Bimini Tops

[showem]

Re: Bimini Tops

I would only open it up if I was anchored some where. If I was trolling along (no wake) I would leave it open and certainly close it up when trailering.

 

[Scott Danforth]

Re: Bimini Tops

Hit 45 with the Bimini up often.

Having it closed on the highway I have hit 80. usually take it off though, I'm tired of scrubbing bugs

 

[bruceb58]

Re: Bimini Tops

I kinda doubt the 3 MPH gains using a bimini. Do you gain 3 MPH by taking 2 200# people out of the boat? That would be the equivalent of getting 400# of lift out of the bimini. Could the Bimini poles even support 400# of force upward?

I don't notice much speed difference when my 80 gallon fuel tank is full or empty either.

 

[QC]

Re: Bimini Tops

Between a full passenger load and no load in my boat I pick up as much as 6 MPH 51 vs 57 WOT, trimmed best I can. Some of this is trim limitations with people in the bow. I do agree 400 lbs lift from the bimini seems very excessive, but that assumes you need 400 lbs to gain the 3 MPH in all boats. For me the bimini is a push up or down, but . . . a lighter boat reacts to weight, or lift, much more than a heavier boat. That is pretty obvious.

BTW, if your tank is aft, I can seen the speed difference being negligible. For me, if I have weight in the bow I suffer the most as I lose some trim as noted above. If I move those people aft and work the trim I'll pick up a coupla MPH for sure.

 

[bruceb58]

Re: Bimini Tops

If Frank is getting that speed increase from the Cuddy with the outboard he has in his pictures, that boat looks fairly light. Maybe it is possible. Looks like his bimini is near the back of his boat too.

 

[Home Cookin']

Re: Bimini Tops

I'm no engineer but I think the hydrodynamics of the various hulls makes it near impossible to say what simply adding or removing weight does. Where the weight is placed is as important as the amount (within reasonable tolerances) on a given hull; there is no way to factor weight change and placement in two different hulls.

That being said, I think the common observation that the amount of fuel doesn't change performance appreciably (again, within reasonable tolerances) is the effect of the fuel being in a constant location: stern for loose tanks; keel for floor tanks.

Captains of larger boats are intentional about water and fuel tanks, which they draw from, balance, etc. but that's a different drill than our <24' pleasure boats.

Coolers/fish boxes and people are variables that are hard to pin down. I've found that annoying people seem to make the boat drag more than the people I like; other people's excessive gear bogs me down but never my own important stuff I carry.

 

[Frank Acampora]

Re: Bimini Tops

The 21 foot manatee is a relatively light hull advertised by the manufacturer at 1600 pounds BARE. As equipped and with a full 30 gallons of fuel she is running about 2300 pounds. The Bimini is mounted near the rear and with 5 poles and 4 straps it is not a stretch to consider a negative 400 pound load tolerated by them.

Before swapping engines the hull only reached about 34 MPH and I never noticed any increase or decrease in speed due to the Bimini. After swapping engines to a 5 cylinder 150, hull speed increased to about 42 with the Bimini down and 45 with it up. As I said: I was quite surprised since I was not looking to observe a speed increase. I can only postulate this: The 21 foot cuddy is a stretched 19 footer with the same transom width. The hull is relatively narrow and so she sits rather low in the water, even at cruise. So, I suspect that any lift, will reduce the wetted area of the hull allowing less water friction and more speed.

I have no ax to grind, I simply report what I observed on my hull, so take this as you will

 

[ricohman]

Re: Bimini Tops

I usually leave the bimini up all the time when on the water. The only time I consider folding it up is when its windy and I'm heading to the dock. A large top can catch the wind and make slow manuvers difficult.

 

[bruceb58]

Re: Bimini Tops

Did you replace that motor with the drawing on it?

 

[crabby captain john]

Re: Bimini Tops

I've had a few bimini tops in the past. Never towed with the top up but it was always up when on the water. Speeds to 55 mph was never a bother, yes they would shake or swirl a little but never enough to loosen a screw or more than flap a strap.

 

[bruceb58]

Re: Bimini Tops

I never tow with my bimini in its stowed position with the boot on anymore. I lost a bimini that way. I did have plastic hardware on it though. My new bimini has all stainless fittings but I take it off completely and store it inside the boat when I am towing though.

I would never have a bimini with plastic hardware again. Doesn't cost much to upgrade to stainless.

 

[Frank Acampora]

Re: Bimini Tops

The "Mermaid" engine was a four cylinder Chrysler 140 and it was getting tired. I found a good deal on a force five cylinder 150 and mounted it on the boat. It made a really big difference in performance.

Never fear: Next season the big black beauty will have a mermaid decorating her.

 

[bruceb58]

Re: Bimini Tops

Never fear: Next season the big black beauty will have a mermaid decorating her.

Awesome! Can't wait to see it!

 

[V153]

Re: Bimini Tops

I dunno. I been building bimini tops for 11 yrs now, but ain't never built one to act as a lifting body. 'Spose it's possible but boy I sure wouldn't try it with a store bought top.

The biminis I make for go fasts are reinforced, double-stitched, etc, etc. Even so I wouldn't recommend trying to lift 400 lbs with one? That'd be a 'non-warranty' item ...

I agree SS fittings make for a stiffer top, but it's not impossible to break one. Stainless is kinda brittle, metal wise. Seen it happen many times. Plus if you use SS fittings on alum tubing you start the electrolysis that will ultimately cause it to fail.

Nuthin wrong with vinyl fittings so long as they're securely fastened. In some cases they're more forgiving than stainless ones.

 

[bruceb58]

Re: Bimini Tops

Plus if you use SS fittings on alum tubing...

Not sure I would ever want to use aluminum tubing.

 

[V153]

Re: Bimini Tops

The "Mermaid" engine was a four cylinder Chrysler 140 and it was getting tired. I found a good deal on a force five cylinder 150 and mounted it on the boat. It made a really big difference in performance.

Never fear: Next season the big black beauty will have a mermaid decorating her.

Sorry I'm a lil confused, as usual. Is that motor goin' on the V153 Frank? Killer!

 

[dingbat]

Re: Bimini Tops

A full tank of fuel (~#720)knocks 2-3 knots off my top end. fill both tanks (~#1120)and I'll drop an additional 2 knots.

Putting my curtains up knocks 1 mpg off the tow vehicle and about 1knot off wot

 

[Frank Acampora]

Re: Bimini Tops



It is not really surprising that you are a bit confused V153. I swap engines as often as I change underwear. ---Ohhhh! Too Much Sharing!

Anyway, the 4 cylinder 140 Mermaid engine is retired pending performance modifications. Then, she is slated to push my 14 foot, flat bottom, go-fast. Perhaps she will get up to 60-65. If she does perform well, the 140 Mermaid engine is destined to power my "James Bond" Glastron GT150 (if I ever get the time to restore the hull)

There IS a different mermaid engine--four cylinder 120 on the Glastron V153. and it does reasonably well considering it is a distributor engine.

The big black beauty, five cylinder Force 150, is currently mounted on my 21 foot Manatee. Next year, if I get time, the engine will get a new paint job and a mermaid decal.

 

[V153]

Re: Bimini Tops

I'd forgotten you had a GT150 Frank. Cool, classic, 'James Bond' boat. Get off yer azz & restore the dang thing will ya! Heh heh heh

The GT might be a lot purtier but I guarantee your 153 will outrun it with comparable power. And smoke it in a chop.

Least mine would ...