From montana riverboats
So my original plan was to bag on the cheap so I didn't end up spending a fortune. I planned on using cheap alternatives for materials, a cheap vacuum setup, do everything on the quick and dirty. Vacuum bagging isn't a super complicated concept, there's plenty of ways to do it, especially for small parts..either flat or contoured around a mold.
I dunno wether it was common sense, or being talking myself into just throwing down on the real stuff I needed where I needed it, but I threw down a little bit to try and make sure this gets done right. Cost a good bit, but whatever...
Some of it was difficulty sourcing alternative materials. Dacron suit fabric makes for great peel ply. However getting 65 yds of fabric wide enough to peel ply a boat with is easier said than done. In the end having the local fabric store order stuff in might have costs barely less than getting real peel ply from fiberglass supply after talking them down in price a bit, so I just went with that. The 60" fabric gives me an extra 12" width of running length extra fabric so ill be able to use that to peel ply all my taping.
Another thing was deciding where to use the real bagging film instead of poly. Most of my parts are flat stock, so ill use the cheap poly bag there. I bought a little handheld sealer...may get another handheld bag sealer to make custom sized bags, then tape over the edges. Ill get some brand name butyl window tape for where I need tack tape. For the hull, ill need the bag to contour around the chine. Decided ill use a few yds of real bagging film for this application. May get one roll of real bag tape for here.
I still plan to use cheap consumables where I can though. Ill use the heavy shop paper towels as breather, maybe a little bubble wrap on smaller pieces. Ill get some poly batting fabric for breather where I need more bulk like around the air hose or between separate pieces of work. Butyl tack tape wherever I can to seal custom made poly bags.
Last order of business was equipment. Pulling a vacuum can be simple or complicated in terms of equipment. Easiest way to do it is to get a small vacuum pump, run it thru a ball valve to a gauge to a check valve and then out to the work. This runs the pump continuously but a vac pump should handle it fine. Alternatively if you have a compressor, you can get a small Venturi adapter to pull vacuum for reasonably cheap. This still runs the compressor constantly. If you don't want to run the compressor you have a few options. First is to babysit the work. Pull your original vacuum, get the bag situated, make sure the work is not leaking..then go have a beer. Come back and check the pressure every now and again, and crank the pump on if it needs more vacuum. Do it till its cured...time consuming, not unreasonable though. The easier way is to setup a pneumatic valve and a vacuum controller to turn the pump on when necessary. This introduces other problems like unloading back pressure and having reserve vacuum. www.joewoodworker.com has plan for auto cycling vacuum presses using both a vacuum pump or a Venturi. He sells the parts either as a kit or individually at a pretty good discount. If you live near a big box store tho u may be able to do the same or better for alot of the stuff locally.
My original plan was cheap and simple. A borrowed 5cfm rol-air air compressor, a $15 Venturi from harbor freight, and. Vacuum gauge, ball valve, check valve, and some readily available plastic soda dispensing caps. It would have worked fine, but I would have been running that loud compressor constantly, and it would have gotten on my nerves and maybe my neighbors too. In addition, the cheap harbor freight Venturi looks chinsy and I have heard reports they gulp air to get to full vacuum and really only produce about 2-2.5 cfm. That probably would have gotten me thru most everything, but bagging the hull is gonna require some juice. I'm sending it back. A real Venturi costs $55 to produce 3 cfm. It would work with my compressor but the compressor is borrowed and at some point in the next month or so my buddy JT is gonna need it back. That's means I would then have to go out and buy a 4-5cfm compressor to finish.
I decided to throw down an extra $30 now rather than have to spend more later and bought a refurb Thomas veneer vacuum pump for $85 out the door on eBay. It pulls 3.5 cfm and should have enough juice to pull the whole hull, especially if I beef it up with reserve reservoirs and a cycling on off system. I threw down another $100 to buy a bunch of supplies from veneer supplies.com, the joe woodworker sister site. Im going to build a version of his project evs vaccum press. I got a bunch of fittings, check valves, ball valves, vacuum gauge, and a vacuum controller. I have some 15" lengths of 3" PVC for the reservoirs and resin trap. And I got all the electrical stuff I needed at the restore for $1. I threw down on a real thru bag fitting too just make my life easier as ill be bagging a bunch of panels. Soda valves would have worked, but work have required to much fiddling to save a few bucks. Looks like the best homemade valves are made from car tire valves with fender washers and rubber gaskets. I may make a second thru bag fitting and keep this harbor freight thing around as a backup or maybe to run two systems at once if I need more vac. Hoping my Thomas pump should get the job done here, I'm not veneering hardwoods here, just trying to pull the excess resin out. I'm in about $200 on the whole pump setup and I figure I can either sell the Thomas pump when I am done for what I bought it for, or sell the whole press on eBay and make most of my money back.
Anyhow, parts should be here next week. Hoping to get side panel material cut and a few temporary formers made in the meanwhile. Still waiting on the big order of glass to get here from raka and fiberglass supply. Then on to manic boat building next few weeks.
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