Still even another after dozens of Der Red Max question.

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Kelley

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Hi all. Living in Germany these days and have been using the metric system for a while. Using 3mm balsa and not 1/8 inch, and I do a lot of conversions. Anyway the question now is, anyone have the angle of the root edge and the leading edge of Der Red Max fins? I have the dimensions and can get the other angles worked out (Other two are 90 ( I think) and the trailing edge to root I can figure out. I just don't trust printing and measuring or trying to measure off of the screen. If someone has those figures handy or can slap a protractor on the plans, I would appreciate it very much.
 

Kelley

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I have a nosecone from an old busted up Hawk. I just need to get the motor guts and a new bodytube from Holland. I am itching to start.
 

Kelley

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I am thinking backwards again. I just have to work it out the other way and Ill have the answer. (DUH) Oh the cobwebs you get at 53 . But looking at the picture in the link made my mind snap back. Thanks again!
 

Kelley

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Spoke too soon math ain't jiving. :sigh:
 

Kelley

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IMG_1663.jpgI am not a math guy, I am not a computer guy. but I got the numbers to fit by getting the 2 1/2 inches measured on the one 90 degrees angles then measured off the other two off of the ends and connected them all. I guess this is all rocket science :/
 

Swissyhawk

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Did you want the angles in metric or English?

I measured off my built MDRM with a protractor. It may not be the most accurate, but here is what I got.

Leading edge sweep (body tube to leading edge) - 120 degrees
Trailing edge sweep (body tube to trailing edge) - 115 degrees
Angle between the leading edge and the outside fin edge - 95 degrees
Angle between the trailing edge and the outside fin edge - 90 degrees

Take it for what its worth.
 

K'Tesh

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There are two methods I use to do the fins for my sims. The manual method, and the digital.

Manual:
I take an image of the fin with a ruler (preferably along the root edge), scale it/print it so that the image's ruler matches mine. Next, using a ruler and a protractor I draw a line along the root edge, and connect each point of the fin to it with a line at a right angle. Then I measure the height and and distance of each relative to the point where the leading edge meets the root edge.

Digital:
Take an image of the sim with a ruler, and crop out all of the "not fin" by making it white, and change the fin's color to black (I do clean up the image as best I can), making sure the root edge is even with the bottom of the image. I import the resulting image in OR, then scale the results to match a known dimension (usually the root edge, but sometimes the height (when the root edge isn't straight)), and eliminate any odd artifacts (points) that are created by the process.

My DRM fins were based on a digital image. I still have the black and white image I used for it.

Der Big Red Max (1977) Fin templates.png

I had to convert this from the .bmp image I used to a format the forum can display. It was derived from an image of the DBRM fins I found on one of the online archives. The DBRM uses the same fin, and is basically the same kit, but with an 18" body tube.
 
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bradycros

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Hi all. Living in Germany these days and have been using the metric system for a while. Using 3mm balsa and not 1/8 inch, and I do a lot of conversions. Anyway the question now is, anyone have the angle of the root edge and the leading edge of Der Red Max fins? I have the dimensions and can get the other angles worked out (Other two are 90 ( I think) and the trailing edge to root I can figure out. I just don't trust printing and measuring or trying to measure off of the screen. If someone has those figures handy or can slap a protractor on the plans, I would appreciate it very much.
I use a hand drawn method. No angle measurements need to be take with this method, they just make themselves.

If your interested I could show you how to do it.
 

Kelley

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Thanks. I had it figured out by doing the manual method. I just needed to take a breath and think about it. Thanks for all the info. Good quick reference. IMG_1664.jpg
 

Kelley

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I ordered what I thought would be a dandy body tube from Klima. It is WAY thicker than an Estes tube and no way can a an Estes plastic nose cone fit :( I will have to try someplace else it looks like. Right now the Euro is close to the British Pound and it is worth it to order stuff from England, and I have not hassles with the post and customs. Temporary setback. I have the fins sealed and have put on the first coat of primer.
 

K'Tesh

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I'd be afraid that sealing fins/painting fins before gluing them to the body tube could fill pores that would strengthen the bond with the body tube. Thus, making them more prone to snap off. Instead, I paper mine, and haven't had any problems with fins coming off (being damaged from falls/things being dropped on them, but not coming off). Of course, if you use the double glue method, you might be able to protect some of that bonding strength (but still weaken it at the filleting stage).

If you're interested in learning more about papering... May I suggest this tutorial:

https://www.rocketryforum.com/showthread.php?65628-Papering-balsa-ply-Fins-A-foolproof-method

The double glue method is demonstrated beginning around the 3:24 mark
[video=youtube;77hOlPvUlro]https://www.youtube.com/watch?v=77hOlPvUlro[/video]
 
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Kelley

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I picked up a little Yankee the other day and papered the fins. Boy are they slick. I used a good German glue stick but I noticed that the on a couple of places when the fins were wet from the primer and later the paint, that there was some bubbles. I pressed them down as soon as the paint was dry enough. I hope they hold up when flying. I will try white glue next time I try skinning. The fins I cut for der Red Max and primed and sand keep warping slightly, even after being under books. I have plenty of balsa and will try and skin those. I have the body tubes coming in from the Netherlands, and I broke down and actually ordered der Red Max kit. (You can't have too many!) I hope it has the skull parachute, there is a lot of new old stock over here and the rockets I am picking up still have the nice colored chutes. Oh besides the Yankee I picked up a Baby Bertha, a Hi Flyer, and 2 Metalizers pretty cheap (all with the colored chutes). So, I will cut out some more fins and try skinning them. Thanks again for all the help!
 

Rex R

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what causes most warpage is uneven drying, you want both sides to dry at about the same rate, to the same moisture content. I use a wire cooling rack(baking) to let my fins dry.
Rex
 

Kelley

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I just got my Der Red Max from the Netherlands! Nice big skull and crossbones parachute too. I am looking at the nice laser cut fins and see that the balsa is kind of shabby and is warped from the get go, and looks like they would split just looking at it. But between the templates you guys sent and just being able to trace off of these fins, I should be OK with new balsa. I got a bunch of tubes (something for a later discussion) and I failed to get any long enough to go with the old Hawk nosecone I have, in order to make a clone. I am waiting for some Elmers pore filler and I got some German dope smelling kind I tried. Ill just make enough fins until something turns out right. IMG_1692.jpg
 
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