"Fav'rit 2 B" - Build and Flight Log

Ok, so I want to do a scratch build because I like to make things and learn well from my mistakes, which I think will be more plentiful if I am not protected from myself by a kit. I also want the most flexibility I can get from a single rocket as I am a cheap man (probably the wrong hobby, but here we are). So I came up with the below design that can be flown on as little as an RMS reload, but can also be easily turned into a DD setup for HPR if I feel like driving a couple hours to Waco...it's not really if, it's when!

By way of explination, I like weird shaped fins, and lots of them...and I hope nothing is wrong with them because they are cut, fiberglassed, and being bondoed (is that a verb?) now. In hindsight I should have asked for advice before making them, but I'm excitable, was at LHS, got a 10% off discount with my new club membership card, was in the plywood section....you been there, so you get where I'm coming from.

Also, the 2 oz noseweight is going to be the anchor for a yet not fully worked out interchangable weight thing-doo-hicky-jobber. I am going to overbuild this, trust me I've know me my whole life it's what I do, so it will need nose weight. Anyway, below are pictures and open rocket files of the setup in single deploy and DD. In an ideal world I would like to fly this from G - I in its different iterations, but it will be kept decidedly subsonic.

Anyhow, please have at.


Single deploy (long since abandoned 6-14-13)


Dual deploy

I am at work, so I do not have access to Open Rocket, however your design looks solid. One thing to keep in mind, when you mount the forward fins, make them as straight as possible. In your SD configuration, they will likely have significant influence if they are askew (much like a car with the front wheels out of alignment). In the DD configuration since they are further back, they will have less of an influence.

Also something to consider, you could fly the DD configuration as singled deploy, motor eject with the addition of rivets (or shear pins) securing the av-bay to the payload tube.

Again, I do not have access to OR so I cannot comment on stability, etc.

Cl(VII) said:

Ok, so I want to do a scratch build because I like to make things and learn well from my mistakes, which I think will be more plentiful if I am not protected from myself by a kit. I also want the most flexibility I can get from a single rocket as I am a cheap man (probably the wrong hobby, but here we are). So I came up with the below design that can be flown on as little as an RMS reload, but can also be easily turned into a DD setup for HPR if I feel like driving a couple hours to Waco...it's not really if, it's when!

By way of explination, I like weird shaped fins, and lots of them...and I hope nothing is wrong with them because they are cut, fiberglassed, and being bondoed (is that a verb?) now. In hindsight I should have asked for advice before making them, but I'm excitable, was at LHS, got a 10% off discount with my new club membership card, was in the plywood section....you been there, so you get where I'm coming from.

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Red Arrow Hobbies is 3 miles from my house. You have no idea.

Cl(VII) said:

Also, the 2 oz noseweight is going to be the anchor for a yet not fully worked out interchangable weight thing-doo-hicky-jobber.

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Cl(VII) said:

I am going to overbuild this,

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Why? If you are going to be decidedly subsonic there really is no need.

Cl(VII) said:

trust me I've know me my whole life it's what I do, so it will need nose weight. Anyway, below are pictures and open rocket files of the setup in single deploy and DD. In an ideal world I would like to fly this from G - I in its different iterations, but it will be kept decidedly subsonic.

Anyhow, please have at.

View attachment 122492
Single deploy

View attachment 122493
Dual deploy

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Looks good to me although with those little cannards it is going to be less susceptible to weather-cocking which is not altogether a bad thing. At 2 oz you are going to be hard pressed to come up with a removable nose-weight option. If it were mine I'd just glue some weight in permanently and call it good. Another option is to make the body tube longer or move the canards aft and eliminate the hassle of the weight altogether. Of course that would significantly change the look of your rocket.

Also, why all those centering rings? You really only need 2 for a rocket that size. Save yourself some $$$, weight and hassle. Plus, eliminating rings in the rear will help with how much weight you need to put in the nose.

Good Luck!

DAllen said:

Why? If you are going to be decidedly subsonic there really is no need.

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I don't know the root of it, If I get it diagnosed then it will be a mental disorder. I come from a long line of over builders, my wife calls it Bender-neering. If a tornado hits my neighborhood my lot will have a concrete slab and a pergola left (as I added that), I stopped fighting it years ago. Same thing on the centering rings and the fin fiberglassing...it's compulsive. Also, I have a nice selection of hole saws and had a 50% off Michael's coupons, so the centerings rings are done, $2 total.

Thanks for the advice so far, very helpful especially regarding the varied effects of a far forward fin set. Please keep em coming, I want to build something fun and flyable, and I really don't want to build something unstable and dangerous.

Thanks,
Chris

Cl(VII) said:

I don't know the root of it, If I get it diagnosed then it will be a mental disorder.

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If you are in rocketry, no shrink can help you now. MWUAHAHAHAHAHAHA!!!

Something else to think about is it looks like you are putting lugs on there. This rocket is getting up to the size where I strongly recommend rail buttons instead. You will be a lot happier with those over rods any day.

One thing I would like to point out is I like the fact you are going with a 38mm mount there. IMHO when you scratch build a rocket that may fly on a G motor that's where I think a 38mm mount is a good idea. I see so many people put in 29mm mounts in a rocket like yours, stay in the hobby a while and eventually they get their hands on a cool little 38mm case and say, "Dang, I wish I put a larger mount in there." Good job.

Thanks for the advice, I will definately be going with rail buttons, and hearing no fortellings of disaster I now have tubes and a nose cone on their way to join the almost fininshed fins on my bench. This may not work out perfectly, but hopefully I learn a few things.

-Chris

Ok, so I cut the fin slots for the big set, and they came out better than I expected. I clamped a piece of flat steel to the tube with hose clamps to act as a guide and made the cuts with an exacto, but i have a few questions.

What do I do with the raw cuts? The slots could be stand to be opened up slightly (<1 mm), so do I just treat with extra thin CA and sand, or will that create a problem with epoxy penetration/adhesion later?

In general, when dealing with the "exposed" edges of LOC tubing is it best to treat with CA to seal it as a matter of course?

Thanks,
Chris

I like my slots to start out tight on the theory that it is easier to take material away than to add later...that said, I've found that a dremel with sanding disk works well to make slots wider. unless you're planning on not applying fillets, there is no reason to treat the edges of the slots(they'll be covered with glue/epoxy). when sanding slots, index the slots to which fin goes in which slot(ex. insert fin(a) into slot(a), repeat until all slots have fins in them ).
rex

Cl(VII) said:

Ok, so I cut the fin slots for the big set, and they came out better than I expected. I clamped a piece of flat steel to the tube with hose clamps to act as a guide and made the cuts with an exacto, but i have a few questions.

What do I do with the raw cuts? The slots could be stand to be opened up slightly (<1 mm), so do I just treat with extra thin CA and sand, or will that create a problem with epoxy penetration/adhesion later?

In general, when dealing with the "exposed" edges of LOC tubing is it best to treat with CA to seal it as a matter of course?

Thanks,
Chris

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I never put CA on my fin slots. I want the epoxy or whatever I'm using for the fillets to be able to "soak in". If a slot is too tight, i just "shave" it with a sharp Xacto knife.

Thanks for the quick responses, gents. I only build in the evening after the kids go to bed, so I can't ask for a better cycle time for getting Qs answered than this. So no CA on the fin slots, but what about the ends of the tubes, is there any advantage to soaking a bit in there?

Cl(VII) said:

Thanks for the quick responses, gents. I only build in the evening after the kids go to bed, so I can't ask for a better cycle time for getting Qs answered than this. So no CA on the fin slots, but what about the ends of the tubes, is there any advantage to soaking a bit in there?

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I've used pieces of coupler or body tube and epoxy to strengthen the aft end. Seems to help some.

https://www.rocketryforum.com/showt...uild-upscale-Estes-Shadow&p=409247#post409247

https://www.rocketryforum.com/showt...r-boring-HP-scratch-build&p=290191#post290191

Cl(VII) said:

Thanks for the quick responses, gents. I only build in the evening after the kids go to bed, so I can't ask for a better cycle time for getting Qs answered than this. So no CA on the fin slots, but what about the ends of the tubes, is there any advantage to soaking a bit in there?

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Soaking the ends of the tubes in CA does make them stronger (I've never done it but seen many on here who have) just make sure you use the thin stuff as using the thicker kinds will just mean lots of sanding to get the nose to fit inside the airframe. Like I said I've never soaked my tube ends but I have done a coupler using medium CA... took forever to sand (hence why you should use the thin stuff), but my coupler is now nice and strong and smooth.

Thanks for the suggestions and answers. I have started working and will appreciate feedback along the way as to better ways to do things, although I realize some things come down to personal preference.

I don't necessarily work "linearly," i.e. I jump around a lot. I began by cutting out the fins; I don't have a bandsaw and my scroll saw is too loud for when the kids are asleep, so the fins were traced and cut individually from 1/8" 5-ply from the LHS. They were then pinned together using 3/8" dowel and sanded to a uniform shape. They were then covered in 5 oz fiberglass using Zpoxy finishing resin, the glass trimmed, and the whole thing glazed with bondo and sanded smooth. The 2 leading and trailing edges of each fins were airfoiled by the highly technical hand-eyeball-sandpaper-sweat method (one large fin still needs airfoiling. It's hard to believe how strong and pointy/sharp these things are.

Cl(VII) said:

Thanks for the suggestions and answers. I have started working and will appreciate feedback along the way as to better ways to do things, although I realize some things come down to personal preference.

I don't necessarily work "linearly," i.e. I jump around a lot. I began by cutting out the fins; I don't have a bandsaw and my scroll saw is too loud for when the kids are asleep, so the fins were traced and cut individually from 1/8" 5-ply from the LHS. They were then pinned together using 3/8" dowel and sanded to a uniform shape. They were then covered in 5 oz fiberglass using Zpoxy finishing resin, the glass trimmed, and the whole thing glazed with bondo and sanded smooth. The 2 leading and trailing edges of each fins were airfoiled by the highly technical hand-eyeball-sandpaper-sweat method (one large fin still needs airfoiling. It's hard to believe how strong and pointy/sharp these things are.

View attachment 123782

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Those fins look Great! I've often thought about glassing fins on a screatch build rocket, seeing as I've got a few going now...

JP

Next up the body tubes. I measured off the tubes and used a hose clamp to cut against (credit Coop for that suggestion, though I have seen it in other threads as well) and used Zona saw to make cuts, some edges still need sanding, the first one was kind of ratty so I soaked it with super thin CA and sanded it...nice now.

Fin slots were also cut for the large set of fins (i am going to sand the tabs off the small set after rationalizing how little force they will experience when landing, I am more worried about the integrity of the tube than the fin mount). I made the fin slot cuts by clamping a piece of flat steel to the tube and using as a guide for my xacto.

Coupler/av bay next...i strengthened the 6" coupler by cutting a 5 1/2" piece of tube, splitting it, removing a slice of appropriate size, glueing it 1/4" inside the coupler using copious amounts of Titebond II. This will hold as of yet undetermined altimeter. Many on here appear excited about a coming offering, so maybe I'll go that route as I am sure there will be a community of users on here.

As it was sneak peaked in the last post, on to the motor mount. I started by cutting a 15" piece of LOC tubing (didn't have an appropriate hose clamp, but the squarness of the top of a motor-mount is hardly something to worry about). Then peeled off the glassine layer and sanded the last inch or so smooth for aesthetics, and I haven't decided on motor retention yet. I previously cut out the centering rings using two hole saws, the larger diameter sanded to size using my drill as a cheap lathe and some sandpaper. I notched the top ring to allow 1/8" tubular kevlar to pass through in 2 places. I tacked the kevlar in place with CA, and epoxied on the top centering ring with 5 min epoxy. I then thoroughly coated the kevlar with 5 min epoxy, epoxied the second ring in place, and gave the top ring fillets on both sides, and the lower of the two a fillet on the fore side.

On the kevlar loop i tied a few knots that will hold a 1/4" launch lug in place on the cord where the opening of the lower tube will be. I am hoping this reduces any potential zippering. It may just be placebo, but it's cheap, and makes me feel better.

what is the purpose of the lug tube?

Great job. I am just getting back into the hobby after a 30 year hiatus, and mid power and high power rocketry were not accessible to me back then. So I have been trying to learn as much as I can about the MP and HP building techniques.

I have learned much more from your thread than I have from some I have read done by more experienced rocket builders. Maybe it is because this is your first thread and we get to see your thought process that other more experienced builders take for granted because they are just doing what they have always done. Or maybe because I too overbuild and overanalyze.

Whatever it is... Keep up the good work. I am enjoying your thread.

JP Morgan said:

Those fins look Great! I've often thought about glassing fins on a screatch build rocket, seeing as I've got a few going now...

JP

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Thanks, I think I am just going to glass MPR and up fins from now on. I recently saw my 2" LOC Iris hit a well worn, hard rut in a dirt road fin first HARD. I knew it was going to be a mess, but it only had a bad paint scratch and a newly rounded edge on the outside of one fin. I had glassed that one as a learning exercise, but I can't imagine that fin lasting otherwise.

accpool said:

what is the purpose of the lug tube?

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I hope it reduces the chance of a zipper, even slightly. The middle of he lug will be equal with the opening in the lower section of body, so when I launch it with motor ejection, if I screw up the delay maybe I have a little more wiggle room. I guess the thinking comes down to one of two conflicts 1) kevlar v. body tube, or 2) kevlar v. Lug v. Body tube. Maybe it just really comes down to a placebo, but it makes me feel better than trying nothing.

Mr Rocket said:

Great job. I am just getting back into the hobby after a 30 year hiatus, and mid power and high power rocketry were not accessible to me back then. So I have been trying to learn as much as I can about the MP and HP building techniques.

I have learned much more from your thread than I have from some I have read done by more experienced rocket builders. Maybe it is because this is your first thread and we get to see your thought process that other more experienced builders take for granted because they are just doing what they have always done. Or maybe because I too overbuild and overanalyze.

Whatever it is... Keep up the good work. I am enjoying your thread.

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Great, I hope this helps you along too. I feel though that I have to add a really big disclaimer here: I by no means have this figured out, any and all techniques and methods employed could be fundamentally flawed, poorly executed, maybe just silly, or even possibly correct...The only thing I can guarantee is that it is in my mind, at this time, with the equipment I have on hand, and within the limits of my abilities the best option I can come up with. I have read a lot of build threads, and from that I realize that there are at least 50 ways to do everything and a lot of it comes down to personal preference, but not all of it...sometimes there really is a better/best way. Finding that better/best way is what I'm glad people here are offering up, actually I'm glad there offering up the personal preferences too.

I'm a scientist, so I operate best in the throw everything into the bright light of scrutiny and move on with your lessons from there. Therefore, please keep the recommendations/criticisms coming.

Cl(VII) said:

I hope it reduces the chance of a zipper, even slightly. The middle of he lug will be equal with the opening in the lower section of body, so when I launch it with motor ejection, if I screw up the delay maybe I have a little more wiggle room. I guess the thinking comes down to one of two conflicts 1) kevlar v. body tube, or 2) kevlar v. Lug v. Body tube. Maybe it just really comes down to a placebo, but it makes me feel better than trying nothing.

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i am ok with that thinking. i just had a launch last month that i did the delay wrong, too excited to be able to handle the very complicated task of subtracting 7 from 12. messed it up of course. Rocket survived.

Catching up...some progress over the weekend, but church, pool prep (it was 80 here this weekend), zoo trip and 2 yr old's elbow dislocation limited progress. On a related note, kids are incredible, dislocated elbow at 2, emergency room at 3, eating a popsicle with the "hurt" arm by 3:30 with no lingering effects. If I had done this I would be scheduled for surgery by now.

First, cut bulkheads from 1/4" 5-layer ply and sanded them to size to fit inside coupler with a nice tight seal.



Worked on the upper section of body, treated the inside of the tube with thin CA, then sanded the top and bottom edges flat and the inside smooth (way btter than the pic looks. I did this because there will be shear pins and screw going through the different ends, and I wanted to strengthen it a bit. I also smeared bondo glazing putty into the grooves, but haven't had a chance to sand yet.



The lower body tube got the bondo and sand in the areas where fins will not attach. I am paranoid about epoxy adhesion to bondo and the strength of the overall fin-bondo-tub joint, but I like to do as much as possible before the fins are on. I also did the 1" section of tube that will be the vent band at the same time, and sanded all tube edges flat with fine sandpaper laying on the bench to get an even edge.



Last i put in the motor mount (top two CR in place) and held straight by a CR not tacked on at the bottom. I put a brad nail in this, so I had something to grip with the pliers to remove after the 30 min epoxy hardened, thereby letting me do internL fillets on this fins later. The hardest part was getting the epoxy 15" inside the tube, but a 10 mL transfer pipet and 5 mL rubber bulb did a nice job. I have no idea what non lab rats do to get epoxy this far inside an airframe neatly-ish. Next up a big drizzle of 30 min epoxy from the top to beef up th joint...I am however a bit worried I don't have a perfect seal around the top CR so I may use 5 min epoxy to give less drizzle through time.

Great job! My weapon of choice when it comes to getting adhesive down inside has been a q-tip taped to a dowel. I am going to have to order some disposible pipettes and give that a whirl.

Cl(VII) said:

Last i put in the motor mount (top two CR in place) and held straight by a CR not tacked on at the bottom. I put a brad nail in this, so I had something to grip with the pliers to remove after the 30 min epoxy hardened, thereby letting me do internL fillets on this fins later. The hardest part was getting the epoxy 15" inside the tube, but a 10 mL transfer pipet and 5 mL rubber bulb did a nice job. I have no idea what non lab rats do to get epoxy this far inside an airframe neatly-ish. Next up a big drizzle of 30 min epoxy from the top to beef up th joint...I am however a bit worried I don't have a perfect seal around the top CR so I may use 5 min epoxy to give less drizzle through time.

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T-Rex said:

Great job! My weapon of choice when it comes to getting adhesive down inside has been a q-tip taped to a dowel. I am going to have to order some disposible pipettes and give that a whirl.

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I just use a long dowel or bamboo skewer to put epoxy inside body tubes. I mark the depth on the dowel with tape so I can apply it where I need it. And for removing the aft centering ring after epoxying the forward ring, most of my builds get tee-nuts. I can remove the aft ring with a long screw. On my few builds that don't get tee-nuts, I use pieces of masking tape put on the aft ring to pull it out later.

First off, thanks again for compliments and commentary along the way.

Some progress over the last few nights...two nights ago I got the last fin airfoiled and extra pieces epoxied to the centering ring that one of the rail buttons will attach to. No way I'm missing that target(I hope). I would have done more, but Darvish had a perfect game going and the radio in the garage wasn't cutting it after the 6th.



Tonight I got the big, rear fins attached with 5 min epoxy...they came out pretty well I think. Lots of internal and external fillets to do. I am planning to embed the 1/8" square basswood strips on the bench into the internal fillets. It's gratifying to start seeing this thing look like something more than tubes. In the larger pic you can see the lower, upper, and electronic bay with vent band. This thing is going to be big, at least compared to my other stuff.



Doubt I'll get too much more done for a few days, but at least it's starting to look like a rocket.