Windshield Reverse Rake

My guess, based on working in automotive aerodynamics, is a moderately forward raked windshield would have slightly higher drag than a moderately rearward raked windshield. But the bigger effects on drag would be sharp vs rounded corner posts and header. A sun visor with any windshield would increase drag.

 

I've always thought the fwd rake as a bit stupid. One needs to protect the wheelhouse glass pretty much at all costs. Aerodynamics, space for instruments or radios, sunlight ect ect. Nothing can top the need to keep the glass intact in the wheelhouse.
Aerodynamics at boat speeds would seem silly to list as important but may be a factor bucking a screaming gale but as a percentage of total boat drag seems silly.
But keeping the water out seems monumentally important. Water passing over the wheelhouse rises as it goes aft so putting the glass closser to right angles to the traveling water seems nonsense to me.

But visability downwards may apply to a few high up wheelhouses of some fish boats or even freighter types but is absolutely silly on a pleasure boat. Who needs a good view of the top of one's forecabin? Reducing sunlight in the cabin may be a slight benefit. I'll bet aircraft control towers use that benefit along with the considerably less rainwater on the glass for greater visability.
Space for electronics seems a silly argument to me. Most all pleasure boats have the wheelhouse windows just aft a basically flat surface that being the forecabin top. Moving the top of the windshield fwd in many small boats means the only place for electronics would be above the windshield. But moving the bottom of the windshield out (fwd) would increase space for electronics at "dashboard" level or lower than line of sight. It's a lot easier to look down than to look up. Looking up would greatly increase the likelihood of looking into the bright sky or even the sun itself. All the above is based on a cabin or wheelhouse of the same size .. the bottom of the window fwd and the top aft v/s the top fwd and the bottom aft. The only way they can be compared objectively.

Vertical or slanted back wheelhouse windows makes much more sense to me. IMO slanted fwd (at the top (on small pleasure boats )) windows can only be justified as an exercise in style or trend. Can't be justified otherwise .... objectively.

 

The forward slanting windows offers a couple of very objective advantages.

1) if you have built in electronic display monitors, the sloping forward windows reduces glare. The last boat that we owned had forward tilting windows and the instruments were always easy to see. The previous boats, window tilted aft, often required us to use the glare shield over the instruments or a shirt/pillow to cut the glare.

2) We boat in high rain areas, and when trolling for fish, with the aft tilted windows the wipers would be on constantly. With the forward tilting windows, rarely at slow speeds were the wipers needed. At 20 knots, into the wind, the rain would get to the windshield

Perhaps they do not look racey, but the functionality is there

 

Barry,
We have a 30' Willard Nomad w vertical front windows and have no instrument glare problems. Actually I do see slight ghost images out the back window at times.
We never run our wipers even in the rain because we have no wipers. Very little trouble seeing in the rain but at times I wish we had wipes.

And if our windows were slanted back we still wouldn't have your glare problem because we basically never run at night. Don't avoid night running overly so but do manage to .. almost avoid it. The Willard does have a 1' visor but I can't see any advantage to fwd raked windows on our boat if the glass went up to the fwd edge of the visor.

But if it works for you run with it.

 

I hope to post my elevations soon. I have an extreme tilt out windshield, From
base to top it tilts out 40" with a 24" rise some 32 decrees. Looks good on paper and a great dash board.

 

You see, to get more standing room in a cabin with forward raked windshield. Perhaps that is why they are popular in compact cabin designs.

In cabins where the windshield is aft-raked you get an area under the windscreen where you can't stand. Often there is a shelf here and when marines electronics were as deep as wide, that was a handy place to mount them.

These days electronics are much flatter and a shelf under the windscreen may just be wasted space. I've been on a couple of small boats where that is the case.

If there is a forward berth, storage locker or some other use of space under the windshield shelf it's less of a waste.