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WiredGoat

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Hello all, I'm a BAR that just got back into the hobby. Like most of you, I did this as a kid with low power Estes rockets. So now I'm putting
together a MDRM and have a question about the fins. I built them up using CA (should have used epoxy), but I'm going to keep this one
mid-power so it shouldn't be a problem. But I was wondering if I should use wood hardener on the fins, or just leave them as is?
 

DAllen

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Hello all, I'm a BAR that just got back into the hobby. Like most of you, I did this as a kid with low power Estes rockets. So now I'm putting
together a MDRM and have a question about the fins. I built them up using CA (should have used epoxy), but I'm going to keep this one
mid-power so it shouldn't be a problem. But I was wondering if I should use wood hardener on the fins, or just leave them as is?
You can do either. Flight stresses are not going to be the issue for a rocket like that - handling between flights is. If you're pretty good about being gentle with your rockets leave well enough alone. If you're like me and throw a bunch of rockets into a box when cruising out to the launch site then yeah, a little extra reinforcement is not a bad idea. Just keep an eye on CP/CG as you add stuff to the fins but I really doubt a little bit of wood hardener is going to make a significant difference.

-Dave
 

KenECoyote

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Hello all, I'm a BAR that just got back into the hobby. Like most of you, I did this as a kid with low power Estes rockets. So now I'm putting
together a MDRM and have a question about the fins. I built them up using CA (should have used epoxy), but I'm going to keep this one
mid-power so it shouldn't be a problem. But I was wondering if I should use wood hardener on the fins, or just leave them as is?
I don't think you need to add the hardener. I flew mine plenty of times without issue and it's finally showing some stress on the fillets due to all the hard landings, but the fins are fine (took a look to check and correction...they look great!). Also note that there may be a greater chance of warpage if you add extra wet stuff to the surface of the fins.

Note that I'm one who normally uses label paper to paper all my wood fins (makes them both smoother and stronger), but in this case the fins were so big and they sanded so smooth that I skipped covering them and went straight to primer and paint. You'll love the MDRM...likely my favorite flier and everyone likes it too.
 

KenECoyote

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Also welcome back to the hobby! You'll feel like a kid in a candy store with all the new goodies available now. :drool:
 

WiredGoat

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Also welcome back to the hobby! You'll feel like a kid in a candy store with all the new goodies available now. :drool:
I know! I ended up buying 4 MDRM kits and a whole bunch of other stuff and I haven't launched a single one yet! LOL
I can't wait to start on the G-Force and LOC 4 kits, but I want to make sure I do them right so I'm going to wait a little while
and read up on build techniques, etc.
 

samb

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Welcome back to the party, WiredGoat ! The DARS crew has launches scheduled on the next couple of weekends. www.dars.org Come on out whether you have any Mega Max's ready or not.


Two suggestions for 4 inch models:


1010 rail buttons instead of launch lugs. Eliminates the chance of rod whip for the bigger, heavier rockets.

1010 rail.JPG

Lots of vendors online. One fine choice: https://rail-buttons.com/1010delrin.html



Internal fillets for models with through the wall fin tabs add strength with little weight penalty. Alter the build instruction sequence to make the aft centering ring removable, allowing access to the fin tab/motor mount tube joint.

mega max intfil 1.jpg

mega max intfil 2.jpg

mega max intfil 3.png
 
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WiredGoat

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I've already joined NAR and have my card, so I should be all set to launch something. I actually live in Rockwall, so I'm real close to Sabine Creek, and within
minutes of Caddo Mills airport. I also have friends near Gunter, so I should be at some of the launches coming up this year. I started on the MDRM before reading
about internal fillets on the fins, so I will have to leave this one as a mid-power only rocket. But the next one I do will definitely be done with internal fillets. Right
now I'm doing the external fillets and then launch lugs, again because the MMT is already epoxied in.
 

ThirstyBarbarian

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If you want, you can always do lugs AND rail guides. If you feel like adding rail buttons after the motor mount is glued in place is not practical, you can glue conformal rail guides directly to the body tube. Or just use the lugs this time and put buttons on the next one...

What motors are you going to use? It can fly pretty well on Aerotech Single-Use G motors. G77 Red, G78 Green, G79 White, G80 Blue all would work great. If it's calm, I think a G40 White would be OK for a slower flight. Not sure about G38 Black.
 

K'Tesh

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Also, with some careful drilling and using some 30 minute epoxy, you could still do internal fillets. Though it would be hard to judge when the fillet has just enough to complete the joint, and not over-do it.
 

WiredGoat

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I bought a few Aerotech single use motors already. 2- G40-7W, 1- G79-7W, and 1- RMS G76-10G and a motor case. I need to look into
the conformal rail guides for this build. Is it not too late to do rail buttons? I think I'll still do lugs on this one just for the versatility. I also
picked up a JLCR and JLAlt2 and can't wait to use them.
 

WiredGoat

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I also have a Pro Series Majestic the G40-7W's will fit in.
 

Donaldsrockets

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The G40W will work fine in the MDRM. The maiden flight of mine was on a G40-7W. However I would only use this motor on a fairly calm day.:wink:

If it is rather breezy, I would use something with a bit more thrust like the G80-7T.
 

wighty44

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My MDRM EX was just finished yesterday - NC painted: CF BT, 54mm MMT; CF composite fins (1/8" thk); with the NC opened to allow more recovery device room. It will take motors from 29 to 54mm (5 grain).

MDRM EX _Comp_011317a.jpg
 

ThirstyBarbarian

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I bought a few Aerotech single use motors already. 2- G40-7W, 1- G79-7W, and 1- RMS G76-10G and a motor case. I need to look into
the conformal rail guides for this build. Is it not too late to do rail buttons? I think I'll still do lugs on this one just for the versatility. I also
picked up a JLCR and JLAlt2 and can't wait to use them.
Those will be nice motors. I'd use the G40's on a calm day and a long rail. The MDRM has a lot of drag, so it's a slow, majestic flyer. The G40 works great for that kind of flight, but it could be slow off the rail, so you want calm conditions to be sure it goes off straight.

I got my conformal guides from Giant Leap. https://www.giantleaprocketry.com/p...nch_systems.aspx#Acme_Conformal_Launch_Guides

If you wanted to still use buttons instead of guides, I think there are fasteners you can use. Or you can also cut two small pieces of wood and sand then to the inside radius of the body tube. Then glue one inside the tube above the forward centering ring and one at the bottom of the rocket behind the aft centering ring. And screw the screws for the buttons into those.
 

WiredGoat

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My MDRM EX was just finished yesterday - NC painted: CF BT, 54mm MMT; CF composite fins (1/8" thk); with the NC opened to allow more recovery device room. It will take motors from 29 to 54mm (5 grain).
Nice job! Hope you can catch some video of it on its maiden flight.
 

hobie1dog

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My MDRM EX was just finished yesterday - NC painted: CF BT, 54mm MMT; CF composite fins (1/8" thk); with the NC opened to allow more recovery device room. It will take motors from 29 to 54mm (5 grain).
Where did you get your material for the composite fins? Looks great btw.
 

wighty44

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Where did you get your material for the composite fins? Looks great btw.
It was my own design that began with a 1/8" G10 FG sheet cut to the original fin shape. Next I cut out 3 FG internal sections similar to the open areas of the kit's fins - only slightly bigger. Then 1/8" balsa inserts were fit inside those cutouts and any gaps filled with wood filler. The last step was the application of a CF overlay on both sides of each fin. The CF came from an eBay vendor.

As follows:

MDRM_Fin Mod_04.jpg
 

WiredGoat

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What kind of lifespan should I expect out of the plastic motor retainer?
 

dhbarr

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What kind of lifespan should I expect out of the plastic motor retainer?
Never seen the tube part damaged, but the ring can get a bit toasted. The 2pk is dirt cheap from most vendors, so a few spare rings runs pretty cheap.
 

TangoJuliet

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I maidened mine this past Saturday with a G40-7. Light/calm winds on 1/4 rod. There was a decent amount of rod whip, but I also had about 15 degrees of tilt in the pad. It was a beautiful flight, even though it went a little further down range than I anticipated. It landed upright in tall grass. The next flight will be on a G80-7!
 

WiredGoat

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IMG_2376.jpg
So this is my next project, turning this flag into a parachute. My MIL has all kinds of sewing equipment, so hopefully I can get her
motivated to sew the edge and the cords in place. The flag is 5x3' so it should make for a nice 36" chute. I think the bottom
bones may get chopped a little, but that's fine.
 

WiredGoat

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IMG_4256.jpgNot sure why this is loading upside down, but here it is. Hope this works out!
 

samb

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That looks cool. And getting your mother-in-law involved in your hobby is very cool !

jolly roger.jpg

This process works for me:

- take picture
- load it into your favorite graphics program, I used MS Paint
- rotate to the left
- rotate to the right
- get it oriented the way you want it
- save
- upload to TRF

And most important...

Keep Your Funky Toes Out of The Picture ! :wink:
 

Cl(VII)

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And most important...

Keep Your Funky Toes Out of The Picture ! :wink:
Don't listen to him. My toes are a staple in all of my build threads, they provide scale perspective...yeah, that's it. The only proper way to build rockets is bare foot...like the cave men did it!

Also, the MDRM flies great on an I200W..just sayin.

 
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WiredGoat

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I did try rotating the pic a few times, and it kept on putting it upside down. Not sure why. Also, the MIL is the one whose toes are in the pic.
I think she used a potato camera. I asked her if she wanted to get into the parachute building business and she politely declined. Oh well, I have 3 more
MDRM kits to build, so I need at least 3 more flags if this prototype works. The next build will probably have a 38mm MMT. That would be a lot of fun!
 

WiredGoat

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No worries. And you'll never see my funky toes in flip flops. LOL
 
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