Fairing planks with a router

[LP]

I originally used this set-up to smooth the interior of a cross-planked hull after trying to plane it with a hand plane. On the flat surface, the router bit was set flush with the three screw heads on the bottom of the router. It turned hours of pain in the pain in the neck planing into maybe an hour of routing.

The three screws create a tripod for the router to sit on. The screws form a "point" contact and will drop into any low spot it encounters causing the relatively "high" material to be routed off. The thing worked great on the flat surfaces in the after part of the hull. The forward sections where the "V" deepens causes an apparent concavity inside the hull. Judicious deepening of the router bit made smoothing of the forward sections possible.

Finally, after planking the forward deck, the hand plane was pulled out again for some preliminary planing. Being intrigued by my earlier success, I decided to try my router set-up on the mahogany topsides. In theory, the router bit centered on the tripod of screwheads, but set above the plane of the screwheads by fractions of an inch/mm, will route a spherical surface. Risky business, but it might work.

Long story short. The routing worked. Some minor planing to smooth the router marks and the deck was faired. Here are the some pics.

[Raggi_Thor]

Nice!

[Andy]

Great to see tips like this here - you can also shape rudder blades with a router and a simple template in a similar way (although the leading and trailing edges have to be parallel for the template to work the whole way down the blade)

Now show us the rest of your boat!!!

Andy

[DanishBagger]

Thank you so much for the tip. I was wondering how to do that when I get that far. Looks like I will plagiarize that method

Originally Posted by Andy

Now show us the rest of your boat!!!

Indeed!

[buckknekkid]

how many Axis does the router have? great idea

[Bentwood]

LP: great idea, thanks for posting. I wonder how the size of the router base (size of the triangle) would affect the fairing capability. Would a larger base create a fairer surface? Would the small base of a laminate trimmer hug a tight radius? Any further thoughts?

[LP]

I think that a larger base would increase the accuracy of the curve since it would cover a larger area and thus "look" at the bigger picture. There would be decreased aberations due to local undulations. Generally, the only placeon aboat with constant radius will be the deck and even that is subject to change when you are approaching the stem. I almost screwed-the-pooch there. The radius tightens there to keep a fair deck profile. I planed by hand forward of the first frame. On the down side, a larger foot print will keep the bit farther from the edge of the surface you are "milling".

Which brings us to a point of technique. The edges of you surface should planed and faired to near their finished profile. The router won't mill the edges because of the nature of the beast AND you don't want to fall off of the edge either! Big boo boo's happen.

On the other hand, a small footprint will mill closer to the edge and I think it will be more forgiving. Too small though, it won't do anyting.

I could see where the optimum base size could depend on the tightness of the radius you're trimming. So, yes, a laminate trimmer could work better on a tighter radius.

(As a side note, a hull is such a complex shape, I could see where this tool might actually complicate fairing a hull and it certainly opens up tremendous opportunities to screw up big time, as with all power tools. It's just a matter of using the right tool for the right job.)

If I were to try it on a hull, I'd start at the tightest convex surfaces(positive curvature) and through flat in to concave(negative curvature). A more positive curvature setting will not cut into a less positive curvature area. By starting at the most positive setting, the tool will tell you when to adjust the depth of cut for the next curvature setting. Just be careful about falling into a previously milled areas.

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This tool was so easy to make it was almost sinful. I took the base plate off of the router and put the baseplate screws back in. A thirty second adjustment. I hadn't this router for years so it was nice to bring it back to life. The router has an adjustment ring on it with graduations down to 1/64th of an inch. The graduations are big enough that I could make adjustments of 1/4 of the graduation. I did 1/2 graduation adjustments which comes to 1/128th of an inch(0.2mm if my math is correct). So you can see that there is some very fine adjustment going on here. I may have to sit down and do the trig just for grins.

In using the tool, I started at the forward end of the deck and worked aft. Generally doing a complete pass. I help a constant orientation of the base screws to the CL of the boat. If you lead with two base screws aligned athwartship, I think you actually get a slightly deeper cut than if you trail them. I hope that makes sense. I worked the tool back and forth athwartship and progressedaft with each cut until I had made an entire pass, for to aft, and then I went back to do it again. If I saw an area that I thought was definitely higher that the rest, I would concentrate there for a while.

The key here is to not be too aggressive. It's going to take multiple passes to smooth the surface. Each pass takes a bit off that allows the next pass to take a bit more off until no more will be taken off. If the surface is not smooth yet, a depth adjustment on the bit is needed.

Three words of advice: caution, caution, caution. I think it's a great device, but just be aware, it can cause damage, too.

[CaptScot]

Great Tip, Did you use a straight edge for each pass to work your way across the surface or just eye-balled it? Thanks, Scott

[LP]

While the depth of cut needs to be fairly precise, the methods by which you do your "passes" is a little more forgiving. I just eyeballed it the whole way. I did find it easier to guide facing forward or aft and guiding side-to-side, rather than standing to the side and working in-and-out. The bit would pull the router left while pushing out and pull right while pulling in.