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jrap330

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Perhaps. But my point was by using a longer hook, which can be cut and ends bent, the forward end of the hook can be located above the motor block, preventing the inevitable tear in the motor tube.
So no instructions indicating you were right, again head scratcher for me.
 

Jeff Lassahn

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The version with a slightly longer engine hook which hooks above the thrust ring rather than just below it, feels like a much better design than the standard Estes version. In that design the force from both the forward thrust of the engine and the backforce from the ejection charge both get transmitted to the thrust ring which seems very sensible.
too bad that they require slightly different hook lengths, so it's not easy to build an existing kit to that design.
 

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I ordered a motor mount kit a while back from either Discount Rocketry or Rocketarium (can't remember which) that came with an engine hook that was a quarter-inch longer than the Estes-style hooks I have, with a single right-angle bend on both ends. It took me a second to realize that the extra quarter-inch was so the forward end of the hook penetrates the motor tube above the motor block, thus giving it greater resistance to the rearward pull at ejection.

These hooks are 4" long (for an E motor), rather than the 3.75" that Estes hooks are.
@hcmbanjo sold some 1/4 inch longer motor hooks under his Odd'l Rockets name for a time. I have a few. Yes the intent was you could put the top of the hook above the motor block. I have installed these in a couple of models. That also would solve the cumulative effect of dozens of ejection charges. I mainly didn't mention them in my long post last night because I checked at jonrocket.com (who normally carries all of Odd'l's products) and they weren't listed, so I figured they're not available at the moment.

That said, one can make hooks from the metal stiffening spines found in car windshield wipers, and making one 1/4 inch longer than standard would be a way to solve the problem I was taking about. Not sure why I didn't think about that last night. Of course one needs a motor mount tube that's also 1/4 inch longer, but that's easily cut from a chunk of the appropriately-sized body tube.

I also did not mention last night that there are some heavier-walled versions of common body tube sizes, though they aren't as easy to find of late. If one is scratch building or making a clone rather than building a kit, this is an alternative for longer-lasting body tubes, both from an ejection-charge-cooking and wear at the top where the nose cone/payload section can snap back and crumple it (or the combination of a really poorly chosen ejection charge delay and a kevlar shock cord can zipper it).

Here is a particularly odd example of snap-back damage. This was on the third flight of my most recent Nova Payloader. Note that the torn-off chunk that's trapped under the edge of the payload section adapter has the inside of the tube facing out. It was a windy day flight and somehow at ejection the payload section collided with the body and tore that chunk out. But, that model has flown 29 times since then (and yes, the top of the tube isn't terribly smooth or pretty anymore). A combination of straightening, CA to help hold the torn out chunk back in place and a couple of turns of Scotch Multi-Task tape around the outside of the tube at the top has done the job.

You can see the 1/16 heat shrink I mentioned last night in this picture. So far it's working as intended.

IMG_2927.JPG


Here's what that model looks like now. The kit's original shock cord is still in the model, tied to the kevlar.

It is true that for many years Estes shock cords have been too short, but in the last few years they have done a good job at addressing that. Another reason to not just throw away what comes in the kit on reflex....!

IMG_3934.jpg
 

Dane Ronnow

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Of course one needs a motor mount tube that's also 1/4 inch longer, but that's easily cut from a chunk of the appropriately-sized body tube.
I went back through my orders and found the kit I was talking about:


The hooks are 4", which leaves .25" beyond the 3.75" motor, accomodating the motor block. The tubes in that kit are 4.25".
 

jrap330

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Not sure what you're asking—instructions that say I know what I'm talking about? Or instructions that say I can take a long engine hook and make it shorter.
instruction state install center ring above the engine hook slot like you assumed
 

Dane Ronnow

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instruction state install center ring above the engine hook slot like you assumed
I install the centering rings according to the design specs for the TTW fin tab, which is usually different than the placement specified in the instructions. And, frankly, I don't know what this has to do with my suggestion to BEC that a longer hook can be used to avoid the problem he was having. Maybe we're thinking about two different things?
 

hcmbanjo

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@hcmbanjo sold some 1/4 inch longer motor hooks under his Odd'l Rockets name for a time. I have a few. Yes the intent was you could put the top of the hook above the motor block. I have installed these in a couple of models. That also would solve the cumulative effect of dozens of ejection charges. I mainly didn't mention them in my long post last night because I checked at jonrocket.com (who normally carries all of Odd'l's products) and they weren't listed, so I figured they're not available at the moment.
Next time I speak to Roger (JonRocket.com) I'll ask about his listing of the Extended Length Engine Hooks.
I thought he had some in stock. Maybe with the new website format they didn't get listed.
I have them available to vendors again.
 

BEC

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Maybe with the new website format they didn't get listed.
That thought did cross my mind....

And also it's possible that his new spiffy-looking web site has them listed where I didn't look......:oops:
 

bronicabill

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As much as I hate to do it, I'm gonna show some ignorance here by asking a question that I should already know the answer to, especially since I've been building and flying LPR for right at 50 years now! :facepalm:

I do not wish to derail this thread, so if there's one I missed that already addresses this question, please just send me there...

So, how do you "paper" your balsa fins??? I've always just used sanding sealer designed for model airplanes (have been building and flying R/C for nearly as long) on my balsa parts to be painted.

Thanks! :headspinning:
 

neil_w

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So, how do you "paper" your balsa fins??? I've always just used sanding sealer designed for model airplanes (have been building and flying R/C for nearly as long) on my balsa parts to be painted.
That has been discussed many, many, times. There are many approaches. K'Tesh has a thread describing one approach. I've described my methods on several occasions. This recent(-ish) thread has a bit of everything: https://www.rocketryforum.com/threads/papering-fins-adhesive-label-paper-vs-glued-on-paper.161986/

I would say there are two main areas of divergence:
1) Adhesive label paper vs. glued paper. Label paper is quicker and easier, glued paper is stronger. I usually use label paper.
2) Cut to size or sand off excess: I always sand off excess.

Then there are smaller variations in process, like what type of glue to seal the edges with (CA probably most common), and whether to fold the paper around the leading edge or use two separate pieces (always two pieces for me).
 

bronicabill

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That has been discussed many, many, times. <<snip>>
I figured it had, but my search skillz are not up to what they should be, so I didn't see them. Will go look at what you've posted. Thanks!
 

BEC

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Interestingly enough, there was a comment in the article on tip-to-tip glass/carbon fiber cloth in the current Sport Rocketry that said that using thin epoxy and tissue (!) was ”known as papering the fins” or words to that effect.

I’ve seen the discussions that Neil alluded to, which are more about applying paper to each side of the fin before installation. I had never seen the term applied to a practice that is similar to the tip-to-tip layups some HPR guys do, though I have to say, that with a different adhesive (dope, thinned white glue or something from the wild array of products from Deluxe Materials) the notion intrigues me. Perhaps using silkspan (aeromodellers of a certain age will know that is) that way would make a very robust “fin can” with balsa fins on a paper tube with tolerable hassle and reasonable weight gain. Hmmmmmm.....
 

cbwho

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I now launch much more often as engines are plentiful (I buy blast packs) in contrast of my allowance as a kid.

BEC mentioned kevlar in a normal Estes trifold mount and I think that's a good idea. I have had kevlar burn thru tied to the engine mount.

My rocket's tubes are getting beat up a bit from using streamers and launching while on ice. Plastic chutes don't open when that cold. I have some nylon chutes on order perhaps that'll help.

My papered fins are mighty strong but sometimes peel away from the tubes. But they are easily reglued.

I've re-tubed a rocket since returning to rocketeering last fall and I am thinking of re-tubing a couple more.

For my fleet, I plan on "painting" the interiors of the tubes with wood glue to strengthen.
 
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BABAR

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Lots of good stuff already posted.

The following applies to low power rockets, maybe to mid power. Being L-0, I know nada about high power construction.

Some of this depends on your goals for your rockets.

If you want beautiful showpiece Rockets, fly them once on a calm day with a large chute in a big field and then relegate them to display/“Hanger Queen” status. Beware even one flight can result in catastrophe. Classic and tragic example is here


Absolutely unique and beautiful design and finish, with an unfortunate maiden (and only) flight

@jeffgeraci

(Note: if you want it to stay pretty, don’t tempt fate by giving it a name like “Suicide King.”)

Even with the best of circumstances, few if any rockets maintain their “show room” looks for more than a few, say five, flights. So “building to last” and “building for looks” are not often complimentary goals.

With great and certainly due respect to @rklapp , who makes and flies beautiful rockets, for low power balsa to cardboard or paper joints, epoxy is overkill. MAKE SURE YOU SAND OFF THE GLASSINE OUTER LAYER OF THE BODY TUBE. Once you do that, wood glue for balsa to cardboard or paper is structurally just as strong, lighter, and smells better. Epoxy is needed if you are attaching plastic or fiberglass, but not wood and paper and cardboard.

If your design allows for forward swept fins (which IMHO look cool regardless), your rocket’s first interaction with terra all too firms (and sometime cementa or asphalta or playa) will be the motor casing or motor hook, either of which generally handle the impact better than the fin tips of the typical Rear swept fins of the quintessential Alpha. If stability allows and you can place your fins a bit forward of the rear edge of the tube (certainly do-able for long skinny rockets) so much the better.

Papering fins, especially with white glue instead of adhesive paper, adds a lot of strength, although many will say even adhesive paper helps.

Nobody has mentioned reliable recovery yet. Lawn darts tend to lose their showroom looks quickly and are frowned upon by most RSOs. Make sure your wadding and chute and streamer are packed loosely enough that you could literally blow them out with a puff of your breath, and the nose cone isn’t too tight. Estes Cosmic Cobra is a Great example of trying to fit too much into too little a space (interestingly the HeliCat is almost the identical rocket, just made a few inches longer, and is a dream to pack and fly.)

Avoid flying on windy days, rockets tend to either weathercock and disappear upwind or drift away and disappear DOWN wind. Putting your name and phone number somewhere on the rocket may help you in getting it back, but may get you in trouble if it drops into, let’s call it “unfriendly “ territory.

Even Kevlar shock cords can eventually burn through and break. Here’s @hcmbanjo ‘s article on a set up that allows you to check and if needed place them.


Best of luck!
 

Back_at_it

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What kinds of things make a difference for the long-term survival of a rocket?
I'm realizing that although I built a lot of rockets when I was younger, I didn't fly all that often so I probably never had a single rocket that flew more than a dozen or so times. Now that I'm Born Again, I'm building more rockets but I haven't flown any of them many times yet either.

So I'm asking for people's experiences with how rockets age as they fly many times.

What kinds of things do you see wear out or go wrong over time?
What kinds of design and build techniques make a difference in how well a rocket survives into its old age?

I'm mostly interested in low power, classic cardboard, balsa and black powder; I imagine the high power world has some differences...
Building for durability comes down to materials used an building technique.

- Use quality adhesives. Titebond I, II and Thick and Quick, Elmers All Purpose (not school). Various thickness's of CA and Epoxy. Never use model cement on an Estes model. It doesn't stick to their plastics. These things work and they are in every hardware store. Why reinvent wheel?

- Sand all the mating surfaces of all items. Especially plastic to plastic or plastic to cardboard/wood.

- Clean plastic parts before assembling as most have some type of release agent or oil on the surface.

- Remove the outer layer of the body tube where the fins attach. Score and peel off the shiny outer coating as glue won't penetrate it.

- Don't use the stock hooks on plastic nose cones. they will break and you will lose the nose cone. Instead, drill a couple of holes and pass the shock cord through them and tie a knot.

- Attach your parachute / streamer to the shock cord, not the nose cone.

-

Examples: Lets start with something simple like the plastic fin Alpha 3. If build to the instructions there are a couple of places for improvement. When inserting the motor tube into the plastic fins, sand the insides of the fin can as well as the outside of the cardboard ring then assemble with a good amount of thick CA. When gluing the upper ring to the mount, sand the inside of the ring so the glue can soak in.

If yours didn't come with on, add a thrust ring above the motor hook. Use Kevlar as an attachment point for the shock cord. This can be wrapped around just below the upper ring of the motor mount. A small slit is cut in the upper ring to allow the Kevlar to pass up. Use a small section of heat shrink tubing to protect the Kevlar at it's base.

When attaching the Fin unit, Sand the outside of the ring as well as the top of the fins where they insert into the body. Glue in with a fair amount of medium CA.

Replace the stock rubber shock cord with elastic that is 2 to 3 times the length of the rocket. This gets attached to the Kevlar. Use thin CA around the inside top of the body tube to add strength to prevent dents and zippers.


Another Example: I recently built / rebuilt a Big Bertha. I knew I wanted something more robust as this one was headed out to AZ with us. Out there I have the room to fly pretty much any motor I can get my hands on so E and F composites are the norm. For this rocket I began by adding a full length coupler that stopped about 3/4 inch from the top of the tube so the nose cone would still fit.

I then built a 24mm motor mount using plywood centering rings and heavy wall BT50 tubing. A thrust ring was added above that allowed fitment of the Estes E motors. A second ring was added to the outside of the motor tube at the very botom even with the end of the tube so that the ring on composite motors had something to push against.

Used 300# Kevlar as a leader for the shock cord and covered most of it with heat shrink for protection. This is attached to a screw eye that is attached to the upper centering ring. Added about 10ft of elastic for a shock cords. Cut the base of the nose cone off and inserted a bulk head with screw eye as an attachment point for the shock cord.

The bottom of the body tube was sanded for good adhesion before the fins were attached.

Finally, Everything was assembled with 30 min epoxy.

This rocket has seen a dozen flights on D and E black power motors and 6 flights using composite E's and one flight on an F44-8. It's still alive to tell the tale and fly again.

Here is a quick snippet. I'll post a full video as soon as I have time to edit all the flights together.


With all that said there are still additional things you can do like through the wall fins that mount to the motor tube, papering fins, Fiber glassing the body tube and fins, coating the inside of the tubes with heat tape or sealer. Etc etc.
 
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Ez2cDave

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What kinds of things make a difference for the long-term survival of a rocket?
( 1 ) Storage / Protection during transport

( 2 ) Usage / Frequency of usage

( 3 ) Flight Damage ( Burns, Crashes, Recovery Failures, CATO's )

( 4 ) Quality of Construction

Dave F.
 

mooffle

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I'm going to mention what most seemed to have touched on but not said outright. For my fleet longevity really comes down to preventative maintenance.
A quick list includes things like: lightly sand engine mounts that have built up residue, dry wipe the insides of tube/nose joints for smooth ejection, seal edges of fins/tubes with glue after hard landings, inspect parachutes for burns or melts.
These are happening quickly after just about every launch and most definitely after a full day of flying. Parachutes get inspected immediately before and after each flight, regardless of whether it was totally successful or not.

Having more complicated mechanisms like heli and glide recovery have made this a necessary habit to build but overall it helps the entire fleet.
 

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As a BAR with greatly improved building skills since I was into model rocketry as a kid, I also came into it with this attitude. I would replace cardboard centering rings with thin plywood, omit the Estes tri-fold mount for kevlar attached to the motor mount, sometimes fiberglass the fins, and in general, using primer and clear coats during paint. The issue with some of these modifications is that they add weight, and it alters how the rocket flies. I'm finding that some of my rockets need the higher end of the recommended motors as a minimum, and some don't fly well anymore (my overweight Big Daddy come to mind).

The other issue is that the more time and effort I put into a rocket, I get more and more nervous to launch it for fear of a CATO, damaging it, or losing it. (Case in point: first flight of my Black Brant II with fiberglassed fins and exquisite paint job was lost when it drifted much further than expected).

My advice to you, and something I'm going to do going forward, is not worry so much about building for longevity, since you never know when a parachute will fail to eject, when a motor will explode, or if the winds up high are stronger than forecast. I'm still going to try my best to do a good job on building my rockets from now on, but not stress too much about building them to last, since it might be out of my control anyway.

Last anecdote: I fully painted my Estes M104 Patriot missile instead of using decals (even the lettering). It was a beautiful rocket when I completed it. First flight: delay was selected too long, so the parachute ejected a few meters above the ground, and the rocket core sampled. It was repaired, but it was frustrating to say the least. After all that work, and it got damaged on the maiden flight! It has since gone on to become my most flown rocket, since it's now a low-stress, no-longer-perfect rocket!
YES!!! I lost my 1st Estes D-R Tomahawk to a CATO on its maiden flight! Lost the 2nd & 3rd versions to shock cord failure, both lost after 3-4 flights. #4 still awaiting 1st flight.
 

Sooner Boomer

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Well, @Jeff Lassahn, are you confused yet? Almost everyone with any experience has their own way of building. Test them out! Buy several inexpensive kits of the same type and build them different ways. You'll probably come up with your own unique way of building durable rockets. Next, ask what type of glue is best.;)



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Woody's Workshop

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Tite bond wood glue is easily sandible, no roughness, bumps or other irregularities?
Yes, it is. Just don't try and go super fast or use heavy pressure. Just sand away and it makes a nice dust that can be used as filler in fillets. I do it all the time, it's how I build all my kits and scratch builds.
 

jrap330

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Yes, it is. Just don't try and go super fast or use heavy pressure. Just sand away and it makes a nice dust that can be used as filler in fillets. I do it all the time, it's how I build all my kits and scratch builds.
Thanks, I do it fast, with heavy pressure......will try you recommendations.
 

Jeff Lassahn

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Well, @Jeff Lassahn, are you confused yet? Almost everyone with any experience has their own way of building. Test them out! Buy several inexpensive kits of the same type and build them different ways. You'll probably come up with your own unique way of building durable rockets. Next, ask what type of glue is best.;)



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I've been on this forum long enough to know what I'm getting into. One shouldn't ask a question like this hoping to get The One True answer, it's nice to see a variety of experiences.

The problem with testing a bunch of ideas out myself is that longevity testing is by its nature a long project. I'm hoping I can get a head start by stealing from people who have already built rockets and flown them for several years, so I don't have to put in the several years myself. You know, standing on the shoulders of giants and all that.
 

rklapp

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The main problem with Titebond II is that it tends to bubble when drying. For fillets, I prefer to use epoxy or TB Quick&thick.
 

neil_w

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The main problem with Titebond II is that it tends to bubble when drying. For fillets, I prefer to use epoxy or TB Quick&thick.
Yes. I like to do one very thin fillet of very quick-drying TBII first, to completely penetrate the joint, then finish with Quick and Thick.
 

BABAR

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Yes. I like to do one very thin fillet of very quick-drying TBII first, to completely penetrate the joint, then finish with Quick and Thick.
In your experience does that make it significantly stronger than just a single Quick and Thick fillet?
 

rklapp

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In your experience does that make it significantly stronger than just a single Quick and Thick fillet?
Good question. TBII has more strength but more failure compared to Q&T?

TBII (fluorescent but couldn't find regular)

1611224911663.png


Q&T

1611224947621.png
 

BABAR

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Good question. TBII has more strength but more failure compared to Q&T?

TBII (fluorescent but couldn't find regular)

View attachment 447283

Q&T

View attachment 447284
What the heck is “% wood failure”?

who puts their rockets in the bun warmer overnite?

does PSI strength account for the much thicker fillet?

as opposed to maple, something tells me that 3000psi exceeds the strength of balsa and cardboard, so anything over that seems like overkill.

back to original question, @neil_w (or any others with experience), does the addition of a small TB2 (or other classic wood glue) demonstably (meaning “in flight or recovery or storage”) improve fin retention?
 

Back_at_it

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Yes. I like to do one very thin fillet of very quick-drying TBII first, to completely penetrate the joint, then finish with Quick and Thick.
this is the exact method that I use. The first fillet with the thinner adhesive soaks into the materials for a significantly stronger bond. You can then come back with thick and quick for a more finished fillet. The nice thing is that the two adhesives will bond to each other as well as the materials

The tensile strength and percent failures really don’t apply as they are both significantly higher than the failure point of balsa and cardboard.
 

neil_w

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In your experience does that make it significantly stronger than just a single Quick and Thick fillet?
I haven't tested, just going on intuition here. But being so marshmallowy, I don't trust the Quick and Thick to fill the very fine gaps in the joint that are often present in my experience. The one thing I know for sure is that air gaps, however small, do not add strength.

I have some vague questions about Q&T's quality of bond with glassine. Normally, when roughing or stripping the glassine layer to attach a fin, I don't include a border area for fillet adherence, which means that the fillet glue is bonding to the fin (good bond) and the glassine next to the fin (???). This would be a good area for testing.
 
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