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TRFfan

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Hi everyone,

I'm building a 24 mm minimum diameter rocket and I was wondering which type of adhesive to use for fin fillets. I do want a good, strong fillet enough to last plenty of flights and the rocket will be going pretty fast, (about mach 1.5 on a G150) so I was wondering which epoxy to use. Also I don't have much experience with epoxies, so if you could recommend one that's easy to use it would be appreciated. Thanks.
 

timbucktoo

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Proline 4500. Perfect for MD and Mach-busters!
 

NateLowrie

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aeropopxy woks too! even started using it to build some of my smaller birds too!

fm
I use US Composites 635 with the fast hardener. It's a laminating epoxy so you need to thicken it. I use glass microballoon filler until the epoxy thickens to a peanut butter consistency. It'll settle and harden to form a glass smooth surface and you can easily shape the ends with a file.
 

Bigcountry0322

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Hi everyone,

I'm building a 24 mm minimum diameter rocket and I was wondering which type of adhesive to use for fin fillets. I do want a good, strong fillet enough to last plenty of flights and the rocket will be going pretty fast, (about mach 1.5 on a G150) so I was wondering which epoxy to use. Also I don't have much experience with epoxies, so if you could recommend one that's easy to use it would be appreciated. Thanks.
I, by no stretch, am as accomplished as most people here. I have though, built hundreds of scratch rockets over the last 15 years. When i say "from scratch" i am talking, hand laying fiberglass BT's and fins , cut balsa/plywood bulkheads,retainers, mounts and fins. i have molded nose cones using resin casting, made homemade rocket engines (dont even ask) lol. The list goes on. Now that my intro is done. I am going to tell you what i wish somebody told me years ago.
www.max1us.com
max 1 is considered a "super adhesive" whatever that means. its so crazy, once opened it needs to be refrigerated and kept in the dark lol. This is no bs, a guy glued his cars fan belt together and drove it for 1k miles. its held up to all my ridiculousness. i recently launched a estees g40-7w and this stuff held the balsa fins on with only two small drops. i the fins break before they separate from bt. the starter kit is 25 bucks. it has a bottle of adhesive, accelerator and hole filler. the accelerator is used on porous items,(balsa,cardboard,wood,porcelain) you brush it on one side and the other side gets glue.
i am a critic, skeptic, call it what you will. unless i see something, feel it, or taste it. i dont believe it. this is my first post on the forum. i dont ever recommend anything unless it is 100% tried and true. see what you think.
ill end this novel by thanking whoever is seeing my post. the senior members,newbies, and the rest of the people who fall in the middle like me, for being here. even if you never post anything here, just reading others info, helps this dying hobby/sport live on.(yes i called rocketry a sport) haha
 

timbucktoo

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I, by no stretch, am as accomplished as most people here. I have though, built hundreds of scratch rockets over the last 15 years. When i say "from scratch" i am talking, hand laying fiberglass BT's and fins , cut balsa/plywood bulkheads,retainers, mounts and fins. i have molded nose cones using resin casting, made homemade rocket engines (dont even ask) lol. The list goes on. Now that my intro is done. I am going to tell you what i wish somebody told me years ago.
www.max1us.com
max 1 is considered a "super adhesive" whatever that means. its so crazy, once opened it needs to be refrigerated and kept in the dark lol. This is no bs, a guy glued his cars fan belt together and drove it for 1k miles. its held up to all my ridiculousness. i recently launched a estees g40-7w and this stuff held the balsa fins on with only two small drops. i the fins break before they separate from bt. the starter kit is 25 bucks. it has a bottle of adhesive, accelerator and hole filler. the accelerator is used on porous items,(balsa,cardboard,wood,porcelain) you brush it on one side and the other side gets glue.
i am a critic, skeptic, call it what you will. unless i see something, feel it, or taste it. i dont believe it. this is my first post on the forum. i dont ever recommend anything unless it is 100% tried and true. see what you think.
ill end this novel by thanking whoever is seeing my post. the senior members,newbies, and the rest of the people who fall in the middle like me, for being here. even if you never post anything here, just reading others info, helps this dying hobby/sport live on.(yes i called rocketry a sport) haha
I smell BS
 

samb

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I, by no stretch, am as accomplished as most people here. I have though, built hundreds of scratch rockets over the last 15 years. When i say "from scratch" i am talking, hand laying fiberglass BT's and fins , cut balsa/plywood bulkheads,retainers, mounts and fins. i have molded nose cones using resin casting, made homemade rocket engines (dont even ask) lol. The list goes on. Now that my intro is done. I am going to tell you what i wish somebody told me years ago.
www.max1us.com
max 1 is considered a "super adhesive" whatever that means. its so crazy, once opened it needs to be refrigerated and kept in the dark lol. This is no bs, a guy glued his cars fan belt together and drove it for 1k miles. its held up to all my ridiculousness. i recently launched a estees g40-7w and this stuff held the balsa fins on with only two small drops. i the fins break before they separate from bt. the starter kit is 25 bucks. it has a bottle of adhesive, accelerator and hole filler. the accelerator is used on porous items,(balsa,cardboard,wood,porcelain) you brush it on one side and the other side gets glue.
i am a critic, skeptic, call it what you will. unless i see something, feel it, or taste it. i dont believe it. this is my first post on the forum. i dont ever recommend anything unless it is 100% tried and true. see what you think.
ill end this novel by thanking whoever is seeing my post. the senior members,newbies, and the rest of the people who fall in the middle like me, for being here. even if you never post anything here, just reading others info, helps this dying hobby/sport live on.(yes i called rocketry a sport) haha
I smell a salesman. A bad one, as I think calling our little fun time activity a "dying hobby/sport" will not endear him to the TRFers. But he made me look so I guess that's something. His link went to a search engine so I Googled "max 1 adhesive" and found this German company with their industrial "super" super glue. Not a good choice for fillets IMO.

http://www.mabrisystems.com
 

NateLowrie

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I smell a salesman. A bad one, as I think calling our little fun time activity a "dying hobby/sport" will not endear him to the TRFers. But he made me look so I guess that's something. His link went to a search engine so I Googled "max 1 adhesive" and found this German company with their industrial "super" super glue. Not a good choice for fillets IMO.

http://www.mabrisystems.com
Definitely not a good choice for fillets. That product looks like a high viscosity CA glue with a separate activator, which is a dime a dozen. FastCap's 2P10 is a good US example. Still, if you are using a CA based glue I would recommend Bob Smith Industries. They have a thin CA glue that really soaks in to material well and a thicker CA glue that's good for root edge bonding of less porous materials. A CA glue is a good choice for LPR where you don't need a fillet.

If you are doing MPR or especially HPR you pretty much need fin fillets and epoxy will be better suited. The fillets need to be something that's not going to run or shrink that has good holding volume and epoxy fits the bill.
 

MikeT

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A quick question along the same lines. I'm building a MadCow DX3 Payloader for my Level 1. Now the fins go thru the body tube and mate to the motor mount. A good glue joint on motor mount along with inside of the body tube seems logical. The addition of using fillets on the outer tube where the fins meet the tube seem like overkill along with unnecessary weight. I'm by no means a expert on rocketry but have built and flown every type of R/C aircraft using every possible glue and material known to man and base my thoughts on this by that experience only.
I'd appreciate any thoughts or inputs on this.

Thanks
Mike

HCRCRocketry(1).jpg
 

Peter Olivola

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There are some rather heated disagreements on this. Most center around the idea that filleting all junctions between body/motor tubes and fins/centering rings is overkill. I disagree. First, it isn't necessary to use full strength epoxy. Micro balloon diluted will cut the weight drastically. It isn't, in many cases, necessary to use epoxy at all as most aliphatic resin joints are stronger than the cardboard/wood they join. The biggest reason, however, has nothing to do with the fins. Cutting through a body tube substantially compromises the structural integrity of the airframe. Filleting all tube/fin/centering ring junctions distributes loads more evenly.
 

rcktnut

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There are some rather heated disagreements on this. Most center around the idea that filleting all junctions between body/motor tubes and fins/centering rings is overkill. I disagree. First, it isn't necessary to use full strength epoxy. Micro balloon diluted will cut the weight drastically. It isn't, in many cases, necessary to use epoxy at all as most aliphatic resin joints are stronger than the cardboard/wood they join. The biggest reason, however, has nothing to do with the fins. Cutting through a body tube substantially compromises the structural integrity of the airframe. Filleting all tube/fin/centering ring junctions distributes loads more evenly.
+1 And exterior fillets meld the fins and BT, making for a nice looking rocket.
 

MikeT

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There are some rather heated disagreements on this. Most center around the idea that filleting all junctions between body/motor tubes and fins/centering rings is overkill. I disagree. First, it isn't necessary to use full strength epoxy. Micro balloon diluted will cut the weight drastically. It isn't, in many cases, necessary to use epoxy at all as most aliphatic resin joints are stronger than the cardboard/wood they join. The biggest reason, however, has nothing to do with the fins. Cutting through a body tube substantially compromises the structural integrity of the airframe. Filleting all tube/fin/centering ring junctions distributes loads more evenly.
+1 And exterior fillets meld the fins and BT, making for a nice looking rocket.
Thanks.
Mike
 

ksaves2

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Proline 4500. Perfect for MD and Mach-busters!
Tim's suggestion is reasonable but for the rocket in question can get away with just about any epoxy except if this is a cardboard/plywood project. If a fiberglass tube, G10 or G12 finned rocket, Proline 4500 with scuffing the tube and the root edge of the fins
with 40 to 60 grit sandpaper and a bit of a hefty fillet will be plenty strong. I'd be worried about finding the thing though.

If cardboard/plywood, would not matter what fillet you'd be using as you should be thinking about laminating the fincan with 2oz fiberglass cloth. The fin/fillet base stands quite the risk of ripping away from the cardboard tube. There is no way to internally
strengthen the internal laminations of paper of a cardboard tube so external fiberglass cloth lamination is mandatory if going stupid fast. If flutter occurs at the right frequency without laminating the fin/fillet will simply rip off the tube. Kurt
 
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ksaves2

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Has anyone used clay epoxy for fin fillets?
On my first Apogee Aspire 12 years ago. Get into HPR range and I believe epoxy will soak into the materials to form a better bond. For modrocs, clay is fine. The Aspire lasted 14 flights until it was lost. Among them was one G80 and three F10-8's
with many lower power motors. The last F10 is what did the permanent disappearing act. kurt
 

mpitfield

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Has anyone used clay epoxy for fin fillets?
Not quite clay but I have used the fixit two part epoxy that apogee sells. Even though they call it a clay it is more like a doughy epoxy but when it dries it dries really hard so it is not the easiest to sand...YMMV. It is also fairly dense and although I have not weighed it I am guessing that it would unnecessarily add weight where you need it the least.

That is comparing it to other fillet materials, and I have tried many at this stage. By far the easiest to sand and likely light by comparison is a combination of the two part red baron flex cure epoxy mixed with micro balloons. For easy to sand non-structural fillets I like this choice.
 

GregGleason

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Has anyone used clay epoxy for fin fillets?
I have, once. And I never did again.

Epoxy clay is heavy (typically not something you want on the aft end of your rocket) and it is not all that strong. It's fine for sculpting and such but there are a lot better solutions for rockets, and some have been mentioned already.

I do have a funny story with my experience with epoxy clay. My experience with epoxy clay is that it begins to harden up and sometimes you are not ready for that to happen. At the time my wife and I were binge watching "24" and as I was working the fillets while listening to the theme song that plays at the end of the show on continuous loop. In my mind I kept hearing Jack Bauer's voice shouting at me "We're running out of time!"

Another technique is to differentiate between the all-in-one fillet (building structure and aerodynamic characteristics at a single application) and a two-part fillet. A two-part fillet consists of a structural fillet at the joint with epoxy and strands of fiberglass or carbon fiber or even cloth. This fillet helps bear the structural loads of the fin. On top of the the structural fillet is the aero-fillet. It is a mix of epoxy and micro-balloons to create a light but smooth surface between the fin and the airframe. This fillet is non-structural in nature and its purpose is to smooth the airflow to minimize interference drag.

Two-part fillets are a little more work, but most of the time it will be stronger than the all-in-one fillet.

Greg
 

Banzai88

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When I first started as a BAR, I got into the whole Apogee videos thing, and learned a LOT. I followed along and did Fix It clay fillets. Learned the technique with the material, did a whole bunch of rockets with it, and they looked nice.

Then I started launching, and those fillets started cracking on landing, so I learned the techniques necessary to repair Fix It clay fillets. It sucked.

Then I came here and learned how to make fillets with RocketPoxy and Proline 4500. Took one set of fillets to figure it out, and my amateur first set looked as good as any I've seen here with no sanding necessary to shape! Since then I only do fillets with 4500 and I've never touched the clay again.

YMMV.
 

ksaves2

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Sims do not need any adhesive at all.
Ok if one wants to live in a sim! Cheaper too. Just buy "a" program. I had a picture of my local modroc site I put into rocksim so it was the background for the visual flight simulation. Probably not many realize rocksim can do that. Kurt
 

blackstool102

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The finest product is 3M EC-3524 a 2part void filler used as a core filler in the aviation world, much lighter then epoxies
 

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