Repowering An Alberg 30 (Part 1)

Introduction

This article is the first of three about installing a complete inboard power train on an Alberg 30. Its focus is on the design. An inboard power train is not the sole engine paradigm compatible with Alberg 30s. Although not covered here, one may also be interested in the design where an outboard engine is installed in the aft lazarette (AtomVoyager, 2020).

As it is the case for all intallation projects, some aspects of this post are specific to the target sailboat. At the time of writing this post, Jean-du-Sud is currently powered by a 10 HP outboard engine fixed on the port hip. This means that the inboard engine space is empty, that the shaft entry point in the hull is fiberglassed, and that the current rudder and hull has no aperture for a propeller. Thus, specific analyses therein may not be relevant to other boaters.

Engine/Shaft Angle

Jean-du-Sud has no inboard power train and so I had to estimate the angle with respect to the waterline at which the shaft pierces the hull. I did so by using various online pictures of Alberg 30’s (Sailboatdata.com, 2022; DingyDreams.com, 2018; The Alberg 30 Project, 2016) and an online protractor (Ginifab.com, 2022)

(Source: Alberg30.org and Ginifab.com, 2022)

(Source: The Alberg 30 Project, 2016)

All estimates are between ten degrees and eleven degrees. As pointed out by James Frederick, the actual shaft angle required for engine enlignement can be deduced once the stern tube is properly fiberglassed into the hull.

If one fixes the shaft point of entry in the hull, an higher angle translates in less headroom in the engine bay. Conversely, a lower angle means less room at the bottom of engine bay. As long as the angle is within the 10 to 11 degrees margin, all checks below are fine.

Engine bay

Jean-du-Sud’s Initial Measurements

The engine bay’s current dimensions were taken directly from Jean-du-Sud (see the diagram below). A box of roughly 16.5″ (H) x 21″ (W) x 21″ (L) can be used as the availlable room for the engine bay above the current engine mounts and oil pan.

(Photo taken by the owner. Orange: wood that can be removed. Green: fiberglassed shaft entry point.)

There is however considerable space below the oil pan, as evidenced in Abroad Reach Travel’s (2021) engine install video and in James Frederick engine install videos (2017) (pictures below).

(Source: Abroad Reach Travel, 2021)

(Source: Sailing Vessel Tritea, 2017b, part 4)

This means that given some structural work, the bottom fitting is much less of an hard constraint than the top and side fittings. There are good references regarding how to change the engine mounts to appropriately position the engine (Abroad Reach Travel, 2021; The Alberg 30 Project, 2016).

SailboatData.com Estimate Measurements

Using the boat plan from Alberg30.org (2022) and an online tool to estimate lengths (eleif.com, 2022), one can obtain additional estimations of the engine bay dimensions. SailboatData.com (2022) gives a length at waterline of 260 inches. Using the online tool and this measurement gives us a good idea of the engine bay’s measurements according to plan.

(Source: Alberg30.org, 2022 with eleif.net calculations).

This provides an engine bay width of 22.48 inches, a depicted engine headroom of 27.41 inches, an overall engine length of 29.54 inches, a shaft length of roughly 26 inches and a top of engine bay to shaft measurement at the proper angle of 21.33 inches.

Engine Choice

I used Nigel Calder’s formula for calculating the engine size as well as the propeller pitch and diameter (Calder, 2006). After simplifications, the required horsepower (hp_r) is determined by:

hp_r = 55 \cdot 4.01 \cdot 1.34\sqrt{27.32}\frac{10}{4}\cdot1.33\cdot0.003\approx 20.64,

where 55 is the resistance of the boat in the water (Calder, 2006), 4.01 is the weight of Alberg 30s in long tons (as per SailboatData.com), 1.34 is the speed to lenght ratio (Calder, 2006), 27.32 is the length at waterline of Alberg 30s, 10/4 is a loss of efficiency factor, 1.33 is a safety factor and 0.003 is a conversion factor part of the formula (Calder, 2006). All in all, Calder’s formula goes to suggest a 20.64 hp engine.

I looked for both Yanmar’s 3YM20 and Beta Marine 20 engines (Yanmar USA, 2022a-c; Beta Marine USA 2022a-c). I chose a Beta Marine 20 mostly because of a 3000 CAD price difference with Yanmar. Both engines fit in the engine bay and both have decent power curves. (At the time of the project, there was not much availlable on the used/reconditionned market, at least as evidenced by Ebay and Craigslist, but it may be different at some other time). If the pricing difference were to be reversed, one could easily choose Yanmar and most of the analysis below would follow through.

Fitting Analysis

Beta Marine 20’s dimensions are given in the picture below. Although not shown, the Yanmar 3YM20 is smaller than the Beta Marine 20 and thus also fits in the engine bay (Yanmar USA, 2022b).

(Source: Beta Marine Canada, 2022b. Note: dimensions in milimeters.)

Sides and Headspace

The engine requires 16 7/8″ of width, wich is well within the current space in the engine bay, even when factoring in for some sound insulation sheets.

The engine block requires 15 7/8″ of headspace above the engine mounts (that is 13.25″ + 2.625″), wich is within the 16.5″ availlable from the initial engine bay measurements. That however assumes that the front engine mounts yield the correct alignment with an 11° angle. The second estimates based on sailboat data yields estimates of a 21.33″ at the proper angle.

There is also evidence that a Beta Marine 20 fits into Alberg 30’s (Abroad Reach Travel, 2021) and anecdotal evidence, as shown on the Alberg 30 facebook page, that the Beta Marine 16 also fits (Alberg 30 Owner’s Facebook page, 2022a-b). Given that the Beta Marine 16 engine block is of the same height and width than the Beta Marine 20 (Beta Marine USA, 2022d), it provides additional insurance that it fits.

(Source: Alberg 30 Owners Facebook Group, comments anonymized)

Shaft Diameter

The standard shaft diameter on Alberg 30s is 7/8″. Discussions with engine specialists rather suggested a diameter of one inch, “but 7/8 inch could also be acceptable”. As Jean-du-Sud does not have any shaft nor stern tube installed, I ordered a one inch diameter shaft from the same supplier as the propeller.

Rudder

Jean-du-Sud does not currently have any aperture in its rudder (see the picture below). Hence, there is no space for a propeller.

(Source: picture taken by owner.)

I decided to have a rudder fabricated. Three companies were suggested to me, and only two answered positively with a design and a quote: The Foss Company (California, USA) and Competition Composites Inc. (Ontario, Canada). Living in Canada, the second company turned out to provide a less expensive quote (the opposite price difference may occur for an american project).

Based on Sailing Vessel Tritea’s loss of rudder control, I asked to include a through hole in the rudder design, so as to make an easy jury rig in case of breakage.

Propeller Size and Pitch

The propeller size is important for performance, but also for the hull and rudder design. Roughly 110% of the propeller diameter size must be carved out of the rudder and the hull to determine the apterture’s height.

I used Calder’s formulas (Calder, 2006) for the propeller pitch (P, in feet), diameter (D, in inches) and blade area (A, in squared inches). The following calculations reflect a transmission reduction ratio of 2.0. The formula for the pitch is:

P = \frac{101.3\cdot 1.34 \sqrt{27.32}\cdot 2.0}{0.95\cdot 3600}\frac{1}{0.575}\approx 0.7216,

where 101.3 and 1.34 are fixed factors, 0.95 is the assumed maximum throttle of the engine (95%), 3600 is the maximum engine rotations per minute, 2.0 is the transmission reduction ratio and 0.575 is the assumed blade efficiency at converting rotations in displacement (slip ratio). The formula yields a pitch of 0.7216 feet, meaning a pitch of 8.65 inches.

The formula for the diameter is given by:

D=632.7\frac{(20)^{0.2}2.0^{0.6}}{(0.95\cdot3600)^{0.6}}\approx 13.23, 

where 632.7 is a fixed factor, 20 is the engine horsepower and the other figures are as in the previous formula. The formula suggests a propeller diameter of 13 inches.

The formula for the propeller’s surface area is given by:

A=100 \frac{20}{1.34^{3/2}27.32^{3/4}}\approx 107.9, 

where 100 is a conversion factor and the remaing figures are as in other formulas. The formula suggests a propeller blade area of 107.9 squared inches, which means a three blade propeller.

A diameter of 13 inches seems reasonnable. Abroad Reach Travel (2021) reports a propeller of three blades with 12 inches in diameter and 9 inches in pitch. Beta Marine Canada suggests a three blade propeller of 13 inches with a pitch of 9 inches (Beta Marine Canada, 2022).

Yves Gélinas (the former owner of Jean-du-Sud) encouraged me to obtain a foldable propeller. Alberg 30s have a maximum theoritical speed of roughly 7 knots and putting a non-foldable propeller is putting drag against that maximum speed. On the other hand, foldable propellers do not fit in Alberg 30’s aperture. Some feasible alternatives are feathering propellers by Featherstream (Darglow Engineering Ltd, 2022). They can fit in an aperture size designed for fixed blades propellers. Darglow provided the specifications for the propeller dimensions (id, 2022).

Aperture Size

According to Calder (2006), any propeller requires roughly 15% of its diameter above and below the propeller to avoid turbulence. The same advice is also provided by the Beta Marine operation manual (Beta Marine, 2022c). For the same reason, they should further have the same margins for and aft of the propeller.

Using the same methodology for the engine bay dimensions, one can find that the standard aperture size is roughly 15 inches in height by 8 inches in length. As the original aperture has been fiberglassed on Jean-du-Sud, there is some room for change on these dimensions. However, the owner of an untouched Alberg 30 may want to consider these dimensions has a given constraint.

Fitting a 13 inch propeller on the powertrain requires an aperture height of roughly 17 inches, leaving two inches on the top and the bottom to avoid cavitations. This means that as a first approximation, 1 inch needs to be carved out from the original design both at the top and the bottom of the aperture. Lengthwise, the requirements for the FeatherStream propeller are of 5.88 inches, which is within the normal aperture size.

Some exchanges with the rudder making company suggests that the changes in the aperture size is feasible.

Stern Tube

I ended up purchasing an epoxy stern tube from lakesterngear.co.uk with a PSS shaft seal, the associated cutlass bearing and a B.Y. Hurth shaft clamp. The stern tube comes 4′ long, which will be cut on installation. I worked with LakeSternGear for a simple reason: in contrast with other companies we contacted, they answer to their emails.

Diesel Tank

There is great material availlable online on the design of a fuel tank. I found the videos from Teds Marine Repair (2021) and AnclaTV (2016) to be useful. There is at least four required lines in a diesel tank. The first is the line for refueling, which is usually fitted on deck and has a one inch diameter. The second is the engine intake line, which requires an antisyphon valve and a rigid extension going down roughly a quarter of an inch in the tank (which diminishes the effective tank capacity, as the bottom fuel is never used). The third is the engine return line, which returns any unburned diesel in the tank and should also go to the bottom of the tank. The last one is a venting line, which relieves any pressure build-up in the tank.

On top of those lines, one may add a valve at the bottom of the tank so as to empty the tank without a pump. Moreover, a broad circular opening may help to inspect the tank interior. Finally, a fuel gage may be added, which requires an additional opening on top. As I am looking for a plastic (semi transparent) diesel tank which will be accessible from a lazarette, I find little usefulness in a fuel gage.

The shape of the diesel tank is mostly driven by the availlable space. I measured the dimensions of the port lazarette to figure out the maximal size that Jean-du-Sud can hold. It may however be useful to think of an inclined tank bottom, so that any sludge or debris formation builds up in that inclined part. With diesel intakes above such part, the fuel quality going to and back from the engine should be better. Dimensions for a lazarette openings were found to be roughly 37 inches long by 16 inches wide on the largest side and 12 inches wide on the smallest side.

Sailboat.com reports an original 57 liters (15 gal.) diesel tank. With a betamarine 20, a partition of fuel in three (emergency, departure, return), and a fuel consumption at 2800 RPM (2 L/hour), this yields a range of action of 9.4 hours. At 6 knots this translates into 57 NM per third (with the current rpm to speed conversion the fuel consumption and the tank partition cancel each other so the tank size immediatly translates in nautical miles).

With all these considerations, two models stem out as good starting points:

• the 60 liters, 800 x 350 x 250 tank (in inches: 31.5 x 14 x 10) from Tek-tank.com;
• the 75 liters, 660 x 279.5 x 406.4 (in inches 26 x 11.75 x 16.25) by Moeller.

Neither have an inclined bottom, but they fit the lazarette dimensions. Tek-tank is cheaper, but does not deliver in North America. The Moeller tank requires an additional spending for a return line, which is not included in the baseline fitting. Some straps to fasten the tank must also be purchased. Furthermore, a small fiberglass stand must be built in the lazarrette, so the tank can sit properly, adding to the overall cost and installation time.

Engine Battery

There are two battery archetypes: deep-cycle, for cabin usage, and starter, for starting an engine. Each type require a different voltage charging profile. If mixed, it shortens the lifecycle of a battery (Solar Solutions, 2021; Pacific Yacht Systems, 2022a-b; Calder, 2015). Jean-du-Sud already has two deep-cycle batteries. Thus, at least one starter battery is required. I examined two circuitry options.

The first one is to leave the two battery banks separated completely. The option is cheap, but does not allow the house batteries to be charged from the engine alternator. The second one is to purchase a single starter battery and connect it to the existing batterie bank through a dc-to-dc converter. This device has for effect to electronically apply different charging profiles to the two battery banks while being on the same charging circuit. This makes the best use of both battery types while allowing for engine charge, but is more costly (roughly 300 CAD is required for a Dc-to-Dc converter). It also requires a deeper look at the alternator’s capacities.

The default alternator from Beta Marine provides 40 amps at top engine RPM and is regulated to deliver a constant 14.1 volts. As explained by Pacific Yacht Systems (2022a-b), this amperage is optimistic and rated at ideal conditions. This means that it does not provide enough amperage to charge both battery banks in a reasonable amount of time. I thus defered option two, pushing it in a future « electrical upgrade » project. After all, solar and wind power already maintains the internal DC system!

Batteries can ranked by price and (roughly) claimed effectiveness: lead acid, gel based and lithium based. Lithium based cost more upfront and seem overall cost-effective over their life cycle. However, as reported by Barrel (2021), reputable brands of lithium batteries are not suited for starting engines and their overall lifespan remains to be proven. Moreover, what is of practical purchasing importance, batteries are hardly shipped, which means I had to purchase within what is availlable locally.

I used the Beta Marine standards to look for the battery requirements: 450 cold cranking amps (CCA) and 70 amp-hours (at 12V). I ended up purchasing an Interstate 24-HD battery, a lead-acid battery availlable and fitting the standards.

Pricing

The prices of each item are described in the table below, before taxes. Exchange rates of 0.75 USD/CAD and 0.63 GBP/CAD were used to provide figures in the table below.

The total cost of the project is roughly 21 140 CAD with all the listed material. It should however be pointed out that 25% of the cost is related to having a new rudder made, a specificity related to Jean-du-Sud. Moreover, replacing an existing engine can cut costs by keeping the same shaft and related engine accessories (e.g. fuel tank, filters).

It still remains a signficant investment for a boat of this age. Besides abandonning the project (!), I can see three ways to cut costs significantly. First, seeking for a used engine. This can cut the engine price up to half of the marked price. The trade-off is uncertainty on the engine’s capabilities and reliability. Second, switching to a fixed blade propeller can also cut the propeller costs by half. The trade off is accrued drag while sailing. Third, modifying the rudder instead of having a new one built. It is a classical tradeoff between time and money.

Planning Assembly

How long will this whole project take? I used a project management software (monday.com) to build a gantt chart, estimating how much time each task should take and how to distribute the workload as efficiently as possible, so as to minimize the overall execution time. The exercice was globally useful, as it made me see the interdependance between some tasks I would not have seen otherwise.

Provided the boat is ready and out of the water and all the different pieces are ready for assembly, the assembly is estimated to take a full month (give or take). Fiberglass takes seven days to cure and all taks related are of critical interdependence. The most efficient use of time tactic is to do several fiberglass tasks back-to-back (e.g. fixing the rear sterntube and fixing the engine mounts) and then do other tasks while waiting for the fiberglass to cure (e.g. installing the engine control-panel). The critical tasks are related to the installation of the sterntube and the engine beds, as the engine cannot be intalled, nor aligned, beforehand. Testing the engine (and flotability) is obviously done in the end.

Conclusion

This article provides a reasonable insurance that the described design can work. As the project needs to be carried out, it is incomplete by nature. Its definitive conclusions are the object of the next article.

Thanks

I would like to thank James Frederick (SV Tritea), Ben Gartside, Donald Proul, Nick Gifford, Julien de Tilly and Yves Gélinas for providing me with feedback and comments. All errors (very little I hope) remain my own.

References

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Alberg 30 Owners Facebook Group (2022a). Comment, screenshot taken by the author.

Alberg 30 Owners Facebook Group (2022b). Comment, screenshot taken by the author.

The Alberg 30 Project (2016). Prop Shaft Prep, Web page, retrieved online in November 2022 at https://alberg30project.blogspot.com/2016/07/prop-shaft-prep.html.

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