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Dustin Lobner

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Last of the fin root fillets (prior to taking the motor mount core out and really going to town with the epoxy went in this morning, should be able to take it out of the body tube tonight.

Also realizing I made a strategic error by fiberglassing both segments all the way up. The Soller sock stuff allows me to basically put the two body tube together with the coupler and then fiberglass the whole 60" assembly. Not a huge deal here, but for the future...

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Dustin Lobner

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Pulled the MMT with fins attached, marked out holes for the guide rods, drilled them on the ring that's on top of the fins. Got that epoxied in...built something of a "dam" of tape so the epoxy wouldn't run everywhere. Tomorrow I'll start with epoxying under the ring, securing the tips of the fins to the motor mount tube to fin and ring.

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Dustin Lobner

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Opened up the tape and liked what I saw for the top fillet. Between a light dremeling on the ID of the centering ring and peeling all the glassine off the tube, there is the tiniest of gaps between the ring and the tube. As can be seen in the pics below, the epoxy leaked through just a bit. Pretty much perfect IMHO, it means I'm not just relying on fillets for strength but there actually is adhesive in the joint.

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Suspended the fins and MMT tube via rope and some tape and then slathered in a crapton of epoxy at the base of the ring and where the fin root meet the tube. Will be doing this for the next day or so all around the sides.

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Dustin Lobner

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Work on this slowing down as the wedding approaches, but still doing what I can. Got some all thread...didn't install it, just put it through the holes and then used nuts to hold the next ring in place. Second pic is holding the coupler up by the body tube as a sanity check that I got the height correct, as the coupler is going to butt up against this ring.

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Dustin Lobner

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Put together the two pieces of the top bulkhead. I put a washer in between the two pieces...I'm going to flow epoxy into the gap, plus it allows basically 4 bonding surfaces for the rings. I am using 2 forged bolts, each rated for 1 ton. Probably overkill, but would rather that than the other way around.

Bolt heads aren't square to make it easier to get the quick link on later.

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Theory

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I am a huge fan of T88.

just enough flow to penetrate joints and it cures to a hard but non-brittle state in most any condition.

yes it takes some time to fully cure (i let my major joints cure for 24hrs) but its worth it
 

DAllen

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Man I gotta get me some of that T88. Looks like it comes in squeeze bottles like the Bob-Smith stuff does. Is that the case?

-Dave
 

boatgeek

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Man I gotta get me some of that T88. Looks like it comes in squeeze bottles like the Bob-Smith stuff does. Is that the case?

-Dave
My kit came with regular caps plus a pair of squeeze bottle caps so you have a choice. It’s a fantastic product and the System Three folks are good people.
 

Dustin Lobner

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My T88 kit is just squeeze bottles with large openings. Don't really need the squeeze cap for what I'm doing though, easy enough to squeeze out just 10mL of each.

The flow through the joints in fantastic, like someone said. The 2nd picture I posted on July 18th kinda says it all.

I'm building this in my 65 degree basement, so I appreciate that it cures fully at lower temps too.
 

pbahorich

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According to the T-88 data sheet: "At 150°F, T-88 will set within 30 minutes and develop maximum bond strength and impact resistance after 2 hours."

Based on this data, I devised a solar powered curing oven which fully cures T-88 using the summer sun in less than 3 hours. See picture:
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I do acknowledge that this curing oven is in need of external cleaning, and some paint.
 

Dustin Lobner

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According to the T-88 data sheet: "At 150°F, T-88 will set within 30 minutes and develop maximum bond strength and impact resistance after 2 hours."

Based on this data, I devised a solar powered curing oven which fully cures T-88 using the summer sun in less than 3 hours. See picture:
View attachment 426334
I do acknowledge that this curing oven is in need of external cleaning, and some paint.
Lol - when I glassed a 3" rocket in April and it wasn't curing right, I left it in my car in the parkinglot at work for a couple of days and it cured it right up. Good stuff.
 

Dustin Lobner

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Got married on Saturday. Amazing time, life is good...and slowly going back to whatever "normal" is these days. That means progress here.

On the back end of the rocket, I'm allowing the 3 pieces of all-thread to protrude out the back and will be using those for motor retention. ...the way I retain motors these days is to 3D print a tailcone that screws into the back of the rocket. Will do the same thing here, but will have nuts going on the back end holding the tailcone/motor retainer on.

Only 3 seems like not enough, so I found these "adhesive studs", basically a 1/4-20 rod with a adhesive washer thing on it. Put three of those in too, so I'll have 6 bolts holding on the tailcone - 3 are all thread, and 3 are these things.

I put the adhesive disc thing between the two plywood motor mount rings, to put some space in between there. Currently gluing the two pieces together...I see the note above about the 150F 2 hour thing, so I put it in my food dehydrator that I use primarily for drying 3D filament spools.

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Dustin Lobner

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Thanks!

Question for the group here. I have put 3 layers of glass on this thing, I need to smooth it out at some point here.

If possible, I'd like to avoid sanding the crap out of the glass - I'm a Materials Engineer, and doing that to a composite just gives me the willies. So, I'm thinking through how to fill the uneven surface.

Options I can see:

1) Bondo auto body filler
2) Something like the light filler epoxy here: https://giantleaprocketry.com/products/components_composites.aspx
3) Something else?

Looking at needing to start doing this in a couple of weeks from what I can see, assuming things keep going OK.

Thanks in advance!

Dustin
 

DAllen

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3. Spray with automotive primer and endlessly sand down to the glass
4. Coat with a tight-weave veil layer of glass
5. Nothing

I often opt for #5 but that is because I am not very picky on the final finish of my rockets. ;)
 

Nytrunner

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1) Bondo auto body filler
Its time your rocket caught a severe case of the Red Plague*

Apply 2-3 thin coats, letting dry for a good bit (~1hr or 2?) between applications to mitigate shrinkage in big fill areas, then sand down and evaluate.

If its smooth enough for you, go to filler primer sand and paint. If still not smooth enough, relapse the Red Plague

*affectionate term for rocket slathered in the red 1-part spot putty
 
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DAllen

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Its time your rocket caught a severe case of the Red Plague*

Apply 2-3 thin coats, letting dry for good bit to mitigate shrinkage in big fill areas, then sand down and evaluate.

If its smooth enough for you, go to filler primer sand and paint. If still not smooth enough, relapse the Red Plague

*affectionate term for rocket slathered in the red 1-part spot putty
"Red Plague" is the first time I've heard of that and is absolutely the correct nick name for that process. Nice!
 

Dustin Lobner

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Lol, red plague, awesome.

I'm thinking about just leaving it unfilled (#5 from Dave). The last rocket I few was glassed but not painted...the glass was colored (Soller Composites). Looked pretty slick.

Been planning a neon green / black color scheme for this one. Thinking what I'll do is so solid neon green base coat and then spray with black and then wipe it off the tops so that the green shows through with black settling in the "valleys" of the glass.

*shrug* or maybe I just fly it naked and not worry about it, lol.
 

Nytrunner

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Been planning a neon green / black color scheme for this one. Thinking what I'll do is so solid neon green base coat and then spray with black and then wipe it off the tops so that the green shows through with black settling in the "valleys" of the glass.

*shrug* or maybe I just fly it naked and not worry about it, lol.
That would be amazing. Great way to highlight the composite work while making it more interesting than clear glass over tube.

Its the L3 flight, do it up nice!
 

Dustin Lobner

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So, this thing has 3/8" plywood fins. Do I need some sort of glass or carbon cloth over the fins to reinforce? I highly doubt they need it from a flutter stability point of view, wondering if I should do something more for damage tolerance than anything.
 

Handeman

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I did my first glassed tube in 6 oz glass. It wasn't smooth so I use the Bondo filler. one coat of that and filler primer and it turned out great.
If I were to do it again, I would top the 6 oz glass with 2 or 3 oz and use it as a sacrificial layer. Shouldn't need any Bondo for that.
 

OverTheTop

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So, this thing has 3/8" plywood fins. Do I need some sort of glass or carbon cloth over the fins to reinforce? I highly doubt they need it from a flutter stability point of view, wondering if I should do something more for damage tolerance than anything.
I think you are right in not needing it from a flutter POV. The question comes down to the quality of the plywood and anticipated landing speed.

I personally have a Velociraptor with dozens of flights. It has 1/4" plywood fins I think, that are a bit up from the aft end. Fins are still almost pristine in condition. Your fins are closer to the aft end and may deserve more protection. Please consider.
 

Dustin Lobner

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I think you are right in not needing it from a flutter POV. The question comes down to the quality of the plywood and anticipated landing speed.

I personally have a Velociraptor with dozens of flights. It has 1/4" plywood fins I think, that are a bit up from the aft end. Fins are still almost pristine in condition. Your fins are closer to the aft end and may deserve more protection. Please consider.
Talked with my TAPs on this, the thought was that it'd be mostly for aesthetics if nothing else...it won't help for severe structural damage. I was also thinking along your lines for dings and whatnot. The plan is to do this...have never done it before, so this will be interesting.

Also - I've put the flight attempt off to next spring sometime. Just got married, changing priorities, etc etc. Wife is supportive, but got some other things to take care of first. Will likely fly at Mini-MWP. Plus, this gives me the opportunity to fly some more dual deploy and get more experience there.
 

Dustin Lobner

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The motor mount/fins are now in the lower booster body tube. I got 3 fillets in on the one side of the centering ring closer to the bottom, and then I put the coupler in and epoxied the ever living crap out of that too.

It actually looks like the bottom 1/3 of a rocket now. (-:

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Dustin Lobner

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I realized that the middle area where the two booster segments come together will be an area where only the coupling is supporting flight loads. Not worried about thrust loads, but I go to thinking about bending loads. I know that the motor mount tube itself will help some, but I figured this might warrant reinforcement. Keeping in the spirit of "Gratuitous Excess", I'm going to put a "stiffy" coupler stiffener in there to take more of the bending loads. Stealing it from the Av Bay, so going to pick up another at some point in time.
 

Tim51

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Looking great. Have you had time to do any updated sims now you're well into the build? I'm curious to know what sort of alt and velocity you're expecting from the M1350?

And congratulations on the wedding btw - all the best for a wonderful life together!
 

Dustin Lobner

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Looking great. Have you had time to do any updated sims now you're well into the build? I'm curious to know what sort of alt and velocity you're expecting from the M1350?

And congratulations on the wedding btw - all the best for a wonderful life together!
I have not done any updated sims. I had initially simmed it to maybe 4-5k feet? Mach 0.4 rings a bell too. Low and slow. Can't even recall for sure at this point.

I think one of the biggest things that will make a difference is not finishing the fiberglass. I flew a 3" rocket that weighed 8 pounds over memorial day weekend, flew on a J450. Same deal, fiberglass without sanding smooth. Sim on that was 4200', reality was 2800'. I think the extra drag from the unsmooth surface really slows it down. I haven't dug into the altimeter data to try and parse out the drag coefficient because I don't care that much, but I'm expecting this one to "underperform" on altitude in the same way.

So, if the initial sim for this one was 4-5k feet, only 3.5k is entirely possible.

Thank you!! Been good so far!
 

Dustin Lobner

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The bottom booster segment with the two doubled centering rings and the stiffy weighs a total of 12 pounds. The "stock" finished weight of the Bruiser EXP is 19lbs if I recall, so I'm on track for well over that. Maybe 25-30?
 

Dustin Lobner

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Starting in on the internal fillets on the fins. I put tape on the outside so it doesn't ooze through the joint...I am going to glass the outside of the fins, so I don't want epoxy there yet.

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Dustin Lobner

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Put the back ring in just to see what it looks like. These 6 bolts will go through the to be printed tailcone, which will then hold the motor in.

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