kirchwey

Hyperopia is usually described (broadly or vaguely, I'm not sure) as inability to focus up close combined with "usually" being able to focus well at infinity except in extreme cases. To me this seems synonymous with (usually) good eye chart performance and poor accommodation. Or does "usually" focusing well at infinity actually mean focusing barely acceptably, erring on the far side? Is there an unambiguous term for inability to focus well at any distance with no exceptions, always requiring a +diopter correction at infinity?

One wheel of my 1500-lb capacity boat trailer got run into an immovable object. (Fortunately there was no boat on it.) The axle is bent but the wheels and spindles are fine. I assume it's unsafe to run an "unbent" axle. I can't find a ready-made replacement so I want to get one welded up. I can buy the beam material (1-1/2" square tube) and spindles, but would prefer to use the existing spindles, saving their cost and ensuring that I can use the existing wheels.

So, can a welder remove the spindles for reuse?

Circuit production engineers: Is there any hope? It went into salt water. I rinsed it in fresh water pretty thoroughly and am now wondering if an additional rinse in denatured alcohol (mostly ethanol) would be helpful (as is recommended for a dunked outboard motor), or will the adhesives and plastic parts of the electronics be adversely affected? Any other ideas for restoration? Thanks.

Is there any hope? It went into salt water. I rinsed it in fresh water pretty thoroughly and am now wondering if an additional rinse in denatured alcohol (mostly ethanol) would be helpful (as is recommended for a dunked outboard motor), or will the adhesives and plastic parts of the electronics be adversely affected? Any other ideas for restoration? Thanks.

I've seen numerous web pages that claim that it will keep the power head dry, and some that even say you can leave the drain plug uninstalled (but I'm not sure if the latter applies to with-engine or not).

One note: The transom has a 1/8" stainless plate installed (non-watertightly) on the inner surface, and the bolts attaching the motor pass through the plate. It looks like originally the center foot or so of the transom was made a few inches lower than the rest of it, but that's been built up to flush with a wooden spacer. The main motor support bracket, which I think normally would hook over the transom, is actually about 1.5 inches above the transom spacer. All this raising of the engine may just be a means of accommodating a longer shaft.

So, do you think my '72 13-foot Whaler with a '92 40 hp Force engine can survive a deluge?

Also, can you guess what my mileage will be at economy cruise?

And, is 40 hp overkill for that boat, and can the motor break the transom, with the usual wave slap happening and being cantilevered up so far?

Many thanks for any info you can provide, especially experience-based.

Structural analysts can identify vibration modes, and often locate defective structural elements, by measuring vibrational responses while applying a driving signal to the strudture under examination. This is referred to as system identification (SI). When you lightly disturb the webs of spiders of particular species (e.g., daddy longlegs) you will see the spider pumping his body to shake the web, sometimes by a reciprocating motion and sometimes by whirling in circular motion. He invariably finds a resonant frequency and his oscillations can become pretty large. Could he be employing SI to detect the presence of, and possibly locate, a prey insect? Web sites I have seen state that the shaking serves either to further entrap the prey, or as a form of camouflage for the spider itself. Could SI also be a reason? Detection/location by SI could be useful at night or if the spider's eyesight isn't very clear.

It grew alone on the cut surface of a firewood log (tree type unknown) and is shaped like a slightly deflated blimp, with the long axis parallel to the wood's surface. It is 1.5 inch long and 0.5 inch wide at its widest point, is black or v. dark brown and has a pebble-like finish with grain size about 0.05 inch. It is pretty tough and is undamaged, seems hollow, has no features like gills, and is attached to the wood via a curved stem at one end. (Toughness, color and finish may have been different when it was younger.)

I am nearsighted but corrected, have hardly any accommodation capability, and have been told I have incipient cataracts. The optometrist says my retinas are fine. Over the past couple of years I have noticed a strange phenomenon: my corrected vision is pretty good at night and at light levels comparable to the optometrist's eye chart, but in bright light it gets blurry. I don't think it's because of cataracts (I don't notice any fogging) but it could be due to an asphericity of the lens or of the eyeball surface, which could cause the average focal length to change as the iris opening changes between wide and narrow. So my question is, would a lens replacement (the recommended remedy for the cataracts) fix the focus problem, or is eyeball surface asphericity a possible cause? Do cataracts change the lens shape? Are there other possible causes given that the retinas are healthy?

but also because of a perceived kinetic energy penalty. Does a crosswind actually steal energy from a cyclist?

Represent the cyclist and bike as a frictionless cart on a track. The cart has the same drag coefficient for any direction of incident wind. It travels at 20 mph along the track and there is a 20 mph crosswind. (To be clear, the crosswind is perpendicular to the track, and the apparent wind felt by the cart is 45 degrees off straight ahead.) State your case for or against additional drag loss due to the crosswind.

Looking for the simplest, most clearly expressed answer to the following. Design the fittings that attach one end of a horizontal beam to a vertical wall, such that the system has the following characteristics:

When unloaded, the beam is horizontal.

When loaded with a weight at the tip, beam is horizontal (with some bending).

When loaded with the same weight at the root, beam detaches from the wall.

Beam and wall fittings are rigid one-piece devices, one welded to the beam, one to the wall; thus no moving parts like levers, springs, etc.