Building a fiberglass bimini/cargo rack?

[1badhusky]

I need a bimini and a cargo rack that'll fit under my tower on my 185 bayliner. These things go for $600 online, so I was thinking I could cut a thin piece of plywood in the shape I want, then reinforce it w/ fiberglass cloth and resin, then paint it.

Could then pick up mounting hardware from westmarine.

Was thinking I'd put some slits/holes in it so wind can vent and angle it down just a bit so the wind isn't pushing the boat up.

My boat does about 55mph. If it's not strong enough, the wind at that speed could rip the whole thing off.

Would reinforce the areas where it connects to mounting hardware w/ extra glass and glass cloth.

Figure this whole thing would cost under $100, weigh about 30 -40 lbs, be able to support 100 lbs, and also provide shade. And I've worked w/ fiberglass before, so I think it might even look pretty cool.

I think this would be a fun project and give the boat a cool, unique look and add some functionality.

Am I crazy?

What am I overlooking?

 

[airdvr1227]

Re: Building a fiberglass bimini/cargo rack?

I now nothing about working with fiberglass but my first thought was there's sometimes when I want my bimini put away. How would you accomlish that? 55 on the water?...what about 65 on a 2 lane blacktop and a semi coming in the opposite direction? Storage?

I don't want to pee in your Corn Flakes but....

 

[1badhusky]

Re: Building a fiberglass bimini/cargo rack?

I now nothing about working with fiberglass but my first thought was there's sometimes when I want my bimini put away. How would you accomlish that? 55 on the water?...what about 65 on a 2 lane blacktop and a semi coming in the opposite direction? Storage?

I don't want to pee in your Corn Flakes but....

See, now that's why I posted up on here - I totally didn't even think about the fact that I trailer my boat and would be doing 70mph! thanks!

Ok, so I'd need much bigger holes, which defeats the "bimini" factor. Back to the drawing board.

 

[airdvr1227]

Re: Building a fiberglass bimini/cargo rack?

Glad I could be of assistance

 

[Grant Brown]

Re: Building a fiberglass bimini/cargo rack?

Ever seen a fiberglass canoe on roof racks at 70 mph - I have and done it too. Never lost one yet.
I think it is totally do able especially if you use extra glass where the hardware attaches. I'd go for it.
Google plywood canoe and you will see the canoes I built out of 1/8" plywood and fiberglass. They've withstood 12 hour days strapped to roof racks at 70mph and never even a hint of structural failure.
I also think that if it did start to go it would most likely show signs of de-laminating or stress cracks or some other indication that is was going to fail. It probably would not completely blow off with the first large truck that went in the opposite direction.
Think of all the large high power boats that use cold molded or stitch and glue construction.

 

[1badhusky]

Re: Building a fiberglass bimini/cargo rack?

I'm still thinking about doing it, but it's gotta be strong and have good venting - maybe I'll make really big holes/slits and then have some fabric I can button on to make a sun block.

 

[smokeonthewater]

Re: Building a fiberglass bimini/cargo rack?

you don't need to vent it but you do need to mount it very well....
You also need to build it as a rigid structure... 1/4" marine ply and glass skin on a hardwood or soft wood/glass framework... lift should be minimal with a flat (from front to back) top.... the real key though is mounting points and structure ... also keep it level... and make sure you have just a little more to the rear of the mount centers than tthe front... this will add stability and tend to stop fluttering ......

I play with aerodynamics a bit with r/c airplanes

 

[solar7647]

Re: Building a fiberglass bimini/cargo rack?

This can be done pretty easy and solve your wind issue.

Cut a piece of Play in the size and shape you want.
Then cut voids in it like in the pic below. You can give all the edges a nice finish with a router then cover in fiberglass. Once it sets up sand and clean the finished fiberglass then I would use a body filler like 3Ms marine filler and give the hole thing a thin cover. The filler will allow you to sand it down so that when you paint it you have a nice smooth finish. I would use a marine filler because they dont soak up moisture as Bondo does.

The voids will make it light and allow air to pass through, getting rid of it air resistance. With the cross members cut in to a single piece of wood you will keep strength and the fiberglass will add more. That should be fine as long as your not standing on it. should hold skis, wakeboard and so on just fine.

Now to make it into a bimini top, get a large enough piece of canvas to cover the rack and use snaps to attach it to the rack. I would make it rap around the edge of the rack and snap on the under side. That will keep it on when speeding around, and allow you to remove it when you dont want the shade.

You can get elastic cord to hold thing down that are stored on it.
Also I would attach would attach it at four points to give it stability.

Now I dont think it will be $100 but maybe less then $200

Just my thoughts on it. Its basiclly the same as the ones they sell but with the wood instead of the aluminum tube.

 

[180shabah]

Re: Building a fiberglass bimini/cargo rack?

I would use a marine filler because they dont soak up moisture as Bondo does.

I thought Bondo soaked up beer..

 

[MyViewGS]

Re: Building a fiberglass bimini/cargo rack?

I would suggest the $600 price is your cheapest route.

^^+1

 

[NSBCraig]

Re: Building a fiberglass bimini/cargo rack?

I'd use bondo not 3m marine filler which is vynilester not polyester based and you'll be spending more for finishing. (like using epoxy)

Bondo is just talc and poly, not much different than make peanut butter for fillets out of poly and wood flour. The flour and talc can absorb water but don't really cause they are encased in resin.

Of course none of that matters after you finish it cause both are sealed from moisture.

 

[smokeonthewater]

Re: Building a fiberglass bimini/cargo rack?

I wouldn't use bondo OR marine filler.... Instead I would fit the parts properly and sand it smooth.... then lay the cloth and resin

 

[Topol_86]

Re: Building a fiberglass bimini/cargo rack?

I've been around fiberglass all my life, expecting under $100 is a bit off, a gallon of resin alone is about $50. as far as putting filler on top of it for sanding, no need. Use what is known as a "veil" (very fine fiberglass mat) on the top and you should be able to sand it down just fine, paint is fine to use on top, although i'd reccommend a gelcoat finish. It'll last longer and won't fade/weather as much as paint does. Just my $0.02. If you do end up going ahead with the home-made route, post some pics, i'd like to see how it looks