40" Saucer Build

[sailmike]

I've also decided to add more LED's, so I have 256 more on order! 240 of them are in the form of flexible strips. The weight of the extra LED's will be negligible. There's currently 88 LED's on there.

 

[sailmike]

I was going to go with four screws to hold the motor mounts in place, but some people were of the opinion that I only needed two. I decided to go with three. You can see the tabs on the 98mm motor mount in the photo. The motor mount in the photo is partly out to show the tabs. This is the business end and the thrust will push the tabs against the centering ring. The tabs serve two duties, one is to keep the motor mount from falling out, and two is to add another point for the thrust to push against. You can't see it in the photo, but there is a 1" square piece of fiberglass on the body tube where the screws go in.

 

[sailmike]

The LED's arrived today. Here's what the LED strips look like. I bought 8 of these strips. They will go on the underside of the saucer.

 

[sailmike]

Got the bottom half of the saucer completed. It weighs in at slightly over 4 pounds making the total weight 7.6 pounds so far. Still have to add the weight of the parachute and electronics. Rather than going with one big parachute, I'm thinking of going with two smaller chutes that I already have and saving my money on the cost of a new chute. I've never tried two chutes together though. Does anybody know of any problems with that? The two chutes would be anchored to that loop you see at the top of the photo. The 29mm tube you see next to the 7.5" tube is the launch lug.

Thanks,
Mike

 

[sailmike]

A couple more views of the bottom section of saucer with the 75mm motor mount bolted in place. Overall weight with the motor mount is just over 9 pounds. The kevlar shock cord will be taped to one of the ribs during launch so it's not in the way.

 

[sailmike]

Got the LED's on the disk done. There's about 120. There will be another 240 in the form of 8 strips of 30 LED's each. I decided to go with a 20 output chaser circuit rather than 10, because I wanted to spread the load out more so that the battery lasts longer. I also have the option of adding more LED's if I want to. If you are interested in the circuit design I used, please PM me.

I made a video of the LED's in action, but it doesn't look like I can upload it from my iPad. Maybe see if I can post it on youtube and then post the link here.

 

[sailmike]

Alright hope this works:

[YOUTUBE]https://www.youtube.com/watch?v=jLPgo9ZVC0A[/YOUTUBE]

 

[redsox15]

the video did not work. When I clicked on the link it said there was a malformed video ID which means nothing to me but thats what it said.

Matt

 

[sailmike]

Yeah I know. This is my first time posting to YouTube and I have no idea how to do it. Ah well. The lights look great! Take my word for it!

 

[cjl]

You don't post the whole youtube link in the youtube tags - just the part that comes after "watch?v=". So, in your case, you would type this:

[youtube]jLPgo9ZVC0A[/youtube]

which results in this:

[youtube]jLPgo9ZVC0A[/youtube]

 

[sailmike]

Ah great thanks for the tip.

Mike

 

[edwinshap1]

so freaking awesome!!! when do you think you'll be putting this bad boy/girl up? october or november?

 

[sailmike]

I have no idea when I'll be able to fly it. I've got two more payments to make for the fall semester and then there's the books. Engineering books are expensive. October or November do look like good possibilities. My first flight will be a day flight on something like an L1150R, L1300R, or L952W. The M650 would be awesome on this, but I'm not sure that has enough thrust. Does anybody know? I wonder if I could get my level 3 certification with this?

 

[edwinshap1]

I have no idea when I'll be able to fly it. I've got two more payments to make for the fall semester and then there's the books. Engineering books are expensive. October or November do look like good possibilities. My first flight will be a day flight on something like an L1150R, L1300R, or L952W. The M650 would be awesome on this, but I'm not sure that has enough thrust. Does anybody know? I wonder if I could get my level 3 certification with this?

you can't get L3 with a saucer. You need to have at least a 4:1 L:W ratio, so you'd need a tube to extend past the saucer, and a nose cone.

just wondering, you go to CSUN?

 

[sailmike]

Yeah I'm an electrical engineering major at CSUN. Sounds like you are a student there too.

 

[modeltrains]

Way cool. This thing could launch one of the grandkids :eyepop:

 

[edwinshap1]

Yeah I'm an electrical engineering major at CSUN. Sounds like you are a student there too.

nah, just bouncing between the community colleges in the area, but i got a few friends who go to csun, and i've been to the campus a lot

 

[sailmike]

I had to order a new vacuum bag, because the old one had too many pinprick holes in it. It arrived yesterday and today had a friend come help me apply the epoxy and get it all in the bag. It didn't take much vacuum to get the two halves together with enough pressure. Here's a photo of the saucer under vacuum.

 

[sailmike]

Here are a couple of post vacuum photos. You can see that I pulled a tad too much vacuum and that caused some wrinkling in the disc, but it's not bad in my opinion. I just have to do a little bit more soldering then I'm done! I just hope I can launch it this October or November.

 

[sailmike]

Just weighed the saucer via a handheld luggage scale and it came to 8.4 pounds. This is lighter than I expected. I'm guessing the electronics and parachutes will add about pound or so.

 

[sailmike]

Seems it was lighter than expected because I forgot to add the weight of the motor mount(s), which don't fit! The central body tube got a bit distorted. The motor mounts just need to be sanded a bit.

 

[sailmike]

Alright, got all the motor mounts sanded to fit. Also finished soldering the remaining lights. I'll have to get a video sometime soon. The weight with the 98mm mount in place is 9.6 pounds. I hope that's light enough to fly the M650 someday when I've got my level 3 certification.

 

[sailmike]

Everything is done. I just have some work to do on the parachutes and shock cord, which I'll do in another month or so when I've got more money to work with. Here's a video of all the lights in action. I hope I got it right this time!

[YOUTUBE]pRHrag-gAZI[/YOUTUBE]

 

[o1d_dude]

Wow! That's crazy impressive!

And a 40" saucer is right up there as well. Gonna be the hit of the next night launch.

Sent from my mobile phone.

 

[T-Rex]

That is awesome, dude!! One day I too will have the 'marbles' to play with a project like that...I hope

 

[RocketManDan]

Very impressive! I like to build a saucer, but nothing like that right now. I might build maybe a 20" and fly it on a cluster? Is there any way to ROCKSIM something like this or do you just eyeball the size and guess at it? Are there any stability issues with saucers?

 

[edwinshap1]

Very impressive! I like to build a saucer, but nothing like that right now. I might build maybe a 20" and fly it on a cluster? Is there any way to ROCKSIM something like this or do you just eyeball the size and guess at it? Are there any stability issues with saucers?

saucer clusters are pretty cool

rocksim doesn't work that well for these shapes. i communicated with art applewhite about simulations, and he said that programs do exist that simulate these types of rockets, but they're rather expensive, even compared to rocksim @ $100.

saucers have almost no chance of being unstable because the CP of a 30 degree front sloped saucer is about 9 inches behind the nozzle of the motor...

I would look at the art applewhite rockets because if you do not intend to use a parachute, you'll definitely need to make sure that the aerobrake recovery system is such that the rocket will not come in dangerously fast.

 

[sailmike]

You want the CG to be far enough forward, though, that the saucer aerobrakes properly. Saucers can come in tumbling and land on edge causing some damage. Also, I think it's almost impossible for a saucer to come in ballistic because of their shape.

 

[sailmike]

I decided to take some more detailed photos, so I borrowed my dad's Nikon D300 with 18-200mm lens.






Here's a close-up of the forward end with the 5 x 54mm MMT. I filled in the gaps with thickened West System epoxy.



The electronics bay with the hatch removed to show the sled. The LED strips are held in place with hot glue.



The birds nest that makes up the control for the lights. I used mini Deans plugs for the battery connection, which you should be able to make out in the photo.



Here's the parachute bay. I have yet to add the shock cord, which I think will go through the center of the hatch. This hatch will be held in place with masking tape. I've thought of using tubular kevlar and running some wires through it to light up the parachute. You can see where I'm going to hook up the ejection charges. I'm planning to use two altimeters.



Here you can see the two lithium-polymer battery packs that fuel the lights. They are held in place with velcro and will be zip-tied for launch. A couple of larger battery packs will be used in place of these to balance out the saucer. The ones in the photo were used to test the lights.



Here's a close-up of the tabs to hold the MMT's in place. The yellow cord is tubular kevlar that makes up part of the recovery system.