Rudder Repair - Cascade 29

[brucephenry]

Okay, got the rudder out (hat tip to @longy for advice on removing the head) and on the bench to ponder my options. I have a few questions.

First off, the rudder was submerged in freshwater for about a week after the “event”. When removed, I can best describe it as being “buoyant as hell”, the rudder shot to the top of the lake with me in tow. How long should I let it dry out for before glassing in a repair?

Speaking of glass, what weight/type cloth would y’all recommend for this type of repair?





I’m also halfway considering cutting away enough of the section that’s damaged to clear the prop. Although I’m seriously doubting the kid is gonna try the reverse the tiller experiment again. 

 

[casc27]

That rudder is just a bit of glasswork. What kind of shape is the prop in?

 

[Zonker]

If you have the time, give it a week in well heated area. I suggest the living room. But seriously after 2-3 days in a warm spot, you're into much diminishing returns with the amount of water left in the foam.

Glass - just equal in thickness to the original skins. But if you use stitched fabrics (biaxial/triaxials) it will be stronger than the original which is probably WR/mat/maybe a finish layer of cloth.

100 gm/m2 = 0.1mm thickness

9 oz = 0.3mm thickness

(both are approximation assuming no mat, good firmly squeegeed hand lamination or vac bagged.

Uh is there plywood there ? Kinda a hint in bottom photo?

 

[brucephenry]

Uh is there plywood there ? Kinda a hint in bottom photo?

Yeah, there's some plywood in there. I think there's a plywood "skin" around the foam.

 

[Zonker]

Ugh.  Then a minimum of a week drying time. With a fan blowing at the exposed area.

And a dehumidifier in the room where it is. Buy a cheap one on craigslist and then sell it when you are done with it.

You want that water that has wicked in to the plywood all gone before even thinking about closing it up.

 

[brucephenry]

Okay, I was wrong. A few fiberglass strands bashed into the wood colored foam fooled me. I've got no wood!

I beveled things at about 3:1 (figuring the trailing edge of a rudder is pretty low load) and sanded back ~2" from the start of the bevel. My plan is to just start laying up layers and build up the whole repair out of glass. is this a crazy plan? Is there something simpler that I'm missing?

Here's what things look like with the grinding complete...

 

[brucephenry]

Oh, and I've got West System 105 + 205 and 1.5oz mat + 6oz cloth on hand that I figure should be perfectly adequate and not require a trip to the store.

 

[andykane]

I would first rebuild the core shape with some thickened epoxy, then glass over that. West 207 filler is easy to shape and strong enough as a core replacement.

 

[SloopJonB]

^ This - building that thickness out of 1.5 mat and 6 Oz. cloth is going to take a jillion layers

 

[Crash]

^^ Both of theses, plus you really want the bevel in the fiberglass skin to be closer to a 12:1 bevel.

Read the west system manual On fiberglass boat repair.  Avail online and really quite good.

 

[brucephenry]

^^ Both of theses, plus you really want the bevel in the fiberglass skin to be closer to a 12:1 bevel.

Read the west system manual On fiberglass boat repair.  Avail online and really quite good.

Oh god, more grinding? Well, I guess I don’t have anything better to do while I wait for core to dry.  :mellow:  On the plus side, that can be accomplished with a beer or two on my bench. 

 

[CaptainAhab]

Okay, got the rudder out (hat tip to @longy for advice on removing the head) and on the bench to ponder my options. I have a few questions.

First off, the rudder was submerged in freshwater for about a week after the “event”. When removed, I can best describe it as being “buoyant as hell”, the rudder shot to the top of the lake with me in tow. How long should I let it dry out for before glassing in a repair?

Speaking of glass, what weight/type cloth would y’all recommend for this type of repair?

View attachment 399606

View attachment 399607

I’m also halfway considering cutting away enough of the section that’s damaged to clear the prop. Although I’m seriously doubting the kid is gonna try the reverse the tiller experiment again. 

Nice ruler. I really like the Shinwa Japanese brand of machinist tools. Nice bevel gauges & unique squares. Switch to metric and your rudder will be more accurate.

 

[brucephenry]

Nice ruler. I really like the Shinwa Japanese brand of machinist tools. Nice bevel gauges & unique squares. Switch to metric and your rudder will be more accurate.

I have a metric one, but I didn't want to confuse the "old salts" on SA.  :lol:

 

[El Borracho]

^^ Both of theses, plus you really want the bevel in the fiberglass skin to be closer to a 12:1 bevel.

Read the west system manual On fiberglass boat repair.  Avail online and really quite good.

Yes, as a general rule, but it doesn't look like a structural repair to me. 12:1 may make an unecessarily big project out of what appears to be a cosmetic repair. Plus, consider what the costs and dangers are if the repair somehow fails in the future?

As for cloth, use what you see inside there, and look at this:

https://www.westsystem.com/the-105-system/reinforcing-materials/determining-laminate-thickness/

 

[12 metre]

Oh, and I've got West System 105 + 205 and 1.5oz mat + 6oz cloth on hand that I figure should be perfectly adequate and not require a trip to the store.

If you're using epoxy, it's not a good idea to use mat - unless it is stitch mat like  1708.  Regular mat will not smooth out as intended using epoxy.

With 6 oz cloth, you will need about 10 lams to build 1/8"  (0.125) thickness. 3 lams of 1708 will get you about 0.15"

For a rudder, I would consider triax.  If you can't source it locally, Fiberglass Supply in Burlington WA, has 19 and 22 oz versions at pretty decent prices.  I've bought quite a bit of fiberglass from them.  Excellent supplier IMO.  Quick order fulfilment IMO: http://www.fiberglasssupply.com/Product_Catalog/Reinforcements/Knitted_Fabrics/knitted_fabrics.html

Triax can be a bitch to cut straight using scissors.  Highly recommend investing in one of those "pizza wheel" rotary fabric cutters with a cutting board.  I picked up one with an 18" board from Michaels for something like $25 and it has been one of my more useful tools.  Leaves a very clean edge.

 

[Zonker]

+1 to the rolling rotary cutter (with a carbide edge). I actually wore out one disc and had to buy another but that was after cutting 100's of meters of glass

Agree on the thickened epoxy as a core repair.

Agree don't use regular mat with epoxy. It will wet out eventually - but poorly and slowly. The binder needs styrene to properly dissolve. I've done it but it's not good practice.

The final skin thickness is hard to tell but more than 1/8" is likely overkill. So a 1/8" x 12 = 12/8 = 1.5" lap. You're fine with 3" taper in the existing glasswork. 

 

[SloopJonB]

You can buy mat that uses a binder that will work with epoxy but you have to specify it.

 

[brucephenry]

OMG! That rotary cutter is the BOMB! I don’t know how I survived without one. Seriously, this thing SO far exceeded my expectations. Great, GREAT suggestion!

Okay, back to getting everything in the garage sticky. 

 

[brucephenry]

Okay, to start out this repair I have ground back a compromise 8:1ish bevel. Being that the whole thing needs to end up roughly in line with the trailing edge I needed something to hold that up. So I laminated a thin sheet of 2 layers of 6oz woven with epoxy and cut it to roughly the right shaper to be the center layer of the laminate on one side. I made it thin enough to be translucent so I could easily trace the area I wanted to cut it to.



Then I mixed up a batch of epoxy thickened with silica and glued it in place after coating both surfaces with unthickened epoxy.

Then flipping the rudder over, I faired in with thickened epoxy to replace the foam I had ground away and stuck the whole thing under a hot lamp to kick. Tomorrow I'll wash the amine off and sand to prep for laying up the 22oz glass that is supposed to be arriving today or tomorrow.