, or wish to pose new questions, or describe various issues you have faced and/or overcome, then please contact us either via the Facebook Group or via the Website.
[Remark as of November 2019: Quite a lot of the links to drawings & photos are not yet reinstated due to workload. However I also know quite a few of the relevant images have gone astray. You may find the relevant photos in the individual boat’s entry. Please email us if you have any of the missing photos, drawings, etc.]
NAVIGATION AIDS and ELECTRONICS and COMMUNICATIONS
What is the best fishfinder to buy ? (asked approx 2005-2010) When I haul #010, Insouciance next month I would like to add a fishfinder in order to cruise and anchor on our large, but shallow San Francisco Bay and Delta.. My current depthfinder gives me reliable readings only when I’m aground. The features I must have are: bronze transducer, large digital depth display, very accurate readings to a shallow and soft bottom, anchoring features of the bottom, and a shallow water alarm. The features that would be nice to have are: keel offset, water temperature, and forward-look ability. I do not need a side looking transducer or detailed info about the fish, except that I don’t want false depth readings. I will place the transducer forward of the keel. I know nothing about: wattage needs, frequency needs, beam numbers, beam degrees, display resolution, or display features (LCD or TFT)/(real-time or otherwise). I am willing to spend up to $1000 for the display and transducer. The display will be mounted in the pilothouse. Perhaps, you can help me best by specifying the make and model of the fishfinder you would recommend, with a few words about why you recommend it. Thank you for your help.
Les Helmus (s/v #010, Insouciance)
a. My transducer is a single frequency unit. I don’t think they offered a dual frequency or a forward-looking unit at the time. The unit does have shallow and deep water alarms, a trip log and gives a little bit of bottom information but not much. You can tell if the bottom is very hard or very soft is about all. I’m sure there are better models out there now but this serves me well. The only problem I have with the unit other than the paddle wheel is that there is an automatic sensitivity adjustment that the unit powers up with. In shallow, silty water you sometimes get false depth readings (usually when you need them most). You can manually adjust this feature and the unit performs well but like I said it powers up in automatic and I forget to set it until I realize it’s not reading correctly. I mounted the transducer just fore of where the keel becomes noticeable. the fiberglass is solid there and about 2 1/4″ thick. I took a belt sander and made a flat spot on the outside of the boat to match the transducer and point it directly down. On the inside there is a noticeable curve to the hull so I used a piece of 1″ teak and beveled it to match the hull and left the top flat so I could draw the nut for the transducer down. This spot is about 2′ 3″ below the water line (that’s why I don’t like to remove the paddle wheel to clean it). My unit doesn’t allow compensation for the transducer depth, which would be nice, so I just add this to the displayed depth. One other note. I did sail the boat for the first 15 years without any depth sounder and I always knew when the water was 5 1/2′ deep! If there are any other questions please ask, Bill Schwartz (s/v #090, Moonshadow)
b. I installed an apelco 350 fishfinder about 5 years ago. I only spent about $200.00 for the unit that came with a transom mount transducer. I spent about $250.00 more for the bronze through hull transducer that also gave water temperature and speed through the water. I mounted the transducer just in front of the keel and it works fine. The only problem I have is that this transducer has a paddle wheel which gets fouled up in the Chesapeake Bay area about every month. I don’t usually use the fish finder function but turn on the large number display (this displays the depth in large numbers and the temperature and speed in small numbers with no fish information). I would definitely get the bronze transducer again but I think they make units which sense the speed without a paddle wheel. Bill Schwartz (s/v #090, Moonshadow)
c. My transducer is just in front of where the keel becomes noticeable. It’s just behind the rear of the 2 forward windows if you drew a line from them to bottom of the boat. It is about 27″ below the water line and never has had any problems with aeration or turbulence. I put it there so it would be in nice clean water for the speed paddle wheel. The forward looking model looks interesting. Bill Schwartz (s/v #090, Moonshadow)
d. We installed an Interphase PROBE two years ago. The learning curve is a little steep but we swear by it now. It allows us to spend less time on the ratlines looking for coral, allows us to look into narrow channels before we enter, and lets us stay in the deeper part of a channel. It has changed the way we size up anchorages. It basically looks forward at 12-degrees either side of the bow. The forward looking ratio is 6 to 1. Six feet forward for every foot it looks down. It protrudes below the hull about 4 to 5 inches, so it would not be good in waters where there is a lot of large debris. It is one of those tools that makes it easier for a husband and wife to get all the tasks performed on a cruising boat. Richard Bacon ( s/v #043, Balmacara ) [Email from Australia]
e. I have just completed installation of a Hummingbird Fishfinder, the Piranha Max20, as a secondary, visual display depth sounder and am very pleased with the results. I wanted confirmation of shallow readings, particularly for anchoring situations. I had been concerned at the possible interaction of depth signals with two transducers transmitting at once and also at the recommended locations for the depth transducer which is normally shown in the bow area, ahead of the keel. However, that is where my primary transducer (Nexus Instruments) is located. Both the primary transducer and my new Hummingbird (transom mount style) transducer are located in “water boxes” inside the hull, filled with mineral oil (from a drugstore). The primary transducer is near the centreline in an area of solid fibreglass. I checked for possible signal interference by attaching the new, powered up transducer to a pole and traversing along the water immediately below the caprail. My preferred location for installation was under the step from the pilothouse to the saloon.hummingbirdtransducerinwaterbox.jpg. Abeam of that location there was no interference between the two depth sounders so I decided to bite the bullet and go ahead with the installation under the step, even though it would be closer to the keel and I didn’t know if that would give a false signal. The actual location is 71″ aft of the mast and 36″ out from the centreline. This is an area of (Airex) coring so I had to “excavate”. I had previously moulded the water box from fibreglass & polyester resin, around a plug made from high density polyethylene, about 2.5″ x 3.5″ cross-section. With some trepidation I cut away the inner hull skin (about 1/4″ thick) using a small cutoff disk attached to a flexible drive from my drill. I drilled multiple perforations near the corners to complete the cutout and levered the inner skin off the 3/4″ Airex with a screwdriver (very well adhered!). I then used a burr bit in the drill to smooth out the inner surface of the exposed hull. The water box was installed with epoxy putty and glassed to the inner hull skin which was also given an epoxy coating. The transducer was attached to the water box and then flooded with mineral oil. I made a clear Plexiglas lid for the box.hummingbirdtransducerinwaterbox.jpg During a test cruise a couple of days ago the new Fishfinder showed good agreement with my primary depth sounder, with an offset of about 3 ft at shallow depths as my primary is calibrated to read for water level and the Fishfinder is not so sophisticated. Also it only reads whole numbers of feet versus tenths for the original unit at shallow depths. The deepest I got was 130′ on the Fishfinder when the primary depth sounder was showing about 138′. The difference in readings went up slightly as depth increased but overall very good agreement was shown. Regards, David Salter (s/v #050, Opportunity).