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L2 Cert Build - SuperSized Hi Flier

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AeroAggie

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Coming off a successful first HPR build (PML Quicksilver) and first-flight L1 cert a couple of weeks ago, I've decided to do something a little different for a Level 2 rocket. One of my favorite rockets as a kid was the Estes Hi Flier, but I haven't seen any supersized versions on here (maybe my google-fu is weak?). I was planning to hold off on the build thread until I get all the parts in, but I'd like to get some feedback while I'm waiting on those.

The parts
  • 4" FW glass tube (red)
  • 4" 5:1 FW glass nose cone (black)
  • 54mm phenolic motor mount
  • fins - TBD
  • chute(s) - TBD
  • Eggfinder/timer/TRS, model is TBD

Scale Factor Challenge
If you look at the original Hi Flier, the fins are quite large in comparison to the body. When you scale it up, you realize just how big those suckers are. I did all the dimensional scaling in excel and plugged those numbers into OpenRocket. Bear with me here, I can't get the picture of my *ork file to upload at the moment. I'll add pics when I can get them to upload correctly.

I rounded off some numbers to make the math easy:
  • Length - 62"
  • Diameter - 4"
  • Fins - 21.5" x 7"

The first challenge is stability. Open Rocket says bare tube, nose cone, and fins are ajust a touch over 1 caliber. Add in all the guts and a motor and that number goes negative in some cases. With the fin length being about 1/3 of the body length, the Cp is pretty far forward. This is easily mitigated with nose weight (which I don't want to do) or a longer body tube. I'll probably take some artistic/engineering license and stretch the overall length a bit to get the stability under control.

The second challenge is fin material and size. I want to use carbon plate, but it's just not in the budget for fins this size. Lots of rockets this size use plywood and G10 with great success, but their fins generally aren't as big. I ran the numbers in FinSim and it ain't pretty. Theoretical flutter speed for 1/4" plywood at 21.5" x 7" is just under 900 ft/s. Divergence speed is a little better at 1200 ft/s.

I can improve flutter margin by making the fins stiffer and/or smaller. Since solid carbon plate is out of the budget, I need to make them a little smaller. If I make the fins about 16.5" x 5", flutter speed improves to 1475 ft/s. I think that's ample margin for a K550 which should push to around 1000 ft/s (Mach 0.94).

The third challenge is sourcing material. FinSim material properties are based on aircraft grade plywood. It seems most kits and scratch builders tend to use Baltic Birch plywood, which as far as I can tell, comes in 5 ply for 0.25". This is not aircraft grade, which would normally be something like 10-12 ply birch. Most of what passes for aircraft plywood at the hobby stores here is also 5 ply, and it just feels awfully flexible. I remember way back when Midwest Products aircraft plywood really was the 12 ply good stuff, but I can't find that here any more.

I have some carbon fabric and a vac system, so I'm leaning toward getting 0.25" 5-ply hobby plywood and bagging it in plain weave carbon.

So the start of my build thread is not so much building as fishing for some feedback on successes/failures with large plywood fins, or substitute material suggestions. I know, tl;dr, Pics or it didn't happen, etc.

Cheers!
 

Rex R

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I have built a bt70 version(and bt60), I would suggest making the fins smaller, something like 80 - 90% of the upscaled size. most folks will not notice the difference, and it will help with your cp location. of course one could make it dual deploy the added weight of the av bay would move your cg forward. I would try the smaller fins first.
Rex
 

chris m

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Look up mega hi flyer here . My fins were canted 5 degree
 

AeroAggie

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I have built a bt70 version(and bt60), I would suggest making the fins smaller, something like 80 - 90% of the upscaled size. most folks will not notice the difference, and it will help with your cp location. of course one could make it dual deploy the added weight of the av bay would move your cg forward. I would try the smaller fins first.
Rex
Exactly my plan. The overall scale factor is a little over 5X, but the fins will be about a 4X factor. The 16.5" x 5" fin I mentioned represents that sizing. I am planning for dual deploy as well.
 

GrouchoDuke

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This is going to be awesome. Can't wait to see it!
 

MClark

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I like any upscale of any rocket.
I would not make the fins smaller than scale, it just won't look right.
When I do an upscale I keep the fin thickness to scale also, thick fins really make the rocket look like the original. I have helped on a few huge Mosquitos and the fins on the 18" dia one were about 2" thick.
If there is a CP/CG issue just ballast it, if you wanted to go high you wouldn't be making an upscale.

M
 
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AeroAggie

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I like an upscale of any rocket.
I would not make the fins smaller than scale, it just won't look right.
When I do an upscale I keep the fin thickness to scale also, thick fins really make the rocket look like the original. I have helped on a few huge Mosquitos and the fins on the 18" dia one were about 2" thick.
If there is a CP/CG issue just ballast it, if you wanted to go high you wouldn't be making an upscale.

M
While I totally respect the scale purist approach, I'm more interested in something that flies well while maintaining a strong resemblance to the original. As an engineer, I abhor unnecessary drag and weight. In terms of scale, I'm really going for the That Looks About Right approach.

Here's the current state of my Open Rocket model. I've stretched it to 76.5" (scale would be 62"), and shrunk the fins to 16.5" x 5.25" (scale would be 21.5 x 7"). It's still a work in progress, but these proportions work well with the stability and flutter and a K550 ought to be a good performing load in this configuration. I think my fin sizing is firm, but still working with tube dimensions and sizing the entrails.

Hi_Flier_K550.jpg
 

AeroAggie

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And here she is at 62" with the smaller fins. The proportions are obviously more scale-like. Just gotta get some chutes and cords and tubes and see how it all fits.

Hi_Flier_62in.jpg
 

Rex R

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are you planning to stuff your main chute into the lower section? I ask because you're not leaving much space in the upper section for a 48" chute. fins look good from here.
Rex
 

AeroAggie

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are you planning to stuff your main chute into the lower section? I ask because you're not leaving much space in the upper section for a 48" chute. fins look good from here.
Rex
Haven't really decided yet. I happened to be watching John Coker's L2 build video just now. It's about the same size and he put the main in the lower section for that reason. My tube stock length is 60" so I can split the upper and lower wherever I want it.
 

Rex R

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one of the things one has to plan for when doing dual deploy. BTW for planning purposes, your av bay will probably weigh in about 1 - 1.5 pounds when finished...I would add a mass object to your sim to reflect this(and give you a better idea of overall weight, aside from heavy :)).
Rex
 

AeroAggie

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One thing you learn as a parent is that if you want to do get anything done, you have to do it when the kids are sleeping. So my trusty rocket brain fired up at 4:30am today and said "Get to work!".

The carbon is a 5.7oz plain weave fabric. Dry fabric thickness is 0.0090". The wood is a 12" x 24" x 0.25" 5-ply aircraft plywood from the hobby shop. Total dry thickness is 0.25" + 4*0.009" = 0.286". I assume the cured thickness will probably be between 0.295"-0.300".

I reran FinSim using 0.300" plywood properties (conservatively assuming the carbon = plywood) and acheived theoretical flutter speed of 1938 ft/s (Mach 1.76) and divergence speed of 2468 ft/s (Mach 2.24). My engineer brain is satisfied that these fins will be adequate for virtually any 54mm motor that I can stuff in there. I know that my plywood is probably not the same as the aircraft grade plywood properties in FinSim but the carbon is at least 4x stiffer than either of those, so I feel like there's still enough conservatism in that analysis.

In order to get quasi-isotropic properties, I'm going to use 4 plies ( 2 on each side of the wood core) oriented at [45/-45,0/90,core,0/90,45/-45]. I'm using blue painter's masking tape to lay out the borders and control fraying after the cuts.

Laying out the 0/90s:
IMG_4050.jpg

You can barely make out the fin outlines on the wood. Assuming the fabric is rolled in the 0 direction, the fins are oriented such that root chord is along the long edge of the wood in the 90 direction of the fabric. Plain weave has the same properties in each direction so 0=90.

Laying out the 45s:
IMG_4052.jpg

The plies in order [45,0,core,0,45]:
IMG_4053.jpg

Notice there's no tape along the factory edge, which is stitched with kevlar to control fraying.

Hopefully I can sneak away to the garage later today when baby is napping and set up the vacuum bag system.

Just got word from Mad Cow that my order is being processed, so hopefully I'll have tubes by the time my fins are done.

To be continued...
 

markkoelsch

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Just a comment. If I were you I would not be thinking of a L2 after one High Power Flight. Do a bunch of H and I flights, get dual deployment down. It is not a race.
 

ksaves2

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Just a comment. If I were you I would not be thinking of a L2 after one High Power Flight. Do a bunch of H and I flights, get dual deployment down. It is not a race.
Ditto. In this day and age, no need to rush it. Twelve years ago with different laws and different rules there was cause to rush the L2 just to be able to fly certified motors at a research launch. I came up when research launches weren't
confined to "research motors only". Yes there was a time that was true plus I just completed an L1 and took a motor course because the group needed the money and my body to complete the number it would take to get the teacher to
travel to our area. Rushed the L2 with a 3FNC motor eject, got it in the can. Didn't touch another J motor for a couple of years until I had flown smaller H's and I's on dual deploy. I did launch the L2 rocket several times with the J350M because
the rocket was so dialed in for that motor. Kurt
 

GrouchoDuke

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I'm a noob to HPR too, so please take this as though I'm being as humble as possible and just continuing our open, friendly discussion. :) Sure he could experiment with cheaper/smaller rockets if he wanted to, but I have no doubt he can have a very successful project with this. I've known him for 25+ years...you should see his resume.

This rocket should fly fine on bigger I motors and should be a straightforward rocket to do DD with. I'm not saying there won't be learning along the way, of course. He's sharing his project here with a healthy attitude & willingness to learn. Caution & safety are important, but I think this will be a smooth and fun step for him in the hobby.
 

AeroAggie

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Fin stock is in the bag.

Wifey went to work and oldest daughter is watching the youngest daughter, so daddy gets to go play in the garage.

After knocking the dust off the vacuum system and changing some leaky fittings, I did a vacuum check on a motorcycle jacket liner. Looks kinda weird under 29inHg:

IMG_4054.jpg

I'm using West System 105/205. I know it's not optimized for rocketry, but it's what I have and it's a really great laminating epoxy. Even though it has a great pot life, I didn't stop to take any pictures during the wetting out so you'll have to be satisfied with a blurry picture of everything laid up and wetted out, ready for bagging:
IMG_4060.jpg

I'm using heavy mylar caul sheet on both sides to get a nice finish right out of the bag. Here it is before suction:
IMG_4061.jpg

And here's everything with vacuum applied. I've got an auto regulator on the system so it will cycle the pump when it needs to (hopefully not too often!):
IMG_4062.jpg

And now we wait...
 

AeroAggie

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I've known him for 25+ years...you should see his resume.
Aww, shucks. :blush:

If 20 years in the aerospace industry have taught me anything, it's that not everyone requires the same experiences to acquire experience. I came into HPR not knowing anything about it, but it didn't take long to realize the construction methods, materials, hardware, and science are things I'm familiar with. A duck to water, so to speak. I still have a lot to learn and intend to do so a pace and level that I'm comfortable with. In the mean time, I do appreciate all the feedback and concerns, but I'd prefer to leave philosophy back at the watering hole and keep this thread as a technical discussion.
Thanks! :cheers:
 

Nick@JET

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I love the looks of the hi-flyer! I too scaled up a favorite Estes rocket , this will be a cool build.
In your first move you broke out CF and they vacuum?? Ok so maybe build techniques not in question here.

There are plenty of large fin flyers, Wildman AAD, Jayhawks, SAAB, interceptor. Wouldn't hurt to search out those rockets and read about the stability numbers and nose weight.

Watching with interest!
 

chris m

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A true up scale of the hi flyer can fly and straight .I'm building it again soon .mine was 38mm but 54mm would be much better . This time around going loc four inch and not carpet tube it works but it gets heavy fast . And the cone had to be hand built . For the fins I will do ply fins but cut most of it out and add foam then glass it .
 

AeroAggie

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The fin stock is out of the bag. It does have a nice gloss to it, but there are lots of pinholes to fill which I'll do before cutting, and a couple other flaws to repair caused by some debris that got between the bench and the bag. I think I can cut the fins out and miss the big flaws though.

Just got word earlier today that my tubes shipped, so hope to have these fins knocked out by the time the rest of the stuff gets here.

IMG_4064.jpg
 

AeroAggie

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Gloss is gone for now. I went ahead and cut out the fins then clamped them together and trimmed them all up on the disk sander. I need to pick up a new router bit to round all the edges, then I'll give them a resin wipe to fill pinholes and seal the bare wood edges. That will get sanded up to about 2000 grit to match the matte finish of the fiberglass tube.

IMG_4067.jpg
 

AeroAggie

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Got my tubes and nosecone in today from Mad Cow, and decals from Stickershock.

I measured and weighed everything so I can update my OpenRocket file. Next task is to build a jig to cut tube slots with my router, then prepare the motor mount and fins for installation.

IMG_4073.jpg
 

BDB

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Looking good! Are there any special blades or router bits that you used to cut the CF-laminated fins?
 

AeroAggie

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Looking good! Are there any special blades or router bits that you used to cut the CF-laminated fins?
Nope. Just a wood blade in the jig saw and a 1/8" round over bit on the router.
 

AeroAggie

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While waiting for my motor mount tube and centering ring marriage to consummate, it's time to cut some slots in the main tube. I printed a fin alignment guide from payloadbay.com and used that to mark my fin locations, then drew the fin centerlines down the tube with an aluminum angle as a guide.

Regular drill bits have a tendency to rip and shatter FW fiberglass, so here I'm using a Unibit to make a start hole for the router.
IMG_4090.jpg

I set up a crude but effective jig to cut slots with a router and edge guide. It works great so long as you don't get heavy-handed and let the thing wander off track.

IMG_4089.jpg

Slots are complete. I added some enlargements along the slot so that I can inject epoxy later when I'm making the internal fillets.

IMG_4091.jpg
 

BDB

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I really like the jig. I'm hoping to do something like this too. I was planning to build a box to hold my airframe with a fence attached to guide my router. Can you share some info on your router guide?
 

AeroAggie

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Can you share some info on your router guide?
I wish I had a router table but this will suffice until I can convince wifey I need another friggin tool...

IMG_4093.jpg
 

AeroAggie

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I've been slowly making progress but a little lax at taking pictures because of time constraints. Progress so far:

  • Fins are all mounted
  • Internal fillets complete
  • Aft Rail Button glued in - tee nut and a 1010 button
  • Fin can foamed
  • Aft centering ring glued in
  • 54mm HAMR motor retainer glued on
  • AvBay bulkheads, threaded rods, and eye bolts assembled to AvBay
    • These bulkheads are currently plywood as MadCow was out of the 4" G10s when I ordered everything else.
    • G10 bulkheads are back in stock, and I have a set on the way
  • Nose cone coupler glued in

Next steps:
  • finish the external fillets
  • cut a G10 sled for avbay and maybe nose cone as well
  • primary deploy altimeter/GPS will be an Eggtimer TRS
  • backup deploy will be a Raven (primary/backup may get reversed, depending on how the programming works out)
  • Weigh everything and get an upper bound to size the parachutes
  • Decide on which parachutes

I'm still debating whether to attach the AvBay to the upper tube with rivets, screws, or just glue it in. I'm partial to gluing it in at this point because I'm not crazy about the look of rivets. It's a 4" tube so I can easily get my hand down in there to adjust anything, and the AvBay bulkheads will be removable from each end. The only reason I'm hesitant to glue it in at this point is I would like to add a camera in the future and I haven't decided whether it needs to go above the AvBay or below. I think the camera should go near the bottom so that I can see what the fins are doing at high speed.

Here she is all stacked up in the 72" configuration:

IMG_4115.jpg
I may shorten the upper when I see what the parachute looks like stuffed in there. The correct length for scale is about 62", so this is the stretched look.
 
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