Wood glue in HPR - how much motor is too much?

I am a believer in wood glue where wood glue is as strong as the material employed. I have recently built and flown a tube fin rocket on an I300T in a dual deployment flight that ended in a crash.

The crash was NOT caused by airframe failure (postal tube) or fin/glue failure (more postal tube with wood glue). On impact with a 'chute acting as a streamer the rocket lost two fins due to delamination of the paper - the glue joint was intact.

However at the launch the RSO, LCO, and others had doubts about an I300 on wood glue. The RSO tugged and pulled on the fins and agreed they seemed secure and alllowed the launch. Boost was great and straight - deployment problems had nothing to do with the construction.

So my long winded question is... do you use wood glue for any HPR use and if so what's the upper limit of motor that you have used with a wood glued fin joint?

Ooops. The subject is misleading. I wish I knew how to rename it. I'll ask the moderators - it should be:

Wood glue in HPR - how much motor is too much?

Honestly, if you are like me, I plan on moving up higher so I bought a set fo west systems pumps fillers, etc. Then I have them. It seems to me that the RSO and LCO (both good buddies of mine) aren't leary of that many of my rockets (29mm Deuce in particular) since they now I use epoxy and they are nice and strong. Might as well get the experince and learn tecniques with smaller birds and epoxy then reap the repracussions (maybe some) on larger birds.

Ben

I love this subject. Wood glue rocks. Epoxy stinks (literally.)

But seriously -

I know of wood-glue built rockets that have flown on high thrust K's (like a K1000). I absolutely guarantee that I'll never build a rocket made of paper and wood (i.e. LOC, Binder, BSD) with anything BUT wood glue.

Different materials require different adhesives (phenolic, plastics, fiberglass, composites, whatever). This is where epoxy comes into play.

My level 2 project is almost completely built (needs finish work, but construction is essentially done) and I used exclusively LOC parts, plywood fins, and wood glue. I know without any shadow of a doubt that it will handle J motors.

If a given rocket was designed for it properly, I wouldn't hesitate to attempt a L3 cert (i.e. M class motor) with a rocket built with wood glue.

Originally posted by Fore Check
If a given rocket was designed for it properly, I wouldn't hesitate to attempt a L3 cert (i.e. M class motor) with a rocket built with wood glue.

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I'm confident it can be done.

The trick is understanding the materials you're working with, and as you said, designing for it.

-Kevin

I voted for LPR and MPR only b/c that is all I have experience with. I imagine you could use i with anything if you really knew what you were doing.

I have used Elmer's Carpenter's glue on rockets up to 2.6" in diameter with 1/8" plywood fins flying on motors up through Aerotech G motors with no problems at all.

I always use a double-glue joint and the fins have broken on landing without failing the glued joint. If you are unfamiliar with this method, you put a thin coat of glue on the mating surfaces of the parts to be attached and let them dry. Them put a thin layer on one part and put them together. It makes a VERY strong joint.

Try double-jointing your root to the motor mount, then add internal and external fillets. You'll have to soak the think in water for days to get the fins to come off. Flat spin landings from thousands of feet will only nick the paint.

While I haven't used it above G's, I would trust a properly constructed rocket with wood glue up to M's.

The power of the motor is irrelevant by itself. The weight of the vehicle and the coefficient of drag need to be taken into account, in order to calculate the acceleration and speed of the vehicle, and therefore the forces on the glue joints.

A properly designed and built HPR bird could be done with wood glue. But since most people use stronger materials I doubt there's much good experience and advice on proper design and construction for HPR using it.

One are of particular concern is the motor tube. HPR motors generate much more heat and transfer that much more of it to the mount. Wood glue can soften with heat (I still remember the old Estes tip about heating a misaligned fin over a light bulb to soften the glue and straighten it). That doesn't mean this is a barrier. It means this is one of the things to take into account in proper design and construction.

My best example of proper design and construction is the Hiroc and Atlas boosters. The airframe was the tank. Tank pressure made them airworthy despite a skin so thin that a dropped wrench could (and did) puncture it. That took some serious engineering thinking. Putting wrist straps on tools to be used around them was just a neat hack.

I built my BSD Horizon with mostly wood glue because I wanted to keep it light. I have only flown it once or twice, but I have no doubt that it is strong enough (the TTW fins help a lot).

Originally posted by DynaSoar
The power of the motor is irrelevant by itself. The weight of the vehicle and the coefficient of drag need to be taken into account, in order to calculate the acceleration and speed of the vehicle, and therefore the forces on the glue joints.

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Agreed...

Originally posted by DynaSoar
A properly designed and built HPR bird could be done with wood glue. But since most people use stronger materials I doubt there's much good experience and advice on proper design and construction for HPR using it.

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Also agreed. If you read my original post my LCO, RSO, and several flyers with much more experience than I have all said... wood glue, are you sure you want to do that? Are you sure it can handle an I300? (Maiden Flight no less). My response was that the glue was stronger than the material itself. And I was right. So I started this thread to find out if anyone else is using wood glue and to what extent. I'm glad to see a number of fliers are willing to use it with large powerful rockets

Originally posted by DynaSoar
One are of particular concern is the motor tube. HPR motors generate much more heat and transfer that much more of it to the mount. Wood glue can soften with heat (I still remember the old Estes tip about heating a misaligned fin over a light bulb to soften the glue and straighten it). That doesn't mean this is a barrier. It means this is one of the things to take into account in proper design and construction.

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Here I'm not sure I agree. The Estes tip may have been related to white glue not yellow wood glue. Also modern wood glues have significant resistance to modest temperatures. Since NFPA1127 requires that the motor itself not get much above 200 degrees this limits our temperature profile. Also epoxy - other than specialized varieties softens quite a bit with heat.

That said - I use epoxy on my motor mounts typically because of the sloppy factor. I'm not a very precise woodworker and since I work with improvised materials often the centering rings are not perfect fits with the tubes. In this case, wood glue would not be a good idea - it doesn't fill gaps with the strength needed. I tend to use high temp epoxy in the motor mount because of this. Where there are more precise joints I am happy to use wood glue where possible.

Originally posted by DynaSoar
My best example of proper design and construction is the Hiroc and Atlas boosters. The airframe was the tank. Tank pressure made them airworthy despite a skin so thin that a dropped wrench could (and did) puncture it. That took some serious engineering thinking. Putting wrist straps on tools to be used around them was just a neat hack.

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Nice example - I had not heard that before.

I only use epoxy. 5-minute Bob Smith epoxy is cheap and effective for small rockets, and for quickly holding parts in place on big rockets, to be followed by industrial strength epoxies.

I would imagine using wood glue only to prove a point or to save money. I'm not against either!

Slower drying, high strength products are:

-- JBWeld (for high heat applications, like MMT's)
-- West Systems
-- Gugeon Brothers Pro-set (who make West Systems)
-- Aeropoxy (Giant Leap)
-- Hysol
-- T33

Plenty of others....

Originally posted by uncle_vanya




Here I'm not sure I agree. The Estes tip may have been related to white glue not yellow wood glue.

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I've performed a version of the estes method, using a hair drier to soften Titebond II wood glue... It took a long time and it softened it only a minute bit, but it did work. (BTW, I didn't use a lightbulb b/c I'm somewhat photosensitive [sensitive to bright light])

Originally posted by TeenRocketNerd
I've performed a version of the estes method, using a hair drier to soften Titebond II wood glue... It took a long time and it softened it only a minute bit, but it did work. (BTW, I didn't use a lightbulb b/c I'm somewhat photophobic [sensitive to bright light])

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I'd like to see the same test on 5-min epoxy... My suspicion is that they both soften.

I know for a fact epoxy will soften with heat. Better epoxies harden back up with no or very little loss in strength but they do indeed soften. People don't realize how strong TB II really is. If the glue joint is done properly it is stronger than the material. In this specific application the TB II was the best choice. I much preferr TB II when dealing with any natural material like wood or paper. Epoxy has it's place but for certain materials and certain applications TB II is a better choice.

Originally posted by uncle_vanya
Here I'm not sure I agree. The Estes tip may have been related to white glue not yellow wood glue. Also modern wood glues have significant resistance to modest temperatures. Since NFPA1127 requires that the motor itself not get much above 200 degrees this limits our temperature profile. Also epoxy - other than specialized varieties softens quite a bit with heat.

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IMHO, this debate of heat from the motor softening up the glue isn't nearly as bad as we think it might be. The glue has to be subjected to a LOT of heat for a LONG period of time to soften. Aside from the max temp that you mention above, think about how long that the heat is present in that part of the rocket. A motor casing is hot to the touch for probably 20 minutes max** (notice: hot to the touch != 200 degrees). The paper/cardboard/phenolic motor tube acts as an insulator & doesn't efficiently transfer the heat much beyond the tube--but what bit that does is certainly cooler than the surface temp of the casing. So in a long winded way, I'm saying that there isn't enough heat to effectively heat up the wood glue nor be a source of prolonged heat to provide a detrimental effect to your rocket.
However, if you happen to have some kind of metallic motor retention that comes into direct contact with the motor tube (like a Slimline or Aero Pack retainer), heat transfer would be more efficient & significant, so as those manufacturers suggest, JB Weld is needed (& wood glue wouldn't work anyway to attach those metallic components).

** - I would say this is a reasonable time estimate for motors up to Is or Js as that is the largest I have flown. Larger motors may certainly stay warm longer, but probably still not radiate enough heat to adversely affect the rocket. YMMV.

Originally posted by uncle_vanya
That said - I use epoxy on my motor mounts typically because of the sloppy factor. I'm not a very precise woodworker and since I work with improvised materials often the centering rings are not perfect fits with the tubes. In this case, wood glue would not be a good idea - it doesn't fill gaps with the strength needed. I tend to use high temp epoxy in the motor mount because of this. Where there are more precise joints I am happy to use wood glue where possible.

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Might I suggest using multiple, thin layers of wood glue can build up to fill some reasonable gaps. I'm a big fan of Elmer's Titebond II & will apply a layer (like on fin fillets), wait maybe 2 or 3 minutes, then apply another, & let dry... Repeat until I get the desired effect. For the time it takes for one application of 5-minute epoxy fillets to cure, I can do 3 or 4 layers of wood glue fillets. IMHO, beyond 4 layers, it's purely aesthetics...

I don't think that it is as simple as just what motor you are using. I think it has more to do with the application that it is being used for. Some flights on G motors would put more strain on a rocket with much larger motors (K, L, M, etc). To me, I think that wood glue has its uses for almost any size commercial motor so long as the flight profile isn't on the extreme end of the spectrum.
Acceleration and top speed are more what I would look for when determining what adhesives are to be used, not just the size of the motor.

-Chris

Originally posted by AIM-54C
I don't think that it is as simple as just what motor you are using. I think it has more to do with the application that it is being used for. Some flights on G motors would put more strain on a rocket with much larger motors (K, L, M, etc). To me, I think that wood glue has its uses for almost any size commercial motor so long as the flight profile isn't on the extreme end of the spectrum.
Acceleration and top speed are more what I would look for when determining what adhesives are to be used, not just the size of the motor.

-Chris

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I think that's fair - but hard to put into a poll. I wanted to see what people thought in both posts and in a simple poll.

I am heartened to see a mix with a large number being "no limits" folks.

I have heard that at least one level three project was successfully built with JUST wood glue. I wonder if I'm brave enough to do that one day...

The bottom line with adhesives is that you have to know your materials. The glue simply needs to be stronger than the materials it is bonding. It's really that simple.

Take Titebond II for example. At room temperature, Titebond II has a strength of 3,750 PSI, rivaling most epoxies. Left at 150 degrees overnight, it weakens to 1,750 psi. See https://www.titebond.com/ProductLineTB.asp?prodline=2?prodcat=1 for the data.

So in this instance, for rockets made of paper and wood, wood glue is plenty sufficient for most any flight, 1/4 A's - M and N's. It is obviously much stronger than the materials it is bonding, simple as that. Oh, and if you think you have to re-enforce fins to be able to take an M, I'll beg to differ. I used 3/8 Baltic Birch Ply on my L3 bird and an M1419 with no issues.

One way to make an M powered rocket using wood glue would be to use sonotube as the airframe, since it's paper and really needs no glassing. Use wood for the centering rings, bulkheads and fins, a loc type motor mount, and you're in business. Again, the glue is stronger than the materials it is bonding.

That being said, wood glue makes horrible fillets and isn't a good filler as it shrinks when it dries. It also doesn't bond to fiberglass well, so if you are using fiberglass in your build, epoxy would be better.

Wood glue has a couple of benefits, besides cost. For starters, there is no mixing, just dribble and go. Second, it's great for folks who might be allergic to various epoxy resins. Finally, it's cheap and can be found just about anywhere.

But while it has some benefits over epoxy, it is also worth noting that while wood glue works well and is certainly strong enough for just about anything, there are some drawbacks with the speed at which the wood glue tacked up during construction. I dunno if this has happened to anyone else who has tried wood glue, but Titebond II tacks up really quick, and while trying to insert a coupler, I found I was unable to get the coupler in as far as needed. This was after I had a similar experience while trying to install a motor mount assembly, again using Titebond II wood glue. I got it almost all of the way in, but as the centering rings were spreading the glue, the tackiness got too tough before I could get it all the way in and the end result was me nearly destroying the rocket in an attempt to get the assembly out. I also nearly destroyed the coupler in question.

So, if anyone has any suggestions on how to use wood glue and avoid this issue, I am all ears! But the bottom line is that you can in fact use wood glue in high power rocketry and be just fine.

Couplers and centering rings... I had the same experience with Titebond II while building my Estes Mercury Redstone and Estes Blackbird. After those experiences i swore i would only use use expoxy for centering rings and couplers.

I think in this same thread someone has mentioned that Titebond III does not have this problem. Could someone else verify this????

Bob

It can definitely happen with Titebond III, but you have a lot more time before it does. The only time it has happened to me was when I was spending a long time getting a coupler in - it grabbed after 20 or 30 seconds. If you slide it right in, it's fine, and it definitely doesn't grab as fast as titebond II.

Originally posted by SpartaChris
The bottom line with adhesives is that you have to know your materials. The glue simply needs to be stronger than the materials it is bonding. It's really that simple.

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Total agreement.

Originally posted by SpartaChris
So in this instance, for rockets made of paper and wood, wood glue is plenty sufficient for most any flight, 1/4 A's - M and N's. It is obviously much stronger than the materials it is bonding, simple as that. Oh, and if you think you have to re-enforce fins to be able to take an M, I'll beg to differ. I used 3/8 Baltic Birch Ply on my L3 bird and an M1419 with no issues.

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I again agree. Obviously this needs to be based on fin configuration (shape and thickness) and expected terminal velocity. You can fly very large motors without reinforced fins but you can't fly very fast rockets with thin fins without reinforcement.

Originally posted by SpartaChris
That being said, wood glue makes horrible fillets and isn't a good filler as it shrinks when it dries. It also doesn't bond to fiberglass well, so if you are using fiberglass in your build, epoxy would be better.

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I've seen some info in this thread that leads me to think it might be possible to do better than I have with wood glue fillets. There was something about many many thin layers. I'd like to try that before I write it off.

Originally posted by SpartaChris
But while it has some benefits over epoxy, it is also worth noting that while wood glue works well and is certainly strong enough for just about anything, there are some drawbacks with the speed at which the wood glue tacked up during construction. I dunno if this has happened to anyone else who has tried wood glue, but Titebond II tacks up really quick, and while trying to insert a coupler, I found I was unable to get the coupler in as far as needed. This was after I had a similar experience while trying to install a motor mount assembly, again using Titebond II wood glue. I got it almost all of the way in, but as the centering rings were spreading the glue, the tackiness got too tough before I could get it all the way in and the end result was me nearly destroying the rocket in an attempt to get the assembly out. I also nearly destroyed the coupler in question.

So, if anyone has any suggestions on how to use wood glue and avoid this issue, I am all ears! But the bottom line is that you can in fact use wood glue in high power rocketry and be just fine.

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This is an issue I have had as well. I have heard that various versions of wood glue perform differently in this respect. I use Titebond III mainly and find it doesn't setup slow either. I think from talking with a woodworker friend that Titebond II is even faster however. When I have to put a coupler in I gob the glue and move fast. I'm not brave enough to do a motor mount without epoxy simply due to this reason - and the previously mentioned sloppy woodworking.

This resurfaced today I suspect due to someone answering the poll. I still find it interesting that the answers have divided the way that they have. As of the time I write this - about 1/3rd of you answered LPR and MPR only, and another chunk (not quite a third) answered that there are no limits.

Personally I have flown up to strong I motors on just wood glue. I have also flown a J motor in a rocket with gorilla glue and a funnel for a fin so I don't think I'm typical. (Not my best flight btw... but the airframe held)

Food for thought here.......
We have all seen rockets built of the finest materials available,carbon fiber, kevlar, various epoxies,etc. FAIL. But is it the failure of the products or the design?
I think in the long run, proper design and construction, within the parameters of the materials being used, account for the success or failure of a given project. But by nature rocketry is, in a lot of cases, about pushing the limits.

Will it hit mach? Is it a long burn motor generating lots of heat? How heavy?Etc, etc, these types of factors are more important in the design, than is it wood glue or not. As long as the glue joints are as strong or stronger than the materials being used,then it becomes a design issue.

I have RSO'd many a rocket, and have denied flight to many more epoxy glued rockets, due to poor construction,than I ever have to wood glue.

If I have had doubts about either, but the design and construction seemed well thought out and good, Then it was OK'd as a heads up flight or sent to a pad farther out for safety. A few pointed questions to the rockets owner always seemed to sort out those that knew what they were doing, and the wanna be's.

uncle_vanya said:

Personally I have flown up to strong I motors on just wood glue. I have also flown a J motor in a rocket with gorilla glue and a funnel for a fin so I don't think I'm typical. (Not my best flight btw... but the airframe held)

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Well, for what it's worth, my latest high power build (MadCow Rocketry Sea Wolf) was done using wood glue. It will be able to take J's with no problems.

blackjack2564 said:

Food for thought here.......
We have all seen rockets built of the finest materials available,carbon fiber, kevlar, various epoxies,etc. FAIL. But is it the failure of the products or the design?
I think in the long run, proper design and construction, within the parameters of the materials being used, account for the success or failure of a given project. But by nature rocketry is, in a lot of cases, about pushing the limits.

Will it hit mach? Is it a long burn motor generating lots of heat? How heavy?Etc, etc, these types of factors are more important in the design, than is it wood glue or not. As long as the glue joints are as strong or stronger than the materials being used,then it becomes a design issue.

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The worst shred I have had was on an I366 on an epoxied cardboard tube fin rocket. Several newer versions of that rocket have been built with just wood glue and they have done quite well on motors almost that potent. I would push my latest one harder but it was decorated by my kids doodling on it (white postal tube) and I probably need to retire it before I crash it.

I tend to use epoxy where my parts fit is less than ideal. Since I like scratch building and I'm not a great wood worker - my parts fit is less ideal than I would like and wood glue is not very tolerant of this. In these cases I use epoxy or gorilla glue (where ok). When the parts fit nicely and the main parts to bond are wood and paper I'm a wood glue fan. The only downside is the drying time. It can take a long time to get a rocket built with wood glue if the steps are sequential rather than parallel.

It's already been made clear that flying wood glue rockets on M's is perfectly do-able, so I don't really have anything to add to the conversation besides another voice of confidence.

I'll be flying my L1 rocket with 99.9% wood glue construction. I've flown it twice now on G64's and it still feels bullet-proof all the way around. I'm comfortable the joints will handle the forces involved in L1 motors. If my cert flight is unsuccessful, it'll be because of some bonehead mistake like assembling the motor wrong or forgetting to put in the parachute - NOT because the wood glue didn't hold.

I've had wood glue grab a coupler before I was ready, but that wasn't the wood glue's fault, that was my fault for not being prepared for it to grab that quickly. I knew wood glue behaved like that and yet I didn't move quickly and smoothly to get the coupler into place before the glue grabbed and I almost ruined the rocket as a result.

So as long as you know your materials and how your adhesives will behave within and between those materials, and you incorporate that information into your design and build, you should be good to go. up.

Here's the cert flight launch pic of my all-wood glue L2 that I mentioned above when I originally posted in this thread (J350W motor):



It has since flown on a J800T as well as a couple of I's. It still has hardly a scratch on it; although the flight on the I300T was a little hairy because the delay selection was a bit long....

Maybe Blackjack will pop in here again and clarify..But, we were talking about some crazy stuff people had done in the building of their rockets and he told me of one where a guy flew a rocket on a big motor(K or L??) with the fins TAPED on and it remained intact!:surprised: