Beginner question on the MAXI ALPHA III

[Sherwin]

Hello, my son and I are going to build the maxi alpha 3, I've read that the fins are quite brittle and want to know if there is a way to make them stronger or reinforce them. I understand fillets will help secure them better to the rocket body, but want to reinforce the rest of the fin. I know this is overkill but would wrapping the entire rocket in fiberglass be a bad thing? I'm not worried about how high it goes, just want something that will last a good long time. In hindsight I should have bought a little beefier kit but this is what I have, besides I don't mind using this rocket as a way to learn some new things.

Background, I am in my forties and built/flew some of the Estes kits back in my younger days. I came across one of my old rockets and thought the kids might enjoy getting into the hobby, so bought the Estes Rascal & Hijinks ready to fly set and we've had a blast with them. I now have the maxi alpha 3 and decided it would be fun to try some different things with the build, like coming up with our own paint scheme, and making it a bit more sturdy. I would like my son to be able to hang on to it for years, kind of a symbolic bonding type thing, would be nice if it flies somewhat decent too. For future builds I plan to keep it simple, stick to the directions etc, but with the maxi alpha three I am more interested in having fun with the build and experimenting a bit.

I realize I may be coming off sounding like a complete goof. Thank you for any advice or comments you care to offer.

Sherwin

 

[paul.nortness]

Fiberglass is going to make that rocket WAY too heavy for black powder Ds and Es. At that point, it isn't a matter of going high it would be a matter of getting off the pad entirely.


In my experience with the MA3, it isn't the fins themselves that break, it's that the fins like to pop off at landing.

 

[Tarasdad]

Looking at the rocket it seems to me that having the fins pop off might actually be the lesser of two weevils (sorry, couldn't resist! ) in a way. Constantly having to repair broken fins seems as if it would stand a better chance of adding weight that would cause lateral balance issues. The fin design appears to be fragility, especially extending as far below the body as they do. Maybe paper lamination?

 

[DavidQ]

My feeling on the Maxi Alpha 3 is to make sure that the fins are attached to the short section of body tube. They're plastic fins, and are pretty resilient. It's the joints that I think are the weak link. I mean, if you had an upscaled Alpha 3 with the complete plastic fin canister, it wouldn't look like a great idea to reinforce those fins.

Oh, and make sure that the parachute is in working order. The fins are the the first to touch down, so landing slowly is a good thing.

 

[paul.nortness]

Another thing you could do is ditch the plastic fins and mounts entirely, go over to Semroc and order a pair of balsa Maxi Alpha fins and epoxy them on if strength is that much of a concern.

 

[windwater]

You could paper skin the fins.

Apogee has a nice video explaining how to do this:
https://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_16

 

[gpoehlein]

One caveat - DON'T fly the Maxi Alpha III on the new E12 motors. I tried it Saturday and the rocket wobbled and spun all the way up. The fins are so thin that I think the E12's higher thrust was causing fin flutter. It flies great on D12s and E9s, so stick to them.

 

[FastCargo]

The fin joint is the weak area of the assembly. So things like papering aren't going to help. The suggestions of using a different tube and fin material, as well as maybe a bigger parachute for a softer landing are good ones.

I'm also a fan of the "break away" method if it is possible. On my Interceptor and Interceptor-E models, the wing pods are friction fitted in position. If on landing, the rocket comes down on one of the pods, instead of snapping off, or worse, transferring the shock to the wing and damaging it, the pod just slides off. You may want to consider something similar if it's possible.

Finally, if it is possible, you could set up the rocket to use rear ejection, so the rocket parachutes down nose first, absorbing the shock of landing first instead of the fins.

FC

 

[Tarasdad]

Didn't notice that the fins were plastic - serves me right for posting when I'm half asleep! After looking at the kit instructions I can see where it could be very easy for them to pop off on impact. If I were building one I'd be tempted to use a small bit of epoxy to attach the fins to the lower tube and fin mounting rings. A small amount, carefully applied, would add negligible weight. Another option would be medium or thick CA. Either adhesive type would require the root edge of the fin to be roughened to give the glue something to grab onto.

(Warning, the following rapidly enters the realm of "excess to the point of major geekiness" - proceed with caution!)

It also makes sense that thin plastic fins would tend to flutter at higher speeds, especially with the shape these have. They depend entirely on the strength of the plastic to provide stiffness and lack any sort of internal structure to add strength. Even balsa fins have the structure of heir fibers to add strength and stiffness. If I were building an RC model with wings or stabilizers shaped this way there would be spars, ribs, shear webs and skins all adding strength. No roo for that in a tiny plastic fin, though.

Hmm...layered carbon fiber with each layer's strands in a different orientation maybe....

 

[JPVegh]

It is what it is. Build it, fly it until it breaks, fix it, fly it until it breaks again then shelve it and scratch build a Maxi Alpha with plywood in all the right places. It's a good flyer but it is not durable.

 

[Sherwin]

Thank you for all the comments and advice. I will do the most reasonable thing, build it, fly it, fix it, etc... In the future I will look into doing a scratch build using some of the advice given here. Also for this rocket I will stay away from the E12's as suggested.

Thank you all very much, this is a great forum!

 

[Sherwin]

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Here are some photos of the Maxi Alpha three on it's third launch, it survived the first two without the chute opening completely. I used Formula 560 for the fillets, the rocket isn't the best looking and didn't fly the straightest, but we had fun and look forward to more launches with this neat rocket. We have a Mega Mosquito in the works as well as a Flutter-By. I also have a second Maxi Alpha three tucked away. Looking forward to more launches, depends on the weather and work schedule. Of course there are a ton of kits I'd love to try. Thanks again for the advice.

 

[rcktnut]

Nice looking rocket, great pictures. Are you using a 3 foot rod for launching? You said you have not been having nice staight flights. A longer launch rod might help. With D-12's and E9's you may not quite have enough velocity off a 3 foot rod for the fins to be doing their job 100% by time the rocket leaves the rod. It will also fly well on E12's, composite E15's 18's F24's etc. Mine did up until lost on a power line.

 

[Sherwin]

I launched using the standard Estes launch pad with the "E" launch rod, the whole set up seemed a bit flimsy for this rocket, next time I will use a longer launch rod. Thanks for the advice.

Sherwin