bow covers - extra speed?

[JY]

Anyone have any real-world numbers on whether you can pick up speed by covering up your open bow with some type of a fiberglass cover? Saw one post that suggested maybe 5 mph gain, although that sounds pretty optimistic to me. I noticed on the week-end that I lost 3-4 mph in my ZT230 when I removed just the center part of the walk-through windshield and it started me thinking about the open bow....

[JY]

Anyone have any real-world numbers on whether you can pick up speed by covering up your open bow with some type of a fiberglass cover? Saw one post that suggested maybe 5 mph gain, although that sounds pretty optimistic to me. I noticed on the week-end that I lost 3-4 mph in my ZT230 when I removed just the center part of the walk-through windshield and it started me thinking about the open bow....

[JUPITER PULSARE]

I USED TO RUN A SPECTRA 170 WITH A MERC 150 XR2. THE SOFT BOW COVER AND CENTER WINDSHIELD WERE GOOD FOR A SOLID 3 MPH GAIN VERSUS LEAVING THEM OFF. GET YOURSELF A GOOD SNAP ON COVER AND MAKE SURE YOU GET A CENTER POLE SUPPORT TO KEEP THE BOWCOVER FROM CONCAVING IN WHILE AT SPEED.

[Chris]

2-3 MPH is what you commonly hear.

[jkeiper]

http://www.checkmate-boats.com/infopop/emoticons/icon_smile.gif I gain 2 on GPS with the snap cover and windshield center in stalled.

Jim

[JY]

Jim, have you ever noticed the difference with the center portion of the windshield on, but the bow open? What type of top speeds are you running? (I think the faster you go the more you are affected by poor aerodynamics like the open bow). Thanks.

[jkeiper]

I haven't tried it with just the windshield center installed. I bought the boat last fall and with the dealer setup I ran 63.9 GPS. I played with engine hights and without a jackplate and the motor as high as I could raise it running a 25 Tempest hit 66.9 gps on the edge of the rev. limiter. Hole shot was terrible. I just got the jackplate as they were on back order forever, and I changed to a 200hp exaust tuner. I'll keep you posted.

Jim

[JY]

Thanks. I'm gonna do some "Monster Garage" rigging this week-end and make a temporary cover to see what results I get when I cover the bow. Good luck with your set-up.

[JW]

On my 21' Pulsare bow-rider, I gained 5 mph by going from a 6" jackplate to a 10" and adding a tight bow cover.

[JY]

For what it's worth: I made a bow cover from thin plywood and duct-tape for my zt 230 this past week-end - worked perfectly - except, saw zero, none, nil, nada speed increase whatsoever versus open bow, gps. Failed experiment, except for the comments I got from people at the beach who asked if the new rigging was permanent - I guess they wanted to make sure I knew that Checkmates and duct-tape don't look good together!

[Chris]

JY.

You would think that adding a cover, at least from an aerodynamics perspective, should help.

[DONCONVINCER]

I have a 1977 convincer... granted it's not what CHECKMATE ever powered a boat with.... Small block 400 .060 over >> Edelbrock Preformer with 780 Holey, Ported small valve heads, Custom ground cam, jacketed S/S headers through the stock outlets... I have had it to a scary 82+ with the bow and the windshield open. The chine walk made me let off... Slaming from one side to the other is no fun... When you have enough power a bow cover won't make a differance...

[Chris]

It has to be supertight.

JW added one to his Pulsare and it made a difference. And he was running 75 Plus. I think he had a good solid support pole under his bow cover too.

[JY]

Chris, I agree that you'd think that you'd have to see a speed increase due to the better aerodynamics - particularly given that the make-shift cover was set up perfectly - very thin and light ply-wood cut to cover the bow, taped firmly around all the edges and two poles underneath to keep it perfectly level - Obviously it doesn't affect the aerodynamics in any net positive way - was worth the try, though.

[Chris]

I know my boat runs all different speeds depending on conditions.

Sometimes it runs a solid 60, other times it runs 57-58. Without being able to have consistent conditions, (air temperature, weight, water conditions, fuel octane etc.) and therefore isolate just the presence of the cover or lack thereof, it's really impossible to say exactly what difference a cover makes. My guess is that it would help. But who knows? http://www.checkmate-boats.com/infopop/emoticons/icon_smile.gif

[JY]

Yeah, except I did two runs each way immediately before putting the cover on and then two more each way once it was on - same gps speeds, all within .5 mph of each other. It might well make a difference on a different model - the ZT230 has a hump in the middle of the bow area - maybe the wind pushes down on the front sloping area, driving the bow down such that any aero effects you gain elsewhere are offset - whereas the open bow lets some of the air flow through the cockpit? who knows - ell maybe an engineer with more brains than me.