Select a hole saw the same diameter orslightly larger than your thru-hull, one witha pilot drill bit, which prevents the holesaw from walking when drilling. Use the step wrench, which engages the ears inside the through-hull, to prevent the through-hull from turning. Measure the deadrise angle of the hull at the selected location (see diagram at right). However, the core material must be removed around the through hull, and solid glass laid up in its place. Be sure to correctly orient the fairing on the bandsaw, so the angle cut matches the intended side of the hull and not the mirror image. Some additional guidelines: Drill bits, hole saws and materials for installation of common Airmar transducers in a cored fiberglass hull: To safely cut the fairing, youll need to determine the hull deadrise angle using your bevel gauge. Very slight error in concentricity can be eliminated by slight grinding of the edges of the through hull or the edges of the mortise, although the best course is to be very careful in locating the center before doing any cutting. Cutting the mortise for a recessed through hull is the hardest job, because the mortise must be flat on the bottom, beveled on the edges. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register. Or FREE standard shipping on $99+ orders. Step 1: Planning the Install The first step is to determine where the fitting will be installed, and as the adage goes, you want to measure multiple time to make sure you won't be encountering any problems down the road. There is some risk of distoring the hull locally from the heat of laying up this fairly large patch, so it is best done a few layers at a time. From inside the hull, slide the backing block (if installing with a fairing) and the hull nut onto the cable. This was also a 2011 production sailboat. Use a hole saw to cut out a disc larger than the footprint of the seacocks flange. The hose coming of the seacock is labeled 1 1/2 inches but the outside of the mushroom going to the seacock measures 1 7/8 with my cheap plastic calipers. This gives you one last chance to check the locationon the outside of the hull to verify all iswell prior to cutting the hole. Once fitted, markthe backing plate so you can properly orient it later. Because polyester resin will kick off quickly in the thick mixture youre going to make, do a dry run before committing yourself to the job. Chances are that it will be lightly bonded in place, no matter how thoroughly you wax it. Bed the through-hulls mushroom flange with sealant and also bed the seacocks flange with enough goo that you can see squeezeout all around after all is reassembled for good. Light tapping with a wood or plastic mallet, or a hammer and a softwood block, should free it from the hull. STEP-2: Measure the total threaddepth of the female NPS threads in thebottom of the seacock (Dimension-B).Add A and B together. What is the correct way to measure for thru hull diameters? Remove the thru-hull nut (it will not be needed), insert . The seacock will be a typical flanged bronze unit with acompatible bronze thru-hull, although Marelon polymerseacocks and thru-hulls would be another option. For the purpose of this The starboard side of the hull where the propeller blades are moving downward provides a cleaner flow of water. For a metal hull, remove all burrs with a file and sandpaper. the hole in your thru-hull will be about 1/2" in diameter if it is labeled as a '1/2" thruhull'. Cutting them shorter would reduce the lever-arm but negate any thread match if a combination threaded thru-hull was used. On the inside, fit the backing plate over it, then install and snug up the flange nut. The hull will be locally reinforced, and there will be no possibility of water penetrating the core. While some builders are off pinching pennies other builders actual do care about below waterline integrity. The transducer you select must be compatible with your fishfinder and include the specific capabilities you desire. Remember, if a thru-hull fitting fails and the seacock is unable to close, the boat will flood and possibly sink. Recessing the through hull flush with the skin of the boat is more effective in creating a low drag surface. All images and diagrams in this article courtesy of Airmar Technologies, the leading manufacturer of recreational fishfinder transducers. To find the location and hours of a West Marine near you, visit. So do not mount the transducer in line with or near the engine water intake, discharge openings or behind strakes, struts, fittings, or hull irregularities that will disturb the water flow. You will need to build a jig out of plywood to safely hold the transducer at the precisely correct angle as you push it past the blade of your bandsaw or table saw. 4. Bronze transducers are recommended for fiberglass or wood hulls. It failed at 458 pounds. If you want to spend the least amount of money and time, youll simply fair in the surface mounted through hulls. When buying a boat with this type of installation please be aware of and know that it is, and can be, a potential week point that may not meet the minimum ABYC safety standards for seacocks and thru-hull fittings, at least in the 3/4 size range. Fill the cavity created with epoxy resin mixed with Cab-O-Sil (silica) filler to create a compression ring. BoatLife makes empty caulking cartridges ($2.88 each; jamestowndistributors.com). To check for stray current, with the boat in the water and the shore power disconnected, take the bonding wire off one of your through-hull fittings so it is totally disconnected from the bonding system. For our discharge thru-hull, the next step is to add a thickbead of sealant to the top of the backing plate hole aroundthe thru-hull, install the thru-hull nut and tighten snugly. Since its above the waterline you could replace it with a thru-hull/seacock now and screw a plug in til you want to use it, assuming you are going to be using a bilge pump with a 1 1/2" hose - that's a pretty . Once the dry fit is complete, disassemble everything andseal both backing plates with three to four coats of epoxyand allow to dry. Belvoir Media Group, LLC. I was able to get 4 full turns on the valve to thru-hull. CHIRP transducers need to be mounted in a cool, well-ventilated area away from the engine to avoid overheating. For stepped hulls, mount it just ahead of the first step. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more! It's a pretty good bet that the existing hose matches the diameter of the fitting, but it doesn't hurt to verify. Using a trowel, wide putty knife, or flexible spatula of the type used in auto body work, trowel the putty onto the wet unfilled prime coat of resin. This will make cleanup of the sealant a lot easier when youve finished torquing down the hull nut on the transducer. Almost any tub can be driven to hull speed with 20 knots of breeze, even if it has foot-long grass and an acre of barnacles on the bottom. As it has no mounting flange, an in-line valve can turn or loosen fromthe thru-hull fitting due to vibration or through normal use. Your fishfinder owner's manual will help you in this regard. Please check local store hours. A forum community dedicated to Sailing enthusiasts. If there is a rib, strut, or other hull irregularity near the selected mounting location, drill from the outside. The load was measured in pounds and set to capture the moment of failure or peak hold. Before final installation of the through hull, heat it with a propane torch to remove the wax. By Frank Lanier, Southern Boating March 2019, Your email address will not be published. Fair Through Hull Fittings: Essential to a Smooth Bottom, PS Advisor: Using Acids to Clean Propellers. We replaced every Thru Hull and Seacock on Sunday with TruDesign. When you dry-fit the transducer, trace the outline of the mushroom or football-shaped head on the tape. Or, make a reamer by chucking the long leg of a hex wrench into a drill, using the short leg to excavate the core. I would start by removing the hose so that you can measure the outside of the threads as woodster suggests. The next step is to tape off the hull with blue #2090 masking tape. Drill a pilot hole through the backing plate and hull, dead center in the diameter of the circle representing the seacocks barrel, which you traced inside the hull. All rights reserved. B260 bronze thru-hull with standard fairing block. If you combine reducing through hull drag with other bottom improvements, such as careful attention to the application of bottom paint, you will be well on the way to measurable improvements in performance, without spending much money. Apply a 1/16" thick layer of marine sealant to the fairing that will contact the hull, the backing block that will contact the hull interior and to the hull nut that will contact the hull backing block. Moving down 1 3/8 on the assembly actually favors the seacock when testing to ABYC H-27 standards. Pompano Beach, FL 33060 If your hull is thick enough, or if youre willing to do a little more work on the inside of the boat to locally strengthen the hull, you can flush recess a through hull designed for surface mounting, using the same method required for the European-type fitting. A seacock is not simply a ball valve. All funding goes towards this production. This is a simple step by step guide on how we did it.--- Before you start ---Your existing . Any thru-hull fittings that are damaged or can't be unblocked must be replaced immediately, as should any seacocks that are jammed or can't fully open or close. You must mix a putty of a consistency that is full-bodied enough not to sag off the hull while it dries, but is not so thick and dry that it cant be smoothed with a trowel. For example, the typical 1 l/2 through hull for a head discharge sticks about 1/4 above the surface of the hull. The result is a perfectly recessed through hull, without replacing any existing fittings. This will ensure there is marine sealant in the threads to seal the hull and hold the hull nut securely in place. For practical purposes, the bottom of a displacement-type sailboat can be considered smooth if the surface varies no more than 2 mils .002! Using a hole saw, cut a circle in the hull the depth and diameter of the through hull flange. Bring it back to gelcoat ready for the new thru-hull fittings. Tilt the bandsaw table to the measured angle and secure the cutting fence (see Figure 2). Some builders do spend the time to make their vessels safe & robust. The bronze UL Marine thru-hull fitting was made by Apollo/Conbraco, the UL Marine valve by Groco and the bronze elbow was also manufactured by Groco. Pass the rod through the fitting from inside the boat, seating the washer flat on the fitting. Removing the waterproof connector or cutting the cable, except when using a watertight junction box, will void the sensors warranty. You can . I purchased everything from Hamilton Marine in Portland, ME. Its fairly conservative to say that if the hull is less than 3/8 thick at the location of the through hull, you should fair in rather than recess the fitting. In addition, making your own putty allows you to control the viscosity, making a putty as wet or dry as you need. EDIT: I later tested a 1 thru-hull & ball valve combo and had it fail at below 500 pounds as well. Be sure the button on the fairing mates with the recess in the transducer housing. Drill a pilot hole through the backing plate and hull, dead center in the diameter of the circle representing the seacock's barrel, which you traced inside the hull. Clean the remains of the core material thoroughly from the inner surfaces of both fiberglass skins. NPT to NPT, NPS to NPS). A flanged seacock would be significantly stronger in this application and should meet the 500 pound standard even using this myriad of hard piping. A Bonnier LLC Company. In the absence of a caliper you may use a large clamp or a cresent wrench and then measure the gap on either. You can begin along the path to a fast bottom by recessing or fairing in through hull fittings that protrude beyond the surface of the hull, particularly in the forward half of the boat. As a general rule, you should fair a through hull over the area of a circle whose radius is equal to about 4 for every 1/8 the fitting protrudes above the surface of the hull. Modern devices that make boating easier, more reliable and more convenient can get very difficult to install without drilling holes in the hull and fitting seacocks.
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