I can't really comment on chute brands (I scratch build), but I'd look for something in the 12"-18" range with a spill hole. Ideal world descent rate under drogue is in the 80 fps range, but don't worry about 60-100 fps predictions if it gets you to a standard size. I tend to go a little high on speed under drogue because the body tubes will likely add some drag as well.So I'm getting to the point of drilling shear pins. I think I'm more nervous about that and shims than anything else here. Anyway, I will hopefully get that done this week.
On another note, I getting much closer to final weight. It's currently right at 3kg (with generic weights for the parachutes and nose ballast). I'm spec'ing chutes and wanted to get an idea of what drogues others are using. As I said previously, I'm looking hard at spherachutes, but not sure about using their chutes as drogues. Which do you all like and use (or which would never touch again)? And any thoughts on sizing for drogues?
My math with drag on the fin can gets me about ~75fps with a 12" flat sheet. I'm perfectly alright with that descent rate, but there is plenty of variation in drogue sizing and construction making it a less than straight forward research project. I appreciate the confirmation that I'm headed in the right direction though.I can't really comment on chute brands (I scratch build), but I'd look for something in the 12"-18" range with a spill hole. Ideal world descent rate under drogue is in the 80 fps range, but don't worry about 60-100 fps predictions if it gets you to a standard size. I tend to go a little high on speed under drogue because the body tubes will likely add some drag as well.
Also, if you choose a vendor, they should be able to give you a chute recommendation for drogue and main given weight at burnout and desired drogue/landing speeds.
That mounting bridge for the switches reminds me of:As previously promised, a little peek inside the av-bay...
I have not done it before, and what I have is a question, not advice. Don't the shims go in between the airframe and coupler? Keeping the sheer force from damaging those, and also cutting the pins like scissors? Doesn't that mean that they are flat against one another? If so, wouldn't that mean that you mustn't put anything like more epoxy on top of them?In other news, I've got just about everything drilled and prepped, so I'm about ready to get brass shims into the airframe. For those that have done it, do you do epoxy over the hole, then shim, then more epoxy?
That is what I'm tracking/planning. But you bring up a good point. I was not planning to go brass to brass... But to do brass on the inside of each - coupler and body tube. Now i'm questioning if I even have the right concept in mind.have not done it before, and what I have is a question, not advice. Don't the shims go in between the airframe and coupler? Keeping the sheer force from damaging those, and also cutting the pins like scissors? Doesn't that mean that they are flat against one another? If so, wouldn't that mean that you mustn't put anything like more epoxy on top of them?
Awesome notes, thank you. I think I'll steal that blind nut idea too.1st 2 pics are the inside of a 1/5th V 2. They are on the inside of the sonotube, sonotube is glassed on outside. Located at the bottom of the NC shoulder. The screws will go through the shim plates and into a tapped aluminum bracket that is bolted to the base of the NC shoulder. Can take a pic of that tomorrow if you like as it is in the paint booth now with primer drying. The last 3 pics are LOCs 4" V 2. Again the brass plates are on the inside of the cardboard tube. With the last pic being the inside of the NC shoulder. I like to glue a plate with a blind nut in place. Just like the big V 2, by screwing into a threaded housing, it will hold the screw securely and does not allow it to roll over. They shear very cleanly. This also allows for very easy removal of the sheared off threaded portion.
Jumping right into this build as I've been tinkering with the kit since I got it last week. I did the Coker nosecone mod to add the tracker bay. Nothing really fancy, but I did scratch build the sled. I used a 4x54 CR and 4" coupler bulkplate for the mount. I had to do a fair amount of sanding to get it all to fit, but it turned out nicely.
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I think I ended up using 6-32 screws and t-nuts because I had some extra lying around.
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The mock up of my sled base. I misjudged the 54mm when grabbing holesaws, but a little extra glue and it sorted out fine. I also used a chunk of 54mm tube to add a little extra rigidity to the base mount.
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After I got the poorly cut 54mm bulkplate glued up, I realized I forgot to cut a dado for the actual sled. Grabbed a coping saw and 10 minutes later it was fine.
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I opted for an Eggfinder Mini for tracking, not because I trust it, but because I had one for a 29mm MD build which I'd like to keep in the arsenal. I've never flown it though, mainly because I've never been able to get it to acquire satellites. I probably need to call up Cris and see what I'm doing wrong.
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My battery placement (sketched in pencil) worked out great until I mounted it in the 54mm tube. It sits pretty low in the tube. I will probably need to cut a bit of the tube to make it easier to fish zipties through.
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It's okay to be jealous of my joinery skills. Mounting up a battery tray to give some more support during liftoff.
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Lots of glue, some beer, and intermittently paying attention to my wife's TV show.
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Fortunately, as ugly as it all is, it will be hidden from view in the nosecone. After the epoxy cured, I decided I needed to widen the CR a bit to make it easier to slide the tracker bay in.
So, you have a good fridge in your shop or your SO is suffering with a sub-standard kitchen.