Vacuum Bagging

[Craig]

I could use some help with a new project I will be starting soon. A friend has talked me into helping him make a hard top for his 52-foot cruiser. The top will be 16'x10'. It was initially to be a bit curved from side to side, however the tubular support frame is dead flat so the curve is out. We have 1/4" ply to layup by hand to accommodate the curvature. The idea was to screw the top layers to the bottom layers one at a time over a curved frame and to remove the screws after the epoxy cured. Lots of pieces and even more screws. With the structure now basically flat I think this is a good candidate for vacuum bagging. The whole assembly could be put together in one operation. I used this method on a hatch cover once and it worked well, however, this is a whole lot bigger piece. I was thinking about heavy construction plastic sealed with duct tape and a long piece of copper tube running in under the plastic on top of the assy. Do any of you have experience with this technique? Your thoughts please....

[Guest]

There is a guy in Pensacola,I guess in your neck of the woods, that will be coming online in a few, that does a bit of this, and has done a lot of trial and error stuff. Warthog is his login. Stay tuned. This is another link for killing time reading. BUt don't stay over there. :wink:

http://media5.hypernet.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=008667

[warthog5]

Is this on a wooden boat? Nidacore is the material of choice.

Dawson Boats in Pensacola uses Nidacore vacuum bagged with a layer of 1.5oz mat and a layer of 1808 on it.

You get a lite weight top that is super strong. He's had them tested in a local lab.

This would reduce the top weight of the boat, where you don't want it.

I do vacuum bagging at the house and have a project going right now.

However it's on a smaller scale than your talking about.

It's going to take a pump with a bunch of cfm to pull that size panel down.

I have a 1/3hp aprox 3 to 3.5 cfm pump. I had a hard time doing my hardtop which was pulled down over a cambered form. The panel was 5ftX6ft.

The latest pix's and text can be seen at;

http://www.classicmako.com/forum/topic.asp?TOPIC_ID=157

[Craig]

Thank you both for the very informative references. No the boat is glass and about as wide as it is long. From the Maco site and the Wooden Boat link it looks like this would be a valid method. Tom has a bunch of things going up on that top, AC, Sat Comm, Sat TV etc, I am confident that we will have sufficient strength with a large margin of error. There are lighter ways to do this but it is his boat so.... FCI suggests a T-170 something exotic cloth for super strength at little weight. It is about the same price as 8 oz cloth. Do you know what this is? We were going to do the glass by hand so the project is a bit more simple than Warthog's. Nice work there. I like that finish left on the surface. As we were just using the vacuum for clamping pressure I was going to leave 8-10" all around and just let the squeeze out run into that area. The article Oyster lead me to was excellent. I suspect for my use a couple of old refer compressors would do fine. Sure cheaper than some of the comercial stuff. Thanks again for the help.

[warthog5]

Glad to help. Not sure what the T-170 is, but would like to know myself.

I'm wondering if it's an "S'" glass as opposed to "E" glass?

[Arnie Eaton]

Could that material be something like Dynel? It is a plastic type cloth and can be used just like glass. It is much lighter and is stronger and not so brittle as glass. Get it the same place as glass and epoxys.