Sheri's Mercury Redstone

[JAL3]

Sheri's Mercury Redstone is an impressive looking rocket on her website. Its also fairly impressive when the box shows up on the doorstep. After delaying for a while, I decided to get this one started.

 

[JAL3]

The first step in construction is to read through the instructions. They are long but easy to read and doing so helps one to understand steps that will upcoming.

The first real "construction" thing to do is to fish out the 2 plywood centering rings and a 3/4" square of plywood. The plywood was eposied onto one of the rings in order to strenthen it of the mounting of an eye bolt for the recovery harness. I used 15 minute epoxy here because I grabbed the wrong bottles.

 

[JAL3]

When the epoxy was set up, I was instructed to drill a hole through the center of the block and through the ring to which it was mounted to receive the bolt. A 1/4" hole was drilled.

 

[JAL3]

The hole being drilled, it was a simple matter to insert the receiver for the bolt and epoxy it into place. It's teeth were forced into the plywood with a pair of pliers. I mixed some 5 minute epoxy and prepared to seat the bolt. Unfortunately, I did not pay enough attention and mounted the receiver on the wrong side. By the time I had descovered what I had done, it was too late and the epoxy had set.

 

[JAL3]

The centering ring without the bolt was mounted in the body tube flush with one end. It was mounted with 5 minute epoxy and a fillet was applied around the perimeter.

 

[JAL3]

The other centering ring, the one with the bolt, was mounted in the body tube 6 inches from the forward end. It too was mounted and filleted with 5 minute epoxy and it was ensured that the ring of the bolt was facing forward.

 

[Pantherjon]

I will be watching this build closely! I have one of those fine kits in my 'Kit Room' I got <cough, cough> awhile ago..No such thing as 'too much detail'..I may learn a trick or two!

 

[JAL3]

I will be watching this build closely! ..I may learn a trick or two!

From me? You gotta be kidding!

You need some serious help, my friend. I do better as the "how not to..." example.

 

[troj]

If it were mine, I'd toss that eye bolt and replace it with one that's either forged (preferred) or welded.

-Kevin

 

[JAL3]

If it were mine, I'd toss that eye bolt and replace it with one that's either forged (preferred) or welded.

-Kevin

That makes sense.

How would you suggest I install it? The CRs are already epoxied into place.

I could use one with wood screw threads but wouldn't it be in danger of pulling out without a nut on the other side?

 

[RangerStl]

Kevin:

Considering that it's anchored to plywood, would that eye opening up under load really be a concern?

Actually, now that I look at it closer, is there a possible "shock cord snag" issue due to the unclosed end? If it's just a snag issue, a little of Billy Mays' "Mighty Putty" shlapped on there might be enough.

N

 

[MaxQ]

Kevin:

Considering that it's anchored to plywood, would that eye opening up under load really be a concern?

Actually, now that I look at it closer, is there a possible "shock cord snag" issue due to the unclosed end? If it's just a snag issue, a little of Billy Mays' "Mighty Putty" shlapped on there might be enough.

N

I understand it is already installed, and if the deployment doesn't place too heavy a load it may work fine for many flights....

I realize your working space is confined by the body tube diameter - but would suggest next time getting a steel washer and nut on the sides to spread the load...I've had eyebolts (w/o a washer) yank and pull right out of plywood ...and a repair that is hard to get to is not fun to deal with after the fact.

In some cases I had to file down one side of the washer to fit in tight spots but I feel better having one.

 

[troj]

I think some folks are missing the point of my concern....

A standard eyebolt is a piece of metal that's been bent to a shape. Under load, the loop can straighten, resulting in a disastrous recovery. Forged eyebolts don't have this issue, because they're a solid, forged loop -- you have to totally destroy the loop to get it to come apart.

Depending on the amount of clearance you have, you may be able to simply unscrew the existing eyebolt and screw in a forged one. If not, it gets more tricky, and without knowing the overall assembly of that portion of the rocket, I can't give an answer.

I use eyebolts when space requires, but in general, I prefer U-bolts with a strap underneath. They spread the load over a much greater surface area an eyebolt (whether forged or not).

If I don't have one with a strap, or I have to use an eyebolt, I usually back it with a fender washer. The more you can spread the load, the less likely there will be a failure.

I'm intrigued by the fact that the kit has you double up the centering ring material at the point of attachment. What type of plywood are the rings made from? Obviously, a bit of reinforcement at a point of high load like that isn't a bad thing, but I've never seen a kit that recommended it before.

-Kevin

 

[Delta-IV]

Thanks for this thread too. I bought one a couple of months ago and was planning to do a summer build. I'l be reading this one closely.

So far, just looking at the parts, my only improvement idea would be on the body tube. It is thick and strong but I am afraid of the zippering or debonding of the wrap layers at the leading edge. I have used these type of tubes and have had that issue.

I may exchange the BT with a phenolic or similar if the OD is compatible (haven't yet looked at it that closely) or use some CA or epoxy to seal the edge.

 

[troj]

I may exchange the BT with a phenolic or similar if the OD is compatible (haven't yet looked at it that closely) or use some CA or epoxy to seal the edge.

I've not seen what Sheri is including for tubes, so I'm going to assume it's comparable to what LOC uses.

If so, wicking CA into the edge works like a charm, if you're worried about it delaminating.

-Kevin

 

[Sheri]

...

 

[Bravo52]

I think you should just quit building this kit immediately. Pack it up and send it to me for proper testing. I will complete the build and fly a series of flights to determine the ruggedness of the design…….

I’ve got a little experience with the SHR kits and I guaranty the provided shock cord will fail before the eye-bolt will. I also think you will more than likely experience a failure of the CR well before the eye-bolt. However, having said that, I think in the end you will not fly this rocket that much and if you do, the system will hold up just fine.

 

[JAL3]

I think you should just quit building this kit immediately. Pack it up and send it to me for proper testing.

ITs strange how my wife has gotten you to support her in this matter...:bangpan:

I’ve got a little experience with the SHR kits and I guaranty the provided shock cord will fail before the eye-bolt will. I also think you will more than likely experience a failure of the CR well before the eye-bolt. However, having said that, I think in the end you will not fly this rocket that much and if you do, the system will hold up just fine.

Unfortunately for me, I don't get to do too much MPR and even less HPR because of time/field availibility. It certainly will not be flown every month but it will be flown for as long as I have it. Once I build one, I try to keep it "alive" for as long as possible. That's where my concern lies. It may well take me 5 years to log 10 flights with this rocket but I want it to come down intact after the 10th, 50th, 100th etc. flight just like the (hopefully) first one.

 

[Bravo52]

ITs strange how my wife has gotten you to support her in this matter...:bangpan:



Unfortunately for me, I don't get to do too much MPR and even less HPR because of time/field availibility. It certainly will not be flown every month but it will be flown for as long as I have it. Once I build one, I try to keep it "alive" for as long as possible. That's where my concern lies. It may well take me 5 years to log 10 flights with this rocket but I want it to come down intact after the 10th, 50th, 100th etc. flight just like the (hopefully) first one.

It will be just fine......I have two kits and the mount is just fine. They are not exactly the same, but the same (more) loads apply and they are holding up great. If anything will fail, it will be the CR. Build it as designed and follow the instructions and it will not be a problem. :2:

Also, you can't go too wrong listening to your wife.......she will win, maybe not today, maybe not tomorrow, but she will win............

 

[JAL3]

Also, you can't go too wrong listening to your wife.......she will win, maybe not today, maybe not tomorrow, but she will win............

So what you're saying is that I should box up everything and send it to you, thereby saving myself the heartache of dealing with it in the future?

 

[MaxQ]

I think some folks are missing the point of my concern....

A standard eyebolt is a piece of metal that's been bent to a shape. Under load, the loop can straighten, resulting in a disastrous recovery. Forged eyebolts don't have this issue, because they're a solid, forged loop -- you have to totally destroy the loop to get it to come apart.

Depending on the amount of clearance you have, you may be able to simply unscrew the existing eyebolt and screw in a forged one. If not, it gets more tricky, and without knowing the overall assembly of that portion of the rocket, I can't give an answer.

I use eyebolts when space requires, but in general, I prefer U-bolts with a strap underneath. They spread the load over a much greater surface area an eyebolt (whether forged or not).

If I don't have one with a strap, or I have to use an eyebolt, I usually back it with a fender washer. The more you can spread the load, the less likely there will be a failure.

I'm intrigued by the fact that the kit has you double up the centering ring material at the point of attachment. What type of plywood are the rings made from? Obviously, a bit of reinforcement at a point of high load like that isn't a bad thing, but I've never seen a kit that recommended it before.

-Kevin

Kevin:

we're on the same page...forged bolts are much better for all the reasons you said, - but I think on a smaller project like this, with the size and shock loads we're talking about, I suspect that the eyebolt would yank out (it hapened to me on a high a speed flight on a Loc Vulcanite - w/o a washer on the eyebolt on the CR)...or like the other guy said ..the webbing would give way before the eyebolt straightened.....just my .02 and experience...

 

[Delta-IV]

John,

I agree with Troj on the gluing the end of the tube if it is a concern.

Thanks!!!

Thanks Sheri, I scratch built my 38mm scale Delta-IV Medium with a similar tube and after the second flight it had a major debond when the shock cord must had been pulling on the side during its descent.

I plan to start my build in about 4 weeks after I get back from my Indy 500 trip and will share my results too.

 

[troj]

or like the other guy said ..the webbing would give way before the eyebolt straightened.....just my .02 and experience...

You'd be surprised at what can fail when things get jerked hard.

Hopefully it's a non-issue.

-Kevin

 

[Sheri]

...

 

[JAL3]

Hopefully it's a non-issue.

-Kevin

You got that right!!:y:

 

[JAL3]

The kit came with 4 plywood fins and a styrene fin template along with a sheet of styrene from which to cut...fins! As it happens, the plywood is just for the core of some built up fins.

 

[JAL3]

The fin template was used to transfer the outline of the fins to the sheet styrene for 8 instances. The instruction recommended to use the template as a guide to score the styrene with a razor knife and then flex it to make clean breaks. The scoring and flexing idea worked well for me but the using of the template as a guide to do this did not. For me, it was much easier to use a steel rule as a guide for the scoring. That kept my poor template in better shape as well.

 

[JAL3]

A fact that may be worrisome for somebody who does not READ the instruction is that the styrene fins are somewhat larger than the plywood cores. There is a good reason for this. The plywood core is set flush against the base and root edge of the styrene. The styrene is then lightly scored with the razor along the leading edge. The rudders on the outer edge are also scored and then snapped off and saved for later.

 

[JAL3]

The styrene along the angled leading edge of the fins was scored but not snapped off. The scoring was to facilitate bending an angle into the leading edge. After trying several methods of getting this right, the one that worked best for me was to put the plywood core into place and then gently bend the plastic towards the centerline of the fin.

 

[JAL3]

When all of the angles were formed, the styrene was glued to the plywood cores using CA. The resulting bevel actually looked pretty good even if it was not yet "perfect".