Okay so no pressure........
Alcubierre Build Thread
- Thread starter neil_w
- Start date
-
- Tags
- build build thread
Help Support The Rocketry Forum:
No worries man, it'll be great. It's a fun build and not without some challenge.
I have learned to tune out the peanut gallery when it comes to the exhortations to make things bigger.
I have learned to tune out the peanut gallery when it comes to the exhortations to make things bigger.
Nytrunner
Pop lugs, not drugs
You have other people for that anyway
I do have some 4 inch phenolic laying around.....That'd be a 15" ring...
4 inch for the pods, got some 7.6 inch for the body....... got some in the attic.....how big would the ring be???? Sorry, but will need to get my level 3 to get this monster off the pad.Sure, I mean, that’ll be good for the *pods*...
Bigger. Bigger. Bigger! Bigger! Bigger!!!I have learned to tune out the peanut gallery when it comes to the exhortations to make things bigger.
25” ring, awesome!
Maybe that 2.6” version would be a bit more practical to get started...
Alcubierre flew yesterday on a D12-5, and once again the up part was picture-perfect. Straight up all the way and looking might fine while doing so. This time the parachute deployed properly, and it landed softly, but *still* suffered ring separations (two of them this time):
Contrary to my initial reaction, I think I am going to repair it one more time and try to fly again. Looks too good going up to give up on it, and it only needs some regluing this time, no paint touch ups. Gonna try epoxy, and might push some pinholes into the pieces to create some glue rivets.
Note that these are glue joint failures. I've noticed that TBII joints to basswood are just not that strong (at least, not as strong as balsa). I've now seen this in three different rockets. Gonna need to research this.
Contrary to my initial reaction, I think I am going to repair it one more time and try to fly again. Looks too good going up to give up on it, and it only needs some regluing this time, no paint touch ups. Gonna try epoxy, and might push some pinholes into the pieces to create some glue rivets.
Note that these are glue joint failures. I've noticed that TBII joints to basswood are just not that strong (at least, not as strong as balsa). I've now seen this in three different rockets. Gonna need to research this.
Or just use epoxy with basswood and fight the tendency to overthink.
Anyway I'm glad to hear she will fly again.
Yeah, that's just not super-convenient all the time (like when I was laminating the layers of my upscale Quinstar frame pieces). I just wanna know what happened to the "glue joint is stronger than the wood itself" promise, which seems to have been pretty thoroughly broken.
But at least for this rocket I shall hope epoxy does the trick. If not, then I'll at least get one more flight out of it and then retire.
I'll just leave this here. Glad to hear it will fly again.
Nice pic, thanks for that one! I was at a bad angle for that launch, didn't get any pics.
- Joined
- Oct 8, 2016
- Messages
- 2,834
- Reaction score
- 1,211
The glue strength rule is valid but, it is also conditional. The condition is that the glue must have adequate penetration into all surfaces being joined. Basswood is not nearly as porous as balsa. I know of two good ways to achieve a better bond with basswood using any type of adhesive.
Note: A prerequisite or each of the following is to sand the basswood with as course a grit as the project can tolerate. Another trick that helps is to wipe down the surface(s) with isopropyl alcohol before applying adhesive.
- Thin a portion of the adhesive to a water like consistency and apply a good coat to all surfaces being bonded together. Immediately recoat surfaces with unthinned adhesive and bond.
- Use a heat gun or hair dryer to warm the basswood prior to applying glue.
Nytrunner
Pop lugs, not drugs
My first thought was surface contamination due to how much you had to handle those pieces during construction. Way to stick with it and work out the issues on a great rocket
- Joined
- Aug 27, 2011
- Messages
- 11,615
- Reaction score
- 6,245
Another option is "cheaters". You used these on your Plasma Dart on the main body, thin balsa strips laid down in that case to provide both orientation and surface area for adhesion of your cut body tubes. Another term for them is "balsa fillets." I use them frequently for putting fins on rockets. Cut a 1/16" piece of balsa strip, as long as the attached surface area, and 1/16" wide. Glue it in place on the flat (or curved) surface onto which the fin or strut will be placed, not on the fin or strut itself (I don't have access to a paint program here at work, think of the top line in a capital T, place it on the undersurface of this line right where you want the upright line to go). Since it is so small and so light, it is easy to place in the EXACT position along your marked pencil line and dries pretty quickly. You may need to use clothes pins or something to hold it in place, as sometimes thin strips tend to curl with water based glues. Once it is dried, you can use this as an alignment base to place your fin or strut. Once that is dry, if you like you can place one on the other side for symmetry and added strength. Once dry, you can use two fillets on each side, one is fin to cheater and the other is cheater to base. You can add a thicker fillet over this if needed that may completely obscure/hide the "cheater", so you don't have the cosmetic or aerodynamic compromise.
Pluses:
1. It is much easier to initial align a tiny strip with a straight pencil line than a fin or strut, so assuming your PENCIL line is right, the "cheater" should be right. Assuming the CHEATER is right, your fin or strut should be perfectly lined up with the strip.
2. If you only use a cheater on one side, it still effectively doubles the surface area bond between parts, triples your contact area if you put a second cheater on the other side. I suspect the actual mechanical effect is even greater.
Minuses:
1. It may be bit less "cosmetic" than a pure joint without the cheater, although you can probably hide the cheater with a moderate glue fillet. In the cases of your ring fins, just by putting them on the inside curvature they may be relatively hidden.
2. It is an extra step, you have to cut and measure them, glue them, and wait for the glue to dry.
3. If you don't cover it with a "thick" fillet, it will add a touch of aerodynamic drag. So this is not something you are going to use in an altitude or duration competition model.
Pluses:
1. It is much easier to initial align a tiny strip with a straight pencil line than a fin or strut, so assuming your PENCIL line is right, the "cheater" should be right. Assuming the CHEATER is right, your fin or strut should be perfectly lined up with the strip.
2. If you only use a cheater on one side, it still effectively doubles the surface area bond between parts, triples your contact area if you put a second cheater on the other side. I suspect the actual mechanical effect is even greater.
Minuses:
1. It may be bit less "cosmetic" than a pure joint without the cheater, although you can probably hide the cheater with a moderate glue fillet. In the cases of your ring fins, just by putting them on the inside curvature they may be relatively hidden.
2. It is an extra step, you have to cut and measure them, glue them, and wait for the glue to dry.
3. If you don't cover it with a "thick" fillet, it will add a touch of aerodynamic drag. So this is not something you are going to use in an altitude or duration competition model.
I had cheaters on the outside of the ring, one of them stayed attached to the ring and lifted with it, while the other stayed attached to the wing and disconnected from the ring.
The fact that the ring pieces were under a bit of tension to fit in place probably didn't help matters...
The fact that the ring pieces were under a bit of tension to fit in place probably didn't help matters...
The cheaters you've got are on the outside of the ring. Adding cheaters on the inside, so the two cheaters form a notch to hold the ring end, would certainly help and might more than double the effect. Something in my head says that it would be better than double, but I can't put a finger on why. Something about one face of the notch in compression while the other is in tension, so whichever way is better it's sure to be covered. But then if it went the right way to start with then the second would less than double the effect, not more. I dunno, it just feels right.
Maybe just rough the surface up a little, wipe with acetone on a Q-tip, use a little epoxy, and stop listening to the voices internal and external alike telling you to overcomplicate this.
(Hmm, Q-tip, Q-Jet? Hmmmm...)
Maybe just rough the surface up a little, wipe with acetone on a Q-tip, use a little epoxy, and stop listening to the voices internal and external alike telling you to overcomplicate this.
(Hmm, Q-tip, Q-Jet? Hmmmm...)
That will be the approach. If it breaks again on the next flight, it will be retired.
Getting ready to upscale the Alcubierre. Just ordered parts from Madcow. Should start posting in a week or 2. 3 inch body tube, 12 inch ring. 38 mm motor mount. Should be fun.
Steve
Steve
I look forward to the thread and photos!
I have to say that your rocket is simply awesome, Neil. Pity you don't have plans available for people to build their own.
If you ask nicely who knows what might happen.
Thanks Neil!
If you're serious about building one, PM me and we can make it happen. I don't have plans per se but I could give you sufficient information (plus using this build thread as a reference) to do it.I have to say that your rocket is simply awesome, Neil. Pity you don't have plans available for people to build their own.
However, given that mine has been damaged on each of its two flights, you have to ask yourself whether you actually want to build it the way I did.
Nytrunner
Pop lugs, not drugs
Upscale thread approved, go do it
Neil can probably provide orks to those who ask nicely
Neil can probably provide orks to those who ask nicely
If you're serious about building one, PM me and we can make it happen. I don't have plans per se but I could give you sufficient information (plus using this build thread as a reference) to do it.
However, given that mine has been damaged on each of its two flights, you have to ask yourself whether you actually want to build it the way I did.
Well I'm only semi-serious, as I don't think my building skills are quite where they would need to be (yet).
Let me tell you a secret. Upscales of rockets like Neil's are easier then the smaller versions. Bigger pieces are easier then small ones. Don't let anyone else know, okay?
That is very, very true!
Definitely true at least into the MPR and Level 1 sizes.
For example: Neil's recurring trouble with this rocket has been separation of the half rings from the pylons/fins. This may be due in part to the ring's being made by laminating bent wood.
An upscaled ring could be made from sonotube, with a fiberglass wrap if you like or just a soak of the epoxy resin (making pseudo phenolic). Also, it would be wide enough to notch halfway across and interlock with similarly notched pylons. Once the interlocked notches are glued and filleted, you will not have the same problem Neil has had.
Will you have a different problem? Probably, but that'll be easier to deal with too.
An upscaled ring could be made from sonotube, with a fiberglass wrap if you like or just a soak of the epoxy resin (making pseudo phenolic). Also, it would be wide enough to notch halfway across and interlock with similarly notched pylons. Once the interlocked notches are glued and filleted, you will not have the same problem Neil has had.
Will you have a different problem? Probably, but that'll be easier to deal with too.
Similar threads
