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J record attempt using Loki J1026
- Thread starter Adrian A
- Start date
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Yeah, I did. It looks like I'm not going to get a high speed test in before BALLS. But now I'm thinking about doing a 2-stage test flight at Alamosa this Saturday with smaller motors that would stay under the 15k waiver.
Adrian, was great to meet you this weekend, but I didn't realize when talking to you just what a superhuman you are. You already got all the way home to Colorado and immediately repaired your fins to your usual impeccable standard? I'm in awe!
It was great to meet you and thanks for the kind words.
I wish my standard were impeccable. My recent results keep reminding me that my standards are quite peccable indeed. Not to mention the Kansas state highway patrol.
I wish my standard were impeccable. My recent results keep reminding me that my standards are quite peccable indeed. Not to mention the Kansas state highway patrol.
Progress photos:
After sanding the fillets and sanding a taper into the carbon I love how this looks: I wish they were strong enough without needing to add layers from here.
I wet out the carbon inside of a garbage bag to make my own sorta-prepreg. Woven is on top and 4.9 oz uni is on the bottom. I use spray adhesive to stick the patterns onto the bag and then cut the pieces out.
last step before peel ply:
In the (garbage) bag. No vacuum sticky tape required if you roll the open end closed. Shop towels for bleeder/breather layers.
After sanding the fillets and sanding a taper into the carbon I love how this looks: I wish they were strong enough without needing to add layers from here.
I wet out the carbon inside of a garbage bag to make my own sorta-prepreg. Woven is on top and 4.9 oz uni is on the bottom. I use spray adhesive to stick the patterns onto the bag and then cut the pieces out.
last step before peel ply:
In the (garbage) bag. No vacuum sticky tape required if you roll the open end closed. Shop towels for bleeder/breather layers.
James Keller
Well-Known Member
Hey Adrian,
Looks great as always, wondering how you are beveling the leading and trailing edge of your fins. Also if you wanted to save yourself a drive the Chili Blaster event at SCORE is happening soon. I would love to see this thing in action!
-James
Looks great as always, wondering how you are beveling the leading and trailing edge of your fins. Also if you wanted to save yourself a drive the Chili Blaster event at SCORE is happening soon. I would love to see this thing in action!
-James
Thanks, James. For the beveling, I'm winging it. I have 100 grit sandpaper taped to a flat granite tile to do some of the taper, and I pinch sandpaper around the edge for the rest.
With Alamosa's 15k waiver, that will allow me to fly an I600 for a supersonic test of the fins. It also has enough time between the flight and BALLS that I could do some rebuilding if something goes wrong. Chili Blaster is just a few days before the motorhome heads out to Nevada.
More progress photos. Here's how it comes out of the bag, with the low-angled sun exaggerating the roughness:
And then after sanding:
I may have sanded too far, because the fins don't feel as bomb-proof as I want them to. The original fin is 0.105" thick, but it includes some surface coat of thickened epoxy that I haven't done to the 2 new fins yet. The new fins are 0.097 at the thickest part. I think I'm going to sand off the thickened epoxy coat from the old fin and add another layer of uni fiber in the mid-chord areas of all 3 fins to improve the strength and stiffness.
And then after sanding:
I may have sanded too far, because the fins don't feel as bomb-proof as I want them to. The original fin is 0.105" thick, but it includes some surface coat of thickened epoxy that I haven't done to the 2 new fins yet. The new fins are 0.097 at the thickest part. I think I'm going to sand off the thickened epoxy coat from the old fin and add another layer of uni fiber in the mid-chord areas of all 3 fins to improve the strength and stiffness.
Maybe I've just now stolen my new .sig line.<<snip>> ... If records were easy, everyone would have one...
Thanks @RocketScientistAustralia -- that's a keeper !
-- kjh
If records were easy, everyone would have one -- @RocketScientistAustralia
Adrian,
slight tangent here, but how much was the Cotronics epoxy that you bought with the long leadtime? I found out today that McMaster P/N 7563A51 is the Cotronics Duralco 4461IP kit. it's $153 and I can have it tomorrow. If you check the SDS on McMaster for that part number, it comes up as the SDS for Duralco 4461IP resin and hardener.
I'm looking at getting some for a future project, but wanted to find out the cost difference vs. buying direct from Cotronics.
I'm following this thread closely, as I am working on a few min dia builds. A lot has changed in the past 15 years where I was mostly inactive in the hobby (university, kids, etc).
slight tangent here, but how much was the Cotronics epoxy that you bought with the long leadtime? I found out today that McMaster P/N 7563A51 is the Cotronics Duralco 4461IP kit. it's $153 and I can have it tomorrow. If you check the SDS on McMaster for that part number, it comes up as the SDS for Duralco 4461IP resin and hardener.
I'm looking at getting some for a future project, but wanted to find out the cost difference vs. buying direct from Cotronics.
I'm following this thread closely, as I am working on a few min dia builds. A lot has changed in the past 15 years where I was mostly inactive in the hobby (university, kids, etc).
Buying direct it was $131. I would have gladly paid $153 through McMaster.
I just searched in McMaster under epoxies and didn't find it, but I see it's listed under potting compounds.
After the unidirectional layup and some very gentle sanding:
What look like waves are some slight high spots from the cross threads that hold the uni together while it's dry.
Next I thickened the 4461 epoxy with colloidal silica and troweled it onto the fins. The goal is to fully encapsulate the carbon:
More sanding ahead, and probably another 1-2 (3?) more coatings to get the surface finish the way I want it.
What look like waves are some slight high spots from the cross threads that hold the uni together while it's dry.
Next I thickened the 4461 epoxy with colloidal silica and troweled it onto the fins. The goal is to fully encapsulate the carbon:
More sanding ahead, and probably another 1-2 (3?) more coatings to get the surface finish the way I want it.
Adrian,
You've mentioned the CTE mismatch between the aluminum foil and the fins being too high. What composite cte do you expect at the fin tips? The carbon is low, the silica is low, but the epoxy is high. Ive seen some papers on the subject, but it varies quite a bit between parallel to the grain vs. perpendicular to the grain.
You've mentioned the CTE mismatch between the aluminum foil and the fins being too high. What composite cte do you expect at the fin tips? The carbon is low, the silica is low, but the epoxy is high. Ive seen some papers on the subject, but it varies quite a bit between parallel to the grain vs. perpendicular to the grain.
Agreed that it varies a lot with the fiber orientation. The leading edge has a high proportion of the fibers going nearly parallel to it, so the CTE is probably lower than the Aluminum. But I wouldn't be very confident about that since the thickness also has a lot of fibers that aren't very close to parallel to it.
I sanded off the thickened epoxy and did another two thin coats of epoxy, with wet sanding with 360 in between coats.
The next flight for this will be on Saturday, and I have decided to
The leading edges are sharp and nicely tapered, and the thickness profile is smoothly rounded. It's hard to convey the thickness profile in the photos, but this one comes close, though also highlighting the imperfections:
The next flight for this rocket will be on Saturday. My latest plan is to fly it as a boosted dart with my BALLS second stage boosting it with a J570 or CTI J530. In the next couple of days I'll be doing progress/results updates in the multi-stage sub-forum, though I'll reply to replies here.
The next flight for this will be on Saturday, and I have decided to
The leading edges are sharp and nicely tapered, and the thickness profile is smoothly rounded. It's hard to convey the thickness profile in the photos, but this one comes close, though also highlighting the imperfections:
The next flight for this rocket will be on Saturday. My latest plan is to fly it as a boosted dart with my BALLS second stage boosting it with a J570 or CTI J530. In the next couple of days I'll be doing progress/results updates in the multi-stage sub-forum, though I'll reply to replies here.
Looks Great, Adrian.
For the boosted dart, are you keeping the empty Loki case inside, as the interstage coupler? I assume you will be doing a separation charge at burnout.
For the boosted dart, are you keeping the empty Loki case inside, as the interstage coupler? I assume you will be doing a separation charge at burnout.
Yes. I need it at both ends; the front of the case also holds the nosecone and recovery gear. I was starting to figure out a combination of cases and adapters that would stay within the waiver before I thought of the boosted dart option.
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