Slightly different Foam Template

[Tim Thompson]

In 1978 I used single templates, Then in1998 I used 2 piece templates. But 2 piece temps can take many hours to make. So last year I started making a variation of the 1 piece temp.

I run a piece of 1/8 music wire the whole length of the temp plus a couple inches on each end. Then support the temp with blocks that hold the temp in the center of the foam and push " Staples" through the temp and around the wire. The blocks are slightly shorter then the halfway point and shims are used to center them

Use a lot of weight to make sure the foam is absutely flat on the table, put the blocks front and back, put the template where you want it and staple it to the foam. Cut the top, wait a couple of minutes, remove the weights and flip the core end for end. DO NOT remove the bed to see what you just did!. Then replace the weights and slide the blocks under the wires and add shims so that they just touch the wires but do not push them up and cut the new top ( bottom) Wait a couple more minutes and remove the weights and templates. You will have a nice straight wing without twists and a straight trailing edge.

Tim Thompson

[Motorman]

What does the wire follow on the other side of the blank?

MM

[Gerald Arana]

What does the wire follow on the other side of the blank?

MM

Same thing. You need a rib on each end of the foam block. Interesting set up!

Jerry

[Tim Thompson]

Correct Jerry! This core is tapered, so you can see the root is longer then the tip. Each temp has arrows so that the same side is always "up"

In this example the foam is 2 inches thick. The center line is 1 inch and 1/2 of the heavy wire is 1/16 inch. So 1 inch minus 1/16 equals 15/16 inch or .937 inch I made all 4 blocks .937. Positioned the templates and made the cut. Then removed the weights and blocks,being careful not disturb the bed and flipped the core end for end or root for tip.

on this example the other side was exactly .937 of and inch. so I was able to use the blocks as they were. But most of the time the foam will not be exactly 2 inches thick or even the same thickness from one end to the other. This is why I use shims to hold the wires from moving. Since the first cut was set at the exact height , all we have to do is prevent the templates from moving.

BTW, on these cores I was in a hurry and lazy and decided it would be ok to skip setting up the blocks. That decision let me screw up 2 cores before I went back to using the blocks!

Also I hold the bow by hand, because I'm to lazy to set up my drop arm. Years of practice helps here.

Tim Thompson

[Tim Wescott]

Someone told me that if you let the layer of foam between the wire and the air get too thin then the wire cools and the foam doesn't cut consistently.  How do you deal with that issue in this setup?

[Tim Thompson]

Someone told me that if you let the layer of foam between the wire and the air get too thin then the wire cools and the foam doesn't cut consistently.  How do you deal with that issue in this setup?

If I understand the question correctly , you're referring to the thin foam above the high point of the root template?

On this wing the tip is thinner , so the area that is thin is relative small. If I had to cut a constant cord/thickness wing I would use a thicker foam. Getting back to the thin foam. First I use .013 Iconel wire. It holds temperature better for me. Second I cut at a low temperature to start with. Third I use a good quality foam. Just because a foam is of a certain weight, doesn't mean it is good  and possibly  a forth thing is I set my templates back from the leading edge about a half inch. My belief is that the wire has slightly longer time to stabilize its heat, can't prove this but it works for me.

If skinny wire , low heat and good foam don't do it then there is always sanding and spackle !

Tim Thompson

[Motorman]

Where do you get your good foam?


MM

[Tim Thompson]

Where do you get your good foam?


MM

Tough question to answer that gets harder all the time. First of all white beaded Styrofoam is an insulating material, not purpose made for model building. Companies that make have to make a profit while defending against special interest groups and government regulations. More then once I've found a good foam only to have it changed by my supplier. living here in Fresno CA. foam isn't high on a lot of peoples list.

Currently I've been able to get a very nice foam from Home Depot! Up to 2 inches thick. The brand name is " InsulFoam " Thicker foam is bought from a local building supplier. However this foam may or may not be suitable . It's pricey and cannot be returned if it doesn't meet my needs.

I suspect that people on the east coast have an easier time finding foam and pay a heck of a lot less then we do in California. I once paid $ 106 for a 4X8 sheet 3 inches thick. Some of the newer foams are made from plant based materials. They haven't cut for sour apples for me.

So all I can say is try to find some small pieces left over from a building contractor and try it out. Cut a thin slice on a small piece will tell you if its good , then buy some from his supplier.

I know that's not the answer you wanted but that's the way it is here in Fresno.

Tim Thompson