measuring and replicating a long curve
#11
  
I've got a problem that needs a better mind than mine. I need to make a splash guard for a rowing scull (an Alden 18) that's missing one. (They don't make spare parts.) I thought I would make it out of a light wood like cedar. It's a V-shaped piece, originally of plastic, that fits on the deck forward of the cockpit and serves to deflect any waves that come over the bow. The problem is that it's long, maybe 30-36 inches on each side, and the deck curves underneath it. What's a good way to replicate that cure on the workpiece? Any suggestions?
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#12
  Re: measuring and replicating a long curve by overland (I've got a problem t...)
As an avid daily sculler, I take particular interest in this...
Is there a chance that you can find a local Alden (with an intact splashguard, of course) from which you can make a copy the profile/shape? If not maybe contact Pete or Karen at Adirondack Rowing, and see if they can make a template from one of their fleet.
I have the same issue with a one off mid 1980's single from Norway. I made a template from one side from a piece of cardboard. I have not taken the next step and fabricated the guard yet... 
On a side note, where are you rowing that you encounter water over an Alden's bow?
Good luck with the project...
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#13
  Re: measuring and replicating a long curve by overland (I've got a problem t...)
To answer the last question first: Lake Michigan. Maybe I won't need the splash guard, but it would be good to have.
 I might try balancing a yardstick at the highest point and then measuring every few inches. That might allow me to make a template.
  I wonder why the boat came without the guard and why someone took it off. But I paid only $400 for the boat, two sets of oars and two rowing rigs, so I can't complain. 
  I wrote to adirondack rowing. They didn't offer to help me make one. Apparently they'd be willing to offer such a part, but the manufacturer hasn't been willing to make them available.
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#14
  Re: measuring and replicating a long curve by overland (I've got a problem t...)
Are you familiar with the scribing process? Your idea of balancing or blocking up a straight edge along the line where the splash guard will go and then measure at regular points will work. However, scribing is a similar process only after getting your straight edge in place, you can use a small compass to scribe a line on the straight edge. Hold the compass horizontally with the pencil straight above the point. Then drag the point on the bow surface while keeping the pencil straight above it and against the straight edge. You should end up with a line parallel to the bow surface. Use that to make a template or, if the straight edge is also your splash guard work piece, you can just cut to the line. If the gap between the straight edge or work piece is small, you can just lay a sharpened pencil down flat on the curved surface and drag it along the surface with the point against the work piece to get your parallel line.

If my description is not clear, just do a web search on "how to scribe a line". You''ll find some videos that explain it better.
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#15
  Re: measuring and replicating a long curve by overland (I've got a problem t...)
I imagine Lake Michigan will develop some chop...I think the splashguards get damaged when the boats get handled/mishandled. They typically spend most of their non active life upside down, and if not properly cradled, especially when being transported, the guards are often unintentionally "sacrificed"...
Great deal on a seaworthy shell...
Enjoy!
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#16
  Re: measuring and replicating a long curve by overland (I've got a problem t...)
cover area with masking tape
Build "sides" of cardboard, etc and masking tape.
fill with wax, clay, "Great Stuff" or other casting type material to make "Master" 
then copy.
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Wild Turkey
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#17
  Re: measuring and replicating a long curve by overland (I've got a problem t...)
All excellent ideas. Thank you, everybody. You've shown a way forward. I think I can do it, one way or the other.
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#18
  Re: measuring and replicating a long curve by overland (I've got a problem t...)
If the splash guard is to be two flat pieces, joined in a V-shape, the correct way to go about this is to create a pattern starting with a flat board or piece of thick plywood, laid across the deck and propped up at the precise angle of the future workpiece. To the flat surface of this board hot-glue appropriately sized sticks such that their ends touch the deck along the entire curve where the workpiece will touch the deck. When completed this pattern can easily be transferred to the workpiece which, after a final scribing/fitting in place, can be itself used as a pattern for the opposite side.

If the splash guard is two curved pieces the process is somewhat more complicated, but still proceeds roughly as described above.
Wood is good. 
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#19
  Re: measuring and replicating a long curve by overland (I've got a problem t...)
Is it safe to say you are referring to the white piece at the top of the shell in the front?




It looks like this guy made his out of teak.




I would use a CMT flexible template.  It is available from Amazon for $70.00 and has good reviews.  https://www.amazon.com/CMT-TMP-1200-Flex...B008AXXH54

https://www.youtube.com/watch?v=wUNWDsVUynQ

https://www.youtube.com/watch?v=zRj6EGr8tAg

I would use the CMT to make a permanent template.  You can either sell replacement parts to scull dealers or sell the templates.
No animals were injured or killed in the production of this post.
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#20
  Re: measuring and replicating a long curve by overland (I've got a problem t...)
Cooler,
Thanks for the link on the CMT flexible template guide. I had no idea such a jig existed...
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