Maxi Alpha 3, Red Flare and broken fins tabs.

[RickGr4]

Rocketry Friends,

After quite a few successful flights, it seems like I break a fin tab just about every time I launch one of these rockets. I have added glue with very limited success. One of my MAIII's has a 24" chute with a bleed hole, the other has an 18" chute without a bleed hole. Both of my Red Flares have 18" chutes without bleed holes.

Are they simply landing too hard/fast?
Are the fin cans and fin tabs really that weak?
Has anyone come up with a reliable and long term solution?
If you are adding glue to the fin tabs, what type are you using? I have not tried epoxy yet and I suspect that is a big part of my problem.

TIA,
Rick

 

[ThirstyBarbarian]

Yep. The best success I've had has been with epoxy. Sand all the existing glue and paint off the fin root and up the fin a bit for the fillet. Rough up the cardboard. Maybe add a few very shallow slices with the xacto in both the cardboard and the plastic fin so the glue has something to bite into. Then use epoxy to create a fillet. It easiest to do it when you first build the rocket, but you can do it after the fact with a little work. The fin tab is just a very weak design and very prone to breaking, so the fin needs to be securely attached all along the root edge, and a fillet that wraps up over the little lip on the root edge really helps. I like the MAIII and have built a lot of them, but the materials leave something to be desired.

 

[Rex R]

put a pillow where the rockets land .
Rex

 

[RickGr4]

I wish I could. I fly on soccer fields which are watered and maintained. I am not sure that I can find a softer "pillow".

put a pillow where the rockets land .
Rex

 

[RickGr4]

Yep. The best success I've had has been with epoxy. Sand all the existing glue and paint off the fin root and up the fin a bit for the fillet. Rough up the cardboard. Maybe add a few very shallow slices with the xacto in both the cardboard and the plastic fin so the glue has something to bite into. Then use epoxy to create a fillet. It easiest to do it when you first build the rocket, but you can do it after the fact with a little work. The fin tab is just a very weak design and very prone to breaking, so the fin needs to be securely attached all along the root edge, and a fillet that wraps up over the little lip on the root edge really helps. I like the MAIII and have built a lot of them, but the materials leave something to be desired.

Mr Barbarian,

Today I grabbed one of my Red Flare's, striped off the old glue and glued the fins back down with epoxy. I am encouraged by the results.

I am going to build another MAIII soon and I plan to follow your suggestions.

Thank you for your input.

RG

 

[Woody's Workshop]

Just a suggestion, order parts and scratch build a MAIII and use 1/8" ply fins with TTW construction. Order a kit if you like for decals.
You can also get Open Rocket for free and draw it and print out full size fin patterns to cut out your fins.
Once you do a scratch build, things start to come together a whole lot better having a better understanding of stress on a rocket.

 

[RickGr4]

I am getting there.

As of this morning I now have two MAIII's where a fin broke clean off. I am not exactly sure if or how I am going to fix them but TTW construction sounds like the long term solution.

Just a suggestion, order parts and scratch build a MAIII and use 1/8" ply fins with TTW construction. Order a kit if you like for decals. You can also get Open Rocket for free and draw it and print out full size fin patterns to cut out your fins.
Once you do a scratch build, things start to come together a whole lot better having a better understanding of stress on a rocket.