A rookie Q on fins.....

Hi guys, err i have a prob with my fins staying stuck to my rocket (?!)

The last 5 times i've lanuched my rocket, when it strikes the ground I always loose a fin or two. So after 3 launches i ditched the balsa fins and stuck on some perspex ones on instead with epoxy resin type glue (Araldite). Launched it 2 more times and still lost a fin on both occasions. Is this normal? its my second rocket (the first wen up and I never saw it again!). Im using a 12inch parachute, the roket weights about 40 - 45 grams, using estes B motors.

Any suggestions or ideas are most welcome.

All the best

James

James...

The weight appears to be in range...it sounds to me like the body tube still has a glassine layer on it, which is very slick and hard to adhere. Did you rough up the body tube with sandpaper in the area where the fins attach? This allows the glue to "soak in" to the body tube and provide a better bond.

Also, if you add some fillets to the sides of the fins, they too will assist in making the bond stronger. Let us know...

Carl

James,

I break fins before they come off.

For Estes and most low power rockets (A through D)

1) Lightly rough up the tube with sand paper just under the fin before you glue it on.

2) For body tubes larger than minimum (rockets with a seperate interior engine tube)
Mark the body with a pencil line for the location of the fins. Then use a very sharp straight pin and punch pin holes along the pencil line.

This will allow glue to seep through the hole and sort of "bulge out on the inside of the tube to for a "glue rivet."

3) Put a thin line of your favorite glue (white or yellow carpenter's wood glue) Make sure it gets in all the "rivet holes) you made and kinda push it into the hole with a toothpick or pin...get very fussy here...you won't be able to do it again later
Allow it to dry a while until it becomes almost dry...but not quite just a little past "tacky".
.

4)Now....one at a time...don't rush this...remember you asked how to keep fins from coming off.
Apply a fresh thin bead of glue to one fin at a time (this will reactivate the glue) and stick the fin into place.
Use your eyes to judge alignment. The fin should stick pretty good but don't disturb it until the glue dries.

5) After all the fins are glued it is time to do a glue fillet.
before you begin have the following things ready, glue, paper towel (dry), papertowel (wet for you fingers) and wooden toothpicks.
With the rocket now horizontal (do this the next day so the fins are dry!) lay a bead of glue along two adjacent fins.

6) Use the same finger (I use my little pinky) for all fillet and make one clean smooth swipe along the fin/body seam. clean up the edges with the toothpick. wait a couple of hours and turn the rocket and do the next pair.

7) When all the fillets are completed use a nice wide brush and paint a coat of glue on all the fins...work quickly so you don't warp the fins and do both sides of a fin at once blending the glue into the filet.

This whole proccess takes probably a full day to complete or a couple of weeknights anyway.

With this method I have had rocket stranded in a tree for over 6 months and when it came down the fins were still usable.

The secret is not in the amount of glue but in the proper aplication and allowing it to "cure" properly.

Ask question

Good luck

sandman

What sorta field do you launch in? I have not had too many problems with fins popping off when launching in soft soccer fields, but in the desert where I fly now, fin strength is an issue.

If you launch in a soft field, do the reccomendations others have listed, If you launch on a hard field, do the reccomendations, and put a larger parachute in it.

Thanks for the advice. Your right, come to think of it I don't think I roughed up the body tube (Opps!). And I launch of a beach, so a bigger 'chute wil be need also I think.

Im in the process of building a Quest Navaho 2 stager at the mo. Ive ditched the balsa fins for 1/16th ply ones, kinda mounted them through the body. That was kinda tedious having to cut slots inbetween the centring rings! (So, I'll give that stickng pins in and filling the holes idea ago next time.) But, hopefully that should work.

Just one more Question. Since I live on the coast, it's pretty windy (normally there is a 15 -20kt wind) , so a good day for launch usually involves a 5 - 10 kt wind, and quiet frankly I'm fed up with having to walk half the beach to find the rocket! If I built a 'X' type 'chute, would this cut down the walking distance?

The slotted body tube is your strongest bet and with plywood fins you might be able to get away with just a steamer on a model the size of the Navaho.

Make sure the model is ballanced for a stable flight. The plywood fins add a lot of weight. I use plywood quite a lot and I always have to add clay to the nose.

Maybe you should go inland and try a softer field.

sandman

There's a school just down the road with a HUGE field! Gonna ask if they mind me using it in the summer hold when the kids ain there.

Thanks for the tip on adding clay to the nose (got a bit left over from a Flat Cat boost glider - yet to be flown)- the CG did look pretty close to the CP on the Navaho (or were I think it is). Better to be safe than sorry! I've alread ditched the 'chute which comes with the kit and made my own - 14 inch in diametre, should be ok.

Thanks again for your help!

Cheers

James

It sound like you are on the right track.

Talk to one of the science teachers at the local school and perhaps, if you skills are up to it, you could help them with a few rocket projects for their students.

You've got to always "pass it on".

Good luck,

sandman

Talk to one of the science teachers at the local school and perhaps, if you skills are up to it, you could help them with a few rocket projects for their students.

You've got to always "pass it on".

Good luck,

sandman

Click to expand...

Excellent advice. I taught a model rocketry program for 7 years at the local elementary school. We launched over 600 rockets in that span. Was lots of fun, and personally rewarding. I still have all the letters the kids wrote to me at the end of each program.

I mostly used Estes Generic E2X bulk packs, but would love to give somebody like Apogee the business if I were to start it back up.

My maum is a science teacher at another school about 7 miles away and shes already pinched the the first one to show the kids, which they loved - since they are doing a project on parachutes. She needed a practical example of there uses. So some time in late July im going down to do a few launches.

Skills should be up to it - dabled in radio controlled boats for a while and me first rocket was a scratch build. Theres also company called "Apollo" which supply body tubes etc in class room packs at reasonable prices.

Just for safty how far should the kids be from the launch site?more than 5 metres?dont want to kill any if anything goes wrong!

James

My mum is a science teacher at another school about 7 miles away and shes already pinched the the first one to show the kids, which they loved - since they are doing a project on parachutes. She needed a practical example of there uses. So some time in late July im going down to do a few launches.

Skills should be up to it - dabled in radio controlled boats for a while and me first rocket was a scratch build. Theres also company called "Apollo" which supply body tubes etc in class room packs at reasonable prices.

Just for safty how far should the kids be from the launch site?more than 5 metres?dont want to kill any if anything goes wrong!

James

My mum is a science teacher at another school about 7 miles away and shes already pinched the the first one to show the kids, which they loved - since they are doing a project on parachutes. She needed a practical example of there uses. So some time in late July im going down to do a few launches.

Skills should be up to it - dabled in radio controlled boats for a while and me first rocket was a scratch build. Theres also company called "Apollo" which supply body tubes etc in class room packs at reasonable prices.

Just for safty how far should the kids be from the launch site?Im guessing they should be further than the recomeded 5 metres?dont want to injure any kids if anything goes wrong!

James

5 meters away is safe enough, that is the length of the Estes launcher electrical cable, but they may want to go back further for a better view.

Say "howdy' to Tony at Apollo11 for me.

sandman

James;

Just FYI - Tony Williams' of Apo11o is a member of the WRS and is happy to bring any orders to the launches to save on P&P.

When launching for schools, scouts etc. it is a good idea to make sure their liability insurance covers such activities. I have done lots of launches of this type, but haven't managed to impale one of the little darlings yet

Just make sure they don't immediately run after any rockets if there are live ones on the pad, and make sure they dont stand on any rockets when the do!

Also, a good classroom project is this kind of thing https://www.geocities.com/CapeCanaveral/Hangar/5421/rocketma.html

Regards;

Richard