"Flying MooMoo" Scratch Build Thread

[Barkley]

I found out that it's maiden flight has been delayed by a week, so my sense of urgency disappeared (even though I still have a mountain to do and most likely needed the time). Still, a lot has happened since my last post:

(1) My 38mm Aeropack motor retainer arrived. The bad news is that my MMT is so thin that it doesn't fit, which means I need to put 2 more wraps of FG on the base of the MMT and increase the diameter of the bottom centering ring hole proportionately.

(2) The Boss said she didn't want to cut the tube if we didn't absolutely need to. She didn't want the rivets... and the purist in me jumped for joy. The rationalist in me said 'crap, now I need to drop that bulkhead 24 inches down the body tube and keep it straight... but I'll figure it out.

(3) I realized I don't have enough FG plate for the sled, so I need to make another sheet of FG stock. Will take pics when that occurs, which will be soon.

(4) Measured out the BT then slotted it with my Fein saw. Measured out and marked where the centering rings need to be.

(5) The cable cutter I ordered arrived, so there's something else to test.

This is going to be a fun rocket...

 

[Barkley]

Update time. Here was the status as of two nights ago:

The to do list was basically the same as above. Since then we taped up the nose cone, then laid in some West thickened with 405 filleting compound:

 

[Barkley]

When mixed with the 405 you're looking for a consistency like really thick peanut butter, so that's what my daughter calls it ("peanut buttering the nose cone"). Liberally applied with a 1/8th dowel:

And the result:

Forgot to take the pic before getting the sandpaper on it. I'm not completely happy with this - the tape lifted a bit, allowing thickened epoxy where I didn't want it, and hardened 405 is like sanding concrete. There are also voids where the tape had flexed inward, so I'll have to touch it up with more 405 to make sure it's good and solid all the way around. The good news is that I made the nose cone for my L2 bird using this same process and when Jim Jarvis looked it over prior to my launch he said my nose cone was almost too light, so the weight of a bit more epoxy won't be a bad thing.

Once it's structurally solid I can get out the microballoons and start to fill and fair.

 

[Barkley]

I didn't buy a mandrel to make couplers and nose cone shoulders, so my process is to make a tube with the main mandrel with 3 or 4 wraps instead of 5, then cut it lengthwise and epoxy it back together. If I cut too big a slice then I use that as a mandrel (wrap mylar around it and make it as normal) or if it is just right then I wrap 3 wraps of cloth and it fits perfectly. Below you can see what will be the NC shoulder, and 3 wraps should make that perfect. Having an extra thick NC shoulder is great when it's taking the load when the chute opens, but given that I'll be using allthread attached to the NC tip I shouldn't need extra thickness.

 

[Barkley]

So my little Miss is in Florida with her mother at the moment, and I asked her whether she wanted me to push on the build or wait for her return. She requested something that looked a bit more rocket-like upon her return... so back to work. First, the design spec changed a bit because the rocket is going to have a passenger:

The "Quackstonaut" will be in the nose cone above the av bay. (I have no idea where they found that helmet, but it seems to work.)

Below, a few more wraps on both the coupler tube and the tip of the MMT. In both cases I didn't put on enough laminate, and while I'll bulk up the MMT with 3 more wraps I think the coupler needs to be treated as a mandrel - there's still a ton of space.

 

[Barkley]

I also needed to make some more FG plate. This is really quite easy. I went to Home Depot and got 2 20x16 panes of replacement window glass. Make sure they're clean, then spray with the Frekote mold release - it doesn't need it, but it literally pops right off the glass if you do. I put on two light coats.

For a 16x20 sheet I cut my peel ply at 16x20 (or bigger, it doesn't hurt) and my cloth at 14x18 to give myself an inch around the outside. When cutting the cloth, assume you're alternating the bias of the cloth. Yes, there's more offcut, but you end up with a MUCH stronger sheet.

 

[Barkley]

Then, quite literally wet it out, get the next piece of cloth and drop it over top, spread it with your brush to get it oriented the right way and flat, wet it out, rinse and repeat, alternating the cloth bias (0 and 90 then 45 and 135 to "mansplain"). Given that I was solo and gloved up, no pics of the rest of the layup. When you've laminated your cloth, drop and smooth the peel ply, then put the second piece of glass down on top and weigh it down. Here I have 2x25 pound dumbells, 2x20 pound dumbells, and probably 50 pounds of crap in the containers.

When it's set, take off the weight, use your epoxy spreader to CAREFULLY take the top glass off (it's quite sharp), then remove your peel ply. If it isn't strong enough or thick enough, just laminate more cloth to what's there using the same process.

It's literally that easy.

 

[REK]

Yes its literally that easy. Now I know where to go get some flat panels. I need to have them ready for making flat panels. I used to use tiles with C-clamps and it can be a pain sometimes.

 

[Barkley]

I ordered a Aeropack 38/29 motor reducer, as I'd planned on using a CTI 3G 29mm case for it's first flight. (Remember, it was going to be my daughter's name on the flight card, so it had to be a Mid powered G). So I test fitted the reducer in the MMT and...:

Which is a yikes. It then got me thinking, is it the retainer or is it the tube? So I tested some of my other cases. No problems with the Dr Rocket:

But my CTI 6XL case could only go as far as the centering ring:

So I went and got the rest of the 38mm tube - remember, I made 4 feet of it, with the remainder to be my MD project:

It's tight, but a perfect fit. Remember, my mandrel is a perfect 38mm and I use a thin wrap of mylar to guarantee a slip fit. So what's the issue?

Heat transfer. When I epoxied the centering rings to the MMT the magic of epoxy and glass happened. As they bond together the whole joint warms, and to greatly oversimplify they literally fuse. And yes, in that bonding process, the whole joint (including the original tube) swells slightly at the joint. The solution in my case is a bit of sandpaper, but in future I'm going to put the MMT back on the mandrel (with mylar) so that the tube can't swell smaller than my slip fit tolerance. I'll also assume that when the fins are applied the same swelling will occur, so I'll have the mandrel in the MMT when the fins go on too.

I can only assume this is happening because the tubes are VERY thin and the tolerances are quite fine. If I'd bought a 38.5mm mandrel I bet the swelling wouldn't be an issue.

These lessons learned are exactly why I scratch build.

EDIT to add: And yes, the Aeropack 38/29mm MMT reducer is larger than 38mm, so I'm going to have to file it down and repaint it. Not really happy about that, but... that's life.

 

[mpitfield]

But my CTI 6XL case could only go as far as the centering ring:

Hey Chris,

I wonder if the label on the case is adding just that extra amount of width to prevent the case from sliding in. I have had this experience once with the OOP BadAzz Mini Missiles. Eric machined a very accurate tailcone/retainer and using a CTI 24mm 1 grain case it was tight and would not go in unless I removed the label. Now strangely enough the 2, 3 and 6 grain cases didn't have that issue even though they have the same label.

Bottom line is if it's tight to begin with then the label may be the show stopper on the CTI cases.

Build is looking good, the passenger is a great addition!

 

[Barkley]

It took a fair amount of pressure to get the CTI that far into the MMT, and the pressure was needed before the sticker saw any tube. But I like your thinking - thanks!

 

[Barkley]

Another rookie mistake.

Was listening to BadMotorFinger during prep, got all gloved up and had just put my first drops of mixed epoxy on the cloth when I realized my mistake - I was near the end of Holy Water, so there was only 1 track left.

ALWAYS make sure you have enough music on your album/playlist to last through your estimated layup BEFORE you mix the epoxy. I hate it when you just start, the music ends, and you have 20 minutes of garage silence.

 

[Barkley]

Last night's efforts were successful. 3 wraps of 4oz on the coupler tube and 2 more wraps on the MMT made for a perfect fit with the NC/BT and Aeropack retainer (respectively). As you can see, a bit of elbow grease with a rounded file gave the CTI 6XL the room it needed, and I dry fit the retainer just to make sure it'll all work as directed. I'm really happy now - time to put the MMT in the BT, then bevel and install some fins. On the NC, the green tape is where I need more internal peanut butter for strength. After that, attach the shoulder and fill and fair.

Here you can see how much was needed to bulk up the aft end of the MMT for the retainer:

The FG plate I made is also too thin and flexible for fin stock, but for the av bay pieces I need it's perfect. I'll cut out what I need and can add more laminate to the remaining depending on the needs of the future project.

 

[REK]

Another rookie mistake.

Was listening to BadMotorFinger during prep, got all gloved up and had just put my first drops of mixed epoxy on the cloth when I realized my mistake - I was near the end of Holy Water, so there was only 1 track left.

ALWAYS make sure you have enough music on your album/playlist to last through your estimated layup BEFORE you mix the epoxy. I hate it when you just start, the music ends, and you have 20 minutes of garage silence.

XD, I wont lie its not fun laminating in silence. I always got music going to get me motivated lol.

 

[Barkley]

The MMT is in. A couple of points to note. The first pic is from the topside of the tube, and you'll notice peanutbutter not just on the BT/CR join, but also on the MMT/CR join. I did that on the middle centering ring too, but only on the top side. The fins need to butt against the aft side of the mid centering ring, so you can't have thickened epoxy there.

This tip I learned from both JohnCoker and Rocketburger. Don't apply epoxy to the aft centering ring (because you'll need it off to apply the internal fin fillets), but put it in place to keep the orientation of the MMT in column.

EDIT to add: you need to wipe ALL epoxy off the aft end of the tube while doing this. I wiped it clean, then wiped it clean again, put the CR in place, then popped it off and put it back in just to confirm I wasn't accidentally epoxying it in place. It takes so little epoxy to cause a problem there. As you can see, the CR isn't all the way in the tube - I've left a lip to help get it out.

From the bottom of the tube. The pic is out of focus, but you can see the aft centering ring is now off and there's no epoxy on the aft side of the middle centering ring. All set for fins.

 

[dmgrime]

Great build thread, and impressive "full scratch" building ... way out of my league for now! Definitely enjoying this one.

 

[K'Tesh]

Having never worked with FG, I'm finding this build really enlightening.

Looking forward to reading more as I *might* have to try this someday.

 

[REK]

Having never worked with FG, I'm finding this build really enlightening.

Looking forward to reading more as I *might* have to try this someday.

I encourage you do do it someday. It is very rewarding building an all fiberglass rocket from scratch.

 

[REK]

Barkley this build has been very amazing love the nose cone making method, I'll need to give it a shot later on. Keep up the good work.

 

[Barkley]

Thanks for the kind words guys. I'm learning with this too, and if I can pass some of it on then all the better.

Nose cone fill and fair night, part 1. The requisite (blurry... sorry) "before" shot:

As you can see, the mix is West 105/206 at 5:1 with 410 microlight fairing compound. Unlike the 405 that hardens to damn near concrete, the 410 sands easily. But it is also epoxy, and holds like epoxy. I still don't get it... I just know it works well. You fully mix the epoxy before adding the 410, then thicken until it's a thick peanut butter consistency. It's really easy to get unmixed clumps of 410, and when applying they stick out like a sore thumb. Just take your applicator, scoop the clumps out, add more mix, fill and spread. Here is the mix ready to apply:

You can't tell in that pic, but I've lifted the epoxy mix and the mix is just holding up the popsicle stick. It needs to be good and thick or else gravity will sag the work. The end result for the evening:

Tomorrow we'll see what we have, sand it down, and fill and fair again - but it'll look a lot more like a nose cone after some sanding.

 

[Barkley]

5 minutes of 100 grit and it starts to actually look like a nose cone. I spun the metal tip onto the all thread and dropped it in to get the transition right. Thankfully the lines are pretty close.

 

[Barkley]

So, good news bad news on the build. The nose cone shoulder had just a bit too much play, so I added one more wrap and it's now a PERFECT fit.... but now see the pic below:

See the difference in thickness between the nose cone (on the left) and the NC shoulder on the right? I just laminated what I had instead of using it as a mandrel, and it came out at 100 gms, which means it's overbuilt by a wide margin. I also weighed the NC and it's 170 grams (without the metal tip, all thread and av bay sled)... meaning this rocket is significantly more stable than the original plan. It also is getting VERY close to not meeting the design spec of being able to be flown with a mid powered motor. According to OpenRocket, the only mid range motor with enough kick to get 12 m/s (40 fps) of speed (aka stability) when it leaves the rail is the Aerotech G76 Green.

So my daughter, bless her, said not to change the fin size (even though stability-wise we could cut almost 1 cm off them) and not to make a new NC shoulder (even though a properly built NC shoulder would shave at least 50 grams of weight and increase the number of motors we could use). I have a very big hearted little girl.... but I also know she desperately wants her name on the flight card, so I have to shave weight from here on out to make sure it can still be flown MP.

 

[Barkley]

If you trace the inside of the nose cone shoulder before it's epoxied on to the nose cone, it lets you make a perfect cut. (Assuming you cut just outside of the line and not on it.)

I don't normally laminate with the 5 minute epoxy, but here it would never make a difference.

And now we have an idea of what the bottom will look like. There will be a lock nut on the all thread holding the ring in place, a cup for the ejection charge, and I still have to figure out how the cable cutter will be positioned. One of the tips Jim Jarvis gave me is that the difference between MPR and HPR is how you deal with shock loads, and that wherever possible try not to have just one piece of material responsible for the whole load. In this situation, instead of the lid taking all the load, the pull on the all thread bypasses the lid entirely and pulls the whole nose cone from the tip. However, I've yet to figure out how to do this with the parachute cord attachment point in the rocket body. If anyone has any ideas, please speak up.

 

[cnjhigham]

Great Job on getting your daughter into rockets. I am looking forward to watching it fly.

 

[Barkley]

Jimmy, first launch should be at NASA in a week and a half, but you should see it soon enough.

TRF member Wizard put me on to these, and if they're half as good as he says I'll never go back:

And here's a busy work bench:

God help me if I get seriously into this rocketry stuff.

 

[REK]

I've used the conformal rail guides with great success and I will prefer them anytime over rail buttons.

 

[Barkley]

Still a fair ways to go, but looking more and more like a nose cone:

So tonight at dinner I opened my big mouth about having video of the flight, and mentioned a previous rocket I'd seen here:

https://www.instructables.com/id/GoPro-Model-Rocket/

Dumb move on my part. Currently OpenRocket sees it leaving the rail at 12.6 m/s with only 1 Mid-powered motor (that Aerotech G76G), and I'm concerned that if I were to mod the rocket to include this with a seat above it for the Quackstonaut that the extra weight would put it into HPR exclusivity. The solution is to build the mod and weigh it and see what OR says - if it's too heavy, it goes in the next 77mm rocket. 3" OD transparent tubing on order, to be delivered Friday.

Tomorrow night we get the fins in. Love that day... it's the day it stops being a collection of parts and officially becomes a rocket. I promised the Miss that she could make the peanut butter.

 

[gerbs4me]

Very nice work so far. Keep it up!

 

[Barkley]

So, the Quackstronaut chosen for this particular mission has been changed. It appears that the smaller Q will fit more easily in the airframe... and I guess it's the same reason why there are no astronauts measuring 6 foot 10 and 290 pounds. The helmet has officially been passed, with the larger duck now in charge of Launch Command. And given that the first launch is scheduled to be at Johnson Space Center in 9 days, we'd better not hear "Houston, we have a problem".

 

[K'Tesh]

Something I learned this week... Tuesday, if I'm not mistaken.

"Houston, we have a problem".

"Uh, Houston, we've had a problem." James A. Lovell

VS

[video=youtube;kAmsi05P9Uw]https://www.youtube.com/watch?v=kAmsi05P9Uw[/video]

Mind you, I'm sure that the film is very good at capturing the spirit of the situation (I was too young to remember it), but it certainly wasn't 100% accurate.