Clearly, this engine has been painted, so conclusions about what came from the factory based on paint are questionable.
An undersized hex probably indicates a non-factory bolt, either different spec or smaller thread.
The metric system uses the same thread pitches for several diameters...
1. Typically, all the bolts performing a particular function will be identical. Pull the others, one at a time, and see what you've got. Metric bolts of different diameters can have the same thread pitch and a size smaller bolt can screw into a larger hole, but will wiggle until tightened.
2...
Standard practice in Colorado for keelboats is a trailer mounted launch wheel that is aligned so that the trailer will roll straight and is retractable for towing; and a long enough strap/rope/cable to get the boat in deep enough while keeping the exhaust pipe dry. Lesser variations involve...
I would expect that wood would outgas slowly under vacuum, possibly producing bubbles. Simple vacuum bagging would preserve the bubbles when cured. Infusion, with a suitable dwell under vacuum and before introduction of resin should reduce the bubbling as well as pressure impregnating the...
Given the OP's premise of removing one day's accumulation, and the habit of growth focusing on the shallowest part of the hull where the sun can penetrate, I'd think one could do a 95% job keeping one's head above water and wielding scotchbrite with one hand while hanging on to the gunwale or...
That's my question. If there's no adhesive the composite has all the strength one expects. If there's a continuous layer of adhesive, it's the strength of the adhesive that rules. Reality is somewhere in between. Unless the resin somehow combines/absorbs/dissolves the adhesive. Which would allow...
Replacing deck balsa core from underneath. Using 71 to hang flow media on outer skin, then possibly 1/4" balsa to the flow media.
Then new inner skin, peel ply, bag and infusion ...
Looking for experience with this stuff: composite strength degradation vs application density, actual tack time window vs temperature, bond strength vs application density, gotchas ...
It's winter in the Rockies and I, thru egregious lack of planning, am doing deck core replacement outdoors in between winter weather episodes. I can get the interior of the boat (I'm replacing the core from underneath) up to 70F by clever application of timing and electric heat.
My question...
The cantilever puts the far fastener in tension not shear. Pop rivets are really bad at tension. I'd use a SS machine screw and nylon lock nut with your favorite smoodge.
This suggests to me that the rivet was not down tight before being set and the fitting could "work" back and forth to fatigue the head off.
No picture, but I'd guess the fitting was cantilevered out into space and the far rivet failed ...
Seems to me that the majority of friction will be due to the scheme for keeping the balls properly spaced (or not: full complement). I've seen cages, spacers, counter-rotating-slightly-smaller-balls, etc. All of these have some sort of drag, especially when used with lubricant and the associated...
Beware of the spreader hole !!! It is a massive stress riser right where your bend is. The pole lift exit block will be somewhere close by also. Schock did a terrible job cutting these holes, leaving sharp corners . Most of the S20 masts I've seen broken, failed through one or the other of these...