Proper way to taper and glue rudder???

[craig]

A cautionary tale and how to fix it if you are in trouble:

Forming the rudder (and the keel, really) shouldn't be challenging: Sand/saw a taper in a block of wood, glue to one side of cut plywood, then glue the other side of plywood. If the wood blocking is tapered on both sides, then the final shape should also taper on both sides. But that isn't what happens! At least for me. I've never seen anybody on a blog or on this forum have trouble with the rudder staying in alignment. Has that been a problem? In the manual it seems very easy.

See picture:

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I think during gluing, the weight of the clamps and wood pushes the blocking "sideways" away from horizontal. Gravity makes one side of the board completely straight, and all the taper is forced into the other side of the wood (which is now "double" tapered, twice what the taper should be). What I should have done to avoid this issue is glue/nail the blocking together FIRST before attaching the plywood sides. That will force the blocking to be in the correct alignment with itself. Then, glue the sides together. Since the blocking is glued in the correct alignment, the sides will be forced together properly.

I don't have enough plywood to correct my problem (and it's not TERRIBLY bad), so what I'll do is mimic the correct taper by removing some material from the "front" of the rudder (facing the boat) to make both sides taper the same amount. Then I'll remove the "bump" from the 5-inch blocking by sanding through a layer or two of the plywood. Since it will be fiberglassed, I don't think it will affect strength too much. The end result will be a constant taper in the rudder from 1.5 inches (or whatever it is) to 0.75 inches.

I'm pretty bummed I messed up at first, but hope this tale can help somebody else not make the mistake.

(Since 0.75inches seems rather thick to end your taper on, I'm also going to glue an "extender" of pine to the end of the rudder, running from the top of the back of the rudder down to the baseplate. It will be flush at the rudder (0.75 inches) and quickly taper back over an inch or two to maybe a quarter of an inch. I also didn't see it in the plans, but I will round-over the front of the rudder and sides of the baseplate so I don't present a square shape to the water)

[DanaDCole]

I'm sorry to say I can't answer your first question. It just does not make sense to me that the plywood could slide around in any way that would result in what you describe. Maybe I didn't read it properly.

I can say, though, that I don't think there is any need to fair the front of the rudder because it is directly behind the keel--almost an extension of the keel. Perhaps fairing might make a slight difference when the rudder is turned to one side or the other, but it does not seem to me that it would be significant. The drag caused by the rudder itself when it is turned would be much, much higher, but that is unavoidable.

[craig]

I think the solid blocking inside the rudder shifted to cause the "bend". When the plywood is clamped together it would look like I described. The same thing happens to the keel on a larger scale - that's probably why everybody has problems with the keel bending towards one side. It's easier to block up one side of the keel than the smaller rudder, and besides, with the rudder I didn't think to do that. My concern was that if not symmetrical, the boat won't go straight with a straight tiller. Although admittedly the effect of wind, drift, etc, will probably far overpower the extremely small effect of having a slightly bent rudder. Anyway, better to get it right now then try to fix it later.

[Shudoman]

As I recall I had this same issue. But it didn't get past the dry fitting stage. I put everything together and clamped it and wired it (as per the manual so the skins can't slide). I noticed that it wasn't symmetrical so I blocked it and weighted it to the table and that seemed to fix it. I took the whole assembly apart and applied glue then reassembled with the weight and blocking and it came out fine.

I also believe that people have problems with the keel for the same reason. A true table, good blocking and a lot of dry fitting will get you where you want to be.

Bill

[DanaDCole]

Mighty glad to get all this info before I build the rudder. It's a very long time before I do though, so I hope I remember it! You're right that the exact same technique should be used on the keel, but I learned how to do that too late. I lucked out though--it was bent, but only a little over 1/4". I was able to pull it over straighter and hold it in place with a cinder block while the glue on the keelson and then lower panels cured. I think it is pretty straight now.

As you point out, the wind and currents are almost always forcing you to shove the tiller one way or another. I think the only way to tell if it is perfect would be coasting on a perfectly calm day on a lake. So who cares? If it slows the boat down slightly on one tack, it would do the opposite on the other tack I would think, so it evens out.

John needs to do a lot more "hand-holding" in the manual. JUST KIDDING--this boat is intended for people with more building experience. The forum has made up for much of my lack of experience.

[craig]

I'm pretty close to "absolute beginner" -- my first boat was a one-sheet dingy in January and February. It was supposed to satisfy my boat-building desire; it obviously had the opposite effect. I chose Chesapeake Light Craft* in no small part because of the high-quality plans and manual, and in almost every case I'm extremely impressed with them. I really appreciate the time people have taken to augment the official manual on this site and blogs, which have saved me from making countless mistakes. Every once in a while I do something that wasn't called out explicitly somewhere, so I figured I'd just post stuff here. Hope it helps!

Odd story on my keel: since almost literally everybody complained about a crooked keel, I took great pains to block it up properly and it actually turned out perfectly straight. BUT, the plywood forming the skin on the aft-most part of the keel was a little warped, so I had a bump/curve OUT on the port side and IN on the starboard side. The upper keel blocking took care of most of the problem.

*Thanks John Harris!

[DanaDCole]

I agree CLC boats are hard to beat, and one of the reasons is their great manuals. It helped me quite a bit to have built the 17LT kayak and the Skerry before this because the manuals were much more detailed--aimed more at beginning builders. But, building a boat you don't really want first is a pretty expensive way to learn! That's why I think the combination of manual and forum is perfect for the Pocketship. Some of the builders could have done a great job without the forum, but thank goodness they contributed to it frequently and helped keep the rest of us on the right track. Also, John Harris's frequent contributions have been invaluable.