[CLONE] Estes Marauder #1922 - fin questions

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Re-Bar Ricky

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Hello all - it's been awhile since I've been on here but I've gotten a bit of the build bug again. I am working on a clone of one my first rockets, the Estes Marauder #1922. I've gathered donor parts from a couple of other kits, but I have a question on the fins. I pulled up the plans and fin sheet from YORF and printed out the fin sheet. The directions state that when printed, they are at their correct size, but I don't think they are correct. There are two smaller balsa standoffs for the launch lugs and the size in the directions are different from the printed plan sheet.

I am wondering if someone could get me the actual dimensions of the fins? I could take the plans and compare actual size to the printed size, come up with a ratio, multiply and divide a whole bunch of numbers, yada yada yada and come up with a pretty close size for the fins. But if anyone a Marauder on a shelf, a physical and accurate measurement would be awesomely appreciated.

Thanks in advance......Rick
 
Like the OP, when I print the image (including the [EDIT] DEFECTIVE [/EDIT] one from plans.rocketshoppe), I'm not certain of the scale. If someone could post the dimensions of at least one edge (say root), I could verify my printouts and scale from there as needed.

My original Marauder became my 2nd Warp II, so I still have its decals.

Thanks!
Jim
 
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Rick,

Just going on an assumption here but the fin standoffs in the directions say they are 1/4 inch wide. When I printed off the standoffs and fins the standoffs measured 1/2 inch wide. Based on that I would assume that perhaps the fin dimensions should be 1/2 half of what the template prints out as.

Rocketron
 
Sorry my bad on the fin dimension guess. I see the decal set is available at Exclesior Rocketry for $14.

Rocketron
 
Dug out my Marauder's plans, and I found that the stand-off's measurements are given. 1/4" high, 7/8" at the root edge, and 5/8" tip cord.

However without the root edge of the fins, sweep, or the height, I can't calculate the shape of the fins to 100% certainty for my OR file I'm making.
 
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warts and all this is what I came up with. you will have to do a copy/paste from one window to another. enjoy,
Rex

Thanks for that Rex...

Here's what I was able to finish w/your file. I should add that the tapering appearance of the fins is an optical effect created by the software.



Rex's numbers are:

0, 0
1.5, 3
2.625, 2;438
1.375, 0


Nuts... Over on a parallel thread on YORF, I've got another set of numbers from someone...

0, 0
1.448, 3.049
2.577, 2.512
1.384, 0

Rex, was yours computed by math or measurements?

I've uploaded both sets of measurements (YORF's is the *1922a.* version).

When I get to school and can print the files, I'll be able to check the measurements, and make my decision as to which version is likely the most accurate. I suspect that there is a chance that both are accurate due to variations in how the parts were cut and sanded.

Thanks!
Jim



View attachment Estes Marauder #1922.ork

View attachment Estes Marauder #1922 fins.pdf

View attachment Estes Marauder #1922a fins.pdf

View attachment Estes Marauder #1922 a.ork
 
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I used the measurements(from Yorf), a mm difference isn't going to visible once you push the button :). I note that two people got the same measurements.
Rex
 
Thanks everybody who pitched in to help me figure this out. Looks like I can now proceed with my build....off to my LHS to get some fin stock. Thanks again!
 
There's more then one way to get from point A to point B.

Here's how I use a process to get to point B.

Thanks to the pictures in post #six, the fin in question can be reproduced because it is shown in a full profile.

The length of the tip as measured in the picture is 1 1/4 inches (1.250") or 31.75 mm.
The length of the leading edge as measured in the picture is 3 3/8 inches (3.375") or 85.725 mm.
The length of the tailing edge as measured in the picture 2 25/32 inches (2.7812") or 70.64248 mm.

20141124_152111.jpg

20141124_124142.jpg
 
The picture showing the fin, ruler and some of the body tube was selected and printed out twice. One copy will have the ruler cut out of it and the other will be used for measurements and will be drawn on.

IMG_1467.jpg
 
The length of the leading edge as measured in the picture is 3 3/8 inches (3.375") or 85.725 mm.
The length of the tailing edge as measured in the picture 2 25/32 inches (2.7812") or 70.64248 mm.

BC, Unless I'm reading that ruler wrong, I keep coming up with these same (different than yours) measurements.
Leading edge: 3 13/32"
Trailing edge: 2 13/16"

Which is negligible really.

Of course if it were necessary, I could bring the pic into CAD, do a trace & scale until the width of the fin was at 1 1/4", as we both see correctly.
 
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Completely disregard the ruler that's part of the original picture butted up against leading edge.

A line was drawn along the length of the fins root edge and the body tube.

A square was used to place a 90 degree angle where the top of the root edge and the body tube meet. The line made with the square was extended with a straight edge (steel ruler).

A ruler was butted up to the square which was aligned with the line just drawn above the leading edge and another 90 degree line was drawn from the top of the tip and extended down the paper.

The square was again aligned with the line along the root edge and the ruler was butted up to the square. The ruler was place up to the corner of the trailing edge and the tip, after adjustments to ensure everything was square and in alignment the last line was made.

The fin is now enclose in a rectangle that is squared up to the body tube and any measurements needed can be made with the ruler cut out of the other copy.

IMG_1468.jpg

IMG_1469.jpg

IMG_1470.jpg

IMG_1471.jpg

IMG_1472.jpg
 
I just used the measurements given in the link from post number 6.

Since I am not building this rocket I'm not going to be overly critical about such a small fraction. Really, really close will work just fine!
 
Reproduce the rectangle on a piece of card stock using A REAL RULER and the measurements in this picture. Make tiny dots were the corners of the fins need to be (again, use the given measurements) then connect the dots with straight lines. Be aware that these measurement were made using the ruler from the photo, which is using tenths of an inch. Converting to mille meters would work if you don't have a ruler graduated in tenths of an inch.
1 inch = 25.4 mm so 2.54 mm = 1/10 of an inch.

No angles needed to be measured while reconstructing this fin! They made themselves!!

Expand the photo to get a better look at the lines and measurements.

IMG_1473.jpg
 
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Reproduce the rectangle on a piece of card stock using A REAL RULER and the measurements in this picture. Make tiny dots were the corners of the fins need to be (again, use the given measurements) then connect the dots with straight lines. Be aware that these measurement were made using the ruler from the photo, which is using tenths of an inch.

No angles needed to be measured while reconstructing this fin!

Expand the photo to get a better look at the lines and measurements.

Yeah, that negligible difference was only 1/32". I was aware that the original ruler measured in tenths though. Given the the length of all sides (except for the root) it was terribly easy to draw those two lengths in Autocad, and connect them with a 1.25" line for the tip, and draw an angle line for the root. I'm attaching a scaled pdf just in case he decides he wants to use it.

View attachment Marauder Fin.pdf
 
However, since I haven't figured out how to enter values in OR for freeform fins, and be certain they are right, I'm stuck asking for the information.

I'm trying to sim it accurately, then maybe later build it.
 
However, since I haven't figured out how to enter values in OR for freeform fins, and be certain they are right, I'm stuck asking for the information.

I'm trying to sim it accurately, then maybe later build it.

If the given measurements were accurate, my PDF file should be dead on. Just print a template and be done.
 
Reproduce the rectangle on a piece of card stock using A REAL RULER and the measurements in this picture. Make tiny dots were the corners of the fins need to be (again, use the given measurements) then connect the dots with straight lines. Be aware that these measurement were made using the ruler from the photo, which is using tenths of an inch. Converting to mille meters would work if you don't have a ruler graduated in tenths of an inch.
1 inch = 25.4 mm so 2.54 mm = 1/10 of an inch.

No angles needed to be measured while reconstructing this fin! They made themselves!!

Expand the photo to get a better look at the lines and measurements.


The first thing needed to make a scale template of the fin out of card stock is to draw the base line (X line) of the rectangle that was drawn around the fin in the previous posts.

A ruler is used to measure two points 50 mm up from the bottom of the card stock. The two points are connected. This X line is the starting point of reconstructing the entire rectangle. I am converting the original measurements to metric because it is easier to use then decimal.

Expand the photo to get a better look at the lines and measurements

IMG_1475.jpg
 
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Thanks for the info bradycross.

GB, the real reason I'm looking on learning how to figure out how to determine the x,y values for OR is that I have other builds (namely a Der Big Red Max II (two stage)) that I'm trying to sim, and despite all the careful measurements I've made of my own DRM fins (which are identical), and the .rkt files I've found on Rocketreviews, the printouts don't match my fins. I want to make my DBRMII with TTW fins.
 
Thanks for the info bradycros.


Your welcome.

The Y line is next. Do the same thing that was done with the X line, but do it on the left hand side of the sheet of card stock.

The bottom and top lines of the rectangle measure 3.3 inches.
3.3 X25.4 mm = 83.82 mm. I am going to round that up to 84 mm. Who is going to notice a .18 mm difference?

Expand the photo to get a better look at the lines and measurements.

IMG_1476.jpg
 
The sides of the rectangle are next.

The sides measure 2.5 inches.

2.5 in X 25.4 mm = 63.5 mm.

Place a dot at the right spot.

Expand the photo to get a better look at the lines and measurements.

IMG_1477.jpg
 
Use a square to connect the dots.


Expand the photo to get a better look at the lines and measurements.

IMG_1478.jpg

IMG_1479.jpg

IMG_1480.jpg
 
Now the fin can be plotted.

The corner of the Root and Trailing edges measure 1 inch up the Y line.

1" X 25.4 mm = 25.4 mm


Expand the photo to get a better look at the lines and measurements.

IMG_1481.jpg
 
The corner of the leading and tip edges is 1.25 inches below the top line of the rectangle.

1.25" X 25.4 mm = 31.75 mm

You can round up the number to 32 mm or eyeball it for the 31.75 mm when the dot is placed, your call.

Expand the photo to get a better look at the lines and measurements.

IMG_1482.jpg
 
The corner of the tip and trailing edges meet .2 inches inside the rectangle on the right hand side of the X line.

.2 inches X 25.4 = 5.08 mm.

I'll round that down to 5 mm and place a dot to mark this measurement.

Expand the photo to get a better look at the lines and measurements.

IMG_1483.jpg
 
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