How to paper 1/4" ply fins?
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dixontj93060
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Paper is really not a suitable matrix for 1/4" ply and will do little to add to the strength of the overall structure regardless of the resin used. In general one should attempt to add a stiffer material as your outermost layer. Paper is suitable for balsa, but given the density/strength of aircraft ply, a better choice would be fiberglass cloth and epoxy resin.
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My experience is with plywood fins for LOC kits (I'd guess that Madcow ply is at least as good). The "grain" is much tighter than either balsa or basswood so adding paper doesn't buy much towards a smoother finish. A couple of coats of sanding sealer and your favorite filler/primer work for me. So two "rocket scientists" come in on the 'paper not necessary' side. 
But if you'd like to paper the fins then by all means go ahead and do so. It's just Tim's and my opinion that the benefits of papering other types of fin material don't show up as much in this case.
But if you'd like to paper the fins then by all means go ahead and do so. It's just Tim's and my opinion that the benefits of papering other types of fin material don't show up as much in this case.
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dixontj93060
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NICE!
I got a quart of water based Deft at Home Depot. Not quite the same buzz as the old Pactra and Midwest dope though.
That is a beauty !
rharshberger
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You can also get a fairly good one made by Minwax from HomeDepot, 1qt can is $16-17.
noffie79
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That. Looks. Awesome. I have to ask, did you use epoxy for the fillets, if so, what kind of epoxy, and did you do internal fillets? And how much weight did you add to the NC?
Kruegon
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I second the Minwax sanding sealer. Make sure to get the water based version. The vapors from the other is seriously nasty.
I find sanding sealer still leaves a bit to be desired if you want to remove the grain. I personally use wood filler on my fins. Elmers is a reliable one. It also makes a fairly decent increase to the fin rigidity. I usually skip the sanding sealer if doing this.
A good option on top of sanding sealer is the Rustoleum Automotive filling primer. It's high build, sands very well, and fills sma imperfections easily. And so far, it appears to be a good, universally compatible primer.
I find sanding sealer still leaves a bit to be desired if you want to remove the grain. I personally use wood filler on my fins. Elmers is a reliable one. It also makes a fairly decent increase to the fin rigidity. I usually skip the sanding sealer if doing this.
A good option on top of sanding sealer is the Rustoleum Automotive filling primer. It's high build, sands very well, and fills sma imperfections easily. And so far, it appears to be a good, universally compatible primer.
JJSR
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I have to admit from the start Penelope was a labor of love, my first HPR. Since coming back to rocketry from the mid/late 70's, my daughter and I have built upwards of 75/100 LPR's (we lost count around 58 kits) never built a mid power kit. But I wanted to get into HP, so I looked for what I thought would be a challenging/hard kit to build. Thinking that anything after it would be a breeze to build.
maiden flight
I don't remember exactly how much weight I added to the cone, but she's at 2.9 Lbs. the whole rocket is 6.1 Lbs.
I did do internal fillets, motor mount to fin and inside BT to fin, with regular 5 min. epoxy, outside I used the epoxy clay Apogee sells on everything else. I liked the fact that I could shape the clay to what I wanted, like the small curves at the aft ends of the fins.
here is a close up picture of the fin and what I mean about shaping the clay.
NOW DON"T LAUGH
she is a little beaten up now a days, spent time out in the soy field in the rain, on power lines in rain, worst place in the back seat of the truck for lots of miles
In the first picture, circle on the right that transition is what convinced me to use the clay. When I dry fitted all the parts I didn't like the way it would finish without something to pull the forward fin and the flat plate together, so to speak. I'm sure you know/see what I mean noffie79, just what ever you do take your time.
FWIW everything else is a BREEZE !
GOOD LUCK we all want to see some pictures, maybe even a build thread??
maiden flight
I don't remember exactly how much weight I added to the cone, but she's at 2.9 Lbs. the whole rocket is 6.1 Lbs.
I did do internal fillets, motor mount to fin and inside BT to fin, with regular 5 min. epoxy, outside I used the epoxy clay Apogee sells on everything else. I liked the fact that I could shape the clay to what I wanted, like the small curves at the aft ends of the fins.
here is a close up picture of the fin and what I mean about shaping the clay.
NOW DON"T LAUGH
she is a little beaten up now a days, spent time out in the soy field in the rain, on power lines in rain, worst place in the back seat of the truck for lots of miles
In the first picture, circle on the right that transition is what convinced me to use the clay. When I dry fitted all the parts I didn't like the way it would finish without something to pull the forward fin and the flat plate together, so to speak. I'm sure you know/see what I mean noffie79, just what ever you do take your time.
FWIW everything else is a BREEZE !
GOOD LUCK we all want to see some pictures, maybe even a build thread??
noffie79
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I've been debating getting that epoxy clay, but since I use regular 30 minute epoxy or RocketPoxy, I didn't see the need. And now I do! I put the forward centering ring on the MMT last night. I need to sand and either use wood filler or sanding sealer on the fins before I go any further. So it'll be a while before I really "start" the build. This isn't my first high power kit, but since it was a Christmas present from my father (and he really likes the look of this kit) I want to get it as perfect as I can. So, needless to say, I'll be taking my sweet time on this one. Thank you for your input. I just hope mine looks half as good as yours does when I'm done! Did you also use the clay on the tips of the forward fins where the little "fork" attachment is?
Rex R
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I papered the fins on my Madcow 4" phoenix mainly to make finishing easier...1st challenge was getting long enough paper, 2nd challenge, getting an even thin coat of glue (less margin for error w/ plywood fins). in the end I didn't save much time or effort over the use of filler.
Rex
Rex
JJSR
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actually thinking I used tite-bond, don't remember, I do think it would of looked better if they were filled in, you know forming a square not a +.
looking at my pictures of her from 3 years ago, I wish there was a way to remove the vinyl repaint and put the vinyl back.
looking at my pictures of her from 3 years ago, I wish there was a way to remove the vinyl repaint and put the vinyl back.
I would think the ply fins would be fine as is
noffie79
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Structurally, they would be. But I don't want to see the grain.
To eliminate grain on ply fins, first sand them smooth with 320 grit or finer. I use Rustoleum Filler Primer. Sand the first thick coat down to the wood with 320 grit. Most of the grain should be gone by now. The second coat also gets sanded to the wood with 320 grit. The wood grain should be completely filled by now. Any imperfections, dimples, etc. gets filled with joint compound and sanded with 320 grit again. A last coat of primer gets sanded with 440 grit but not enough to allow the wood to show. I usually do a base coat of white paint after that.
I've found that sanding the ply fins smooth before assembly makes the whole process go faster and easier. YMMV
noffie79
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Been using the Fix-It epoxy clay that I got from Apogee for the fillets on this. I have mixed feelings on the clay. I like the fact that I can do more fillets at a time because this stuff is the compete opposite of messy. Not smelly at all either. But I'm really hoping it sands down well. I used my finger dipped in alcohol to smooth it out. I didn't spend as much time doing fine details as I could've, as I'm not particularly picky about how stunning it looks under a microscope. I think once the epoxy cures and I sand it, I'll be using some wood filler to fill in some low spots and even everything out.
noffie79
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Ok great! Thanks!
noffie79
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Do you happen to remember how much weight you added to your NC?
JJSR
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Well I can say she has reached over 3000' as for motor size, I don't know since my old computer crashed I lost all of my files. Just let me worn you about drift, with that big chute if there is any wind she will drift and far. LOL
I attempted "DD" with a deployment bag & drogue a few times, but I just can't to get the bag to work right. So she is semi-retired now LOL
I attempted "DD" with a deployment bag & drogue a few times, but I just can't to get the bag to work right. So she is semi-retired now LOL
noffie79
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I can imagine she would drift a ways on that big chute. But I plan on picking up a Jolly Logic Chute Release and using it on this bird for that very reason. I'm almost done with my fillets, then I need to figure out nose weight. After that's it's on to primer and paint. Definitely be flying her at the March launch!
noffie79
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Ok, someone asked for pictures. I don't have any of the beginning of the build, such as installing CR's or the eyebolt, or the aftermath of the internal fillet process. All I can say is that the (thankfully) never to be seen inside of the fin can is a disaster area. Epoxy all over the place. I used long wooden dowels to reach up into the BT to place the epoxy, but it's just so far to reach. My first time doing fins this large or this far forward. But, I think the fillets will hold these fins just fine. They're definitely sturdy, and I'm sure I used enough epoxy. I did choose to use the epoxy clay from Apogee. My first time using it, and general consensus is, I like it. I haven't sanded them down yet, but here they are. 
I also used the epoxy clay to cover the forward rail button so that the laundry doesn't snag on it.
I have the pretty Aeropack retainer in place.
And I have the NC prepped for what will be a lot of weight. Drilled holes and will be installing a 5/8" dowel to give the epoxy something to grab onto. I'll be adding quite a bit of weight, and when it's all said and done, the NC should end up somewhere between 2.5-2.9 pounds.
I also used the epoxy clay to cover the forward rail button so that the laundry doesn't snag on it.
I have the pretty Aeropack retainer in place.
And I have the NC prepped for what will be a lot of weight. Drilled holes and will be installing a 5/8" dowel to give the epoxy something to grab onto. I'll be adding quite a bit of weight, and when it's all said and done, the NC should end up somewhere between 2.5-2.9 pounds.
