Fatty Finn - Fanga’s L3 design and build

[fanga]

Hey Gang

Been a while since I’ve posted here. Thought I’d start a thread for my L3 design and Build. More details to come. I just wanted to share that all my tubes have arrived. Aaaggghhh. Now I need to focus on getting design signed off so I can start the build.

More deets to follow

 

[rfjustin]

Hey Gang

Been a while since I’ve posted here. Thought I’d start a thread for my L3 design and Build. More details to come. I just wanted to share that all my tubes have arrived. Aaaggghhh. Now I need to focus on getting design signed off so I can start the build.

More deets to follow

8", 98mm hole?

Did the booster tube get dinged in shipping? That's frustrating to see...

 

[fanga]

Yeet a bit of a ding but I should be able to fix up when Im doing the T2T on the fins.

 

[fanga]

Here's the design details from my doc:

Goals

• Meet all Tripoli L3 cert requirements
• Go Low & Slo to see the event at Apogee
• Designed to be reusable for lower altitude testing
• COTS parts with flight heritage used where possible to reduce risk

Design Overview

• Dry Weight: 21.67 Kg
• Length: 3.154 M
• Airframe: Wildman 8in G12 Fiberglass tubes
• Motor Mount: Wildman 98mm G12 Fiberglass tube
• Fins: 4 x G10 Fibre 4.5mm thick
• Fin Mounting: Through wall mounting with internal and external fillets. Fins will have a 3 layer Tip to Tip fiberglass layup
• Recovery: Dual deploy drogue and main chute
• Avionics:
• Main: Featherweight Blue Raven
• Backup: Missleworks RRC3
• Launch Buttons: Large 1515 rail buttons
• Motor: Ceseroni M1830 in 75mm 4-grain case
• Expected Altitude: 4837ft (modelled)

I will post more as I go.

 

[Hobie1dog]

I'd like to see everything you need to submit to get approval before starting the build. TRA or NAR?

 

[fanga]

??? Not sure what you mean but construction will not start until design is signed off from TAPS as per the process.

This is for TRA. New South Wales prefecture in Australia.

 

[Hobie1dog]

??? Not sure what you mean but construction will not start until design is signed off from TAPS as per the process.

This is for TRA. New South Wales prefecture in Australia.

I wanted to see what you turn in initially to get them to approve the project. I know you don't turn in a completed project document showing that you already built it.

 

[fanga]

Ahh cool. I see. Yep Im happy to share the docs and the OR design once signed off. Hopefully by next week. I m just working on things like the check lists and risk mitigation components of the design doc.

 

[fanga]

In case anyone is wondering if I am completely mad for going with such a big design, it all started by me buying the nosecone from someone. The rest of the design was done to fit the nosecone oh and the design goal of Low & Slo.

 

[RocketRev]

As one of those pesky TAP members myself, there are reasons that the design is supposed to be submitted before you start to build. One of which is that TAPs tend to start asking questions that could radically change a person's design once they come up with the answers. And that could require purchasing different parts. I'm not saying that's the case with this design because one cannot tell the design from one pic of a pile of parts.

Your next move before you do anything else ought to be to FIND you a couple of TAPs who can work with you. And at least one of them needs to be close enough to actually oversee the certification flight itself. But you are a long way from that last step. Find your TAPs and go from there.

Brad

 

[Hobie1dog]

As one of those pesky TAP members myself, there are reasons that the design is supposed to be submitted before you start to build. One of which is that TAPs tend to start asking questions that could radically change a person's design once they come up with the answers. And that could require purchasing different parts. I'm not saying that's the case with this design because one cannot tell the design from one pic of a pile of parts.

Your next move before you do anything else ought to be to FIND you a couple of TAPs who can work with you. And at least one of them needs to be close enough to actually oversee the certification flight itself. But you are a long way from that last step. Find your TAPs and go from there.

Brad

I'd like to hear exactly what you want to see in the original proposal . I assume an OR drawing, all the materials you want to use throughout the rocket, and why you chose this model?

 

[fanga]

As one of those pesky TAP members myself, there are reasons that the design is supposed to be submitted before you start to build. One of which is that TAPs tend to start asking questions that could radically change a person's design once they come up with the answers. And that could require purchasing different parts. I'm not saying that's the case with this design because one cannot tell the design from one pic of a pile of parts.

Your next move before you do anything else ought to be to FIND you a couple of TAPs who can work with you. And at least one of them needs to be close enough to actually oversee the certification flight itself. But you are a long way from that last step. Find your TAPs and go from there.

Brad

Yep all good. I had already asked my TAPS prior to buying the tubes if it was OK to go ahead and purchase. I knoew it would take a while to get shipped here to Aus so I had to buy them early. Ive only got the check list and risk mitigation parts to go so the design is pretty much locked and ready to go.

 

[fanga]

I'd like to hear exactly what you want to see in the original proposal . I assume an OR drawing, all the materials you want to use throughout the rocket, and why you chose this model?

I would have loved some guidance here too but it appears, well from my experience anyways, that it could be differing requirements depending on the TAP you go with with.

I found a few templates online after digging a bit further and went from there.

 

[fanga]

OK So the design is almost signed off. Just going through some final bits. Since I have started the build process I thought I would upload the design for reference.

I'm not sure if anyone thinking of going for the L3 can use my design doc as a starting point but please feel free if your TAPS are OK with this. I found it hard to find any templates out there so I just came up with my own.

Photos of build process to follow

 

[fanga]

I took the tubes out to our local launch last weekend and finally set them up.. She's a tall rocket.

 

[fanga]

Alrighty so the build process has begun. I will share photos here of each stage of the build.

The first task, drill the bulk plates and centering rings.

I created a hole guide for the bulk plates to mark the holes for the threaded rod, eye bolts, wiring and the charge wells. I then pre-drilled with a 3mm drill followed by an 8.5mm where required.



I then used the Thrust Plate as a template to mark the required holes for the threaded inserts, pre-drilled then drilled with 5mm drill for the final hole.



I also drilled the forward centering ring to place the recovery eyebolt.

 

[fanga]

Before we get into the real fun stuff, here are a few photos of me prepping the Epoxy. Im using Proline 4500 for my construction epoxy. the mix ration is 100 parts resin to 16 parts hardener. I have halved these amounts per use as I ahvent needed more than half.



UPDATE: I just realised I hadn't covered off the curing process. Will put it here.

I have built a hotbox from Foil Board and using a hair dryer to maintain a temp range of between 48^ to 52^C for 30 mins then allow to cool slowly for another 30 mins. From testing this seemed to be the best time for the Proline 4500 and the temp is well belwo the manufacturer stated max of 220^F.



I have also used this approach a couple weeks back to test the T2T fiberglassing I will do. Same process works well with the West Systems laminating epoxy.

 

[fanga]

Checking the fit of the Thrust Plate

 

[fanga]

The next thing I did was to mount the switch band on the outside of the eBay coupler.

To prep I gave both the switch band and the coupler a thourough cleaning with acetone to remove any mould release and checked for fit. I then used 120 grit sandpaper to prepare surface for epoxy then wiped clean with Acetone and lint free wipes.

I then measured 200mm from one end and placed a ring of blue tape around the coupler. This allowed the switch band to be placed against the tape to locate it in the center and to stop any epoxy from running out. I then mixed epoxy and placed a small bead around where the switch band will be located, placing the switch band in place and rotating to help the distribution of the epoxy. Some epoxy had leaked out, which I cleaned up straight away with Acetone.

 

[OzHybrid]

Is this launching at Mullaley?

 

[fanga]

Next up, motor mount.

Here I cleaned up the MM tube and the centering rings, prepped again with 120 grit paper and cleaned with acetone on a lint free wise. I then measured and placed blue tape on the edges where the centering rings are to be placed.

Next i applied a small bead of epoxy on appropriate side of blue tape, moved the centering ring into position, twisting it to make sure the epoxy was well distributed. I also placed a small bead of epoxy on each side of the recovery anchor to lock it in place.

I found out how hard it is to keep parts clean whilst working with Black dyed epoxy I got it in lots of places I didnt want it.

It was then cured in the hot box for 1 hour as per my approach.

 

[fanga]

Is this launching at Mullaley?

I hope so. Working towards it and should be ready by then.

 

[OzHybrid]

Top tip.... It's quicker to mask off the areas you don't want epoxy than to clean it up. All extra epoxy adds up in dead weight. Remember the 1 gm rule. They all add up.

 

[fanga]

Top tip.... It's quicker to mask off the areas you don't want epoxy than to clean it up. All extra epoxy adds up in dead weight. Remember the 1 gm rule. They all add up.

Thanks Norm. I got a bit excited on the first time around. Black dye made it even harder to clean up. I plan to tape up everywhere I don't want epoxy from now on.

 

[fanga]

Time for fillets on centering rings. I did the fillets on one side of each centering ring, cured then repeated the process on the other side. I also added more epoxy to the anchor eyebolt as extra fillets to help secure it.

On top side of both centering rings I did surface prep with 120 grit sandpaper and acetone as per normal.

As these were internal fillets, I didnt worry about masking off the edges. I will do this on future builds as you can see I made a bit of a mess with the black dyed epoxy and as Norm pointed out, this is just adding extra weight. Since one of my design goals is Lo and Slo I don't mind adding a few extra grams here and there and I have accounted for this in my design.

I applied the epoxy to each of the top joins on the centering rings. I then used the end of the mixing sticks to form the 15mm dia fillets as per the design. The mount was placed in the hotbox to cure.

Once cured the process was repeated on the bottom side of the centering rings.

This lead to my first mistake I made so far. I forgot to mask off where the fins will attach to the MM tube on the underside of the second centering ring. Doh. I cleaned this up after cure with the Dremel and acetone.

 

[OzHybrid]

OMG. ....... Have you got shares in ( insert any epoxy manufacturer here)

 

[OzHybrid]

As your outer tube is red, either don't use dye or a tiny amount of red. 2 drops, not squishes....... A little dye goes a long way.. When that tube slides onto the motor mount, there won't be any way to mask it off.

 

[MClark]

Your flight should go great.
We did a very similar 8” rocket on a full M. Memorial flight with 11 pounds of ashes dispersed. About 7000’

 

[fanga]

OMG. ....... Have you got shares in ( insert any epoxy manufacturer here)

I got a little excited on the first ones

Just practicing fillets now for the externals to get them right. I will post the process shortly.

Unfortunately I ordered the epoxy and had not realised it was going to come with Black Dye already in it. I know it will be a waste with these awesome tubes but I am thinking I will paint them anyways.

 

[fanga]

Your flight should go great.
We did a very similar 8” rocket on a full M. Memorial flight with 11 pounds of ashes dispersed. About 7000’



View attachment 602823

Oh yeah. Looks awesome. Im thinking I might end up painting mine. Now that I see yours I think I will go white.