Carbon fiber tip to tip

[rocketcharlie]

Hi,

I am thinking about a carbon fiber MD project. I have seen some beautiful CF rockets at launches using the twill type fabric that is left unpainted. If I apply the fabric in a tip to tip configuration how do I handle the juncture of the fin tip to tip layup to body tube. It seems like there would be a nasty looking joint there on an otherwise cool looking rocket.

 

[dhbarr]

Fillet first.

 

[JimJarvis50]

These links might give you some ideas.

https://www.raketenmodellbau.org/repository/archive/167792?view=true
https://www.raketenmodellbau.org/repository/archive/167793?view=true

Jim

 

[rocketcharlie]

Jim, I read your article this morning. I cant believe how much effort you put into this- bravo! The photos were so very helpful. It is a gracious thing to do for our hobby. Now that I am seeing all that is involved I'm wondering if I would have time for this. Though we are supposed to "shelter in place" here in CA now.

 

[JimJarvis50]

Jim, I read your article this morning. I cant believe how much effort you put into this- bravo! The photos were so very helpful. It is a gracious thing to do for our hobby. Now that I am seeing all that is involved I'm wondering if I would have time for this. Though we are supposed to "shelter in place" here in CA now.

Thanks. It was a lot of work to put this together, but Part 1 was done as a real-time build thread over several months, so not that bad (good thing it worked!). Keep in mind that about two-thirds of the work is strickly for appearance. If you want to cut a few corners on that, or if you're not flying over Mach 2, there are many simplifications. If I ever wrote a Part 3, it would be about how to do the whole thing but spending a lot less time and effort. But, I thought there might be some ideas you could extract from it.

Jim

PS - Everyone should have a minimum diameter rocket!

 

[o1d_dude]

Thanks again for posting your CF Rocket Construction treatise.

I lost the previous links to these so now I downloaded the documents and they will soon reside on the iCloud.

Amazing work, sir.

 

[MoreCowbell]

Thanks. It was a lot of work to put this together, but Part 1 was done as a real-time build thread over several months, so not that bad (good thing it worked!). Keep in mind that about two-thirds of the work is strickly for appearance. If you want to cut a few corners on that, or if you're not flying over Mach 2, there are many simplifications. If I ever wrote a Part 3, it would be about how to do the whole thing but spending a lot less time and effort. But, I thought there might be some ideas you could extract from it.

Jim

PS - Everyone should have a minimum diameter rocket!

Jim, I totally agree that everyone should have a minimum diameter rocket, or maybe even more than one. I have built several, but it has been a few years. I have a couple more in the planning stages, and would like your opinion on best epoxy for the tip-to-tip layup. I used Proline 4100 in the past with good results, but I am not sure that is still on the market. The projects in question are 75mm and 98 mm minimum diameter. The 75mm will be a FWFG frame, G10 fins, and CF layup on the fins. The 98mm is CF frame, CF fins, and CF layup on the fins.

I generally do not try for ultra-high velocity and usually stay below Mach 2. I have a good vacuum bagging system, but no curing oven--need to stay with a room temperature cure. In your articles, I noted that you used Aeropoxy--is that still your preference? I would need to use a different hardener for the room-temp cure, of course.

I greatly appreciate your opinion. The monolithic-appearing layups that you created in your articles are magnificent, but I have no such aspirations. These rockets will get painted.

Thanks,

Mark

 

[JimJarvis50]

Jim, I totally agree that everyone should have a minimum diameter rocket, or maybe even more than one. I have built several, but it has been a few years. I have a couple more in the planning stages, and would like your opinion on best epoxy for the tip-to-tip layup. I used Proline 4100 in the past with good results, but I am not sure that is still on the market. The projects in question are 75mm and 98 mm minimum diameter. The 75mm will be a FWFG frame, G10 fins, and CF layup on the fins. The 98mm is CF frame, CF fins, and CF layup on the fins.

I generally do not try for ultra-high velocity and usually stay below Mach 2. I have a good vacuum bagging system, but no curing oven--need to stay with a room temperature cure. In your articles, I noted that you used Aeropoxy--is that still your preference? I would need to use a different hardener for the room-temp cure, of course.

I greatly appreciate your opinion. The monolithic-appearing layups that you created in your articles are magnificent, but I have no such aspirations. These rockets will get painted.

Thanks,

Mark

Thanks Mark. Unfortunately, I have never used anything other than Aeropoxy for laminations. The 3665 hardener that I mention in the articles indeed needs some heat to cure, but the 3660 hardener works without heat and still gives a decent pot life. It would be fine for any tip to tip work. Good luck on the projects!

Jim

 

[MoreCowbell]

Jim,

Thanks for getting back to me. The Aeropoxy looks like a good product; if it holds up to your flights, I doubt that I will push its envelope to any great extent. I reviewed their website earlier today, and saw that they have a new hardener PH9663, which has a pot life of 90 minutes. Will cure at room temp, although an elevated temperature during cure increases final strength.

90 minutes is sufficient for my layups, so will probably go that route. I do fin layups in my garage, mainly to contain the mess, but once the bag is ready I set up several Little Buddy propane heaters to take the temperature of the garage up to 80- to 90-degrees, which seems to work well.

Your input is much appreciated.

Mark

 

[JimJarvis50]

Thanks for pointing out the new hardener. I hadn't seen that. Please report back if you use this.

Jim

 

[MoreCowbell]

Will do. I am waiting for the spring weather to warm up a bit and get the garage ambient temperature into the 60's or 70's.

Mark

 

[SDramstad]

If you use the same fabric for tube and t2t it kind of blends together. If you look close you see it but at first glance it looks good.

 

[curtisheisey]

Jim, I read your article this morning. I cant believe how much effort you put into this- bravo! The photos were so very helpful. It is a gracious thing to do for our hobby. Now that I am seeing all that is involved I'm wondering if I would have time for this. Though we are supposed to "shelter in place" here in CA now.

Jim's articles are certainly a work of art, and I appreciate him sharing them. For starting out in tip-to-tip, as Jim mentioned, you might consider some simplifications. While vacuum bagging is certainly preferred, you can get good results using sand in zip lock bags to hold the laminate stack against the fins and BT. And you can use epoxy that does not require an oven. Also, you can use off the shelf fiberglass body tube and fins. Maybe not for the most optimal min diameter performance or mach 2.5 busing rockets, but for many projects, yes. Then work up to more advanced techniques. And to your original question, a nice wide fillet does the trick.

I use FiberGlast system 2000 resin, which cures at room temperature, and carbon fiber cloth from Soller Composites. https://www.sollercomposites.com/index.html I use rocketpoxy for fillets.

 

[REK]

Thanks for pointing out the new hardener. I hadn't seen that. Please report back if you use this.

Jim

Jim,

I’ve used the 90 minute hardener before. The room temperature cure works great. I even had a tube cure in the winter at 65F.

The exotherm reaction is just right, that an oven is not required.

 

[MoreCowbell]

Thanks for pointing out the new hardener. I hadn't seen that. Please report back if you use this.

Jim

Jim, I finally got around to using the PH9663 Hardener, and was pleased with it. The pot life was as described, and I had plenty of time to lay up the CF and get the bag in place before pulling vacuum. My only caution is that this hardener is a fairly thin liquid, and pours fast. That may also be true of their other hardeners, but I was a bit surprised at how fast it came out of the can compared to the resin.

I appreciate the input and advice that you have provided.

 

[JimJarvis50]

Jim, I finally got around to using the PH9663 Hardener, and was pleased with it. The pot life was as described, and I had plenty of time to lay up the CF and get the bag in place before pulling vacuum. My only caution is that this hardener is a fairly thin liquid, and pours fast. That may also be true of their other hardeners, but I was a bit surprised at how fast it came out of the can compared to the resin.

I appreciate the input and advice that you have provided.

That's good to know. Next time I order, I'll give it a try. The other hardeners are thinner than the resin too, so your observation may not be unique to the 9663.

Thanks for the feedback.

Jim

 

[REK]

That's good to know. Next time I order, I'll give it a try. The other hardeners are thinner than the resin too, so your observation may not be unique to the 9663.

Thanks for the feedback.

Jim

It is unique in where the mixed viscosity will be lower in order to wet out fabrics better without applying too much.

 

[JimJarvis50]

View attachment 422487

It is unique in where the mixed viscosity will be lower in order to wet out fabrics better without applying too much.

OK, interesting ....

Jim