T2T fin fiberglassing questions

[Banzai88]

So, some dummy head figured that it would be cool to make a new booster section to one of his 3" rockets, this time using a 38mm motor mount instead of a 29mm. Same dummy head bought and installed 1/8 5ply fins. In fact, he got all the way through putting in very nice 4500 fillets before deciding to look at other similar 38mm motor mount rockets.

Uh oh! :y: Most of them come with 1/4" fins.

Then, after consulting FinSim, the dummy head decided that tip to tip fiberglassing was the answer to possible/probable fin flutter and durability.

Everything is in place on the table: West systems 105/206, 2oz and 5 oz fiberglass cloth, peel ply, gloves, mixing sticks, brushes, etc.

Trouble is, dummy head has no idea how many layers of each cloth are appropriate?

I was thinking one layer of 5 and a veil layer of 2? Would this be enough or too much?

Is there a science to this or is it experience and SWAG?

 

[markkoelsch]

I would do two layers of five and skip the veil layer. You do not want to sand your laminate- weakens the structure you are building. I would do the two layers, let them cure, and then put an epoxy based sandable filler over the top. Sand the filler.
I like and use Polyfiber Superfill.

 

[TopRamen]

I would do two layers of five and skip the veil layer. You do not want to sand your laminate- weakens the structure you are building. I would do the two layers, let them cure, and then put an epoxy based sandable filler over the top. Sand the filler.
I like and use Polyfiber Superfill.

Can't go wrong with that, and probably the best answer you'll get.^
Save the 2oz. stuff for something else.
Peel Ply will yield a finish similar to the weave of properly wetted out 2oz. cloth anyhow.

 

[FredA]

3" rocket with only a 38mm MMT .... T2T NOT needed.
IMHO.

 

[dford]

If I were me, wait I am me. Smee is that me? Ya anyhow, i'd do three layers. 3-2oz
45/90/45. Less weight than 2-5oz. Structurally as strong with a 45 laying on top the tube and finishing with a 45 (assuming the tube is glass at 90 top layer)
It'll give you plenty of strength either way so why not keep weight down? Save your 5oz for a more serious strength addition later. Or for corner tapes. Yesss smee likes me some good corner tapes.

Anyone out there use BST (bag sealant tape) for bagging material sealant? It is the bomb diggity especially for oven cures

I also really like Pro Set 125/229 resin/hardener

Yes, three layers of laminate. It'll work. I'd also skip the sandable filler and use what you have. Get yourself a good squeegee and resin wipe a layer until you don't have "runs" and is smooth. Once cured, wet sand. Again. Wet sand. And one more time. Maybe even only twice depending on how efficient you are.

It'll finish like glass. If that is your intention of course...

+another tip if unknown is to pour about a quarter inch into a paper cup before your layup. After the suggested cure time is up, try to break the sample with a hammer. If it shatters, your good to go. If still gummy, wait longer.

 

[KenRico]

T-FISH has a nice video of an almost tip to tip .

He layed out a few 1/3 fg, bigger 2/3 fg partial and a 'almost' tip to tip .. added some strength and helped shape fin a bit ...but he did not try to bring the fg to a point on the bevel of the leading and trailing edges -- he stopped where that angle begins --"almost"

If it were me would do one partial ..smaller than the almost tip to tip , but not carried across the fin spanse --only past where the fillet meets the tube .
Or the single only 'almost tip to tip ' across and be done .

I think your boost will be fine ..but may help asorb or bounce off the shock of all that kinetic energy on a harder landing or the occasional rock .

[video]https://youtu.be/PtYYsX3VEmc[/video]

Kenny

 

[TopRamen]

T2T is not needed on my Estes Patriot either, but it got it anyway.

 

[watermelonman]

3" rocket with only a 38mm MMT .... T2T NOT needed.
IMHO.

Strongly agree.

Tip to tip is for landing, not flying.

 

[TopRamen]

But that is not any reason to not go ahead and learn the technique just for the sake of learning the technique.
A lot of things are not "NEEDED", but life would be pretty boring if we only did the "NEEDED" things.
I'de have left rocketry long ago out of boredom if I only built them to the bare necessities required.

 

[watermelonman]

But that is not any reason to not go ahead and learn the technique just for the sake of learning the technique.
A lot of things are not "NEEDED", but life would be pretty boring if we only did the "NEEDED" things.
I'de have left rocketry long ago out of boredom if I only built them to the bare necessities required.

Also strongly agree.