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Thread: A question for the NAs

  1. #1
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    Default A question for the NAs

    Two designs, one outboard. Itll plane with a 30hp outboard at @ 15knots.
    The the other an inboard. With a 13.5hp inboard does 6.6 knots.

    They look very similar, except for the keel of course. If the keel was removed and a 30hp outboard installed could one expect similar performance?

    B547BEE8-D53B-4A96-9674-4FFC6DF6251B.jpg

    0F085122-8F4D-43DE-8C10-B16A46BB1C17.jpg
    Fight Entropy, build a wooden boat!

  2. #2
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    Default Re: A question for the NAs

    Superficially similar profile and deck drawings to not tell much though these boats are normal enough that, with specified assumptions, answers could be essayed. But really, it's a bit like saying these hulls are similar because one end is pointy and the other is flatish.

  3. #3
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    Default Re: A question for the NAs

    Hold your ruler on those bottoms, the lower has a bit more rocker, less straight a run.

    I'd say you might get 6.6 knots out of the top one with that same inboard though
    2019: returning from being sidelined with medical probs, crossing fingers worst is over, still in "armchair enthusiast" mode for time being.

  4. #4
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    Default Re: A question for the NAs

    The boat in question is actually 23’. I need to find the plans out in the shop. Harry only has the lines for the 20’ on his site.
    Friend of mine suggested we to a bit of empirical testing. He’s drives for the local marine towing service.
    Run a line to the bow eye and pull her at increasing speeds and see what she does. A rough test, but if she points her bow way up at anything above say 8 knots or so then we know.
    Fight Entropy, build a wooden boat!

  5. #5
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    Default Re: A question for the NAs

    Decision made. If no sale and the towing tests prove successful I’ll pull her into the shop once Catnapper is out and start the conversion.
    She’s a pretty boat and if I can make her useable here I’d prefer to keep her.

    One side benefit, with the engine box removed there’d be quite a bit more room in the cockpit.
    Fight Entropy, build a wooden boat!

  6. #6
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    Default Re: A question for the NAs

    I'm not an NA, but I fear that (as you imagine) the tucked up stern of Rambler will merely dig the boat into a hole if more power is applied. Our Gartside 25' has a run and transom that is immersed about as much as yours. The engine is a 33hp diesel, top speed at WOT is nine plus knots, barely. She digs a hole and squats at that speed.

    I hope I'm wrong, though. Let us know!
    Last edited by rbgarr; 07-31-2019 at 10:38 AM.

  7. #7
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    Default Re: A question for the NAs

    Thanks. Indeed that may happen and hopefully towing her will demonstrate her willingness to go faster.
    Fight Entropy, build a wooden boat!

  8. #8
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    Default Re: A question for the NAs

    How about building up the bottom to flatten out the run aft and remove some of the rocker?
    -Jim

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  9. #9
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    Default Re: A question for the NAs

    Quote Originally Posted by Reynard38 View Post
    Two designs, one outboard. Itll plane with a 30hp outboard at @ 15knots.
    The the other an inboard. With a 13.5hp inboard does 6.6 knots.

    They look very similar, except for the keel of course. If the keel was removed and a 30hp outboard installed could one expect similar performance?



    0F085122-8F4D-43DE-8C10-B16A46BB1C17.jpg
    The chine aft is lost in the boot topping or just did not reproduce, but it seems to be rising from around midships, so that is most likely a displacement hull form, probably not even semi displacement, although there is nowhere near enough info available from that drawing to be sure. Which is why this Naval Architect is all probably and most likely.

    There is a lot of fullness to that run.
    I strongly suspect that you will not rise much above hull speed. If you do put an outboard well into her there is no need to remove the keel. Keep it and the rudder to make the outboard installation simpler and benefit from the keels protection to the outboard leg, and ease of grounding and slipping.
    It really is quite difficult to build an ugly wooden boat.

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  10. #10
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    Default Re: A question for the NAs

    I'm not a NA...but plain experience tells me there is NO way that 23' hull will plane at 15 mph with a 30 hp ob. Not gonna happen with those lines on that size boat with that size motor. It probably won't plane with a 100 hp. ob. Good luck anyway.

  11. #11
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    Default Re: A question for the NAs

    That’s why I want to tow it first. See what happens. Not gonna invest the time and $$ until I do.
    Fight Entropy, build a wooden boat!

  12. #12
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    Default Re: A question for the NAs

    Quote Originally Posted by Reynard38 View Post
    The boat in question is actually 23’. I need to find the plans out in the shop. Harry only has the lines for the 20’ on his site.
    Friend of mine suggested we to a bit of empirical testing. He’s drives for the local marine towing service.
    Run a line to the bow eye and pull her at increasing speeds and see what she does. A rough test, but if she points her bow way up at anything above say 8 knots or so then we know.
    Have you got a beefy spring balance to put in the tow line so that you can plot the increase in resistance with increasing speed?
    It really is quite difficult to build an ugly wooden boat.

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  13. #13
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    Default Re: A question for the NAs

    Quote Originally Posted by Peerie Maa View Post
    Have you got a beefy spring balance to put in the tow line so that you can plot the increase in resistance with increasing speed?
    I do have one around here somewhere, and I like that idea, thanks!
    Fight Entropy, build a wooden boat!

  14. #14
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    Default Re: A question for the NAs

    Both of those boats will be slow, and be wave makers when you push them to their speed limits. If I remember correctly, you just built a boat that was too slow for your usage. In my humble opinion you need a true semi-planning hull in the low 20' range:

    0.2* L^3 for weight
    3.25 Length to beam ratio
    35 pounds per HP

    Speed is 5*(LWL)^(1/2) at cruise
    About 28 knots at WOT
    Good economy

    For example:
    22' LOD
    6'-3" Beam
    2100 Lbs
    22 knots cruise
    60 HP

    And deep V entry makes for a good all-around boat in open water.

  15. #15
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    Default Re: A question for the NAs

    Quote Originally Posted by Skiff Man View Post
    Both of those boats will be slow, and be wave makers when you push them to their speed limits. If I remember correctly, you just built a boat that was too slow for your usage. In my humble opinion you need a true semi-planning hull in the low 20' range:

    0.2* L^3 for weight
    3.25 Length to beam ratio
    35 pounds per HP

    Speed is 5*(LWL)^(1/2) at cruise
    About 28 knots at WOT
    Good economy

    For example:
    22' LOD
    6'-3" Beam
    2100 Lbs
    22 knots cruise
    60 HP

    And deep V entry makes for a good all-around boat in open water.
    ]

    Sounds good. Got a pic of that design?
    Fight Entropy, build a wooden boat!

  16. #16
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    Default Re: A question for the NAs

    So, I had a crazy thought about this at lunch today. I was looking through the most recent issue, and noticed AFRICA QUEEN. Thoughts from the NAs on modifying your boat like that one?
    Heute ist so ein schne Tag...

  17. #17
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    Default Re: A question for the NAs

    The Devlin Curlew 20 is a good example, but at 20'. https://devlinboat.com/curlew-20/

    They look similar to the boat below. CG is 63% of the LWL from the bow. Curve of Areas is straight aft.

    low-power planing.jpg

  18. #18
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    Default Re: A question for the NAs

    Quote Originally Posted by Don Z. View Post
    So, I had a crazy thought about this at lunch today. I was looking through the most recent issue, and noticed AFRICA QUEEN. Thoughts from the NAs on modifying your boat like that one?
    If you want to go from full displacement to semi displacement you have to increase the Prismatic Coefficient. That requires filling out the bow a bit as well as straightening the run.
    The keel line on that Rambler dives deep, so the only way the front end can be made to plane is by building a deep V stern from midships back.
    It really is quite difficult to build an ugly wooden boat.

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  19. #19
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    Default Re: A question for the NAs

    Good point on the deep Vee, just flattening it out with a shallow V likely adds too much volume, then if back more floaty, front more sinky, relatively.
    2019: returning from being sidelined with medical probs, crossing fingers worst is over, still in "armchair enthusiast" mode for time being.

  20. #20
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    Default Re: A question for the NAs

    Sounds like I just need another boat. Looked at an Albury a couple days ago. I really liked it. ​LYNDA DID NOT.
    Fight Entropy, build a wooden boat!

  21. #21
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    Default Re: A question for the NAs

    Or pretend you are a sailor, and 6 knots is making great time. Life is too hurried as it is.

  22. #22
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    Default Re: A question for the NAs

    Have you considered the Ninigret?

  23. #23
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    Default Re: A question for the NAs

    Quote Originally Posted by Reynard38 View Post
    Sounds like I just need another boat. Looked at an Albury a couple days ago. I really liked it. ​LYNDA DID NOT.
    Maybe you've mentioned it before but what does Lynda want in a boat?

  24. #24
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    Default Re: A question for the NAs

    Quote Originally Posted by J.Madison View Post
    Or pretend you are a sailor, and 6 knots is making great time. Life is too hurried as it is.
    That’s what my old Catboat is for!
    We really want to use the powerboat to go places. From out dock that are 5-6 places to go by water for lunch/dinner. I can use a boat to go get a haircut and do a lot of other shopping/errands. At 17 knots or so this a doable, at 6, well you’ll take the car, and also some of these places are only reachable by boat.
    Add in a 3 knot current and 6 knots becomes impracticable.
    Fight Entropy, build a wooden boat!

  25. #25
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    Default Re: A question for the NAs

    Quote Originally Posted by rbgarr View Post
    Maybe you've mentioned it before but what does Lynda want in a boat?
    Very good question. She’s never been a boater, but I think overall its gotta be safe in her mind. That probably means freeboard and decent seats. A feeling that you are in the boat rather than on it. She likes the classic style as I do. Can’t abide most of the new boats, and certainly not a center console.
    I was out recently on a forumites converted lobster boat. 36’. Very solid. I took a lot of pics, she loved it. Now 36’ is a good bit bigger than I want to go, but the owner of the boat suggested a Dyer 29. I showed her a few pics of the flush deck version and she really liked it. I like it too. Classic looks, very seaworthy and fast enough.
    Fight Entropy, build a wooden boat!

  26. #26
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    Default Re: A question for the NAs

    Possibly a stupid question, but is this to be a build-it-yourself boat, a buy-a-hull-and-finish-it boat, or a get-it-quick-buy-it boat?
    Hope for the best, but plan for the worst.

  27. #27
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    Default Re: A question for the NAs

    For what it's worth, I own a Handy Billy 21 with a Honda 30 hp. outboard motor. It will reach 14-15 knots (measured by GPS) if lightly loaded, but it is not a planing boat. It's just an efficient hull shape developed from William Hand's early inboard power boats from the early 1900's.

    Add a couple of people and you're going to see 11-12 knots as max.

    It is a nice boat though, just not "fast".

    Bill

  28. #28
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    Default Re: A question for the NAs

    Quote Originally Posted by mmd View Post
    Possibly a stupid question, but is this to be a build-it-yourself boat, a buy-a-hull-and-finish-it boat, or a get-it-quick-buy-it boat?
    The latter option. I’ve got Catnapper in the shop now, and once the Rambler is sold I am ready to have a boat to use. Something that needs a bit of TLC ( and I do mean a bit) is fine, but its gotta be ready to use.
    Fight Entropy, build a wooden boat!

  29. #29
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    Default Re: A question for the NAs

    Dyers are nice. There's one near us here that's in good shape: https://www.yachtworld.com/boats/197...owse%20listing

    This Lyman maybe, not far from you? https://www.yachtworld.com/boats/197...dard%20listing

    Maybe too modern or more than you/she'd want, but Hawks are well-built. https://www.yachtworld.com/boats/198...dard%20listing
    Last edited by rbgarr; 08-02-2019 at 11:10 AM.

  30. #30
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    Default Re: A question for the NAs

    Quote Originally Posted by rbgarr View Post
    Dyers are nice.

    These maybe, not far from you? https://www.yachtworld.com/boats/197...dard%20listing

    Maybe too modern or more than you/she'd want, but Hawks are well-built. https://www.youtube.com/watch?v=vyQh...Pln4Nd8ckvTiZk
    Didn’t realize Lymans were made in glass. That’s a pretty boat! I’ll show it to her when she gets back in a bit, thanks!
    Fight Entropy, build a wooden boat!

  31. #31
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    Default Re: A question for the NAs

    My in-laws had a wood Lyman for decades. They can be loud (the engine boxes can do with enlarging and/or soundproofing) but the rumble of the engine is a sweet sound. You can just make it out in the listing's video. It's good that one has a blower to evacuate any gas fumes from the bilge. It also look like it has a spark arrestor on the engine. The early wood ones didn't!
    Last edited by rbgarr; 08-02-2019 at 02:59 PM.

  32. #32
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    Default Re: A question for the NAs

    Then there's this of course, if Lynda wants to go 'uptown'. The I/O would need to be kept on a lift at the dock. Warm southern water grows barnacles on I/Os something fierce. https://www.yachtworld.com/boats/199...dard%20listing

  33. #33
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    Default Re: A question for the NAs

    Have you looked at Sea Way boats? ( No connection; just making a suggestion) They give you Downeast-style with outboard power. Not cheap, but not priced at top of market either. Here's a 21 cabin model.

    Screen Shot 2019-08-02 at 5.25.35 PM.jpg

    Screen Shot 2019-08-02 at 5.28.32 PM.jpg

    Kevin
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  34. #34
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    Default Re: A question for the NAs

    Tripp Angler 18?

  35. #35
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    Default Re: A question for the NAs

    Arch Davis Jiffy V-22
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