Sharpie Schooner 42 with an outboard motor

Discussion in 'Boat Design' started by valery gaulin, Apr 6, 2018.

  1. goodwilltoall
    Joined: Jul 2010
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    goodwilltoall Senior Member

    Having put in an inbaord diesel engine recently there are many more accesories than just the engine which can cost more than engine alone.

    Engine beds, engine mounting bolts, shaft, shaft log, shaft log hole, stuffing box, props,coupler, cutlass bearing, transmission, fuel tank, fuel pumps, fuel filtration system, engine/tranny controls, wet/dry exhaust system, grease fittings, etc... all of which take up space to properly access for service, which take careful consideration of placement, time consuming labor to be within accuracy tolerances for alignment, and some of it custom with all of it feeling at least as though its custom fitted.

    OB's also have thier requirements but i would guess prolly much simpler.
     
    Last edited: Apr 14, 2018
  2. JSL
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    JSL Senior Member

    Engine beds, engine mounting bolts, shaft, shaft log, shaft log hole, stuffing box, props,coupler, cutlass bearing, transmission, fuel tank, fuel pumps, fuel filtration system, engine/tranny controls, wet/dry exhaust system, grease fittings, etc...
    a 'rough' ('ball park') cost figure for a 'normal' installation is the 'accessories' will cost as much as the engine/transmission.

    re: prop diameter.
    remember the prop, as well as pushing the boat is also 'stops' the boat... an under sized prop may be risky in an emergency.
     
  3. goodwilltoall
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    goodwilltoall Senior Member

    Btw, james baldwin at atom voyages has ideas for installing OB inboard in the lazarette of mostly older sailboats although, smaller units that can be lifted out. He is much happier 4 several reasons with that setup than the previous standard inboard. My biggest concern is the air supply is vented right at seats in the cockpit and perhaps with a failure engine can spew fumes there rather than through prop.

    In your situation i would mount it to vertically movable post able to take it up n down. If you got really creative make it possible to turn the post for steering with ob. Biggest obstacle would be keeping engine well small enough just for engine needs and keep drag minimal as well as amount of water intrusion but still be able to satisfactorly plug hole.

    High thrust is the obvious type for displacement boat use and from my basic understanding prop size and speed of prop would be the main factors for efficeincy, yamaha i think was first to develop so they would be point of reference in decision when comparing, but still wonder about everything involved when it comes to deciding the "best" with same hp amongst the brands
     
    valery gaulin likes this.
  4. chinaseapirate

    chinaseapirate Previous Member

    Love the chain link fence on that Terrapin 34 homebuilt. I just used a leash. Oh, and be sure to get a diesel generator, I didn't notice it wasn't.
     
  5. valery gaulin
    Joined: Jan 2017
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    valery gaulin Senior Member

    @goodwilltoall

    This the reason that if I go with a diesel engine i am considering a saildrive complete package. From what I understand it isnonly neeeded to bring you fuel line!

    The price I got for a saildrive, 38hp Beta diesel + fiberglass engine bed was 18 000.00$CAN.

    To me is alot of money to put on the power plant and like you said there probably alot more accessories needed!!!

    The is a reason why I try to figure out how to get a descent outboard installation for my project!

    A Suzuki outboard 40HP that I just checked at the store, complete is only around 6000.00$CAN!!!

    This is my delima! If money was not in the equation, this post would not exist!!!
     
  6. goodwilltoall
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    goodwilltoall Senior Member

    18G can get u a 38hp inboard professionly installed and imho is better than a saildrive. Save u time as well for other endeavors.

    If you plan on mostly sailing the OB will get the job done
     
  7. M&M Ovenden
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    M&M Ovenden Senior Member

    Hi Valery,
    Why a saildrive ? What about a regular prop/shaft/transmission/diesel ?
    Mark
     
  8. JSL
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    JSL Senior Member

    regardless of power & installation, the prop should be folding, feathering, or lockable. This looks like a boat capable of good performance and it would be a shame to slow it down with added drag, burn out the tranny, or put boat at risk, with a free wheeling (auto-rotation, back driving) prop.
     
  9. chinaseapirate

    chinaseapirate Previous Member

    I guess I'm way behind times in sequential context here... The original opening that you designed for a 60sp outboard is great. Except that you don't need that much power. If the idea of a bulky but cheap (derated to whatever at 1200RPM) mini truck engine/low mileage reefer unit permanently installed ahead of the opening and manually connecting the shaft to a another bulky large outboard motor lower unit with a 90 degree angle is unappealing, and a smaller permanent magnet electric motor ($299) mounted onto an existing 10 hsp longshaft outboard with blown engine ($50) (what too slow ? even considering the toy prop should go 5+ easy), then go with this - 6 1/2 knots for sure-any used 20 hsp tohatsu ("blown eng/parts only", "salt water damage-as is", etc, $50) , aftermarket 30" shaft kit for it (shaft and leg extension only - don't need gear linkage), 17 X ?? 25%DAR two blade fixed pitch prop ($300 - europe/$60 +shipping-asia/not recommended(unavailable-north america), 24/36/48V golf cart engine ($500 new),misc wires and relays from from heavy duty tuck junkyard ($20), 160# 3.2V, 3AH 26650 LiFePo4 batteries with tabs ($160), solder gun. The Tohatsu is easy to grind off the stupid prop size governor. The pitch is not specified because you need to get a $2500 14" variable pitch propeller with 30 day money back guarantee, and figure it out empiracally, but you will find the lowest battery drain for the final speed you want. Group the batteries in sets of 10 parallel, set of 16 series. Ideally you will be able to return the expensive prop, order the $100 one at 14" x 14.5", file it down to 50% of its original weight (mostly around the hub and inner radius) and find that 4 sets in series of 40packs in parallel gives you your 6 1/2 knots. Then rearrange the batteries into 5 sets in series of 32pack parallel , and shave another 10% of the original weight off the prop and your set. You now have emergency slow(three manually operated switches down),slow (two),med(one),cruise(default), and 100%(no reserve power left- one switch up) and reverse (another pair of contact relays behind the power selection contacts). 6 1/2 knots at 550 propeller RPM using 2.3 kwhr battery drain. Assumptions- 1) 9.0 long tons displacement 2) 15 lbs/ton resistance flat water at 6.5 knots, 3) 73% prop efficiency 4) your displacement figure only grows by the volume of water the keel would displaces if it were to sink rapidly as it is not yet connected to the hull.
     
    Last edited: Apr 19, 2018
  10. valery gaulin
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    valery gaulin Senior Member

    @M&M Ovenden

    I am not against a standard diesel installation. But I am trying to keep everything related to the engine in the cockpit area. The location of a standard diesel installation would be right in front of the cockpit even under the stair going in the cabin to have a descent prop-shaft angle. Also this location for my need is not desirable because I want my helm station exactly in the forward part of the cockpit. I want my wheel for steering the sailboat installed on the bulkhead of the cabin. Probably one wheel on port and one on starboard.

    I also try to minimise as much as possible through hull fitting. With a standard diesel there is alot of through hull needed. A saildrive or an outboard motor does not need any through hull or minimal!

    I also like to locate the engine in the center of the cockpit because once the cover/box covering the engine is open it should be really easy to work on the engine, having access from all the 4 sides. It will also gives the opportunity to have a table over the engine cover/box giving a good area to entertain. Locating the engine in the middle of the cockpit will also provide a place to braise your feet against it when sailing. Another feature that might be interesting of having the engine in the middle of the cockpit is that it means less volume of water if the cockpit ever get swamped by a wave.

    I am still trying to find the best compromise. I have something in my head from thinking of all the comments received in this post. When I find sometimes I will update my drawing and share my new interpretation for the engine.
     
  11. M&M Ovenden
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    M&M Ovenden Senior Member

    It would be good to get the weight forward anyway of such a light boat. Wheel steering ? That rudder is screaming for a tiller which gives far more options for self steering. I'd be trying to keep things as simple as possible.

    Mark
     
  12. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    The original drawing with a well installation is basically not a bad idea. However, you only need a 10-15HP outboard. Also, the location can be further aft. Many boats have the outboard offset to one side with no problem. You can use the outboard for steering, so it is easy to compensate for the offset thrust. KISS;)
     
  13. valery gaulin
    Joined: Jan 2017
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    valery gaulin Senior Member

    @gonzo

    My original drawing might have a conceptual problem that I overlook. Someone on this post, I think it is Angelique, made me realize the lost of boyancy with a well this much forward might be a problem.

    Like you are saying, I am redrawing a new proposition with the well more aft. This time the engine will not be tilted with the powertilt option coming with the outboard, instead it will be raise vertically. The only thing I hate about raising the engine verically it is that the center of mass gets a little high to my taste, especially with a 225lb outboard.

    When I calculate the engine requirement from the website Psychosnail it looks like around 40hp would be good to get hull speed, something like 8 knots plus.

    I might be happy with smaller engine, maybe the 25 hp high trust from Yamaha. But it is the same weight and price as a standard 40 hp outboard!!!

    The offset location is something that my mind can't get over it, it is psychological!!!

    The steering option an ouboard offer is one of the main features this type of installation provide.

    Thanks gonzo for you positive comment.
     
    Last edited: Apr 15, 2018
  14. valery gaulin
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    valery gaulin Senior Member

    @M&M Ovenden

    Tiller steering will be my emergency option.

    You are right that this sailboat looks like it is screaming for a tiller. The only problem that I realize with my Grampian 26 is the cabin top prevent you from seeing ahead. This is the problem with a shallow draft sailboat with standing head room, the cabin is high compared to the cockpit floor and cockpit seat height. Therefore steering with a tiller sitting in the cockpit is not practical to get a good view forward. Even being tall like me, 6'2", it is a problem that I realized sailing my Grampian 26.

    I will probably installed the wheel steering system similar to the Dutch Tjalk way. They have a shortened tiller with rope going back to the wheel. When switching to the emergency tiller I can just stick it in the shortened tiller.

    Hope it makes sense what i just explained.
     

  15. goodwilltoall
    Joined: Jul 2010
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    goodwilltoall Senior Member

    Any design power or sail where u can not see fwd while sitting to me is flawed. You can raise cockpit and add coamings but then you are on top of the boat rather than in it. Short of redesigning sheer line and adding freeboard that is your only option. Further, its been hashed out already regarding pro/cons of enclosed cockpits or lightly semi protected, personally am a strong proponent for something permanent, if you agree your plans should include that as well so it dont look freaky aftwds and to be sure ergonamics work out as planned.

    Plenty of boats with offset OBs and no issues , would like to see how you make vertical lift/steer mechanism, my preferred option.
     
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