Tunnel for LM18

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Ryan
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Re: Tunnel for LM18

Post by Ryan »

Wow that tunnel is huge! How does it perform? Boat is beautiful by the way!

~Ryan



TomW1
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Re: Tunnel for LM18

Post by TomW1 »

Not really Ryan looking at the prop, it is propably 2.5,3 x 10,12i If you click on the poc you will get an righside up photo the will let you enlarge it.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

Ryan
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Re: Tunnel for LM18

Post by Ryan »

Got a question for the experts here! I am not going to put a skeg in the center of the boat per plans (since I’m doing the tunnel). I was wondering if I were to run two 1” tall strips on either side of the tunnel- if that were to negatively effect anything? Also how far from the tunnel do you recommend and and how long?
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fallguy1000
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Re: Tunnel for LM18

Post by fallguy1000 »

I would be a bit worried about aeration from the runners. But Jacques is the best man to answer.
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TomW1
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Re: Tunnel for LM18

Post by TomW1 »

The LM18 is not made for speed and does not require skegs. With the tunnel there really is not a good place to put them on a narrow boat like the LM18. Instead install reverse chines. They will do will two things reduce spray and help in turning. The negative is that the reverse chines may increase slapping a little bit but not much since they are an 1-2" below the normal chine.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

Ryan
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Re: Tunnel for LM18

Post by Ryan »

Thanks Tom! I think I’ll go with your suggestion and just not put anything on it. It’s definitely going to be no speed demon with a 40!

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VT_Jeff
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Re: Tunnel for LM18

Post by VT_Jeff »

I would probably add the skegs if I were you, just based on my experience with my FS14LS with no skeg(top speed around 25mph). I'll probably add a skeg or strakes at some point, other priorities at the moment.
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fallguy1000
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Re: Tunnel for LM18

Post by fallguy1000 »

Isn't Barraman running this boat/sim?
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Cbuf
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Re: Tunnel for LM18

Post by Cbuf »

My lm18 runs 34mph with a 50 you will probably run around the same with a 40 because your planning lighter than I built. I'm not sure what the answers is for the skeg with a tunnel, but when you have a small boat running 30+ it is a lots faster than you think. Also, when I turn at speed, I couldn't imagine not having a skeg especially when it is bumpy because the back 6-8' of the boat is basically a flat bottom boat. Maybe two strakes, to not interfere with the tunnel. The chine might work, but it would have to be a pronounced.
See my LM 18 build here.
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See my LM 18 Questions here.
viewtopic.php?f=2&t=64299&hilit=lm18\
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Ryan
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Re: Tunnel for LM18

Post by Ryan »

Hey CBUF do you have any videos of your boat running? I’d like to see how this boat turns.

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