Belatedly Doing a Test Run

I'm finally listening to good advice and doing a test run. At least this way if I crack it again I'm only out some scrap plywood and epoxy.

Why will this time be different? (feel like I'm getting back together with an old girlfriend)

1: I will mask the epoxy goop fill line to insure no excess goop bead width. If you open the picture below you can see all the extra goop I was getting all over).

I waited about 25 minutes before pulling the tape off. hopefully this helps.

2: After goop bead is cured, I will apply thickened goop bead to outside leading edge (to prevent delamination of the plywood). I'm getting better at manipulating loose goop

3: Will defer bonding in AYC spar until rudder is compressed. Locating strategy-TBD.

4: Updated wedges (also considering putting tape on jig faces to reduce friction).

Parting thought. R3 was very nearly closed when it cracked. So the hope is that some marginal improvements will be enough.

R.I.P. R3

Bad things continue to happen.  I cracked the rudder again.  Not only that, a good part of the leading edge delaminated, the plywood just tore itself apart. Here a the gruesome pictures.

Bryan Cox (builder and sailor of a Duo 480) and I have been discussing these misfortunes (see comments on prior posts).  Most of our discussion has been about how to compress the rudder while the various epoxy steps are completed. While this is important I suspect we are missing something. I don't think you get plywood delaminating itself as above because you chose an awkward way to compress the rudder faces.  This delamination is a function of the geometry at work. 

I hold Bernd's design as above reproach. So without changing the geometry, and putting aside for the moment the question of how to compress the rudder. What could cause the plywood to come apart like this?  My theory of the case is that the design is fine, the jig is fine, and even the wedges are fine. I think the issue is that my rudders must not reflect the design in some meaningful way.  Let me interject an observation that the cured epoxy goop is very rigid (feels like a hard thermosetting plastic).  It may be hard to tell from pictures, but I know I'm a bit of a mess when putting the epoxy goop in the groove.  I'm thinking I'm leaving a small radius of goop at the edges, and given the remarkable rigidity of the cured goop, I effectively still have a goop bead that is too wide.

Another observation, is that the rudder faces only delaminated where the goop did not leak through and cover the leading edge.  So next time after glueing in the jig, I will fill the outside leading edge joint. Similar to what I'm doing with R1. 

Lastly Bryan is right that pre-gluing the spar into the rudder seriously increases the stiffness of that face (how could it not). Having one side stiffer than the other is likely creating some stress concentrations that should not be there. Locating the spar in a compressed rudder presents some challenges, but right now I'm just producing broken parts.  

BTW: The link to Bryan's Blog is in the links section.

Updated Wedge Design

I think I figured out why my rudders were walking out of the jig.  As always a picture is worth a thousand words.

 I think every time I let go of the clamps the rudder would tilt the wedge just a bit. Then when I clamped down again first the wedge would slide against the rudder till flush on jig and then compress the rudder more. Repeat many times on both sides and you have a rudder that walks out of its jig. Luckily the solution is simple. I just moved the 1x2 from the trailing edge to the leading edge of the wedge. This should balance much better.

Kinda hard to see in this picture but the top one is before, the bottom is after.

Rudder 3 Problems

Not sure how to organize my thoughts on this mess so I'll just let you, my poor reader, have it.  I tried to close R3 (as I'm affectionately referring to my 3rd rudder attempt). At first all seemed well but as I got it closer to closed I noticed that the leading edge of the rudder was not sitting down in the bottom of the jig.  I thought that must be why I'm having such a hard time on the clamps. So I found that my track saw clamps have very narrow arms and fit nicely inside the rudder, I proceeded to use those to hold the rudder down in the jig.

So with this "fix" done I continued to crank away on the clamps. I was getting really close to having the rudder closed when I heard the dreaded cracking sound.  So I quickly undid everything and pulled the rudder off the jig. Turns out that the the goop bead had started to separate at the leading edge at one end of the rudder.

I think my genius move with the clamps came back to bite me. I think the tang of the clamp must have acted like a lever to pull the plywood off the goop. That said the jig should have been holding this together.  I think there is something about the geometry that is pulling the rudder up and away from the jig as I crank down on the clamps.  My theory is that because the part of the wedge that slides on the angle is longer (in the vertical) than the part that slides on the rudder, I'm getting a little turning moment. Its working on both sides and bit by bit wants to walk my rudder out of its jig.  I haven't done any actual calculations (I would have to make so many assumptions that any answer I could get on this would be meaningless).  But I am going to fiddle with the wedge shape a bit before getting back to this. As far as R3 goes I epoxied (no filler) the crack and will try to see if I can still get R3 to close.  I will also be sure to post before and after pictures of the cross section the wedges.

AYC Spar Glued Into Rudder 3

I didn't get much boat time today since I spent all day at my older son's water polo regional tournament. The good news is we got 3rd place. State championships here we come. 

Thanks to my astute purchase of a very bright work light, I was able to glue the AYC spar into rudder three tonight. Not much work (approx 10 minutes) but getting the epoxy curing now saves a day long wait. BTW, it was not that hard to mark the spars location with the rudder faces glued.

Continuing Work on Rudder #1

I got a chance to get back to work on the good rudder. I noticed that the leading edge looked a lot better where some of the epoxy goop had squirted through.  Of course this did not occur uniformly. So I figured that an extra thick batch of epoxy-microballoons-silica goop was in order. I used "L" brackets (made for my son's birthday party) and some scrap pieces to make fences to hold the rudder up.

Here is a picture showing where the goop did not spill through.

Next it was time for the goop. I made it really thick, about like toothpaste.

I may have gotten a little carried away with the goop. It just sands down so nice that I figured putting some extra down wouldn't hurt.

Rudder #3 Under Construction

I applied my lessons learned and so far....so far (I dont want to jinx it).  He are the two rudder faces I cut and bevel cut today.

Might be hard to see here but I actually have two red stripes on one of them because I  measured wrong and didn't catch it until I noticed how differently the lines on each board were located, close call. 

With that done I got them taped together and am embarrassed to report that the taping was easy. All I did was lay them flat on top of each other and tape the edges together. I was making that so much harder than it needed to be. 

With that done it was short work to put them in the jig and pour in the goop. This time being very careful of the fill-to lines.

Besides this work I also milled down another AYC spar for my 3rd rudder attempt. I did have one oversight. I meant to mark the location of the spar on one of the inside faces before this step. Not a huge deal, making the mark will just be a little more fiddly now.