Suggestions on fin assembly

Hello,
I am having trouble with fin assembly. Sometimes when I glue fins they may come off. Any suggestions will be greatly appreciated.

Xan

Try using TTW (thru the wall) method...

By using this method, they will most likely break before they come off...

Some may say that it is over building or whatever...

Who cares, it is your rocket...

Build it the way you want...

You could even fiberglass the whole thing like TopRamen...:grin:

Do they come off before or after the glue dries? But first things 1st, do you "prep" the body tube before gluing? Prep the surface of the body tube by sanding the surface with a course grit. I use 320 grit, but that is my preference. This helps the adhesion by giving "tooth", surface for the glue to grip. Not prepping the body tube could be a reason the fins come off after the glue dries. If you are having problems keeping the fins on before the glue dries, try a "double glue joint". You can find this method here in this forum or on the Internet. Hope this helps.

Xan2482 said:

Hello,
I am having trouble with fin assembly. Sometimes when I glue fins they may come off. Any suggestions will be greatly appreciated.

Xan

Click to expand...

Xan;
One of the easiest and best ways to aid in fin attachment is NOT to try TTW "through the wall fins". but rather use the White Elmers or Yellow Elmers Carpenters Glue attached using the "DOUBLE GLUE JOINT METHOD".

This method is as old as our hobby but is one of the strongest and quickest setting methods for Wood to Cardboard or Wood to Wood joints.
Once Dry this butt-on glue joint is Stronger the the materials it is bonding.
* To use this method first mark all fin line on the Body tube. Number the fin lines
* Cut-out and Sand all fins to the shape needed. number each fin.
* Apply a full line of glue to the root edge of the fin.
* apply the fin to the body tube line in the position intended, then immediately remove. Set the fin and tube aside to dry.
* Repeat the above step with all remaining fins.
* Once all glue lines are dry to the touch. Start with fin #1 and line #1, Reapply another full but light line of Glue to the root edge and attach to the body tube in the same position as the original coat. The second application reactives the original glue which will seize fairly quickly.

What I do at this point is stand the body/fin unit upside down on a dowel or spent motor casing epoxied to a 3" square of cardstock or scrap woods. This allow the fin/body joint to set vertically which helps prevent the fin from slipping from perpendicular to the body tube.

* Repeat with all other fins.

TTW fins are a completely unnecessary Over Building Technique for LPR & MPR models, It is used widely in HPR applications. TTW however is simply not needed with any model under 3.3lbs. I have all kinds of LPR and MPR models up to 3.3lbs that are attached using the Double Glue Joint method with added epoxy fillets that have never had a single fin issue many with more the 30flights. None of the UpScale Multi-Motor Clustered models pictured below have a single TTW fin.

Don't fall into the Bad practice of over building your models. Build as light as practical will eliminate many of the problems the Excess mass over building adds to the models. We should NOT be trying to build bullet proof models, They are ment to absorb kinetic energy rather than transfer it to the object being hit.

Hope all this helps with your problem.

A little more info please....
What is the body tube and the fins made from? And what type of glue are you using?

If typical cardboard tube and balsa/basswood fins then a little sanding of the body tube and the double glue method work great. Titebond II glue is great, although you could get by with Elmers glue (just not the "School glue" version)

Micromeister said:

...One of the easiest and best ways to aid in fin attachment is NOT to try TTW "through the wall fins" ... TTW fins are a completely unnecessary Over Building Technique for LPR & MPR models...

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Like I said, it is your rocket and you can build it any way you choose...

I have never had a TTW assembly fall off...

This debate, every time it pops up, is ridiculous...

Any additional weight using TTW is "negligible"...

Next they will tell you not to ever wet sand your rocket... EVER

Or the NAR god will smite you...:grin:

Thank you for the wonderful advice about carpenter's glue. I will definitely use it.

Xan

Xan2482 said:

Thank you for the wonderful advice about carpenter's glue. I will definitely use it.

Xan

Click to expand...

I know this is a thread about gluing on fins, but:

Just a reminder when using carpenters or yellow wood glue it seizes fast, if you use it to glue couplers don't put a thin coat on then attempt the coupler, put it on thick and immediately slide the coupler all the way in, you only get one chance. white "Elmers Glue-all" is a better choice for couplers. This isn't usually a problem with fins.