Quote:
Originally Posted by MetroMPG
You could duplicate this tail by simply replacing the cardboard with coroplast, then paint the outside to UV-protect it. That would make it durable. Could even retain the "scrap wood" frame.
It might take two or three 4 x 8 sheets (rough guess) and might require some different attachment methods. (EG. the hot glue gun may not be the most appropriate way to make a durable plastic version!)
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Good Points.
One thing in favor of cardboard as a first step is it could be gotten for free. I would look for double or triple corrugated stock at appliance retailers; Best Buy, Sears, etc.
There's hot glue and then there's HOT GLUE. Most hot glue that you see is low-mid range temperature for hobby use. Then there's high temp hot glue, allegedly has higher holding strength. IIRC, it is only available in the larger 1/2 inch diameter, longer sticks. And yes, it's really hot, quite painful, it will instantly cause blisters on your skin. Keep away from children.
[Edit: WIth the following structure, it may be possible that the wooden interior framework is not needed. But, care would be needed at the attachemnt points for the hold-on straps; Sizeable pads with a srewed through backing piece on the otherside of the cardboard. This because the face ply of cardboard is just glued to the interior corrugations. Any pulls outward from the face ply risks failure due tension/shear between the two pieces.
On further thought, the following is also applicable to Coroplast construction with a few additional considerations. (A heads-up here. I have not yet actually used Coroplast, ;-0 Caveat Emptor, etc.)
* I would use the old-style non-waterbased contact cement for the flanged/tabbed joints.
* I would rough-up the areas to be glued on both pieces with 100-150 grit sand paper to provide some 'tooth,' just to add some additional grab.
* I would double-up the two main fore-aft bulkheads -- walls -- and two crosswise buldheads located near the front and back of the structure. I'd have the corrugations crossing at 90 deg. I'd join the two pieces of Coroplast with glue on their complete joining faces.]
Thinking of longevity of both cardboard or Coroplast structures...
In my earlier post, I indicated that there are ways to significantly improve the strength of joints where pieces meet at or near 90 deg in the inside of the structure. The intention is to increase the glueing area between the two pieces. Here's a little more info that I think would be helpful:
* The first method of joint strength improvement is to include material at the appropriate edge of an interior piece so that a flange or tab can be bent over where it meets the exterior piece. I'd say 1 to 1-1/2 inch wide. (It is best to layout pieces so that the flanges/tabs occur on the side of the piece that run parallel to the corrugations. The flange or tab should be cut into 6 inch or so inch lengths. Bend alternating tabs to either side.This helps assure that you have time to get each tab bent over enough to be flat to the external surface and not induce local distortion in the skin.
* Second level of joint strength improvement is to double the glueing area of the method above is to add additional material at the the edge of the interior piece to create continuous flanges/tabs on both sides of the piece. This additional piece would be about 3 inches wide; 1-1/2 inch for glueing to the piece and 1-1/2 inch for the flange. Again, you would cut the flange/tabs into 6" or so lengths to simplify glueing and minimize the chance of exterior surface distortion. This method mightbe used instead of the first method for single side flanges/tabs. All in all in may prove easier to do, especially lay-out, at only the cost of some small amount of glue.
Sometimes you should have flanges/tabs on two adjacent edges of an interior piece where one edge shows the ends of the corrugations. It is a PITA to bend flanges/tabs here. This can be overcome by using the second method above, even if the intermittent flanges/tabs of the first method will be used. You have to cut clearance notches where the flanges/tabs are bent across the edge of the base piece.
It is not typically necessary to have flanges where two internal pieces cross in what I call an "egg crate joint." These are joints where each piece has a long notch cut halfway along the length of the joints from opposing ends so that the pieces can be slid together. (Cut the notches so that they are a tightish fit.) All that is typically needed is a bead of glue run down one or both sides of the completed joint.
You might consider adding flanges/tabs to egg crate joints where the interior structure is fastened to the cardboard nearby. The interior structure should contact the cardboard on a hard, low deflecting pad say 1/4 inch plywood. I'd say 3"x3" as a minimum would do, larger if you see fit.
I would waterproof the cardboard both inside and out, In long term use it is quite possible, even probable, that from time to time there will be condensation on the inside of the structure. It will be necessary to close-up the openings in any corrugations in exposed ends/edges. I have used strips of heavy craft paper for this. If you can get them, paper shopping bags are excellent and free.
Afterthought: The above comes from my experience as a boat builder. It reflects a cardboard boat's use in/on the water, especially high point loadings and the immediately destructive nature of water intrusion. Some may see parts of it rising to the level of overkill for automotive applications... but I don't think so. As always YMMV ;-)
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