I kinda screwed up the fins...

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veebirdman

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I only now after the rocket is finished discovered that the balsa fins are cut so that the grain is parallel with the root chord, and not with the leading edge. They're still fairly sturdy, is this a big problem?
 
It certainly can be a problem.

In addition to Kuririn's questions I add these:

1) How big is the rocket?
2) how thick is the fin stock?
3) Is it painted yet?
 
From the bottom of the tube to the nose is 13 inches, the tube is bt 50. The fins are 1/16 inch thick, and it's all painted including the fins.
 
OK, so it's a small rocket, but it's gonna scoot on a C6. Just my opinion, but I would not expect 1/16" fins with wrong-way grain to survive the flight.

Papering would strengthen them up quite a bit; tricky after the rocket is built but possible. Gluing up the paper gives the most strength but I'm not sure the best way to do it after painting, unless you sand off all the paint. Adhesive label paper could adhere will to the paint (lightly sand it smooth first), but doesn't add as much strength. Either way, make sure the leading edges of the fins are well sealed up, or add an extra fold of paper around the leading edge.
 
It's hard to say exactly what the difference between a B6 and C6 would be regarding fin survivability. If you can manage a decent papering job, then I'd try it on a B6, and if it survives then try a C6.

And then you will know. :)
 
You might be able to paper the fins after installation.

There's always the "operate and find out" option. :)
Papering unlikely to help (I speak from experience.)

K’tesh however has the solution. Since you painted it, you would need to sand down to bare balsa before you can do anything, including papering, which as I said probably won’t work.

BEST bet if you used wood or white glue would be use a heat gun to remove the fins and replace with new properly oriented fins.

If you can’t do that, then cutting duplicate shaped balsa fins with proper grain direction (I would go with 1/16”), and placing this OVER your existing fins with a good final fillet on the new fins side would work. Note: the new fins will tend to curl with glue only on one side. You can get around this by using plastic hotel key cards over the new fin, held in place by clothes pins, while the fin dries.
 
Well if papering won't do much i'll try that. Is 1/16 inch balsa a good choice for the fins?
 
Well if papering won't do much i'll try that. Is 1/16 inch balsa a good choice for the fins?
For a small rocket it is good alone. If you “ply” it (two pieces with grain opposite directions, glued together) it is very good, but a bit heavier due to the glue than 1/8” non ply. You will need to keep the fins flat to create your own “ply.” I usually wrap the fins in wax paper and stick them in a thick old useless book with a weight on top.

I also also do that when I paper fins with glue. Glue papered fins are much stronger than label paper fins, but the technique is messier. ymmv.

If you are designing your own rockets, one fin saver technique: either forward sweep your fins or move your fins forward a bit so the engine casing takes the initial impact on landing. FiNs done this way are a bit less efficient (you will need either slightly more fin surface area or more nose weight to get same stability) but they break less frequently. I also think forward swept fins look cooler.
 
if you haven't cut the fins off yet I would sand the leading edge square and then glue a 1/16 by 1/16 piece of balsa or bass wood along the leading edge. Or maybe 1/16 by 1/8. That should make it strong enough.
 
Agree with AfterBurners. Since its already painted dont bother fixing it. Anybody thats been in this hobby awhile has done that at least once. And for crying out loud, dont tell anybody. At 15 feet away and 400 mph nobody will notice. Until the fin comes off. heheheh

PS: actually in flight it will probably be fine. Transporting it or landing, if the tip of the fin hits anything first it will probably crack along one of the grain lines. Fix it then. Or just fly it a Bong. Youll probably lose it before the fin becomes a problem. hahahah
 
Nothing will help your fins unless you can get what ever covering over the fin to body tube joint. Not even to glue something on the LE or TE. It is that one grain at the joint that will snap off. Now if you glued something on that also went into the BT, that might do it. But again, it would be an awful lot of surgery to do so. Since it is LPR and if you choose to fly it anyway, please do so in a safe area with few onlookers, safety wise.
 
just fly it until it breaks. Dont waste your time fixing it.

Fins will be easier to remove/replace after one breaks off (likely on landing).
If the fins do not break-off, then there was no need to replace them!

Papering unlikely to help (I speak from experience.)

For what it's worth, I find the increased strength from papering (and optionally soaking in super-thin CA) to be somewhere around an order of magnitude. I used to damage balsa fins just by sanding them. Not anymore.
It's not even an option for me - I paper 100% of the balsa fins for both strength, and clean grain-free finish.

YMMV.

P.S.: Papering after gluing them on is possible, but still leaves the weak area at the root edge of the fin (especially with TTW fins).
P.P.S.: You could reinforce that weak point with thick/tall epoxy fin fillets that rise well over the papered edge of the fin.
 
For what it's worth, I find the increased strength from papering (and optionally soaking in super-thin CA) to be somewhere around an order of magnitude. I used to damage balsa fins just by sanding them. Not anymore.
It's not even an option for me - I paper 100% of the balsa fins for both strength, and clean grain-free finish..
I was referring to papering fins as a retroactive means of correcting errant grain direction. Papering, especially with glue rather than adhesive backed paper, definitely strengthens fins but in my experience doesn’t prevent breakage with the grain. I am with you, anything I plan on painting gets papered both for strength and for ease of finishing, but I keep track of the grain direction, either perpendicular to the long axis of the rocket or parallel to the leading fin edge.

Fins with the grain parallel to the long axis break easily, papered or not.
 
Good morning. Getting my initial ideas together for a space shuttle scratch build, mid power. Of the things I am thinking, though not scale and may upset the purists. I would like a two stage having the outside tanks fall away. Then at apogee the main tank chutes down, the glider is RC. I can't info on the dos and donts of a remote powered thrust idea for a shuttle flyby before landing. Should I scrap that one.
 
how about try clear packing tape over the fins to reinforce if you don't want to redo?

However if I were you, I'd just take them off and fix it right. Too many times I realize I did something wrong and the amount it bugs me and time it makes me hem and haw is more bothersome than if I just bit the bullet and fixed the darn thing. I've never regretted such fixes and peace of mind is priceless. :)
 
Good morning. Getting my initial ideas together for a space shuttle scratch build, mid power. Of the things I am thinking, though not scale and may upset the purists. I would like a two stage having the outside tanks fall away. Then at apogee the main tank chutes down, the glider is RC. I can't info on the dos and donts of a remote powered thrust idea for a shuttle flyby before landing. Should I scrap that one.
First thing would be to start a new thread under scratch build or boost glider or staging forum.

Don’t sweat the purists, it’s your rocket, build it safe and the way you want it.
 
Good morning. Getting my initial ideas together for a space shuttle scratch build, mid power. Of the things I am thinking, though not scale and may upset the purists. I would like a two stage having the outside tanks fall away. Then at apogee the main tank chutes down, the glider is RC. I can't info on the dos and donts of a remote powered thrust idea for a shuttle flyby before landing. Should I scrap that one.

Bob, I have seen an RC space shuttle before. It was quite a while ago. You might try doing a search on RC Groups and RC Universe. That might lend you some ideas.
 
First thing would be to start a new thread under scratch build or boost glider or staging forum.

Don’t sweat the purists, it’s your rocket, build it safe and the way you want it.
You're right. It's MY rocket. I will consult for safety but you're right. Thanks.
 
Regarding all the talk on papering fins, what's a recommended method? Just regular copy paper and wood glue? Or is there some special type of lightweight paper/glue?
 
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