Zephyr Jr fin design change / launch lug

[Angel_of_the_Skies]

I bought a Zephyr Jr which I built and flew which was honestly a very fun model to build that I decided to re purchase the kit with the intention of having this rocket as a shelf rocket (with a possibility of launching at future club events).

The fins have a slot that I am not sure if it has a function. Frankly it is a PITA to work with as I can’t really sand or seal the inside of the slot. Wanted to ask if anyone has had these problems and how you solved it or filled it. I’m thinking using CWF to fill, not sure how it would hold up if I were to launch one day

 

[Angel_of_the_Skies]

 

[neil_w]

It's cosmetic. I certainly wouldn't worry about filling the grain on the inside of the slot.

To sand in there, use a thin file or a commercial sanding stick or make your own by affixing sandpaper to a popsicle stick or tongue depressor or the like.

 

[Angel_of_the_Skies]

It's cosmetic. I certainly wouldn't worry about filling the grain on the inside of the slot.

To sand in there, use a thin file or a commercial sanding stick or make your own by affixing sandpaper to a popsicle stick or tongue depressor or the like.

I guessed it was cosmetic as well. Thank you for the tips. Going to try to fill em in with CWF, I’ll see how well it holds

 

[neil_w]

I guessed it was cosmetic as well. Thank you for the tips. Going to try to fill em in with CWF, I’ll see how well it holds

You don't need to fill them for strength. And anyway, CWF won't really add much if any.

If you want to fill them because you don't like how they look then go right ahead, but those slots are part of the distinct appearance of the Zephyr.

 

[Angel_of_the_Skies]

You don't need to fill them for strength. And anyway, CWF won't really add much if any.

If you want to fill them because you don't like how they look then go right ahead, but those slots are part of the distinct appearance of the Zephyr.

I used the back of a #2 exacto knife blade to scrape off the CWF. It is easier to scrape off if done within 30 mins - 1 hour of the CWF drying. Furthermore, I sandwich the fins in between wax paper and add books over the fins to prevent them from warping. Works great.

Also, I’m about to be on the sanding phase of the fins after a applying 3 coats of Duplicolor Filler & Sandable Primer. How much of the primer do you and off ? I always seem to sand too much where I maybe knock off the CWF in the spirals or hit substrate

 

[neil_w]

Also, I’m about to be on the sanding phase of the fins after an applying 3 coats of Duplicolor Filler & Sandable Primer. How much of the primer do you and off ? I always seem to sand too much where I maybe knock off the CWF in the spirals or hit substrate

Less than that.

Often you want to sand off as much as possible without knocking off the CWF. I am not obsessive about removing all of it except what’s left in the cracks. A little bit extra left on will add a bit of weight but nothing else that is problematic. Sometimes (as with a plastic nose cone I did recently) I’ll leave a thin coat over the whole thing, which still means that *most* has been removed.

There is no sure-fire trick to ensuring that you don’t sand too much. You just need to pay attention as you go. Edges and corners are particularly vulnerable to over sanding.

 

[Angel_of_the_Skies]

Less than that.

Often you want to sand off as much as possible without knocking off the CWF. I am not obsessive about removing all of it except what’s left in the cracks. A little bit extra left on will add a bit of weight but nothing else that is problematic. Sometimes (as with a plastic nose cone I did recently) I’ll leave a thin coat over the whole thing, which still means that *most* has been removed.

There is no sure-fire trick to ensuring that you don’t sand too much. You just need to pay attention as you go. Edges and corners are particularly vulnerable to over sanding.

To be fair I’ve never really mind the weight on a rocket, as long as I’m able to recover and launch again I’m happy.

Thank you for the simplicity, in other words you said : if you’re sanding too much, sand less, lol. Sometimes I get to out of my head and don’t think.

I def learned that on my first MPR build, I’m reinforcing the BT ends with CA, and barely touching the edge of the nose one, and only hitting 400 grit on the edge of anything

 

[Lotronex]

I filled mine in on my full sized Zephyr. I cut some balsa scraps to size and glued them in. It works, but after the first landing if you look closely you can see a little outline in the paint of where the balsa is. If I did it again, I'd use plywood to fill, or paper over the balsa.