vacuum bagged fiberglass layup for box

[colinJ]

I want to make a storage locker out of fiberglass. I previously did a hand layup onto core material for the transom/deck rebuild that I posted about here where the end result is perfectly functional. Although in hind site I planned it terribly, and as a result I ridiculously overbuilt it to the tune of probably 75 pounds heavier /$700 more than it needed to be.

I am trying to plan better for this next project which as previously stated will be a storage locker, roughly triangular (flat in the "z" dimension) about 20x30x12. For the material I am planning to use 1708 with V/E laminating resin and gelcoat.

I am thinking this would be a good place to use a vacuum bagged layup and I already have a vacuum pump from doing A/C work on my house.

How thick should I make the layup? there will be no core I am thinking 3 layers across the middle would be good with a few extra layers tapering down at the corners on either side.

Can anyone recommend a video that can go over the process?

I have searched youtube a bit but as an amateur its sometimes hard to separate BS from expertise.

[ghostn']

Colin what are you planning on putting in it? #Shelves? Avg. Total Weight of Contents??

[XstreamVking]

You may have overbuilt the transom, but it will not fail. You could have under built it and had a failure in the future and needed to go into it again. For your box it might be difficult to do sharp inside corners with a vac bag. Hand lay might be best. 1708 is very strong stuff, as long as the stuff you plan on putting in the locker cant break thru it just a couple of layers of 1708 will be plenty.

[colinJ]

Colin what are you planning on putting in it? #Shelves? Avg. Total Weight of Contents??

Its going to be an anchor (5 pound at most), chain and rope in one section and a 5 gallon Jerry can in the second section.

[colinJ]

I went through the top of the transom for the outboard rigging with a hole saw, there is nearly a 1/2 inch of glass on either side of a 2.25" core. I probably would have been fine with a quarter inch of glass on a 1.5" core.

I could slope the sides if that makes it easier to form.

So if I was going to do a hand layup should I use a plug or do it inside a form?

You may have overbuilt the transom, but it will not fail. You could have under built it and had a failure in the future and needed to go into it again. For your box it might be difficult to do sharp inside corners with a vac bag. Hand lay might be best. 1708 is very strong stuff, as long as the stuff you plan on putting in the locker cant break thru it just a couple of layers of 1708 will be plenty.

[ghostn']

Colin have you considered vac infusion. If you have some experience w bagging and weight and efficiency are a goal you may find an infusion to be your solution. Keep it simple and have everything ready when you begin. Here are a couple sources for details etc. Hope it helps and turns out as you want. let us know

http://www.fiberglasssupply.com/How_To/how_to.html
https://www.fibreglast.com/category/Learning_Center

[ghostn']

XStream has a good point about the sharp corners. you dont want pooling. If you are willing to build or mold rounded edges and inside corners you can still bag or infuse it otherwise he's right about the layup. Good luck either way you choose

[GregAdams]

The stiffness of the laminate will be a higher priority than strength with that load. Stiffness is proportional to the thickness. For a given thickness a vacuum consolidated solid laminate is heavier than a hand laid laminate. Not a lot heavier, but if your sole reason for vacuum bagging is saving weight you might want to rethink it. You can reduce the thickness slightly because of the higher fibre content. But the end result is no weight savings for a lot of expense and additional consumable materials that go in the bin at the end of the job. Not to mention you will have to think carefully about what you make your mould out of.

[colinJ]

If I make it using a hand layup would you guys recomend doing it on a plug or a mould.

I have a cnc Mill that I could use to make the mould out of mdf.

[XstreamVking]

Make a male mold. (Where you glass on the outside of the mold.) Use some melamine board for a decent smooth finish. Round the corners and use some wide celophane packing tape to smooth them also. Wax or use pva liquid release to make the part not stick. If wanted apply gel cote before glassing to get a gelled finished part.

[GregAdams]