CF Fin attachment

[HyperSonic]

Here is a pic of the strips of IM Unidirectional Carbon Fabric (4.3 oz) .006 inches thick. The tows run
perpendicular to the airframe. It is difficult to see in the pics I posted earlier. I very much want your input,
and if you see something that you don't like, or is iffy, please tell me just like you did with this CF strip. The
reason I'm posting this process on the forum is to get your opinion. You guys give great advise. I know alot of you
are saying, who does this guy think he is, wanting to go "stupid fast". He must be stupid!!! Well let me tell you
that I am not a college student who wants to reach space, I am a senior citizen with a much slower pace!! (I like
that!) Why so fast you ask? Because it is difficult, challenging, and will be very rewarding when successful. I am
not a record chaser. I launched my first estes rocket back in the 1970s. I bought it from G.L. Perrys. I used to
repair TVs by going to hooks drug store to test the tubes.(black and white before color) I have been in and out of
rocketry ever since. I am amazed at where we are today in rocketry. I got to see it back in the 1970s, all the way
till now. Just incredible what people are able to do today! Its been a fun ride that is not over yet for me. It
might be getting close, but I want to accomplish a few more things before I die, and breaking mach 3 is one of
them!
Each fin has 3 layers(strips)of CF on each side of each fin, all layed up with 4461SS. Next is the fillets. Some
might say the L brackets are not needed. That might be the case. Then we will just call it overbuilding. The great
thing about PePe, is his ability to fly many different motors, maybe down to a J. He will fit 54mm, 75mm, 98mm. The
goal is 14 pounds minus motor, but you know how things add up quickly.

 

[blackjack2564]

Looks good to me.

 

[HyperSonic]

Looks good to me.

Thanks for keeping an eye on me, as I value your feedback very much! It's nice to talk to someone once in a while, as I feel like I have the plaque sometimes. lol

 

[Theory]

Asking as I do not have much experience with this, but is this type of carbon significantly stronger than a 2x2 twill of the same weight? I know the twill would likely “use” more resin resulting in a heavier finished product, but would the final strength be close?

 

[blackjack2564]

I built my 3 in carbon "Go fast" with carbon uni-pre preg tube...Dragon plate for fins and just glued them on with Hysol. Test flight was with CTI 6xl M green. But will use the I-max 6xl also when I get back out west where waiver allows. Got one sitting around waiting for flight day...lol
Full confidence fins will stay on with just glue as others I know have gone over M-3.5 & fins held up fine, even done this way on 4in minimum using N's
Yours should be just fine especially with the extra tow re-enforcement. We all overbuild when starting out.

 

[GrouchoDuke]

I built my 3 in carbon "Go fast" with carbon uni-pre preg tube...Dragon plate for fins and just glued them on with Hysol.

Which Dragon Plate did you use? Quasi? High modulous? High temp?

(I think you said their quasi plate somewhere else: https://dragonplate.com/quasi-isotropic-carbon-fiber-sheets )

 

[blackjack2564]

Quasi- matte finish. They had a sale on plate with [darn can't think of name..brain fart. the texture release sheet?] what ever the barrier from breather cloth/ that soaks up excess epoxy is called leaves a texture on surface. Damn I know this too, since my surgery my memory goes now & then.
Any how the 12x24 sheet was 225-230ish [3/16] was 50 bucks less than with a finish, 5minutes and 220 they [fins] were smooth. I would use 1/8 next time.
Don't give a hoot about carbon looks since I paint it white to keep everything cool in sun.[form follows function] I use 1200 temp white, no primer [primer would bubble/peel under paint] cause this always happens when M-2.5-M-3 approaches, and I use paint stripper then re-paint. No more colors they peel bad, not white doesn't flake, it acts like ablative. The NC was coated with 800degree high temp 1 part post cure [oven] epoxy. NC was almost completely stripped of paint. This flight was the CTI 6xl green...can't remember darn number.



What they look like before sanding. Stacked with double sided tape & cut.
Bevels had to be dulled after a sliced my fingers just handling them they were so sharp.
Only held on with Hysol fillets.
Sorry if I horned in on your thread..thought you might want to see how I attached fins.
Beveling tool 7 degree router bit.

 

[rharshberger]

Peel ply CJ?

 

[blackjack2564]

Thanks it was driving me nutz trying to remember. I was about to go to shed where I have a roll...lol just to see label.

My hat off to ya for making your own plate HyperS...I took the lazy route.

 

[GrouchoDuke]

Quasi- matte finish.

Awesome, thanks!

 

[HyperSonic]

Sorry if I horned in on your thread..thought you might want to see how I attached fins.
Beveling tool 7 degree router bit.

Finally starting to thaw out here in the midwest. It got down to -20 F! Many have died because of it.

Thank you for posting Cj. I could sit around and read about your flights all day! I want to ask you about my homemade plate, and its strength compared to the dragon plate. I am worried about delamination of the leading edges. Dragon plate is made with more pressure during construction than my homemade stuff. Might not be as dense and could come apart easier. What do you think?

 

[HyperSonic]

Asking as I do not have much experience with this, but is this type of carbon significantly stronger than a 2x2 twill of the same weight? I know the twill would likely “use” more resin resulting in a heavier finished product, but would the final strength be close?

Thats a good question. If both fabrics had the tows aligned in the same direction, and the loads were coming from that same direction, than Uni will outperform the 2x2 twill. Just how close is close. I would only be guessing if I told you an answer. Uni is only good in a single direction, where as 2x2 twill would handle loads better than Uni when the loads varied from that single direction. When the loads vary 90 degrees from that single direction, the Uni is basicly useless as Cj has pointed out earlier. By rotating the tows of many thin layers of fabric stacked on top of each other, say by 45 degrees each layer, it becomes better at handling loads from any angle.

 

[blackjack2564]

I really can't speak with authority about home made vs Dragon Plate. That's what I just bit the bullet and bought mine.
Again I am in no way an expert in aerospace carbon manufacture. I just have SOME practical experience and a lot of others[I know] with much knowledge base in calculating this stuff, to call upon when I need advice.
I have seen many Tip-Tip delaminate from [excessive speed/heat] Best way to prevent[that I've seen is wrap a "cuff" over leading edge to prevent lifting of T-T. Whether stainless or carbon/etc.
There is a thread somewhere here about using a leading edges made of phenolic and carbon over G-10 core butting up to it so there is no lip or overhang. It was then coated with high temp epoxy/ceramic/phenolic granules for ablative. That one hit M-3.6 if I recall
I have seen DragonP erode on edge but not delaminate. When going that extreme I would build as single use as worst case & if i got it back flyable again as best. You tend to realize ya don't need things thought about if trying to build re-usable.
My worst fear is coupler failure anywhere one is used, so mine was rolled with double wall thickness of airframe. Bear in mind I personally did not roll tube or coupler Charlie made them for me. So even though I saw/knew what was being done I cannot give detail as to how many wraps etc. Another tube was made identical, cut into 6in. sections and crush tested [hoop& compression] in school lab. Suffice to say it would survive a semi rolling over it.

Eventually this will fly on a 6xl I-max and we'll see if it holds up to the hype.

Coupler on left [obviously lol] of airframe.



Fincan with stainless "cuffs'. It looked virtually the same after setting O-3400 record and M-3.7 not a scratch or blister on it.
This is Nic's rocket not mine.

 

[HyperSonic]

I really can't speak with authority about home made vs Dragon Plate. That's what I just bit the bullet and bought mine.
Again I am in no way an expert in aerospace carbon manufacture. I just have SOME practical experience and a lot of others[I know] with much knowledge base in calculating this stuff, to call upon when I need advice.
I have seen many Tip-Tip delaminate from [excessive speed/heat] Best way to prevent[that I've seen is wrap a "cuff" over leading edge to prevent lifting of T-T. Whether stainless or carbon/etc.
There is a thread somewhere here about using a leading edges made of phenolic and carbon over G-10 core butting up to it so there is no lip or overhang. It was then coated with high temp epoxy/ceramic/phenolic granules for ablative. That one hit M-3.6 if I recall
I have seen DragonP erode on edge but not delaminate. When going that extreme I would build as single use as worst case & if i got it back flyable again as best. You tend to realize ya don't need things thought about if trying to build re-usable.
My worst fear is coupler failure anywhere one is used, so mine was rolled with double wall thickness of airframe. Bear in mind I personally did not roll tube or coupler Charlie made them for me. So even though I saw/knew what was being done I cannot give detail as to how many wraps etc. Another tube was made identical, cut into 6in. sections and crush tested [hoop& compression] in school lab. Suffice to say it would survive a semi rolling over it.

Eventually this will fly on a 6xl I-max and we'll see if it holds up to the hype.

Coupler on left [obviously lol] of airframe.

View attachment 373421

Fincan with stainless "cuffs'. It looked virtually the same after setting O-3400 record and M-3.7 not a scratch or blister on it.
This is Nic's rocket not mine.

View attachment 373422

Once again, thank you Cj for sharing your wisdom with me. I really love that SS leading edges fin can!! M3.7 and not a scratch! Just incredible!

I think I would be mistaken if I thought my homemade plate (Hyperplate) would be of similar properties as the famous Dragon Plate. The L brackets, thicker fins, tip to tip, and protecting my leading edges are all ways that I have decided upon to level the playing field.

 

[HyperSonic]

When I first saw the pic I did a double-take on the uni as well. But I think what we're seeing that looks wrong is actually the binder that holds the fibers together and runs perpendicular to the fibers.

I'm interested to see/hear more about the build!

I am sorry for not responding earlier, and I dont want you to think I am ignoring you. I work alot of hours and my
rocket time is limited.
I wanted to ask you about your experience with making CF plate. If I remember right, you said once you got the
orientation right, it came out better. What was the orientation of your plate, if you dont mind me asking? I get
the impression that the order of things were not known at the time. Did I just get lucky when making my plate? That
does not sound like me! I have made 4 or 5 diferent plates now, and they all turned out very flat using the same
orientation every time. I just vac bagged everything to my granite piece, without trying to press any harder than
the vacuum would allow. One atmosphere at pee level is 14.7 psi. My thought process was really very simple. Once I
found out that everything needed to be balanced and symmetrical (thanks to Aero Aggie) I put myself in the middle
of my stack, and said do the exact same thing to the left as I did to the right. It seemed to work out well for me
as I was able to duplicate the process multiple times. I used 2x2 twill, but I think I could have used any fabric
with the same results. I am planning to make a plate out of all Uni in the near future. If there is anything else
you might want to know about how I made this plate, or about PePe, just let me know.

 

[Nytrunner]

One atmosphere at pee level is 14.7 psi. My thought process was really very simple.

Wherever your atmosphere is, I don't think I want to be there....

 

[watheyak]

I am sorry for not responding earlier, and I dont want you to think I am ignoring you. I work alot of hours and my
rocket time is limited.
I wanted to ask you about your experience with making CF plate. If I remember right, you said once you got the
orientation right, it came out better. What was the orientation of your plate, if you dont mind me asking? I get
the impression that the order of things were not known at the time. Did I just get lucky when making my plate? That
does not sound like me! I have made 4 or 5 diferent plates now, and they all turned out very flat using the same
orientation every time. I just vac bagged everything to my granite piece, without trying to press any harder than
the vacuum would allow. One atmosphere at pee level is 14.7 psi. My thought process was really very simple. Once I
found out that everything needed to be balanced and symmetrical (thanks to Aero Aggie) I put myself in the middle
of my stack, and said do the exact same thing to the left as I did to the right. It seemed to work out well for me
as I was able to duplicate the process multiple times. I used 2x2 twill, but I think I could have used any fabric
with the same results. I am planning to make a plate out of all Uni in the near future. If there is anything else
you might want to know about how I made this plate, or about PePe, just let me know.

The plate I think you're referring to was made with unidirectional pre-preg. It had 0, 90 and 45 degree layers and getting the order of the layers correct was what kept it from warping. I remember the middle layers being a 45 and 135, then 0 and 90, so on and so forth. I think the 1/8" plate I made had 24 layers.

I have made a bunch of plate with 2x2 twill and laminating resin and just stacked them so everything was 0,90. In those cases I never had any problems with warp.

 

[Nytrunner]

Unidirectional fiber matts, does the presence of the glue beads cause any problems? I imagine them as little bumpy lines of inconsistency.

 

[HyperSonic]

The plate I think you're referring to was made with unidirectional pre-preg. It had 0, 90 and 45 degree layers and getting the order of the layers correct was what kept it from warping. I remember the middle layers being a 45 and 135, then 0 and 90, so on and so forth. I think the 1/8" plate I made had 24 layers.

I have made a bunch of plate with 2x2 twill and laminating resin and just stacked them so everything was 0,90. In those cases I never had any problems with warp.

Have you used any of your plate as fins? If so, how thick were they and how hard did you push them?

 

[HyperSonic]

Unidirectional fiber matts, does the presence of the glue beads cause any problems? I imagine them as little bumpy lines of inconsistency.

In my case, using it for the L brackets, the polyester thread is only on one side. If you turned it over, you would not even know they are there. It is very thin, and you dont feel any glue beads. When using pressure while curing, they blend in with the fabric. But they are still there, and could cause a little inconsistency. After using peel ply on top of the fabric under pressure, to get my texture for more CF, they disappear.

 

[Nytrunner]

Thank you for the explanation!

My composite experience stops at G12/G10 airframes, and doesn't pick up again until industrial pressure vessels, so there's a bit of a gap there.

 

[HyperSonic]

Wherever your atmosphere is, I don't think I want to be there....

It took me over 2 years and 70+ posts to finally say something that somebody else liked. (Thank You Aero Aggie) My first like ever! Then I had to mess it up with my "pee level" comment. I hope they do not take it away, or worse yet, make it a negative 1! lol

 

[Nytrunner]

To be fair, it's a relatively new feature.

Meh, likes are overrated. In fact there have even been studies recently on the effects of likes and view-counts on young people (.....which probably means people my age now that I think of it) through the increasing self comparison and dissatisfaction. I was one of the folks that wasn't chomping at the bit for it being implemented here lol

 

[Grv_boulder]

Thank you for your input. My 4461SS is over its six month life span but I hate to throw it away! I think I'm going to try the 4460 on my T2T with some spread tow fabric with a twill weave I seen at Composite Envisions. I got the idea from reading your thread. I like the look of light and dark checker board with the twill weave to it. Yes the 4461 does cure at room temp which is nice sometimes, but I still bake it at 150 F for 6 hours to come closer to those optimum properties. After curing for 24 hours at room temp, the 4461SS has a slight sticky feeling to the touch. Then bake it at 150 for 6 hours and that sticky feeling is gone.

Do you think this epoxy on the leading edges of my fins would work as an ablative? What makes a good ablative?

Mark

Great information in this thread! My rocket team is looking into using either 4461 or 4461ss as a high-temp laminating epoxy, however we cannot find good information on their pot lifes. How long would you estimate these epoxies are workable for, specifically for the purpose of fiber winding?

 

[AeroAggie]

It took me over 2 years and 70+ posts to finally say something that somebody else liked. (Thank You Aero Aggie) My first like ever! Then I had to mess it up with my "pee level" comment. I hope they do not take it away, or worse yet, make it a negative 1! lol

Aw shucks. I remember my first time too.

You want likes? Less talk, more pictures!

 

[HyperSonic]

Great information in this thread! My rocket team is looking into using either 4461 or 4461ss as a high-temp laminating epoxy, however we cannot find good information on their pot lifes. How long would you estimate these epoxies are workable for, specifically for the purpose of fiber winding?

On cotronics web site there is a pdf which states the workable time for 4461 is 30 min at 75 degrees F. I did not find anything on the 4461ss. From my experience working with the 4461ss, you will get about 90 to 120 minutes at 72 degrees F. The cure time is very temperature dependent. A few degrees change can make a big difference on the ability of the epoxy to flow how you want. If you are sure you can get everything done in 30 min or less, than go with the 4461. If you have ANY doubt that things might take a little longer (like doing something for the first time) than go with the 4461ss. The 4461 will cause a problem if you are not fast enough (like me) where as the 4461ss is the answer to that problem. Go with the 4461ss and put time on your side.

Do not take my word for it. Verify this for your self. Mix up a 25 gram batch of 4461ss and watch it cure with your own eyes. Keep track of the temperature and time until you think it does not flow like you want it. Hands on experience is the best teacher. Welcome to the forum and good luck with your project.

 

[HyperSonic]

Aw shucks. I remember my first time too.

You want likes? Less talk, more pictures!

 

[HyperSonic]

This is the first section prepped and ready for tip to tip

 

[HyperSonic]

If you go with this order, cut the fin in a way that the 0° layer is perpendicular to the body tube. The 45° is probably best orientated if it is swept backward (roughly parallel to the leading edge). This way, the fin will be stiffest in the direction that you need it the most. Maybe it would be slightly better, if the 135° and 90° layers would be swapped, but the inner layers don't contribute much to the fins bending stiffness, so there will not be much difference.

Reinhard

Could you explain to me why the inner layers don't contribute much to the fins bending stiffness? I would think all the layers would contribute equally for a total stiffness. I'm not saying you are wrong, I just would like to know why that is. Thank you for your time.

 

[Nytrunner]

Bending stress is highest on the outer limits of a bend plane. We'll assume the neutral (unloaded) fin is the bend plane here.

That's where you want your fibers to be aligned straightest, so the worst tension and compression is running up and down solid fibers instead of acting on glue/fiber interfaces.