Fin Gluing Problem

[Bruiser]

Ok, I'm not trying to start a new "what's the best glue" thread but I have a question regarding gluing fins

I am about to finish, well was about to finish up my latest build when I ran into this problem just now. I was making some decals for the rocket and I left it laying on it's side for a few hours. I just went to put it away so that it was safe from the cats and the fins are splayed out.

It's a 13mm two stage with BT-20 body tubes. Both the booster and sustainer have four fins each. I glued them on with regular Elmer's glue and I used Titebond Thick and Quick for fillets. The fins are 1/32 basswood. The two fins that were in contact with the desk top are not 90 degrees to each other anymore. They are more like 120 degrees.

I think I glued them on this past Monday. I was able to bend 3 of them back for the most part but one fin is not fully attached anymore. I'm not sure what to do at this point. The paint is all done and it just needed decals.

So what do you all think? Glue to old? Fins not thick enough to hold well? Something else?

-Bob

 

[David Schwantz]

If it as bad as you say, I would cut them off and start over.

 

[justforfun]

Hair dryer, warm (just enough, don't cook it) glue, bend back to original position. It's called deflection temp.

Roy

 

[billeblurzz]

My thoughts are incompatibility of two different glues. Whatever you glued fins on with stick with that for fillets.

 

[David_Stack]

How much time elapsed between when you initially glued the fins to the body tube, and when you applied the fillets?

If the Elmers glue used to adhere the fins to the body tube had not fully cured (all the moisture evaporated), then perhaps when the Quick & Thick was applied and it 'skinned over' it resulted in the 'base layer' Elmers not fully drying...

 

[neil_w]

Weird. I will say, though, that I've had mixed results over the years gluing basswood. A 1/32" basswood joint sounds dicey to me right from the get-go, until everything is completely hardened up.

 

[Scott_650]

I’ve used the combo of Glue All and Q&T for years and dozens of rockets with no results like Bruiser recounted - I have had Glue All go “bad”, it went from it’s normal consistency to much thinner, almost runny. Thought maybe it had separated like latex paint can with age but no amount of shaking or stirring (which was a bit problematic considering I used a chopstick through the small opening in the bottle ) got it back to normal so I tossed it, Elmer’s is fairly cheap. But if the Glue All was ok I have no idea what went wrong other than an excessively long cure time needed for some unknown reason - very odd!

 

[Bruiser]

Today, all of the fins but one are solid again. I didn't mention it yesterday because I never even considered it but this morning it occurred to me that it may have been because of the paint. I used some Duplicolor for the fins and I haven't used that for some time. With the masking line at the base of the fins there may have been some build up there. It's a downscale of this design (this is the original).


Like John I have been using Elmers for gluing and Q&T for the fillets on most of my rockets for a while. Never had an issue before. I don't remember how long before gluing the fin on and applying the fillets. Probably wasn't long though. I've also noticed the fillets are not as large as I wanted them.

So what's the take-away? Well a new bottle of Elmer's and I'm going to use at least 1/16th inch stock for fins on future builds. I am going to make larger fillets and I will wait a day before I apply them.

I'll need to clear coat after the decals. It'll be interesting to see if the fins joints go "soft" again. I'll post back afterwards.

-Bob

 

[Back_at_it]

Couple of things come to mine.

- Did you sand the tube where the fins attach? If not then the glue is just sitting on top of the slick outer layer and you don't have a good bond. The good news is that you should be able to pop them off with a little bit of pressure.

- Other though is the Elmers glue. Did you use School glue or the all purpose "glue all"? School glue doesn't stick to anything except paper and it does a poor job even doing that. The Glue all works great. I used it to build rockets for 20 yrs before I switched to TiteBond. The one thing about Elmers is that it will become soft with any amount of moisture regardless of how long it has cured. When rebuilding some of the rockets I built as a kid, I use a little warm water and the fins pop right off, motor mounts slide right out etc.

I'm thinking the Thick and Quick softened the Elmer and let the fins move. My guess is that they would eventually harden back up given enough time.

 

[flyingeagle]

What are the vent holes for in the booster? Will this help with using a booster?

 

[lakeroadster]

What are the vent holes for in the booster? Will this help with using a booster?

Gap staging vent... more here ---> https://www.apogeerockets.com/downloads/Technical_Publications/Tech_Pub_06.pdf

 

[flyingeagle]

Ok I’m lost. What is gap staging. I’m going to build my EXTREME 12 soon and wondering if I should use this method. Is gap staging have something to do with when the booster motor isn’t tapped to the second stage motor. I’m just guessing.

 

[flyingeagle]

As far as glueing fins I did a Estes Nike rocket. It did turn out very well with primer but I noticed a couple of the upper fins are just ever so slightly off to one side from the lower fins. This was caused from the guillotine being off. Now the jig is fixed If I place the rocket in a fin alignment guillotine and use a blow dryer to warm up the glue can I straighten it out?

 

[neil_w]

Ok I’m lost. What is gap staging. I’m going to build my EXTREME 12 soon and wondering if I should use this method. Is gap staging have something to do with when the booster motor isn’t tapped to the second stage motor. I’m just guessing.

Correct. In that case, you need vent holes just below the sustainer motor so that the cold air can get pushed out without causing ejection. There are various ways to do the venting; straight out the side as shown in the pic is one typical way.

If the motors are taped together (as in most Estes kits) then there is no need for venting since there’s no extra air in between the motors to push away.

 

[flyingeagle]

So if there is space between the booster motor and the sustainer motor then vent holes will be needed to push out the air? How far apart on average are the motors that would need vent holes and what diameter is the holes for drill size. Other question is how dose the booster motor ignite the sustainer motor being they are not against each other?

 

[flyingeagle]

I just looked at the pic lakeroadster is showing. It looks like I need a fuse or something to ignite the sustainer motor but it must me a very quick fuse!

 

[lakeroadster]

So if there is space between the booster motor and the sustainer motor then vent holes will be needed to push out the air? How far apart on average are the motors that would need vent holes and what diameter is the holes for drill size. Other question is how dose the booster motor ignite the sustainer motor being they are not against each other?

All those questions are answered in the link I included in post #11 above...

 

[lakeroadster]

I just looked at the pic lakeroadster is showing. It looks like I need a fuse or something to ignite the sustainer motor but it must me a very quick fuse!

No 2nd stage motor fuse needed for black powder motors... as long as you use a booster motor in the booster stage.

 

[flyingeagle]

Got it. All new to me but you learn something everyday. Thanks

 

[Bruiser]

I was going to answer about the vent holes but others beat me to it. I've used them on both of my boosted designs and I've had no problems so far with the second stage igniting. One is 24mm to 24mm and the other one is 24mm to 18mm

I also have a Pro Series booster that I use with my Majestic and it has always worked. I built it per the instructions and it is gap-staged but it does not have vent holes. It's 29mm to 29mm

This new design (well, down scale) is 13mm to 13mm. I decided to use vent holes to give it the best chance of success.

Staging is a lot of fun to watch.

I'm clear coating the inkjet decals this evening. I'll get them installed sometime this week and the rocket clear coated. I'll report back afterwards.

-Bob

 

[86mustang408w]

I was using Gorilla or Elmers Carpenter glue to set the fins, then 5 min epoxy on all the area where the fins meet the tube(obviously)after they dried.

 

[flyingeagle]

Why are you having glue problems? I use carpenters yellow glue doing the double glue joint method then followed by yellow glue fillets then Tite bond Q&T molding. My fins are as solid as a rock. I also paper them for strength.

 

[Gtmike200]

Why are you having glue problems? I use carpenters yellow glue doing the double glue joint method then followed by yellow glue fillets then Tite bond Q&T molding. My fins are as solid as a rock. I also paper them for strength.

I’ve tried to search but I’m seeing lots of references to double glue method for fins but I cant find an explanation as to what it is. I would be curious since I’m at the stage to attach fins now.

 

[SolarYellow]

I was using Gorilla or Elmers Carpenter glue to set the fins, then 5 min epoxy on all the area where the fins meet the tube(obviously)after they dried.

Epoxy doesn't adhere to those wood glues. It will look like it does, but if you stress it, it will peel fairly easily.

 

[Rex R]

Apply a thin coat glue to a fin root, then apply fin to the body tube, remove fin and set it aside to dry. Do the same for the remaining fins. Once dry apply another line of glue the root edge, press and hold the fin to the body(10-15 sec) if you're gentle with it you can do the remaining fins, let the glue dry throughly before you handle the rocket again. also written up in the handbook of model rocketry.

 

[Bruiser]

I think the biggest problem was old Elmers. Since I have replaced my bottle I have built a new booster for the mini Tempest and yesterday I glued 12 fins on a mini Nike X and they are very solid.

-Bob

 

[flyingeagle]

I always do the double glue method using Tite Bond 2, not white glue. Apagee Components site shows how to do this. I to have been thinking is applying wood glue to the root edge, touching the fin to the body tube then let set for about a minute. Repeat the process again whipping away 80 to 90% of the glue off the root edge then apply the fin.
The only thing I noticed is when I touched the body tube the first time with the glue on the root edge it left a little raised amount of glue on the tube. When it dried and I repeated the process the second time but the fins root edge wasn’t flush against the body tube with the first bit of glue dried. My opinion and it’s just an opinion the root edge should be against the body tube without a gap caused from the glue drying on the tube upon the first application. I myself could use some help here.
I know a lot of guys do it this way and it works fine for them but for me I would rather not have a gap between the fin root edge and body tube caused by the ridge of glue drying on the tube. Maybe I could also learn something new on this. From watching Tim from Apagee he just puts glue on the root edge, wipes 80 to 90% of it off, lets it dry about a minute then repeats this again and the fin quickly sticks. This is how I’ve been doing mine right along. The glue I use for fin fillets is Tite Bond Quick and Thick which was called molding and trim glue. This glue also adds extra strength for the fin. Maybe I might be missing something here but I do have an open mind for other opinions or suggestions.

 

[BABAR]

Apply a thin coat glue to a fin root, then apply fin to the body tube, remove fin and set it aside to dry. Do the same for the remaining fins. Once dry apply another line of glue the root edge, press and hold the fin to the body(10-15 sec) if you're gentle with it you can do the remaining fins, let the glue dry throughly before you handle the rocket again. also written up in the handbook of model rocketry.

Agree, slight variation.

apply light glue to fin root, place in position, wiggle it a bit, just to get both fin and body tube surfaces with a very VERY thin coat. Let dry.

I started this before @flyingeagle posted his, his is good too.

step 2 is to again put a LIGHT coat of glue on the fin root, touch it again to the body tube, rub it around a tiny bit, then set both down for 1-5 minutes (may vary with type of glue.) this lets it start to set.

now reattach. The amount of hold time should be minimal, and the LESS glue you use the faster it will tack (and the stronger the final joint will be.

as has been said, you don’t want a THICK dry glue layer between the fin and the tube.

the THIN layer dries much faster.

I chase it when dry with a THIN fillet of WOOD glue. This gives a very strong bond. When dry, you can chase it with a cosmetic fillet with TITEBOND Quick and Thick or Moulding glue or whatever the current designation is.

maybe @kuririn can chime in, he does a tag team with CA and wood glue which sounds great, not sure i understand it, but sounded good.

 

[bjphoenix]

Why are you having glue problems? I use carpenters yellow glue doing the double glue joint method then followed by yellow glue fillets then Tite bond Q&T molding. My fins are as solid as a rock. I also paper them for strength.

This is what I do. I use a lot of yellow glue (Titebond II) in woodworking and that stuff is a little bit sticky when it is close to dry. If you put a thin layer on a fin, touch it to the body tube then remove it, you have a thin layer of glue on both surfaces. Let those dry a little bit and the glue gets stickier. Then put the fin back in place and it might be able to hold itself. I lay the rocket on its side with the fin sticking straight up in the air so there isn't much gravity trying to pull the fin off of the tube. Let that one dry 10 minutes or so and then rotate the rocket and put on the next fin.

I usually put the fin on and hold it for a couple of minutes until it will hold itself, then let it dry 10 minutes. I can usually get a fin aligned pretty well by eye but not always. I recently built 5 rockets at one time and so I used that as an opportunity to design and build my own fin jig. Someone pointed out to me that there was a simpler and better design posted here in the past so I agreed it was better and built one of those. That jig is very easy to use- put glue on the fin, set the fin on the jig, slide it over until it touches the body tube, leave it alone for 10 minutes, perfect results with no muss, no fuss.

 

[flyingeagle]

One thing I had forgotten to mention is I use 220 or 320 grit sand paper to rough up the body tube where the fin is to be glued on. I don’t sand hard enough to go through the outer paper. I just scuff it up enough to get the shine off the tube. This will help create a stronger bond instead of trying to glue to a slippery surface.