4" Madcow Tomach Build Thread

[Ccolvin968]

I have started on my winter project, and also my L2 certification build (possibly my L3, keeping documentation on build as well just in case.)
This is my largest and my second rocket I have built. Very Excited!
Without further words, I'll post the pictures and what I have completed already.

I have taken an inventory of all the parts. (Everything was there and in good shape!)


I have started construction on the nosecone coupler.
It is a 1/4" forged eye bolt through G10 bulkheads. JB Weld was applied to the washer and Loctite to both the screw threads and the nut.


After sanding both parts with #60, parts were fitted together and 30 minute epoxy was applied. After initial fillet dries, another on the inside of the coupler will be added for additional support. A 1/8" hole was drilled to prevent pressure build up and vent the nosecone.


That's all for now!
This may be a slow build due to my work schedule and a newborn that is barely a month old.
My goal is to have it built and flyable by May (ish) so I can fly it and get my L2 during my clubs first flying month of the year.
Thanks for reading!

 

[Ccolvin968]

Update on build progress!
I have completed the avionics bay and test fitted everything together.
The bay needed some additional sanding because I didn't have the bulk plates lined up perfectly.
I have also decided that this will only be for my L2 certification and not my L3.
The skills i learn from this will be used on building additional rockets, then onto my L3 eventually. No rush obviously!

Here is the avionics bay assembled. Still need to drill vent holes for altimeter usage.
I have recently assembled an Eggtimer Classic for the altimeter and deployment charges.



All of the parts test fitted together except for the fins, centering rings, and motor mount.
Much bigger than I expected. 7.5 ft. sounds big... but it's BIG. (at least to me).



Up next is the lovely dance of putting on the centering rings, then a button... then a centering ring... then another button.
Can't wait to get her finished! It's coming along much faster than I expected.
After that though... that's the hardest part of any rocket project... What color should it be?!?!

 

[ColumbiaNX01]

Update on build progress!
I have completed the avionics bay and test fitted everything together.
The bay needed some additional sanding because I didn't have the bulk plates lined up perfectly.
I have also decided that this will only be for my L2 certification and not my L3.
The skills i learn from this will be used on building additional rockets, then onto my L3 eventually. No rush obviously!

Here is the avionics bay assembled. Still need to drill vent holes for altimeter usage.
I have recently assembled an Eggtimer Classic for the altimeter and deployment charges.
View attachment 307874


All of the parts test fitted together except for the fins, centering rings, and motor mount.
Much bigger than I expected. 7.5 ft. sounds big... but it's BIG. (at least to me).
View attachment 307875


Up next is the lovely dance of putting on the centering rings, then a button... then a centering ring... then another button.
Can't wait to get her finished! It's coming along much faster than I expected.
After that though... that's the hardest part of any rocket project... What color should it be?!?!

This is the second rocket you have ever built and your already saying this is your L2 and possibly L3 rocket??????? This should be interesting. Just saying.

 

[Ccolvin968]

Originally I was going to use it as my L3. Like I said, I have decided against that. Not s good idea.
It's my second fiberglass rocket I have built, (I should have specified that... sorry.)
I have built numerous low and mid power kits.
This will for sure be my L2 rocket.
Hopefully it won't be as "interesting" as you're implying. Haha!

 

[crossfire]

There is no need to be in a big rush moving up the levels. Levels 1&2 you can do and learn a lot before you even do a L3 rocket. Have fun with the hobby don't turn it into some kind of race to the top. Slow down and keep having fun.

 

[Ccolvin968]

It will be a long time before I can realistically get my L3.
Cost is a big factor of that.
Otherwise, this is my L2 rocket, and my next few kits will be either 1 or 2.
No race to the top... I just like rocketry!

 

[Ccolvin968]

No pictures on this, but just an update with what I plan on using for recovery.

In DD setup, I will have a drogue chute in the lower section for apogee deployment or shortly after.
For my main, I will be using a Fruity Chutes deployment bad with an 18 inch pilot chute for extraction of the main 68 inch chute.
As stated before, I will be using the Eggtimer Classic for the altimeter.

 

[kevinkal]

I'm soon to start construction of the very similar 4" FG Frenzy XL kit. I'm currently in the planning phase.

What type of epoxy are you planning to mount the centering rings and fins with?

I'm going with Glenmark G5000 RocketPoxy for bonding and internal and external fillets.

It's likely that most motors you'll fly this bird on will be plugged... so it might be worth considering a second altimeter and charges for some redundancy.

I'm loosely planning to go with a StratologgerCF and an EggTimer Quantum. For tracking, I'm currently planning to mount an EggFinder TRS in the nosecone. I don't intend to use the EggFinder TRS' deployment capability at this time.... but.. it's still early in the planning phase.

 

[Ccolvin968]

My primary altimeter is the Eggtimer Classic.
Backup (if I use one) will be the stratologgerCF
For my Epoxy, I'm using the standard 30 minute slow cure that I am for the rest of my rocket.
I don't have plans for a GPS in this rocket.
Maybe my next one!
The I'm actually not going to use the plug on the motor tube for recovery.
I'm attaching the shock cord down through the centering rings and attaching to the mmt itself.

 

[kevinkal]

My primary altimeter is the Eggtimer Classic.
Backup (if I use one) will be the stratologgerCF
For my Epoxy, I'm using the standard 30 minute slow cure that I am for the rest of my rocket.
I don't have plans for a GPS in this rocket.
Maybe my next one!
The I'm actually not going to use the plug on the motor tube for recovery.
I'm attaching the shock cord down through the centering rings and attaching to the mmt itself.

I'm assuming the 30 minute you're using is similar to Bob Smith Industries 30 minute epoxy.

I want to be sure to use higher end epoxy for the critical joints/bonds. There's a reason that Madcow placed this note in the build instructions:
"Use only a high quality epoxy like Aeropoxy or West System to bond parts together. You can use a colloidal silica filler like West System 404 or 406 to thicken epoxy when making fillets. When using a filler for fillets a consistency like peanut butter or syrup is best For extra strength you can add 1/16” or 1/32” milled glass fiber."

I did a quick google search to try to find some strength numbers on BSI 30 minute epoxy. I found an Amazon.com description that stated it has a maximum tensile strength of 4,500 psi. By comparison, the RocketPoxy datasheet shows that it has a tensile strength of 7,600 psi. Something to consider.

As most do, I plan to use the higher temp rated JB Weld Epoxy to mount my AeroPack 75mm motor retainer to the motor tube. The longer burning 75mm motors are going to make this important.

 

[Ccolvin968]

It's exactly that brand.

I'll definitely get some rocketpoxy. I hadn't read that far yet, but that's the step I'm on now.
JB weld will for sure be used for the Aeropack retainer. I used it on my L1 as well.
Rather do it right the first time!

 

[kevinkal]

View attachment 307620

How true are the bevels in your 4" Tomach fins? I hope they're better than the fins I received. I have both the 4" FG Frenzy XL and 4" FG DX3 XL kits to build, and I've noticed that the bevels are not even on the fins... some irregularities across the length and they taper wider at the ends of the fins. Some bevels are wider than others and not symmetrical. I suspect thy were manually cut, as opposed to machine cut. This will likely cause the rocket to roll. I'm after as little roll as possible. I'm disappointed that they are not straight across.

 

[boatgeek]

What color should it be?!?!

I am partial to flat or satin black with a bright nose cone and switch band. It hides imperfections and looks cool on the pad.

 

[Ccolvin968]

Kevin, mine are pretty good. Some very minor irregularities, but nothing like you're talking about.
You should call MadCow and tell them your issue.
I've heard they have really good customer service if there are issues like that.
Just ordered the rocketpoxy.I'm at a standstill until it gets here.

Geek, that is a really cool idea.
I want to do that, one color for the nose cone, switch band, and the fins.
For the switch band, I will use the primary and secondary colors in a diagonal alternating pattern.
Each diagonal stripe 1 inch wide, kind of like a caution pattern... \Black\Bright Color\Black\bright color\ ... etc.

 

[Ccolvin968]

So tonight some progress was made.

I had received the Rocketpoxy in the mail about two days ago, but I've been quite busy.
So happy I waited. That stuff is like gold. A little difficult to work with if you're new at it... But dang. Awesome stuff.

I started out by attaching the centering rings to the motor mount.
Since I plan on flying this rocket on 54mm more often than the 75mm it's built for, I opted to mount the shock cord to the side of the mmt.


Dry fit of the fins: I was really excited to get the mmt in, so I forgot to take pictures.
I put epoxy all around the inside of the airframe right above where the fin slots were.
It pushed up and made a really nice fillet on the inside.


I slightly deviated from the instructions that were included with the kit after trying to let the Rocketpoxy drip down the sides from the end.
Instead of it forming a nice fillet along the side, it kind of clogged up before it could run the length of the root chord.
I removed that fin, and just ran a good amount of the Rocketpoxy directly through the fin cut outs then stood it up on end.
I ended up with some very nice fillets and any extra that was left created the fillet for the second centering ring just a couple inches below the forward one.



The aft centering ring was installed after the last fin cured (3-4 hours later) followed shortly after by the Aeropack retainer.
Took some super glue and tossed her on there. KIDDING. (I used JB Weld Standard... Don't hurt me!)


All that is left now is to let her dry overnight and then run the outside fillets over the fins.


I didn't include pictures of the drilling and tapping of the shear pin placements at the nose.
There are three 2-56 that are holding on both the fore and aft portions to the Electronics Bay.

Not a bad way to end my day or ring in the new year.
Can't wait to start painting it up after these last couple steps are complete!

Thanks for reading!

 

[Hobie1dog]

Thanks for sharing this with us.

 

[4kids49]

Is this a custom rocket? The 4 inch carbon Tomach is a minimum diameter rocket with surface mounted fins. The 54 mm Tomach rockets are the same. You have TTW fins. Nice work though.

 

[Ccolvin968]

No, this is not a custom rocket.
I bought it from Madcow on Black Friday. Here's the link: https://www.madcowrocketry.com/4-fiberglass-tomach/
Everything that is pictured is completely stock. No changes to fins, fin slots, or anything.
Thanks!

 

[4kids49]

No, this is not a custom rocket.
I bought it from Madcow on Black Friday. Here's the link: https://www.madcowrocketry.com/4-fiberglass-tomach/
Everything that is pictured is completely stock. No changes to fins, fin slots, or anything.
Thanks!

Nice. I hadn't seen that before. The TTW fins should be quite strong. Your rocket will be able to take some heavy duty motors, should you decide to do that. Good luck with your build.

 

[Ccolvin968]

Thanks! I obviously haven't flown it yet, but it's a solid kit.
Pretty straightforward build.
I will eventually fly it on some bigger 75's.
I already have 54mm hardware and bought the adapter.
Keeps costs down until I feel like going higher and faster after the first few slower and lower flights.

 

[Ccolvin968]

The rocket is complete!
I didn't expect to have it finished so soon, but it was a fun build.
The quality of the kit overall was good.
Another member posted early on that their fins were manufactured less than desirably.
One of my fins was 1/8" shorter than the rest upon measurement.
Also, one of the fin slots was cut a little wide, so I had to shim it in place while the interior fillets dried.

Here are two pictures of the outer fillets on the fins.



And the (almost) finished picture. Just needs paint!



Thanks for following this build!

 

[Nytrunner]

That looks deceptively similar to the Super DX3-XL. If it performs similarly and weighs ~25 lbs with motor, You could be looking at ~13k ft on a baby-M M1297 (when you go L3 of course)

 

[Ccolvin968]

NY,

I just put the entire rocket in OR and matched weights and everything else.
With the M1297 installed, the rocket weighs 21.4 lbs.
Simulations show 15,375 ft.
Not bad! Haha!

 

[Nytrunner]

Sounds reasonable. This thing is similar to the DX3-XL then! This will be a great multi purpose rocket for you.

There have got to be some K's that will get it off the ground well with the 75/54 adapter.

 

[dixontj93060]

Sorry, I have to ask... How tall are you? (4" Tomach 90"; picture seems 2/3rds filled with human, thus human is 5-feet tall.)

 

[Ccolvin968]

It's 98 inches.

I'm 5'6" haha!

 

[Ccolvin968]

Very close guess by a picture though! Haha!

 

[dixontj93060]

Very close guess by a picture though! Haha!

.

 

[watermelonman]

Nice. I hadn't seen that before. The TTW fins should be quite strong. Your rocket will be able to take some heavy duty motors, should you decide to do that. Good luck with your build.

I love Madcow but all the Tomach variations confuse the heck out of me too. It is best known as a 54mm minimum diameter, so you expect the other sizes to be minimum diameter too, but many are not.

 

[rocketsam2016]

NY,

I just put the entire rocket in OR and matched weights and everything else.
With the M1297 installed, the rocket weighs 21.4 lbs.
Simulations show 15,375 ft.
Not bad! Haha!

Isn't the m1297 a 10lb motor? Madcow lists the 4" tomach at 90" and 14lbs (raw parts weight I aassume), so I'd have expected 25lbs or more!

Is 21.4 the full loaded weight ? (Propellant, parachute etc) or burnout weight? I'm about to start a 4" frenzy that madcow also calls 14lbs and I was assuming would end up fully loaded except motor around 17 because of epoxy, electronics, parachutes, etc.