Spruce(?) Source

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JAL3

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I am slowly chugging away on my semi scale of the PEPP Aeroshell and have come to a grinding halt looking for the right material.

I need to make a total of 12 trusses to support the aeroshell. My first thought was to get some Plastruct or Evergreen angle sections to make it more like the prototype but an examination of the products revealed that they are not stiff enough, even when the truss members are added.

I've thought about trying to use metal but worry about the weight, my nonexistent metal working skills and can't really find the correct section.

Balsa will not do and basswood has been recommended against.

I have been told that model aricraft spruce would be a good choice and I suppose it would but I don't relish the idea of trying to glue together angle sections. Besides, I have not been able to find any stock like I would like to use. I am thinking 3/32x1/18. I checked aircraftspruce.com but nothing remotely small enough.

Any suggestions as to material or source?
 

MarkII

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What was wrong with basswood? You can get it in a variety of widths and thicknesses for spars, trusses, etc.

Sig has spruce. (The link is a frame pulled from their online store. To go to the site, click here, then click on the "Fly On In" logo, then click on the "Building Supplies" bar on the menu bar on the left side of the page, and then click on "Spruce" and finally click on one of the images that come up to show a product page. Whew! Talk about burying the information!)

Also, this thread provides links to several sources of spruce sticks.

MarkII
 
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SecretSquirrel

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I have real doubts about my ability to uniformly cut the requisite number of pieces. I know I don't have the tools.

Do you have a vector illustration of what you need? I have 1/8" light and 5 ply birch in stock and can cut them.
 
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gpoehlein

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I have real doubts about my ability to uniformly cut the requisite number of pieces. I know I don't have the tools.
Cutting 1/8" ply isn't as bad as you might think. I'f you are planning to cut strips, all you'll need is a metal ruler and a good sharp hobby knife. I recommend the Testor's Model Master blades for the Xacto - they are surgical steel, are really sharp and stay sharper longer. Don't try to cut the ply in one swipe - take several shallower cuts to cut it. But it should be tough enough for your purposes. Heck, the thinner stuff (1/64 & 1/32) can even be cut with a good pair of scissors.
 

powderburner

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I am slowly chugging away on my semi scale of the PEPP Aeroshell and have come to a grinding halt looking for the right material.

I have been told that model aricraft spruce would be a good choice and I suppose it would but I don't relish the idea of trying to glue together angle sections. Besides, I have not been able to find any stock like I would like to use. I am thinking 3/32x1/18. I checked aircraftspruce.com but nothing remotely small enough.

Any suggestions as to material or source?
I understand your problem with finding anything like that in the plasi-strut line, or anything else, but....

Isn't 3/32 x1/18 kind of small? I am not sure I have ever seen any spruce cut down to "common" sizes that small. And even if you did find it, it's not going to be terribly strong anyway (in a size that small).

I don't know the details of what you are trying to model but have you taken a look at using some other material or approach to model a framework suitable for model-rocket-powered flight and just using strips of cardboard/balsa/whatever to make a sort of "parasitic" model of the structural details? This is only "thinking out loud" and not based on any actual flight-testing, but I would think that if you fashioned the basic conical shell out of cardstock (maybe even two layers; I mean, who's going to measure it?) and then soaked it with CA or wood hardener it should be tough enough by itself to handle low-power loads. (Or are you going for a bigger motor?) Then you could add truss details to the lower surface....

Or here's another thought: Could you use some 1/16th or 1/8th clear plexiglass to cut out your overall truss shape, and use a sharpie or strips of tape (automotive trim tape?) to mark out a representation of the truss elements? (You did say semi-scale, right?)
 

JAL3

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What was wrong with basswood? You can get it in a variety of widths and thicknesses for spars, trusses, etc.

Sig has spruce. (The link is a frame pulled from their online store. To go to the site, click here, then click on the "Fly On In" logo, then click on the "Building Supplies" bar on the menu bar on the left side of the page, and then click on "Spruce" and finally click on one of the images that come up to show a product page. Whew! Talk about burying the information!)

Also, this thread provides links to several sources of spruce sticks.

MarkII
Thanks for the links. Those would work out better.
 

JAL3

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Do you have a vector illustration of what you need? I have 1/8" light and 5 ply birch in stock and can cut them.
I can generate a vector file in Autocad R13 but don't have any newer than that. I do have Illustrator but am not competent to use is. A former employee did that stuff for me.

Would a .DWG file work?
 

JAL3

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I understand your problem with finding anything like that in the plasi-strut line, or anything else, but....

Isn't 3/32 x1/18 kind of small? I am not sure I have ever seen any spruce cut down to "common" sizes that small. And even if you did find it, it's not going to be terribly strong anyway (in a size that small).

I don't know the details of what you are trying to model but have you taken a look at using some other material or approach to model a framework suitable for model-rocket-powered flight and just using strips of cardboard/balsa/whatever to make a sort of "parasitic" model of the structural details? This is only "thinking out loud" and not based on any actual flight-testing, but I would think that if you fashioned the basic conical shell out of cardstock (maybe even two layers; I mean, who's going to measure it?) and then soaked it with CA or wood hardener it should be tough enough by itself to handle low-power loads. (Or are you going for a bigger motor?) Then you could add truss details to the lower surface....

Or here's another thought: Could you use some 1/16th or 1/8th clear plexiglass to cut out your overall truss shape, and use a sharpie or strips of tape (automotive trim tape?) to mark out a representation of the truss elements? (You did say semi-scale, right?)
It looks like I made a typo.
the depth of the upper and lower cords should have been 1/8 and not 1/18.

It is only a semiscale project but the truss support will be needed. its a 12x cluster and it looks like I may have to add a central 29mm to get enough thrust.

With the trussing of the main chords, I think the thin stuff will be strong enough but will be building several test trusses to see. Even then, they will be larger than scale.

I had not thought of your idea on the clear plastic. I can do that if I must but would rather not.
 

SecretSquirrel

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I can generate a vector file in Autocad R13 but don't have any newer than that. I do have Illustrator but am not competent to use is. A former employee did that stuff for me.

Would a .DWG file work?
If you have Illustrator you can import the .DWG file and save it as an .AI file.

I used to say a DWG file is ok until I started getting them from people and I had to completely recreate some. Email it to me if you want and we can go from there. Take your time, I won't be able to look at it until Monday. I'm off to a Shelby meet this weekend.
 
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JAL3

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If you have Illustrator you can import the .DWG file and save it as an .AI file.

I used to say a DWG file is ok until I started getting them from people and I had to completely recreate some. Email it to me if you want and we can go from there. Take your time, I won't be able to look at it until Monday. I'm off to a Shelby meet this weekend.
Thanks.

I have tried importing DWG into AI and the results look OK but the scaling always comes out screwy. I need to clean up the DWG files a bit and then will give it a try.

I'm in the middle of my busy season so I don't expect I will get it out extremely fast.

Thanks again,
 

MarkII

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The truss work was a really major feature of the PEPP Aeroshell, so I can fully understand why you would want to model it. And you have already flown a version of it with just the outer shell, right? So for this one you want to get serious.

MarkII
 

JAL3

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The truss work was a really major feature of the PEPP Aeroshell, so I can fully understand why you would want to model it. And you have already flown a version of it with just the outer shell, right? So for this one you want to get serious.

MarkII
The closest thing I have flown to this is an Applewhite saucer...a much smaller one.
 

aerospike

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In CAD draw a box of known size around your parts, then export as a eps and open in Illustrator. Then using the 'transform' tool in illustrator scale the box to the correct size, then delete the box. What's the file for, laser cutting??
 

JAL3

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In CAD draw a box of known size around your parts, then export as a eps and open in Illustrator. Then using the 'transform' tool in illustrator scale the box to the correct size, then delete the box. What's the file for, laser cutting??
This is where I really show my ignorance with AI. In the past I have been able to get through all the steps you mention right up to importing into AI. The scale is always off and that is where I get hung. Until I read this, I did not know of the existence of the transform tool.

AI is a package that I had because it rarely comes in handy, was bundled with other software that I do use and I have been able to put off learning it because I formerly had a guy working for me who could do what I needed done. He no longer works for me.:(
 
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