Mercury Engineering - RDR 1

[JAL3]

Eventually it drifted over the flight line and into the field behind us. Since this was my last flight of the day, I decided to pack up and pick up the rocket while driving out.

 

[JAL3]

As I drove up it looked like all was well. That was as I expected since everything about the flight seemed positive.

 

[JAL3]

Closer examination, though, showed that 2 of the 3 fins had chunks broken loose on the trailing edges. The fin that was not affected was the one that was coated in epoxy several repairs back.

I was at a loss to explain this based upon what I had seen. I now wonder if it could have been due to fin flutter at speed but I have no experience with this. In any event, I will try to repair it.

 

[TheAviator]

That really doesn't look like flutter to me. When a fin flutters, you usually lose material at the tip. My guess is it just hit something particularly stubborn on landing and was dragged away from the culprit by the time you got there. I have been wrong before, though.

 

[terryg]

The most likely candidate is the nose cone itself. I have had fins damaged when the nose cone rebounds and catches the fins in just the right position to damage them.

 

[JAL3]

I thank y'all for your input. Have no experience with the issue, I'm clueless.

I like the RDR1 but have had a bad feeling about the balsa fins since day 1. I just realized that the last posted photo only shows the damage to one fin. A second fin has similar damage in the analogous place but it is much less severe, being more of a cracking and spliting than what the photo shows.

 

[JAL3]

The last flight of my RDR1 resulted in some more broken balsa on the trailing edges of the fins. While I do not care for the balsa, I do like the rocket and decided to fix it up...again.

 

[JAL3]

The broken pieces seemed to fit back together again well so I dabbed some Titebond II along the edges and pressed the pieces back together.

 

[Handeman]

To me, that looks like transportation damage. Sometimes something will crack the balsa fins and you don't notice it until it's worse after a flight. I had one rocket that came back with half of one fin missing. No pieces around where it landed. It had to have come off during flight and that would only have happened if it had been damage pre-flight.

 

[JAL3]

To me, that looks like transportation damage. Sometimes something will crack the balsa fins and you don't notice it until it's worse after a flight. I had one rocket that came back with half of one fin missing. No pieces around where it landed. It had to have come off during flight and that would only have happened if it had been damage pre-flight.

Interesting idea.

There is one more piece of significant damage not shown yet where a divot was popped out of another fin, not along the edges but centered in the bottom half. I have some pics along the the repair in progress that I will try to get up soon.

In any event, this rocket has performed well but the balsa fins seem to take damage at every outing.

 

[Handeman]

Interesting idea.

There is one more piece of significant damage not shown yet where a divot was popped out of another fin, not along the edges but centered in the bottom half. I have some pics along the the repair in progress that I will try to get up soon.

In any event, this rocket has performed well but the balsa fins seem to take damage at every outing.

Don't feel too bad. I broke fins off two rockets today and never even flew either one of them. :y:

 

[JAL3]

Don't feel too bad. I broke fins off two rockets today and never even flew either one of them. :y:

What a bummer.

I was supposed to fly with my club today but have had to sit around the house instead because I'm not feeling up to snuff. I have to shake this by in the morning. I've spent the day doing a few minor repairs, cleaning up my shop and hiding when SHE WHO MUST BE OBEYED looks to have something to occupy my hands.

 

[El Cheapo]

John, I'm not so sure its the balsa per se rather than material used to laminate. Currently I am building a 4" version of the Merury Invader as well as Pemb Tech Screamin Green Meanie. I'm using 3/16 balsa laminated with Christmas clothing gift boxes. They are light and crazy strong. As an example, the 4" - 2.6" centering ring done this way weighs have as much as a 2.6 - 29mm light ply ring I have.

 

[JAL3]

John, I'm not so sure its the balsa per se rather than material used to laminate. Currently I am building a 4" version of the Merury Invader as well as Pemb Tech Screamin Green Meanie. I'm using 3/16 balsa laminated with Christmas clothing gift boxes. They are light and crazy strong. As an example, the 4" - 2.6" centering ring done this way weighs have as much as a 2.6 - 29mm light ply ring I have.

I was going to say that mine are just the balsa with no laminations then I took a closer look. Its like the paint chipped off in a little patch but what threw me is the depth of the paint layer. It also looks like the paint formed a shell around the fin without actually adhering.

 

[JAL3]

The picture shows the divot but does not do justice to how deep that thing really is.

 

[JAL3]

I mixed some 5 minute epoxy and used a foam brush to fill in the hole and then tried to spread it out some.

 

[El Cheapo]

I should have remembered yours were not laminated. I just re-read your EMRR review the other day looking for do's and dont's.

 

[JAL3]

I should have remembered yours were not laminated. I just re-read your EMRR review the other day looking for do's and dont's.

This is another of my early ones. When I built it, I remember having doubts about the balsa but I hand never heard of laminating outside of the glass and carbon stuff the HPR crowd does...and I was just barely aware of that.

 

[JAL3]

The repaired cracks still needed some work so I applied some Bondo putty to them and let them dry.

 

[JAL3]

A couple of days later, I sanded the putty down.

 

[JAL3]

The ragged fin edges still needed more putty and, while doing that, I decided to try and even out the ridges caused by my inexpert epoxy application.

 

[Scotty Dog]

I mixed some 5 minute epoxy and used a foam brush to fill in the hole and then tried to spread it out some.

Was it bird season! Looks like someone took a shot at it.:y:

 

[JAL3]

Was it bird season! Looks like someone took a shot at it.:y:

As a matter of fact, it was dove season when that happened.