Teardrops n Tiny Travel Trailers

It might work for shallow stuff, but my gut tells me that anything with a deep draw will need to have sections removed from the flat pattern.

by GPW » 13 Mar 2012, 05:17
What about cutting the foam into strips and glue them on like a canoe ??? . Going to be skinned like one eh ?

Sorry, I'm not trying to hijack this thread but this stirred up a question I've always had about strip canoes. The pictures of the canoes I've seen are just beautiful.

Do the strips bend in two directions so as keep a constant thickness as they are bent over the forms? I know one method of planking large boats is to shape each wide(er) plank as they bend toward the front and stern. They wind up being narrow at the ends.

After someone answers this, back to your regular programing...

-- Teri

I built a stripper canoe back about ten years ago. The 1/4" thick by about 3/4" wide strips are milled with a bead on one edge and a cove on the other. I beleive the router bits you use to form the edges are the same as those used for a roll top desk. When you lay the strips down, they twist to form over the molds. They're glued with TBII, sanded smooth and then fiberglassed. The strength comes from the light weight wood sandwiched between the fiberglass and not so much the wood joinery but I'm sure that helps.


TL

by tony.latham » 22 Apr 2014, 20:50
I built a stripper canoe back about ten years ago. The 1/4" thick by about 3/4" wide strips are milled with a bead on one edge and a cove on the other. I beleive the router bits you use to form the edges are the same as those used for a roll top desk. When you lay the strips down, they twist to form over the molds. ...

Okay, do the strips bend in two directions?

Bending in the thin direction is intuitive but sideways too? It seems they would have to.

-- Teri

The answer is yes, but more twist and forming along the x-axis (flat way) than longitudinally bending along the y-axis (hard way).

In the dry fitting stage of this video you can clearly see that the stem and stern of the pieces being fit need to be bent down to meet the prior piece as they are being wrapped and twisted along the contour.

by KCStudly » 23 Apr 2014, 16:24
The answer is yes, but more twist and forming along the x-axis (flat way) than longitudinally bending along the y-axis (hard way).

Thanks KC,

That confirms my long held suspicion.

I studied sailboat boat building in my fascination in the '60s with the America's Cup after Life Magazine had articles on those beautiful boats. In those days, the boats were made with (relatively) wide planks which were tapered on the ends over frames. The planks could basically bend in only one plane. Now, the 'Cup boats are molded from carbon fiber in female molds. Expensive. Not that they were ever inexpensive!

-- Teri

Back to foam kerfing.
But before I ask my question/make my suggestion, I want to say this is my first post. I found this place by accident while researching building my own camper and I was immediately stricken with foamy fever.

Now on to my question/suggestion. Would a solder gun or wood burning gun (the hand tool you use to burn letters into wood) run at a good temperature to kerf foam?

Both seem to run at round 800 - 900 deg F, or thereabouts from what I've found on the internet.

If that is too hot, you can buy or build regulators to adjust the heat output. http://pcbheaven.com/projectpages/Homem ... ic=worklog

I haven't seen a recommended heat for burning through foam without setting things on fire, if thats even possible.

Steve, not only that , but a solder Gun could be fitted with a special tip that would cut triangular shaped kerfs, which fit better ... Good ventilation is required ...

steveonzakon wrote:Now on to my question/suggestion. Would a solder gun or wood burning gun (the hand tool you use to burn letters into wood) run at a good temperature to kerf foam?

Both seem to run at round 800 - 900 deg F, or thereabouts from what I've found on the internet.

If that is too hot, you can buy or build regulators to adjust the heat output. http://pcbheaven.com/projectpages/Homem ... ic=worklog

I haven't seen a recommended heat for burning through foam without setting things on fire, if thats even possible.

The issue is not how hot it can get but how quickly it can recover as it cuts. You would need at a minimum a pistol grip soldering gun of around 180 watts or this.

http://www.harborfreight.com/130-watt-h ... 60313.html

We really must further investigate Heat Bending foam , eliminating the need for kerf cuts entirely ... It really is possible ... 190F degrees is the magic number...

GPW wrote:We really must further investigate Heat Bending foam , eliminating the need for kerf cuts entirely ... It really is possible ... 190F degrees is the magic number...

I think the foam's insulating properties would make it difficult. You need it to get to 190F inside the foam while making sure the outside of the foam doesn't get any hotter. It may work for 1/2" but not the 1" or more that you would want to use.

If you could do this you then have to deal with the issue that the outside of the curve has to expand while the inside has to shrink. I'm pretty sure it would buckle, tear or fold before you could get a good bend. I think its just too soft. You would have to use various tricks that wood benders use like a metal backing strip but over 4 or 5 feet.

Also you would probably crush the foam as you tried to manipulate it.

I think in the end what would happen is that the middle will bend less than the outside.

I just don't know maybe you could do it like glass. A big oven, a mould and slow heat. Like this.

https://www.youtube.com/watch?v=HDR7kwPdiQg

I didn't examine all the responses in detail, but can add some "rule of thumb" calculations from kerf-bending wood.

You make a sample kerf the distance from the end equal to your radius. Bend the piece up to close the kerf. The distance that the end if off the plane is the distance between kerfs. No math, no trig.



Details here: http://www.shopsmith.com/academy/tblsaw_spops/index.htm

Thanks! That's more my speed...

I have a spreadsheet that does all the math for you if you want to give it a try I could share it. It's not well documented at this point but I would be glad to clean it up some next week.

https://docs.google.com/spreadsheets/d/ ... Hs/pubhtml

I don't kow what would be easier, but it seems a drywall router might work really well also. Not just for kerfs, but throughout for foam cuts.
Of course, that's just thinking, and I'm really not that good at it.