Re: New TTT - The Boxcar - New Sliding Bed

[angib]

At the risk of being a smart-arse trying to spoil Bruce's day, when he's making such good progress..... no, go on, I'll be a smart-arse:

Adding diagonals to the framework to resist sideways loads is perfectly sensible for a house, but completely unnecessary for a trailer where the skin is bonded on properly.

Diagonals are added to houses because the 'skins' are not continuous and are not that well fixed-on. In the trailer, the skin itself/themselves act as the diagonals, just like they do in aircraft and in boats, neither of which have diagonals (at least in stressed-skin construction).

And you can't get an example of skins that are better bonded-on than Bruce's. How come you have a vacuum pump at home, Bruce, or are you using a shop vac? (I've never had the confidence to try that, as I assume it'll burn out the vac motor.)

Andrew

[bdosborn]

Adding diagonals to the framework to resist sideways loads is perfectly sensible for a house, but completely unnecessary for a trailer where the skin is bonded on properly.

<snip>

And you can't get an example of skins that are better bonded-on than Bruce's. How come you have a vacuum pump at home, Bruce, or are you using a shop vac? (I've never had the confidence to try that, as I assume it'll burn out the vac motor.)

Andrew

Andrew,

In retrospect, the diagonals don't do much for the final wall but they helped * a lot * to keep everything square during framing. I put them in after I framed the perimeter of the wall and noticed how floppy is was. I didn't want anything to move before I finished the framing and skinning. It probably would have been a lot easier to just tack a diagonal across the the frame but I didn't think of it till later and it was nice to have everything flat while skinning.

I got the vacuum pump off eBay specifically to try the vacuum bagging. It works, but just barely, I'm not very happy with it. It leaks oil and despite the continuous rating I can only run it for around 30 minutes before it starts smoking. Luckily, that's the clamp time for Titebond II glue. I'm looking at other options because I don't want to risk burning up my shop vac either.

Wow Bruce...your putting us all to shame!!! Glad you are back at it...we were really enjoying the build and learning alot from your techniques!!!!

Juneaudave,

Thank you! I consider that very high praise after watching you build your tear.



Bruce

[bdosborn]

I got to work this weekend skinning the first side wall. First I skinned the outside with 1/4" plywood. Nothing fancy, just titebond and staples.



After the exterior was skinned and insulation added, Jean and I glued and vacuum clamped the 1/8" plywood interior skin. No nails or staples, just a few 27 gauge pins to keep the skin from sliding around in the bag. My vacuum pump couldn't keep up with all the leaks in the larger bag so I used the shop vac. We used packing tape to close up the bag and there's just too many little leaks for my 4 cfm vacuum pump. I was more than a little worried the shop vac would burn up but it held up for an hour of clamp time.



We skinned it in two passes. Here's the front skin clamped and glued:



Then we moved on to the back half. We had a little trouble getting it sealed so we added some weight at the corners. I think we got a little careless checking the seams and there were a lot of little leaks. I got a good clamp after I checked the tape again. The string in the bag gives the air a path to the vacuum.



How did it work? It worked GREAT!!! The 1/8" plywood was really wavy and there's no way I would have been able to staple it flat. I'm really happy with the results.



Just need to skin the exterior with filon and I can move on to the other side.

Bruce

[planovet]

The vacuum bag is a different way to go. I just used a lot of clamps and a lot of weight.

[bdosborn]

That's what I did on our teardrop but I used 1/4" plywood for the inside skin. I'm using 1/8" plywood on this build and it has ripples in it so its a lot harder to get it to sit flat. With the vacuum clamp, its lies nice and flat and I'm pretty sure I don't have any gaps inside the wall between the skin and the frame.

Bruce

[Cliffmeister2000]

Wow! I almost missed this because it is in General Discussion rather than Member Designs. What a work of art! I cannot wait to see it complete!

[bdosborn]

Finally got around to sanding and gluing my cabinets together. I've had them roughed together for awhile but I hate sanding (makes my back hurt). So here's a few pics.
Gluing the sides of a cabinet together:

Here's one pf the panels for the bed.

Refrigerator cabinet and sink cabinet.

Here's everything - Two cabinets, a bed frame, closet and drawer frame. Not a very big pile for how much work it is. But it is pretty light...

Next its gluing and staining the cabinet doors.

Bruce

[Steve Frederick]

Wow!
What a great build!

What about the vac bag? Poly, rolled and sealed?

Looking terrific!

[bdosborn]

Wow!
What a great build!

What about the vac bag? Poly, rolled and sealed?

Looking terrific!

Thanks Steve!
The bag is made from 10mm poly from the paint department at HD. I tried rolling and clamping it but it leaked too much that way. We ended up just taping it shut with packing tape. First, I squirted titebond glue on the framing and Jean spread it out with a foam paintbrush. We laid the plywood down and shot a few pins to keep it in place while we bagged it. Jean held the edges of the bag together and I taped it down. The hard part (and it wasn't really that hard) is to get the tape on without bunching up the plastic and causing leaks. Then we turned on the vacuum and made sure the tape was stuck down everywhere ( you can hear if there are any leaks). 30 minutes later and its done! I was worried about burning up the vacuum because of a lack of air flow but my vacuum leaks enough internally that it wasn't a problem.

Bruce

[starleen2]

Cool idea - lets see, I have a similar vac, and need to build some walls, Have a lot of 5 mill plastic. . . .

[GPW]

Done a lot of vacuum bagging in the past on model airplane projects.... a real vacuum pump makes all the difference, giving tremendous clamping pressure to parts... much better than a Hoover... Just FYI..

[bdosborn]

Done a lot of vacuum bagging in the past on model airplane projects.... a real vacuum pump makes all the difference, giving tremendous clamping pressure to parts... much better than a Hoover... Just FYI..

Do you have a link to a good vacuum pump? The ones I came across for something this size where pretty spendy...
Thanks,
Bruce

[Cliffmeister2000]

Done a lot of vacuum bagging in the past on model airplane projects.... a real vacuum pump makes all the difference, giving tremendous clamping pressure to parts... much better than a Hoover... Just FYI..

Do you have a link to a good vacuum pump? The ones I came across for something this size where pretty spendy...
Thanks,
Bruce

Here's some from Harbor Freight. Don't know what would be required.
http://search.harborfreight.com/cpisearch/web/search.do?keyword=vacuum+pump

[bdosborn]

I got a pump kinda like the 2.5 CFM pump off eBay, but it's a 5 CFM instead. It starts smoking after 20 minutes of running, so I'm not sure how good that type will work. I think they're made to draw a deep vacuum on refrigeration equipment for a short time, like 5 minutes or so. 30 minutes makes them heat up enough that the vacuum oil starts to smoke. At least it does on the one I got.

Bruce

[Cliffmeister2000]

I wonder if an air driven vacuum pump would be better for long duration work?
http://www.monstronix.com/rob34970-p-57004.html

Of course, if you don't have any air leaks, you could put a check valve in line with the vacuum pump, and once vacuum is achieved, sut the pump off.