Shelf weight

[Sue and Henry]

I'm making a shelf over the front window of my 13 foot burro.



This is what I have so far. There are three layers of cloth fiberglassed on the top and bottom of a 1/4" sheet of board (repurposed from an old waterbed base). The burro manual does not say what their shelf is made out of, but my plan is to fiberglass a front lip on and after finishing the surfaces, fiberglass it in place.







Picking this up in its unfinished state, it seems too heavy. My scale tells me it is currently 14#. Add another pound for finishing glass.

I plan to store clothes, extra bedding, towels...on top. Not the heavy stuff. Does this seem reasonable? Should the wall be strong enough?

[Thomas G.]

I think that the walls are strong enough, but the shelf itself seems unnecessarily heavy. I'm also working on a set of similar shelves but I'm using 3/16" underlayment and extruded L shaped aluminum.

By giving a shelf "section" via an upturned portion you can gain a lot of strength with little weight. Sort of the way a piece of angle iron is much stronger than a a flat piece of steel of the same weight.

[honda03842]

I made our rear cabinet out of a sheet of 1/4 inch birch plywood, probably using less than half a sheet. The rear cabinet holds 3 blankets, two sets of sheets, all our jeans and holds up our 19" TV. It is supported off the window frames.

[Sue and Henry]

Originally Posted by honda03842

I made our rear cabinet out of a sheet of 1/4 inch birch plywood, probably using less than half a sheet. The rear cabinet holds 3 blankets, two sets of sheets, all our jeans and holds up our 19" TV. It is supported off the window frames.

That is really attractive. I especially like that it is closed. I had planned open with a lip. Hum. Time to reconsider.

[Thomas G.]

Originally Posted by honda03842

...... It is supported off the window frames.

My design also is supported off the rear window frame plus the side curtain attachment screws. Having a smooth interior like the Burro, I didn't want to do anything to the fiberglass that was permanent.

[Sue and Henry]

Originally Posted by Thomas G.

I think that the walls are strong enough, but the shelf itself seems unnecessarily heavy. I'm also working on a set of similar shelves but I'm using 3/16" underlayment and extruded L shaped aluminum.

By giving a shelf "section" via an upturned portion you can gain a lot of strength with little weight. Sort of the way a piece of angle iron is much stronger than a a flat piece of steel of the same weight.

By section, do you mean the shelf is divided up bridging the short crossways? What about that long 5 1/2 foot length? How are you keeping it from sagging?

[Sue and Henry]

Originally Posted by Thomas G.

My design also is supported off the rear window frame plus the side curtain attachment screws. Having a smooth interior like the Burro, I didn't want to do anything to the fiberglass that was permanent.

I see. Sounds like a very good plan. Thanks Thomas.

[honda03842]

Sue my shelf is supported off the side and rear windows. It required no holes thru the shell of the trailer. Unfortunately the side windows and rear window are not at the same height so I had to add a piece of wood to the top of the side windows to support the sides of the shelf. I'm going to look for a picture for you.

I used three pieces of aluminum angle to support the shelf, one for each window. I drilled holes in the angle that aligned with the window's screw holes and used these screws to hold the angle. I painted the angle black to match the window frames.

I first made the bottom and then glued a 1 x 3 to the front edge of the bottom. Then added the verticals and a cross member between the verticals. The verticals are to strengthen the area around the openings. Finally I added the front all screwed and glued together. It's very strong. I believe I described it in Preparing a 1991 Scamp under Modifications.

Since I added a piece of wood to even out the window heights, I added small shelves on each side. Besides providing storage space for little things, It also prevents the shelf from moving forward.

After thought... I probably glued the verticals to the face piece before installing it.

If you want more detail let me know.

By the way the height of the front face maes a pretty strong section.

[Thomas G.]

Originally Posted by Sue and Henry

By section, do you mean the shelf is divided up bridging the short crossways? What about that long 5 1/2 foot length? How are you keeping it from sagging?

No, section is an engineering term referring to the cross sectional dimensions of the structural piece. By having a relatively tall aluminum lip on the front, my design gives the long front piece a lot of resistance to sagging. I found this extruded stuff at a recyclers, but one could use aluminum angle from a place like Home Depot or Lowes. In Norm's design the front to the cabinet provides section to resist sagging..

[Sue and Henry]

Originally Posted by Thomas G.

No, section is an engineering term referring to the cross sectional dimensions of the structural piece. By having a relatively tall aluminum lip on the front, my design gives the long front piece a lot of resistance to sagging. I found this extruded stuff at a recyclers, but one could use aluminum angle from a place like Home Depot or Lowes. In Norm's design the front to the cabinet provides section to resist sagging..

Got it. Time for yet another trip to Home Depot. I'm putting their kids through college! Not a bad thing. : )

[Thomas G.]

I'm at a point where I can post a few pictures of my shelf project instead of virtually waving my arms. I added a shelf to each end of the trailer with two side shelves in back and one short side shelf in front. Each shelf is made from 3/16" underlayment painted with exterior gloss paint to match the interior color. The aluminum is extruded in an L shape. Rather than drill holes, I attached to the window clamp ring, existing screws, or attached brackets with 3M Extreme double faced tape. The next step is to cover the screws to prevent snags and add a shock cord at mid level to hold things securely on the shelves. I may steal Raz's idea and add a mesh curtain to the shock cord.

[Sue and Henry]

Your shelves look great Thomas. I just returned from Home Depot with thin plywood to replace the 14# sheet. I am still going to skin the new one with a couple layers of fiberglass to stiffen it up a bit then put on a layer of gel coat since I already have it to match.

[Thomas G.]

Originally Posted by Sue and Henry

Your shelves look great Thomas. I just returned from Home Depot with thin plywood to replace the 14# sheet. I am still going to skin the new one with a couple layers of fiberglass to stiffen it up a bit then put on a layer of gel coat since I already have it to match.

Thanks. If you are fiber-glassing over, the plywood itself doesn't add much strength, mostly weight. Sort of like an I beam, all the strength is in the top and bottom surfaces. Things like boats and surf boards are made of fiberglass over a foam core. But at any rate, a thinner board and aluminum angle should save you a lot of weight and be stronger, too.

[Jared J]

If you're fiberglassing anyway, and worried about weight, use honeycomb.

[Sue and Henry]

Yes. I looked for honeycomb but I couldn't find it in a manageable and affordable size. Do you have sources? The section is about 5 1/2 feet by 15 inches.

[Jared J]

http://www.sandwichpanels.org/store/store.html They might be able to get you a smaller size.

I would look more, but my new comp died, and I just have my phone now.

[Shirley LaMoine]

Thom - OMG!!! I think I'm in LOVE!!! Your shelves are perfect. Thanks for posting the pics. Lovely, indeed.

[Thomas G.]

Originally Posted by Shirley LaMoine

Thom - OMG!!! I think I'm in LOVE!!! Your shelves are perfect. Thanks for posting the pics. Lovely, indeed.

Thanks. My wife says that if she hits her head on them I'm gonna pay. If you see them advertised in the free camper parts section, you will know what happened.