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Tip-to-tip papering fins

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BDB

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As I was repairing a fin on my Solar Warrior this weekend, I noticed how flimsy the balsa fins are. I now paper all of my balsa fins for added strength, but that doesn't do much for the BT-fin joint. Sure, I lay down healthy filets, but that didn't stop my Solar Warrior's fin from detaching on landing a few months ago.

In the HPR world we would add tip-to-tip glass or carbon fiber cloth. Does anyone do something like this with paper for LPR?
 

GlenP

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Is that where you lay down a sheet from the tip of one fin to the root, then along the body tube to the root of the adjacent fin, then to the tip of that fin?

No, never heard of that in LPR, usually fins are papered by folding over the leading edge and go from trailing edge to trailing edge before the fin is attached to the body. but this is a clever concept, and probably would work with paper, if you could solve the warping problem. Usually the moisture in the glue can warp the balsa, so you have to keep it flat under some heavy books or bricks while the paper is drying. Not sure how to tackle that on two adjacent fins that are already on a body tube.
 

BDB

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Is that where you lay down a sheet from the tip of one fin to the root, then along the body tube to the root of the adjacent fin, then to the tip of that fin?
That's what I mean. I paper fins like you do right now, but I'm interested in strengthening them and their bond to the BT. Check out post #218 in this HPR thread. The poster used flour and lead shot to evenly apply pressure for a FG T2T. I think something like this could be done with paper and wood glue on LPR models. You would probably need to peel the glassine from the BT in the area between the fins and construct a apparatus to support the fins and BT under the pressure. I may give it a shot sometime this winter.
 

GlenP

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The poster used flour and lead shot...
I think something like this could be done with paper and wood glue...
I may give it a shot
(Rim shot!)

With a jig like that you should be able to keep the fins from warping, might be worth a try. Typically, white glue shrinks less than yellow wood glue.
 

les

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As I was repairing a fin on my Solar Warrior this weekend, I noticed how flimsy the balsa fins are. I now paper all of my balsa fins for added strength, but that doesn't do much for the BT-fin joint. Sure, I lay down healthy filets, but that didn't stop my Solar Warrior's fin from detaching on landing a few months ago.

In the HPR world we would add tip-to-tip glass or carbon fiber cloth. Does anyone do something like this with paper for LPR?
What actually broke when the fin detached? And what type of glue did you use?
A balsa/cardboard tube joint with a good wood glue should be stronger than the materials themselves.
So did the body tube tear or did the fin material break? Or did the actual joint let go?
 

K'Tesh

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The OP is asking about tip to tip papering for strength, not warp prevention.

BDB, I'd say no, it wouldn't help, or it would help only a little, and would greatly complicate the repair process of a damaged fin. If you want to improve the strength, try slotting the tube, and using fin tabs glued to the motor tube w/internal fillets.
 

BDB

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What actually broke when the fin detached? And what type of glue did you use?
A balsa/cardboard tube joint with a good wood glue should be stronger than the materials themselves.
So did the body tube tear or did the fin material break? Or did the actual joint let go?
@les - The fin tore away from the BT, but left the fillet on my Solar Warrior. It seems like the glue didn't bond well to the balsa. I think I was using Elmers wood glue on that build.

BDB, I'd say no, it wouldn't help, or it would help only a little, and would greatly complicate the repair process of a damaged fin. If you want to improve the strength, try slotting the tube, and using fin tabs glued to the motor tube w/internal fillets.
@K'Tesh - You make a good point. Papered TTW fins would be plenty strong, and that could easily be done on a fresh build of a Solar Warrior. (I have a spare kit.) In HPR, people usually reserve T2T for MD rockets that can't accommodate TTW fins with internal fillets. If I want to test this, maybe I should try it on an Estes Yankee or Wizard. They are notorious for losing fins.
 
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rharshberger

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@les - The fin tore away from the BT, but left the fillet on my Solar Warrior. It seems like the glue didn't bond well to the balsa. I think I was using Elmers wood glue on that build.
Did you peel the glassine off the airframe, where the fin root bonds?
 

neil_w

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I guess I'm having a bit of a hard time with the idea that the SW really needs further reinforcement. It has very long root edges; if properly glued and filleted I'd think they ought to be OK.

Mine has always found soft landing places so far (including water) so to be fair it hasn't really been "tested". But they sure feel strong to me.

Based on your description of the failure, it seems like there was a glue problem more so than a fundamental deficiency in the way it's designed. Certainly, if you slot the tube and go TTW it should add a lot of strength, though I'm not sure whether you'd get the full benefit if you glued tabs onto the existing laser-cut fins, or if you really need to cut new ones with the tabs build-in. If you attached tabs to the existing fins, maybe papering them all the way down would do well to reinforce the joint.

Maybe just removal (at least partially) of the glassine layer would ensure a better bond between the fins and the BT. Dunno.
 

BDB

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Did you peel the glassine off the airframe, where the fin root bonds?
I guess I'm having a bit of a hard time with the idea that the SW really needs further reinforcement. It has very long root edges; if properly glued and filleted I'd think they ought to be OK....Maybe just removal (at least partially) of the glassine layer would ensure a better bond between the fins and the BT. Dunno.
I honestly don't remember if I peeled the glassine layer. This was one of my first serious builds as a BAR. I used to just rough up the surface with some sanding; maybe that is what I tried, and it wasn't sufficient.

That said, fins popping off is a routine problem in LPR, right? Surely I'm not the only person with this problem. (If so, we have found the weakest link, and it is me!)
 

Woody's Workshop

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I had an idea on repairing an old rocket that had the fin break off at the root edge.
I'm going to try it on my next build.
Using a pin drill on my dremel, drill into the root edge for 2 toothpicks.
Drill through the body tube as well.
Cut the toothpicks to length.
Glue in the toothpicks, and epoxy the other end to the engine mount.
Should make them pretty strong I would think.
 

samb

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I think the tip-to-tip technique has some merit for low power models, especially those with fins with a longer span. Mr. Vern Estes provided a modified TtoT method in the instructions for his very first model rocket kit, so there is some precedence for it.

Scout fin reinforcement.jpg

I used model airplane tissue and dope on a Solar Sailer clone just because I felt like it and I thought that that particular kit could benefit from a little strengthening. I was quite pleased with the results and the rocket gods were as well. They saw fit to direct it to a dirty stinkin' rottin' voracious rocket eating tree many moons ago. Some things you just don't get over.

pdr_solar_sailor01.jpg
 

neil_w

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Fins do certainly pop. :)

I popped a fin on my Elliptic II on its second flight, but that fin has much longer span and shorter root, so it wasn't too surprising. It also seemed to be at least partially a glue failure (the fillets didn't seem to have adhered very well) although the fin itself did take the outer layer of the BT with it, so *that* glue held pretty well.

I haven't ever peeled the glassine layer under fins, although I do usually at least rough it up.
 

rharshberger

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I too have had LPR fins pop off, but very few since I started reving the glassine from the fin root area and a bit under the fillets.
 

les

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Are most people using the double glue technique?

Apply a bead of glue to the fin root and press onto the body tube
Remove fin and wipe fin edge and body tube to only leave a thin layer of glue - more glue is NOT better
Wait at least a minute
Apply a new thin layer of glue to the fin edge - again, more glue is NOT better
Carefully locate the fin onto the tube. It will grab quick. Let dry.

This gives a real strong joint. The BT should tear or the balsa will break before the joint lets go....
 

BDB

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I think the tip-to-tip technique has some merit for low power models, especially those with fins with a longer span. Mr. Vern Estes provided a modified TtoT method in the instructions for his very first model rocket kit, so there is some precedence for it.

View attachment 306333
Super-interesting!

I probably just screwed this one up somehow. Another method that I have had good success with in the past is "glue rivets:" poke a line of small holes in the BT where the fin will be attached. The glue then fills the holes and forms small "rivets" on the inside of the BT. (Of course, this wouldn't work on MD rockets.)
 

samb

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Are most people using the double glue technique?
...
This gives a real strong joint. The BT should tear or the balsa will break before the joint lets go....
Yep, happens every time I fly my Estes Goblin with the stock streamer. :blush: Some designs are just prone... that's what I keep tellin' myself anyway.
 

TangoJuliet

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Yep, happens every time I fly my Estes Goblin with the stock streamer. :blush: Some designs are just prone... that's what I keep tellin' myself anyway.
I have yet to fly my Goblin, but I had already determined that the stock streamer appeared too minimal for the weight of that rocket with a "D" motor casing in it and the clay weight in the nose cone. Mine will either fly with an enlarged Mylar streamer or a parachute.


And I agree, it sounds like the OP's issue has more to do with an improper glue joint than anything else. A double glue technique and repeated glue fillets seem to work well for me using Tite-Bond II.
 

Pointy_end_up

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I'm in the middle of building a Goblin and thought about this thread. I decided to paper the fins and leave the paper along the root side long. I then folded the paper along the root edge and glued everything with titebond. Then added fillets using titebond.

20161212_183541.jpg

It isn't exactly like the tip-to-tip method but I'm hoping this will prevent the fins from popping off. Murphy and his laws always end up with my streamer rockets finding the hardest random thing to hit in a grass field. I'm also building it to where I can clip in a streamer or parachute to leave my options open on that front.
 

Forever_Metal

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I'm in the middle of building a Goblin and thought about this thread. I decided to paper the fins and leave the paper along the root side long. I then folded the paper along the root edge and glued everything with titebond. Then added fillets using titebond.

View attachment 307191

It isn't exactly like the tip-to-tip method but I'm hoping this will prevent the fins from popping off. Murphy and his laws always end up with my streamer rockets finding the hardest random thing to hit in a grass field. I'm also building it to where I can clip in a streamer or parachute to leave my options open on that front.
i cut the glassine layer off the tube where the papered fin meets, then use 5 minute epoxy (sparingly) to make the fin to body bond. I then fillet with either wood glue or more epoxy. I built my goblin this way, pretty sure the fins will never come off (except of course when a 12 year old who shall remain nameless decides to walk and talk without looking...)

Oh, did i say that...

Looks like those fins shouldn't go anywhere, even with a D. The goblin was so much fun to build bought another...

fm
 

Woody's Workshop

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I'm sure these will be very strong fins.
I'm curious what your method is to hide the joints on the BT?

I'm in the middle of building a Goblin and thought about this thread. I decided to paper the fins and leave the paper along the root side long. I then folded the paper along the root edge and glued everything with titebond. Then added fillets using titebond.

View attachment 307191

It isn't exactly like the tip-to-tip method but I'm hoping this will prevent the fins from popping off. Murphy and his laws always end up with my streamer rockets finding the hardest random thing to hit in a grass field. I'm also building it to where I can clip in a streamer or parachute to leave my options open on that front.
 

Andy Greene

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I know its overkill, but on my larger low power stuff- and all my scratch lpr stuff- I have been re-making the factory fins to make them thru wall as well as paper them.
I dont break fins off the BT anymore :facepalm:
 

Pointy_end_up

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I just added in a little filler, sanded it, and two coats of primer. The paper transition is gone and now I'm hoping for warm enough weather to paint tomorrow.
 

Forever_Metal

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I have yet to fly my Goblin, but I had already determined that the stock streamer appeared too minimal for the weight of that rocket with a "D" motor casing in it and the clay weight in the nose cone. Mine will either fly with an enlarged Mylar streamer or a parachute.


And I agree, it sounds like the OP's issue has more to do with an improper glue joint than anything else. A double glue technique and repeated glue fillets seem to work well for me using Tite-Bond II.
Is the TB3 worth using or should someone stick with TB2? I'm a sigbond guy myself but maybe i should switch...

fm
 

K'Tesh

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I'm in the middle of building a Goblin and thought about this thread. I decided to paper the fins and leave the paper along the root side long. I then folded the paper along the root edge and glued everything with titebond. Then added fillets using titebond.

View attachment 307191

It isn't exactly like the tip-to-tip method but I'm hoping this will prevent the fins from popping off. Murphy and his laws always end up with my streamer rockets finding the hardest random thing to hit in a grass field. I'm also building it to where I can clip in a streamer or parachute to leave my options open on that front.

Who knows, I might be dead wrong, but it seems to me that fillets would be severely compromised by the paper layer preventing bonding to the body tube below. Then again, if the glues are identical or at least compatible/complementary, it could greatly increase the area that the fin is attached by.

I'd love to see someone scrap test this. I'd do it myself if I had the materials and resources.
 

rharshberger

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Woody, whats the Estes PNC-50S for, the nose cone with the canard fins peaking out from behind the V2 in both pictures (left side), an Aries SST or a Jayhawk?
 
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