Looking for Madcow Tomach 2.2" Minimum Diameter ORK file

[johnnypep96]

Does anyone have a basic or even a modified design file to share (ORK or RKT), or know where I can find one? I plan to do both L1 & L2 flights with this rocket but first want to work it up in OpenRocket before sending the money to Madcow. I've looked here, Rocketreviews and elsewhere on the net, but so far, no luck. Much appreciated.

 

[mrwalsh85]

I don't have an ORK but I do have a Tomach in kit form... I may be able to get measurements if you'd like.

Send me a PM if you'd like.

Thanks,
Mike Walsh

 

[jkovac]

Does anyone have a basic or even a modified design file to share (ORK or RKT), or know where I can find one? I plan to do both L1 & L2 flights with this rocket but first want to work it up in OpenRocket before sending the money to Madcow. I've looked here, Rocketreviews and elsewhere on the net, but so far, no luck. Much appreciated.

Great rocket, but are you sure you want to do a minimum diameter project for your cert flights? You certainly can, but MD does add some challenges.

 

[jkovac]

Regarding an existing file, there is a recent thread about this rocket that has screenshots of a sim file for it, so you could ask the OP.

Thread '2.2 tomach min dim'
https://www.rocketryforum.com/threads/2-2-tomach-min-dim.180229/

 

[johnnypep96]

Gentlemen: Thank you for the info. I didn't realize that OpenRocket now has many of the kits already preloaded. It's been about 4 years since I built my last rocket and used the program. I appreciate the concern about choosing to build a MD for my certifications. I probably scratch built about 40-50 rockets over the course of a few years, most of them with PVC motors (KNSU & KNSB) so I'm quite familiar with the challenges. I used to live way out in the country with lots of wide-open space, so I went a little crazy with it alongside my pyrotechnics hobby. This will be my first kit with a real motor case, though. I bought an Aerotech 54/1280 back then and never got around to using it. Special thanks jkovac for the link to the 2.2 tomach thread. I'm quite surprised I hadn't come across it already, as I've done numerous searches on this forum over the past couple of weeks, entering similar search strings. Excited to dig into it now.

 

[johnnypep96]

I don't have an ORK but I do have a Tomach in kit form... I may be able to get measurements if you'd like.

Send me a PM if you'd like.

Thanks,
Mike Walsh

Mike,
Thanks for the offer. I'm having trouble finding specific dims for the fins. I do have the exact shape profile (I think), and have put that into OR, but am left to make an educated guess as to the actual size. Would you mind measuring (exact or eyeballing it) the length of the root chord for me? I think I estimated it to be somewhere around 6.5" with the height approx 1 caliber. I could be way off, as other MD rocket kits I've seen (Wildman's for example) use much longer fins. I've attached the fin profile image that I'm working off of.

It's going to be another week at least before the kit arrives from Wildman and I've got 4 weeks to complete the design, choose optimal motors and sim it. I couldn't reach Madcow this week, so I placed my order for the Tomach w/WM.

Oh, one other thing you can confirm for me, please. This kit does *not* come with a 1" switchband, correct?

With appreciation, John

 

[jkovac]

John,

Hopefully Mike’s info will confirm, but here is what I get, quick measurements with a ruler but will let you know if you’re close:

Root chord 19cm
Leading edge 13cm
Trailing edge 6cm
Tip chord 4.5 cm
Span 5.5 cm

I don’t remember if mine came with a switchband. I added a long one for internal camera mounting.

Your fin diagram looks good to me. Fin photo attached.

Edit- this photo is skewed so it looks like the trailing edge is horizontal but it’s not. The way it looks in your diagram is right.

 

[lakeroadster]

Gentlemen: Thank you for the info. I didn't realize that OpenRocket now has many of the kits already preloaded...

There are a number of examples... but there are no "Kits already preloaded" with the standard Open Rocket program.

​

​

 

[johnnypep96]

John,

Hopefully Mike’s info will confirm, but here is what I get, quick measurements with a ruler but will let you know if you’re close:

Root chord 19cm
Leading edge 13cm
Trailing edge 6cm
Tip chord 4.5 cm
Span 5.5 cm

I don’t remember if mine came with a switchband. I added a long one for internal camera mounting.

Your fin diagram looks good to me. Fin photo attached.View attachment 613365

Edit- this photo is skewed so it looks like the trailing edge is horizontal but it’s not. The way it looks in your diagram is right.

Many thanks! Exactly what I needed. Apparently, the image profile I imported into OR was spot on. A small, simple scale up based on your root chord alone resulted in a match up with all the other dims you provided.

Nice paint job. How did you retain the motor? Which motor(s) did you use? Performance specs? My eventual plan is to push this rocket to around 1.5 Mach, so do you think a fin layup with FG or CF is necessary? I've seen a couple of plus Mach Tomach examples without it. My concern is weight, but also survivability.

I'd already asked Wildman to include a 1" switch band. I plan to incorporate something like an 808 keychain camera, but haven't incorporated that into the design yet. Worse case, I'll attach to the outside and 3D print a low-profile hood to place over it. Not ideal, I know, esp. for flights #2 and beyond. How did you incorporate yours into the switchband with the AV Bay? Btw, my shipment is currently delayed awaiting the nose cone, so I still have time to adjust the order if a wider SB seems like a good idea.

I greatly appreciate the support you've provided already. You've been helpful.

John

 

[jkovac]

Many thanks! Exactly what I needed. Apparently, the image profile I imported into OR was spot on. A small, simple scale up based on your root chord alone resulted in a match up with all the other dims you provided.

Nice paint job. How did you retain the motor? Which motor(s) did you use? Performance specs? My eventual plan is to push this rocket to around 1.5 Mach, so do you think a fin layup with FG or CF is necessary? I've seen a couple of plus Mach Tomach examples without it. My concern is weight, but also survivability.

I'd already asked Wildman to include a 1" switch band. I plan to incorporate something like an 808 keychain camera, but haven't incorporated that into the design yet. Worse case, I'll attach to the outside and 3D print a low-profile hood to place over it. Not ideal, I know, esp. for flights #2 and beyond. How did you incorporate yours into the switchband with the AV Bay? Btw, my shipment is currently delayed awaiting the nose cone, so I still have time to adjust the order if a wider SB seems like a good idea.

I greatly appreciate the support you've provided already. You've been helpful.

John

Motor retention was an Aeropack Min Diameter retainer. I’ve flown it on an L990, an L265, and an L935. Best altitude was 22,700 on the L935, mach 2.1.

I did not do anything beyond West Systems Six10 fillets, but I would not discourage you from doing tip to tip. It doesn’t necessarily add a lot more weight than big fillets do.

I used a 3” switchband but I cut it from the payload tube, so the overall length of the rocket didn’t change. I could have probably gotten away with 2 1/4” and still fit the camera shroud.

The camera carrier and lens shroud were made by Liquid Fyre, which unfortunately no longer exists. I attached some pics.

I built this a few years ago and I’d do some things differently now. I would use a Mobius or Runcam instead of an 808, and I would separate the lens from the camera body with a cable, or maybe use a Runcam Split.

I would personally not go to the trouble of building and flying a minimum diameter rocket and then put an external camera shroud on it, although some flyers would also say that about even the little lens shroud on my rocket, because it’s then a near-minimum diameter rocket. I used fly-away rail guides but the lens shroud is probably bigger than a rail button anyway.