Carbon Prepreg Airframe build for the Loki 54/4000 - Fins Attached

[watheyak]

I got some more work done on this project, as well as a cool new part.

I got started on the parting board assembly to make the nosecone mold. lay-up for the mold starts tomorrow, hopefully.


Charles Ogino at Carolina Composites made a phenolic nosecone tip. I was going to make it from graphite, but when I saw the one Charles made for Jim Hendrickson, I decided this was better.


Sorry for the odd orientation of the pictures, I've rotated them every which way outside of the forum to no avail.

 

[littlemisterbig]

The project's coming along really nicely, Scott. I may have missed it if this was answered in a previous post, but are you flying it bare? Or are you going to have ablatives on surfaces like the nosecone and fins? And what are you using for the cone layup?

 

[claytonbirchenough]

Love the nosecone tip...

Cool project. Definitely following.

 

[watheyak]

The project's coming along really nicely, Scott. I may have missed it if this was answered in a previous post, but are you flying it bare? Or are you going to have ablatives on surfaces like the nosecone and fins? And what are you using for the cone layup?

If I can finish the nosecone in time, John Derimiggio has offered to apply his experimental ablative. Fins are going to get a leading edge treatment, exactly what is still being decided. Mcmaster has titanium and SS foil that I could apply with Cotronics. That sounds great, but I've seen that method cause more problems that it's solved. The Jarvisonian painted-on Cotronics is another method which has been proven in the real world many times.

I have a bunch of 5oz Kevlar twill and 4hs from old sailplane projects laying around so that will most likely be the fabric of choice, as long as it doesn't drive me insane. 2x2 Kevlar twill is a huge pain to cut and keep in shape, even with Kevlar shears. I have some tricks, but there's definitely a reason I have a ton of it left over.

For the nosecone laminating resin I have this stuff on the way-
https://www.fibreglast.com/product/high-temp-epoxy-resin-3000/Epoxy_Resins
But I seem to remember a thread where it was really thick, making it difficult to wet out the fabric. I'm going to give it a try on a practice nosecone, first.

 

[REK]

If I can finish the nosecone in time, John Derimiggio has offered to apply his experimental ablative. Fins are going to get a leading edge treatment, exactly what is still being decided. Mcmaster has titanium and SS foil that I could apply with Cotronics. That sounds great, but I've seen that method cause more problems that it's solved. The Jarvisonian painted-on Cotronics is another method which has been proven in the real world many times.

I have a bunch of 5oz Kevlar twill and 4hs from old sailplane projects laying around so that will most likely be the fabric of choice, as long as it doesn't drive me insane. 2x2 Kevlar twill is a huge pain to cut and keep in shape, even with Kevlar shears. I have some tricks, but there's definitely a reason I have a ton of it left over.

For the nosecone laminating resin I have this stuff on the way-
https://www.fibreglast.com/product/high-temp-epoxy-resin-3000/Epoxy_Resins
But I seem to remember a thread where it was really thick, making it difficult to wet out the fabric. I'm going to give it a try on a practice nosecone, first.

That resin is really thick, I dont know how well it wets out glass and kevlar, but I have done a 3" carbon tube with 35% resin content with that resin.

I recommend some adhesive spray like Super 77 to keep the fabric intact. Just a suggestion, but I do recommend making the cone with glass and kevlar. That should ease the pain of sanding into kevlar . Also make sure your final layer is glass and not kevlar.

Messy aint it lol.


Sent from my iPhone using Tapatalk

 

[watheyak]

That resin is really thick, I dont know how well it wets out glass and kevlar, but I have done a 3" carbon tube with 35% resin content with that resin.

I recommend some adhesive spray like Super 77 to keep the fabric intact. Just a suggestion, but I do recommend making the cone with glass and kevlar. That should ease the pain of sanding into kevlar . Also make sure your final layer is glass and not kevlar.

Messy aint it lol.


Sent from my iPhone using Tapatalk

Funny you should mention the 3M77, I'm a huge fan. For the twill fabrics many times I will ever-so-slightly mist the piece with the 3M77, then lay down .5oz fiberglass as a stabilizing layer to keep everything from shifting. Works great, but may not be so good in the compound curve of a nosecone. I intend to find out.

I've sanded into Kevlar often and on purpose. There are ways to make it ok afterwards. But in this case there will be no sanding into either the Kevlar or the fiberglass.

 

[watheyak]

The nosecone mold is finished, mostly. I had some issues with the surface quality once I pulled the plug out. I tried using the Frekote mold release that works so well on the tubes, rather than wax and PVA. It seems to have crazed the finish on the plug. I think. That's what I get for trying to fix something that's not broke. Here's some pics of the process, all of them sideways for some reason.



I also made a bulkhead for the forward closure/nosecone coupler. It's made from the same plate I fabricated for the fins.



One of these will go through the center hole and thread into the forward closure for recovery harness attachment. It doesn't take up much space.

https://www.mcmaster.com/#3796k11/=14n2b2h

 

[TRFfan]

Any updates?

 

[watheyak]

I haven't been working on this much. I've been travelling for work a bunch, plus I had Mike at MAC performance make a custom 4" kit for me. That has been quite a distraction. I should post some pictures of that, it's the nicest kit I have ever seen.

However, I *really* want to start the nosecone lay-up next week. There is a K project I want to start that will use the same nosecone. In fact, I have a radical idea for the K fin can that I'm really excited about.