The rudder is starting to come together. And the lamination took a serious family effort. All four of us were mixing epoxy, wetting out the carbon on the work bench and laying it out on the rudder.
The process basically goes in 5ish steps. They are something like this.
Step #1 - Know what you are doing and why. Design for your known loads and add a fudge factor for what you don't know. Chad posted a rudder load estimator on the i550class.org forum and it was clear that my designed layup schedule was not up to the task. Especially at the critical high load point where the rudder leaves the bottom of the cassette. That's where the rudder is trying to flex one way and the cassette and tiller are going the other way. That load is what cracked my first rudder and what has messed up about 5 other i550 rudders that I know of. I basically doubled the lamination thickness at max cord at the planned waterline of the rudder. I then tapered from there to not add too much unneeded weight and bulk. Here is my rudder lamination schedule...
Flying foam cut core cut from spyder foam. at 2.3 pounds per cubic foot.
Spline down the length of the rudder at it's max width made from 2 layers of 17 oz. -45/+45 degree bi-axial e-glass. Cut to fit the rudder and filleted into the rudder core with a 3/32" radius minimum to spread the load from skin to skin.
Skin layup from the inside out with all layers starting at the top of the rudder, which is called the head.
twill is 5.8 oz 2x2 carbon twill fabric. uni is 6.7 oz uni-directional carbon.
1. twill - full length.
2. twill - 25" long cut on the bias (so this is -45/+45 essentially)
3. uni 27" x 6" strip at max width
4. uni 33" x 4.5" strip at max width
5. uni 39" x 3" strip at max width
6. uni 45"
7. uni full
8. uni full
9. twill full
10. twill full
Resulting skin has...
70oz skin thickness at the max width at the waterline. Tapers down the rudder.
39 oz skin at leading edge in the rudder head
34 oz skin at leading edge in body of rudder
30 oz skin at leading edge at tip.
Put full uni and twill on the out side to help blend any transitions in layer thickness as much as possible to minimize fairing. This worked to a large extent.
Step #2 - get everything ready. Cut all your cloth and lay them out in order. Cut your peel ply, which is light weight sport nylon cloth. Cut absorber cloth, which is cotton knit fabric.
Step #3 - Prep the foam core by coating in a thin layer of epoxy with just a little filler in it. I used some micro fibers for bonding strength to the spline and silica to thicken it.
Step #4 - Wet out cloth and start positioning it on the core. I used the pipes to hold up the cloth which worked for the most part. I wish I had added fittings on the ends so that when a layer was slide up or down the rudder it wouldn't have been able to go anywhere. The fell several times and the clang of metal pipe on the concrete floor was a delight to everyone in the shop at the time. I used plastic scrapers to work the cloth to the foam core and previous layers. In general this worked out well. My fabric wetting out crew did a great job of keeping up. In the middle they got the fabric a little too wet. We worked the final layers on the table with a spreader to get out the excess which was a good thing. But we still had more than enough epoxy in the lamination.
Finish the lamination by laying on the peel ply and absorber cloth. Use care so that there are no wrinkles in either layer.
Step #5 - Clamp it all together. This step worked really well with only one error. On one side we had it too load at the head end of the rudder and adjusted it upwards. We created a wrinkle in the peel ply & abosrber cloth when we did that. We should have pulled it way from the rudder before raising it but we didn't. Something to remember the next time I layup a rudder or other large part like this.
After step #5 is done, all you can do is sit back and watch. I had a fair amount of oozing epoxy coming up out of the top and dripping out of the bottom so I know I was on the heavy side epoxy wise. The picture was taken right after I finished clamping it all together.