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Discussion in 'Low Power Rocketry (LPR)' started by BSNW, Jan 19, 2020.
Those foam sanding blocks are very handy to use.
The next step will be some small fillets on the wings and uppers. They will add only a few milligrams to the overall weight. I use Loctite water based construction adhesive. This is a great product for fillets that is not only very strong but it is inexpensive. It is easy to work with as well. I use it on my models and my large high power rockets too. More to come as things develop!!
THANKS! I did saturate the voids with watery CA prior to filling with the spot putty. I then "seal" the spot putty after sanding smooth. I get it "coming and going!". Thanks for you kind words!
Just an FYI this is similar to what I use for sanding. They work great and can used formany applications.
I used to do all my fillets with epoxy. After seeing another guy using using this technique for his L3 project...I was hooked. It is fast, cheap, non-toxic and you can do an entire rocket at one time. You need a cup of water, a Popsicle stick, some tape and a wiping cloth. Here we go....
Mask off the area. Wider for larger fillets or smaller for narrow ones.
Using your caulk gun put a bead down. NOTE: this bead is messy, as the dog was horsing around my chair when I put this down. No worries....I have tape!
Take your Popsicle stick and DIP IT IN WATER. Then, keeping the same angle, run it down the tape.
Now pull the tape. Then dip your finger into the water and slide it down the fillet. Do NOT "plow" the glue. Rather, use your finger to feather down and smooth the edges of the fillet. This is why it is important to dip your finger in the water as the glue grabs and drags really fast. Make sure not to over work it or use too much water.
Boom! you are done. As I mentioned....you can do the entire rocket at one time. This stuff will NOT move unless touched. Let sit overnight. It will be VERY smooth!
One last thing....This stuff will lose half or more of its mass. In this case it is okay as I wanted a small-tight fillet to aid in strength and make the finish really smooth when I paint. On my larger rockets....I use a MUCH larger bead. I will post what the bead looks like when it is done drying.
THANKS! I will check it out!
Have a good day.
Couldn’t you use that as the filler too ?
I guess one could...but I would NOT.
You want fillers that sand as easily as the thing you are sanding. They should be close to the same density. Fillers powder up (when sanding) and sand smooth. The fillet material is a glue...and has some elasticity to it even though it dries hard. It does not lend itself to sanding smooth like a filler.
Thanks for the filet tips - looks pretty simple!
I do mind the same way. I only use epoxy on materials other than wood and cardboard
Wing area scales by length squared, Weight tends to scale with Volume, or length cubed. So, if you wanted to maintain a similar wing loading, W/S, for similar gliding performance, then you would need to use some different materials that are lighter than balsa, or the weight may get too heavy for a decent glider. Check out the fairly large size and lightweight rocket-boosted gliders from Dynasoar for some examples of foam construction.
In fact, I imagine his gliders perform even better than this little one.
I've seen his gliders and they are outstanding. He does exceptional work!!
So if you look at Post #40 then see below....you will see the difference of the fillet after drying overnight. It is a tight, smooth fillet that blends in well after priming and painting. I really like this material to do fillets. It is really easy to work with, it is inexpensive and non toxic. Good times.
I went on to do the fillets on the top side. It took only a few minutes. After this dries, I will seal the balsa with one coat of BIN (white pigmented shellac). I will post about that product when I apply it. I am happy how this glider turned out. It is still very light...as I used only CA for the glue. The fillet material....after it dries, weighs next to nothing. 99% of the filler I used was sanded off. I also will be mindful of the paint and try to use as little as possible and still make it look good. I am not a plane/glider guy....so I have no idea how to "trim" it before flight. I know what the instructions say...but I am scared of dinging it up before its first launch. We will see....All in all this is a really nice kit.
ONE MORE thing....I know I am getting ahead of myself, but I am seriously considering doing a cluster on the booster - (x2) 24mm mount on this. I really want a good straight boost on this. The kit, for a model rocket is big. Lots of drag and such. I was told I need a very long rod and a calm day....which almost never happens. I also don't want to "blow it away" with a composite like an E18 or F24. I think the F12 would be too soft. I was thinking two black powder motors MAY be "softer" (compared to a composite) at lift-off....yet give it more "umph" and give it a better boost. YES...I have to study the thrust curves and look at all the profiles......I am simply thinking out loud to maybe get some thoughts from you all. After all this work....I will want a good-straight liftoff that does not lumber into the wind and is a "under-powered white knuckle ride". All the videos I have seen of liftoffs on the web of this kit...show them sorely under-powered and arcing over badly....thoughts?
Thinking of 2-E9's or 2-E12's
You would be better off going with a single 24mm composite motor like a E30 or something similar.
Thank you so much for sharing this fillet technique. I've very much been in an improve-my-fillets mode. I was thinking of going down the epoxy route, reluctantly, as I am trying to minimize my use of that stuff. Now if I can only remember where I put my caulk gun...
Thank you for your reply. I will look into that for sure. ALSO, Thank you very much for such a fantastic kit! I LOVE it! I can tell it was well thought out from the construction and from the order of operations etc. It is also a beautiful model. Well done. I like this along with the Odyssey and Conquest. Later this year I am building the Black Star Voyager.
Beautiful work so far.
What I did was glue some scrap wood/fin stick to some scrap tubing and practiced. It is a technique that is easy to learn. I use it on my small models all the way up to my 5.5" High power projects that fly on K's. My friend who showed me this technique, used it on his L3 project...and still uses it on his larger projects. Cant remember the last time I used epoxy for external fillets. ENJOY!
Does he use the same adhesive / glue you use? (that white caulk gun stuff?) or just the technique?
From past experiences, I've found CA to be extremely hard to sand. it will sand, but you tend to sand more of the 'bare wood' than the CA soaked wood..
Have you thought of using a light weight balsa filler, the stuff R/C plane builders use? Light, easy to use, thins with water, and no smell!
I agree with the balsa filler, but that stuff is hard to come by. I thought they discontinued it awhile back. At least the "Aerogloss" brand. Nevermind...I thought you were talking about something else.
I would do 3 motors
1) I don't sand CA either. I don't use CA to fill. I do use watery CA to saturate/seal open grain on balsa edges. That sands nice and smooth.
2) Yes this is the same glue...same stuff (for the fillets) he uses.
3) I use BIN because I can get a quart at Home Depot for about $15. It will last years....soaks into wood like crazy, sands like glass, fills grain and is pigmented white. It also cleans up with household
ammonia and water (see my Conquest thread)
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