Der Red Max

[Dad of Sapling]

Finished my first Red Max. I learned a couple of lessons. First papering the fins is a pain to get them smooth and I think they added more weight than I realized. According to open rocket my CG has shifted 2cm. Guess I need to add some nose weight. I think I may go back to sanding sealer. Second is to double check that the fins are perfectly parallel to the body. One of the fins ended up slightly off. I guess I put too much blind trust in the fin jig. Overall I'm happy with the results and can't wait to launch next weekend. So what to build next?

 

[K'Tesh]

My method of papering is documented here: https://www.rocketryforum.com/threads/papering-balsa-ply-fins-a-foolproof-method.65628/

It's really easy, and likely doesn't add a ton of weight.

 

[Huxter]

So what to build next?

How 'bout a Der Big Red Max!?



I'm trying to work up the courage to paper these fins, but have never tried. Thanks K'Tesh, I'll try it your way!

 

[Dad of Sapling]

My method of papering is documented here: https://www.rocketryforum.com/threads/papering-balsa-ply-fins-a-foolproof-method.65628/

It's really easy, and likely doesn't add a ton of weight.

Funny. I just happened to stumble across your papering post while I was checking out all of your wonderful open rocket files when you replied. I'm going to give it a try on the next build. As a side note, thank you for all of the files. As someone who is just starting out they have really helped me understand more about design and has inspired me to start thinking about my first scratch build.

 

[Dad of Sapling]

How 'bout a Der Big Red Max!?

View attachment 508970

I'm trying to work up the courage to paper these fins, but have never tried. Thanks K'Tesh, I'll try it your way!

This is definitely on the short list.

 

[tsmith1315]

This is definitely on the short list.

If you're not already, watch this thread and you may be able to get one at a price you can't resist:

https://www.rocketryforum.com/threads/21-99-der-big-red-max-kit-on-amazon.171244/

 

[Scott_650]

Finished my first Red Max. I learned a couple of lessons. First papering the fins is a pain to get them smooth and I think they added more weight than I realized. According to open rocket my CG has shifted 2cm. Guess I need to add some nose weight. I think I may go back to sanding sealer. Second is to double check that the fins are perfectly parallel to the body. One of the fins ended up slightly off. I guess I put too much blind trust in the fin jig. Overall I'm happy with the results and can't wait to launch next weekend. So what to build next?

My built with the kit parts plus papered fins DRM goes up perfectly straight with no added nose weight - the additional weight from the papered fins had no effect on performance. I do wish I’d redlined it with a 24mm motor mount just to have a bit more flexibility in motor choices though - then I definitely would’ve added some nose weight

 

[Dad of Sapling]

My built with the kit parts plus papered fins DRM goes up perfectly straight with no added nose weight - the additional weight from the papered fins had no effect on performance. I do wish I’d redlined it with a 24mm motor mount just to have a bit more flexibility in motor choices though - then I definitely would’ve added some nose weight

As I worked on it this morning I discovered the CG shifted more like 5cm which narrows the distance between CG and CP to 4cm rather than 9

 

[DigBaddy]

My built with the kit parts plus papered fins DRM goes up perfectly straight with no added nose weight - the additional weight from the papered fins had no effect on performance. I do wish I’d redlined it with a 24mm motor mount just to have a bit more flexibility in motor choices though - then I definitely would’ve added some nose weight

No nose weight in my DRM with a 24mm mount. Haven't tried a D12 yet, but C11 still flies perfectly.

 

[Scott_650]

As I worked on it this morning I discovered the CG shifted more like 5cm which narrows the distance between CG and CP to 4cm rather than 9

I chimed in on your other thread about adding n/w - as long as the added weight doesn’t push the stability factor past the original design it’s not going hurt anything though it might not go quite as high. Way overstable rockets can really take off in a big arc into the wind (weathercock) on a breezy day, which isn’t a problem as long as you know it’s going to do it. The DRM is a very forgiving design - folks have stretched it, shortened it, added stages…it just seems to keep doing it’s thing…

 

[K'Tesh]

Funny. I just happened to stumble across your papering post while I was checking out all of your wonderful open rocket files when you replied. I'm going to give it a try on the next build. As a side note, thank you for all of the files. As someone who is just starting out they have really helped me understand more about design and has inspired me to start thinking about my first scratch build.

Glad to be of service!

Pointy Side Up!

 

[EvryThngIsAOk]

Build a GOBLIN OR TWO

 

[dpower]

Looks great! I've found a smooth finish is easier with sanding sealer & primer too, but papering certainly adds strength, and is less effort. If you find you want more altitude, try the 18mm Q-Jets, C12/C18/D16/D20.

 

[Dad of Sapling]

My method of papering is documented here: https://www.rocketryforum.com/threads/papering-balsa-ply-fins-a-foolproof-method.65628/

It's really easy, and likely doesn't add a ton of weight.

I tried this method this afternoon on a set of fins for my latest project. It worked great and was easy. Thanks for the tip.

 

[K'Tesh]

I tried this method this afternoon on a set of fins for my latest project. It worked great and was easy. Thanks for the tip.

Glad I could help!

Now remember this... If the paper "bubbles up" when you apply your primer, don't panic. Let it dry (w/o peeling it off). then *TRY* to find the bubble after the paint has dried.

 

[icyclops]

Finished my first Red Max. I learned a couple of lessons. First papering the fins is a pain to get them smooth and I think they added more weight than I realized. According to open rocket my CG has shifted 2cm. Guess I need to add some nose weight. I think I may go back to sanding sealer. Second is to double check that the fins are perfectly parallel to the body. One of the fins ended up slightly off. I guess I put too much blind trust in the fin jig. Overall I'm happy with the results and can't wait to launch next weekend. So what to build next?

Sorry you had so much trouble with papering the fins….next time use Spraymount 77 spray adhesive by 3M. Takes me about 10 minutes to spray, paper, trim both sides of the fins (do them all at once). That’s the trick. Use bond to cover stock and it will be so smooth and save tons of time from sealer, sanding…

 

[Dad of Sapling]

Glad I could help!

Now remember this... If the paper "bubbles up" when you apply your primer, don't panic. Let it dry (w/o peeling it off). then *TRY* to find the bubble after the paint has dried.

Don't Panic, words to live by.

 

[4regt4]

Glad I could help!

Now remember this... If the paper "bubbles up" when you apply your primer, don't panic. Let it dry (w/o peeling it off). then *TRY* to find the bubble after the paint has dried.

Just primered my first papered fins using the Elmer's general purpose glue stick. Several fins bubbled/de-laminated. And after 24hr dry time, I still have noticeable large bubbles. They didn't settle down.

Experimentally, I coated a scrap of balsa with Duplicolor Primer FILLER. 3 heavy coats, not sanding between, and they sanded out glassy smooth after a lengthy dry time . I think that is going to be my go-to going forward.

Hans.

 

[OverTheTop]

I papered fins for a DBRM recently. I took a sheet of copier paper and put a line of white glue on it. I spread that evenly across the target area using a wide scraper tool that plasterers use when joining drywall (I had one laying around). Placed balsa on that. Butter up another sheet and place it on top. Smooth out all air bubbles then place a sheet of baking paper around the lot and put it between two very flat wall tiles I have for this purpose. Allow to dry overnight, then remove carefully, trim and allow to completely dry (not much air circulation when sandwiched between tiles, but the moisture absorbs into the balsa somewhat).

I think the trick is to have a blade wide enough to smooth the glue in one go. Multiple passes with a narrow blade only caused me ridges.

YMMV. I don't paper fins often so don't rely on my ideas too much

 

[4regt4]

I liked the result using the primer/filler as a complete solution, especially since it was quick and didn't warp the wood. And you only sand once, as opposed to potentially sanding between coats of dope or wood filler.

Oh, I also applied the primer/filler to the whole balsa sheet, not separating out the fins. Then bulk sanded the bunch. Then separate, contour the edges, CA the edges, sand, done. I masked off about 1/8" on the root edge of each fin while still in the whole sheet, thus leaving pristine wood for the inevitable wood glue to the body tube. Also a slight smear of wood glue on the ends of the root edge before applying the CA.

But also experimented doing a paper laminate using thick slow cure CA. Paper stuck TOO well. It conformed to the grain of the wood, thus negating the whole purpose of papering. It would work great if you filled the wood, then do the CA/paper laminate. But that completely negates the convenience factor. However, I'm sure it would be very strong.

Hans.

PS: The primer/filler on the body tube totally hides the spiral seam. No need to take the time to fill it.

 

[4regt4]

Just primered my first papered fins using the Elmer's general purpose glue stick. Several fins bubbled/de-laminated. And after 24hr dry time, I still have noticeable large bubbles. They didn't settle down.

Hans.

I have to eat crow.

It's actually not bad with some hot sauce.

With apologies to @K'Tesh, the bubbles finally went away. Here's the blow by blow account:

Shortly after applying the primer, large bubbles appeared. Maybe a half dozen, 3/8" by 1" to 2". Brief panic, but I re-read K'Tesh's original write-up and realized that I needed to give it a rest. After 12 hours, no change. Next day (24 hours), still no change. Now I'm getting rather disappointed. 36 hours, maybe, just maybe some improvement. But this morning, a full 48 hours, the bubbles are gone.

I'm guessing, and this is only a guess, that my very heavy coat of primer/filler saturated the paper. The surface was dry enough to sand well after only a couple of hours, but the paper subsurface must have retained some of the solvent (or whatever...).

Roseanne Roseannadanna (Gilda Radner) said it best. "Never mind".

Hans.

 

[K'Tesh]

I have to eat crow.

It's actually not bad with some hot sauce.

With apologies to @K'Tesh, the bubbles finally went away. Here's the blow by blow account:

Shortly after applying the primer, large bubbles appeared. Maybe a half dozen, 3/8" by 1" to 2". Brief panic, but I re-read K'Tesh's original write-up and realized that I needed to give it a rest. After 12 hours, no change. Next day (24 hours), still no change. Now I'm getting rather disappointed. 36 hours, maybe, just maybe some improvement. But this morning, a full 48 hours, the bubbles are gone.

I'm guessing, and this is only a guess, that my very heavy coat of primer/filler saturated the paper. The surface was dry enough to sand well after only a couple of hours, but the paper subsurface must have retained some of the solvent (or whatever...).

Roseanne Roseannadanna (Gilda Radner) said it best. "Never mind".

Hans.

Ok... I missed your original post about bubbles until now... Sorry about the panic.

Thank you for the follow up. I have edited my post to make this issue more obvious, and to add a wait time, as I hadn't had such a long period with a bubble. I'm glad it turned out for you, and I hope you'll find the results worth the effort.

All The Best!
Jim

 

[4regt4]

Ok... I missed your original post about bubbles until now... Sorry about the panic.

Thank you for the follow up. I have edited my post to make this issue more obvious, and to add a wait time, as I hadn't had such a long period with a bubble. I'm glad it turned out for you, and I hope you'll find the results worth the effort.

All The Best!
Jim

I'm wondering......

Perhaps the solvents in the paint dissolve the glue stick glue. It then no longer adheres until the solvents completely evaporate. It's possible that (if this is the case...) the paper will re-attach itself better than it was originally. Just conjecture. I might experiment with this on a scrap piece of balsa: Attach paper with glue stick. Wait a bit, try to peel a portion just to test adhesion. Then primer, give 48 hours. Try peel test again.

Hans.

 

[bjphoenix]

I've papered fins on my last 4 builds. It's a lot of work and creates a smooth fin but not extremely smooth. I've gotten smoother results in the past with elmers wood filler. I don't paper them to be smooth, I paper them to be strong. I like my rockets to look good but I don't obsess over them because I build them to launch and they get beat up when you launch them, they get beat up laying around in my garage, they get beat up going out to the range in my car.

 

[icyclops]

OMG

 

[Hobie1dog]

papering, wood fillers, wood glue thinned, sanding sealer, finishing resin, Elmers white glue, will it ever end?

 

[K'Tesh]

papering, wood fillers, wood glue thinned, sanding sealer, finishing resin, Elmers white glue, will it ever end?

Not as long as there are options to people on how to build.