67 SN Resto/Mod rev. 2

I agree that static CR doesnt tell the whole story... but since we know that exact cam does just fine on pump gas in a 340 with a static CR approaching 11:1, cant we say with pretty good certainty that he'll be safe with a static CR of 10.1:1? The only additional variable would be if he were to install it off center, right? Otherwise Im missing something.

It'll be interesting to see how your boat runs. A few of your assumptions are contrary to what we've found to be true when building a fast ski boat. I think that cam is a bit warmer than you think- did you measure your stocker? 50-51mph may not be out of the question. Clearly these tractors dont have the same speed potential as a purpose built outboard, but the BFN's in particular seem to respond pretty well to power... well, at least they dont behave too badly when pushed well beyond their factory ability. 92 may be out of the question, but I dont think 70 is.

Mark, yes, the part I disagree about is how a ski boat will respond to hp/torque and where those peaks best benefit performance... most people think that low end torque is what gets these tractors moving quickest but I have not seen that to be true. Im not seeing those hp numbers out of the mods youve described, but Ive only built one BBC so Im hardly the authority. If it runs into the mid 50's like the 425hp HO 454's of the mid 80's then that'll prove me wrong! To get it moving that fast at such a low RPM will require a pretty huge prop... such a wheel may not exist for a 1" shaft. It should be faster than stock though, and that should have you in the 50mph range anyways. Thats definitely faster than I care to fall, but I can think of a few uses for extra power- pulling a huge line of footers or barefoot racing come to mind.

oldcuda wrote: Think keeping small port ovals would be a big Boo-Boo.I am a major torque junkie but the engine will have to breath a little better to get into rpm range you need for all around performance.I am planning a lot of prop for mine but 565ci,10.4 comp,with a lot more cam think it can handle it.

I dont recall the details of your engine build, but the sheer number of cubic inches you'll have on tap would make me think you might approaching prop limitations if youre staying with a 1" shaft and trying to keep the revs down... or are you going to 1-1/8"? Our BFN will pull some props made for 1.23 boats (15+" pitch) north of 5500... How fast you planning to spin yours?

Sorry Craig, Im afraid we've gone off on a tangent here!

No more than 5500 and yes a propshaft upgrade is going to have to be done.Maybe not for this season but definitely been thinking about it.Picked up World tall deck block 4.6 bore and 4.25 crank that makes 565 was thinking 598 but that roller cam I have been saving just won't support that many cubes.I sold the Edelbrock heads now thinking Brodix BB-2's have to find that happy medium between velocity and volume

Time to get back to work on the 67. I apologize that I haven't done very well at documenting each step, but I have been making progress.

The first step this winter was to finish getting the floor installed. I debated the different options with the floor, but ultimately decided to permanently install the floor and glass the floor to the hull sides. The lateral supports and the floor have a minimum 1/8" gap between the side of the hull.

I bedded the lateral supports with thickened epoxy.



The floor (5/8" ply) was test fit with the engine/trans installed, then pre-drilled for countersunk screws. All floor panels were soaked in CPES and have a layer of 4oz cloth on the bottom. I installed the floor using biax on the stringers and lateral supports. I screwed the panels down until the epoxy cured overnight, then removed the screws and back-filled the holes with epoxy.




The floor was then glassed to the hull sides using 2" tape, 4" tape, then a layer of cloth from the primary stringer to 3-4" up the hull sides.

Here you can see the gap between the floor and hull under the 2" tape.


Laying out the cloth.


All glassed down. I have been fairing the bilge as well in-between glassing the floor.




I was happy with the result of the floor. It isn't as flat as a pool table but I think it looks good and it's super solid.

After the floor was down I moved on to the part of the project I have been dreading. This hull has a ton of cracks in the gel, and I was never going to be happy with just wetsanding/buffing. So I decided to re-gel the whole hull. I have never done anything like this before so I don't know what to expect, but regardless, I have started grinding off all the old gel so I'm on my way.

I separated this portion of the garage with plastic and got to work on grinding. I started with a DA and 24 grit and got nowhere. Then I tried an inline with 36 grit and also got nowhere fast. This gel is hard, and it's thick. I used my angle grinder with a 60 grit flap disk but this was too hard to control and be smooth and I ended up gouging a few spots so I quit with that. Ultimately I ended up using a sanding disk adapter for my 4-1/2" angle grinder with 36 grit. I'm pretty happy with this method as it's a good balance of speed/control. To anyone contemplating doing this to a boat, this is a nasty job that is going to take quite a while. I'm wearing a Tyvek suit, respirator and lab goggles but the amount of dust is incredible.




So far I ground the transom, 90% of the top deck, and about 1/3 of the port side. I hope to be finished with the hull sides by this weekend. I will then flip the hull and start on the bottom. Anyone have any tricks on sanding the gel from the tight inside corners around the raised lip on the bow?

I think Pete B knows of a product of tool to remove gel

Wow, grinding all that gel is an incredible amount of work, good for you. I'd love to see a pic of the tool/attachments you used that resulted in such a nice finish. I've used flap discs on my 4.5" angle grinder and the finish was not pretty. I have the deck of my 67sn to do as well so I'd love to leverage what you've done! Any estimate on how long it's taken you thus far?

I've probably only spent 6 hours doing what I've done so far with the sanding/grinding. I haven't sanded the real hard details like the small radii/corners so that'll take quite a bit of time as well. For just the deck, I'd probably budget 8-10 hours to get the gel removed.

To flip the hull, I utilized the single beam I have in my garage. I wasn't sure if I could get it done with 1 beam, obviously two parallel beams would be the best solution, but this is all I had.

I started by lifting the boat by the lifting rings, then setting it down on "slings" that are attached to the beam. These were 20' straps, and the length worked out just about perfect.



Then I attached the chain hoists to a strap that runs around the boat. This allows me to tighten the hoist and slowly roll the boat inside the slings. The only issue was when the boat was about 90°, the boat was able to sag just enough in the slings to barely touch the floor. I added a 2x4 inside the hull from gunnel to gunnel to help keep the side of the hull from flexing.






Overall this process took about an hour, but I was able to do it all by myself in a what I consider a pretty safe manor. I did attach a strap to the two beam dollies to prevent the front sling from ever wanting to start sliding towards the bow due to the hull taper.

Craig,
Good work and thinking using your single beam for flipping the hull. Those light spots look like where there isn't enough resin. I feel they should fill in with a coat of resin. I'd leave the hook but am sure others can add to your question.

ReidP is the one you want to talk to about how much hook you want in a 1gen hull. He's measured and modified the hook in more vintage cc's than anyone, I suspect.

It's tough to tell in those pictures, but the light areas look more like air bubbles or delam between layers than simply a lack of resin in the surface coat. If the spots are springy or spongey then I'd grind them out... And I might do so even if they feel mostly solid. Is your theory on the gel cracks due to bad gel, environmental conditions (storage in the water, etc) or have you pinpointed structural hull issues?

FWIW I have a CC in my backyard the same color and age that had few hours and decent storage and still has some serious gel coat cracks, the gel is super thick as well. I would tend to agree it was more a gel issue than structural one.

TRBenj wrote: I wonder if trying to reach the void (small hole drilled) and then filling with (thinned?) resin would be acceptable instead of grinding, filling and fairing.

Excellent technique.

[QUOTE=TRBenj] I would assume it's a gel issue too- but looking for any other obvious hints as you deconstruct is a good idea. My '67 1gen has hull gel that is in reasonable shape- most imperfections look to have been caused by use. The deck is a different story, it is just littered with cracks eminating from nowhere. Just a bad batch (bad mix? Shot in less than optimal conditions? Too thick? Who knows). So it definitely happened- and not uncommonly in the 60's.
/QUOTE]

The Gel on Dad's 64 is VERY shiny and looks great from 10 feet away, but as you approach there are literally thousands of these spider cracks. They started appearing in the late 80's on the hull and really have increased in number in the last 10 years. This boat has been waxed before it goes into the water for the first time every year and is towel dried every time it is used. So the cracks are not from any sort of neglect.

ReidP calls them the "beautiful patina on a great old boat." I will stick with that, because the work going into this 67 is way more then anything I would want to tackle!!! Can't wait to see the end results, that of course may change my opinion. Keep up the GREAT work!

8122pbrainard wrote: I suspect but never have confirmed that the spider cracking is caused by the plasticizer leaching out of the gel. Now all we need is the EPA to come down on that emission!