BFN prop clearance improvement

Seems like the rotary file may be a better fit for the material (it says it works for fiberglass) but not for the tool... 2500rpm max speed must be for a drill? My router's range is 8000-25000rpm. I may have to go with router bits like Pete suggested.

Pete, the 5200 I had filling the recess around the edges of the strut and rudder did not hold up well. At least half of it was gone after just a few years. I will add some small radiuses to allow for fitment and stress reduction but I plan to make this recess as tight as I possibly can. Smoothing the flow of water in this area of the hull can only help things, especially at the uncharacteristic speeds this boat is capable of.

Oh, and thanks Eddie. I guess the fear of breaking something is significantly reduced when you feel like you can probably fix it afterwards.

I finally got the notch reasonably flat, so I commenced grinding out a few small problem areas. I opened up a few voids and tackled an area of disbonded glass on the stbd side.





The disbonded layers actually continued further than I was willing to grind- I got it to the point where it felt semi-solid and then cut a groove along the disbonded seam. This groove got filled with thickened resin and then the span was glassed with 3 layers. I filled a little more on top of that. It'll take more filling and shaping (as will a few other voids I filled) but it should be solid now.



In this pic, you can see towards the front of the notch where the material that was removed extends all the way through the original hull glass and into the new (epoxy based) layers that were added to the inside of the hull.

Once I have the hull back in shape and smoothed out, it'll be time to cut the rudder port recess.

Eh, there's delam all over these old boats. If you tried to grind it all out you'd be left with swiss cheese.

Nice work Tim, had to be fun grinding over head. Good for building biceps!! Are you planning on spotting in the gel coat or more extensive?

raw dog

Slow but steady progress on this project... Lots of iterative filling and sanding, and epoxy dries slowly in the winter.

I finally got to the point where I was happy with the keel shape.





Today I made a jig for the rudder port recess and gave it a test cut. I think it's ready for prime time.

I think you should gel under and around the port now. Even if you decide to make more modifications to the area later, removing the sealing/bedding compound (4200?) from the raw fiberglass would be a nightmare! Then would the gel stick? At least if you get some smoothish gel in there now cleanup of that bedding compound would be easier and not risking an adhesion problem later. If you decide on more mods.

That was my thinking john... I don't plan to buff the gel out or anything though. Not sure if rough-ish gel will be any better or worse than (relatively smooth) bare glass. Definitely only using a sealant this time (4200 or boatlife caulk) and not a strong adhesive (5200, etc).

I have some gel in dads basement Gary... It's a few years old but I suspect it's fine based on your experience. Definitely just brushing.

Another round of filling/smoothing done and I put some gel in the recess. The 2-3 yr old (unopened gel) separated and I couldn't get it reconstituted.... But the 5 yr old stuff that I had tinted for the seat pedestal and stored in a sports water bottle seemed a little better. It had thickened significantly but some thinning with acetone made it workable again. Added more wax (couldn't remember if I had added any when it was mixed), and went for it. We'll see if it sets up.

Ha, no. This is one of many projects this spring. Aiming for 4th of July.

Is that clamp support from a Malibu?

I've not noticed that a BFN is clamped at the strut, but that is how Malibu does it.

Ha, when did CC start doing it that way?

Hollywood wrote: 1989 You're not crazy though Bruce the [DD] BFN always had it bolted through the stringer like old CCs.

That would be the year they went to single exhaust and they must have put the exhaust in the bilge? That is why Malibu has always done it that way. No room to attach to stringer.