1.6" diameter--rail buttons or not?

[duodenumnums]

Hi everyone, I'm working on my second mid-power kit, the LOC Precision "park flyer" Black Brant X. It can allegedly reach >2800' on a G motor, and can handle an H motor as well (though I'm not yet certified). I plan on doing several launches with an F motor and eventually put a G in it. The kit comes with a launch lug. Would rail buttons be beneficial or would the increased drag not be worth it? The rocket's diameter is 1.6" and I seem to recall reading that buttons greatly increase drag on rockets under 2" in diameter.

My other question is regarding the buttons themselves, if I do end up putting them on--I have several from Erockets that include the button and screw but no nut. Do I need to go to my local hardware store and get a nut for each button?

 

[messedupryan]

When I built my 1.6" Weasel I had similar questions. I went with BOTH! That way I figure I can launch it from whatever is available. I put a launch lug tube on one side and rail buttons on another.

To attach the rail buttons, I pre-drilled a hole, and slathered the small bolts with JBWeld and screwed them in. This ensured I got epoxy on/in/behind the hole a bit. At my club launches 1010 rails are the most readily available option, so that is what I used so far. I have not had any issues with them.

Got any pictures of your BBX? I am currently building the 2.6" and would love to see what you are doing

 

[waltr]

The LOC Park fliers I built I put only 1010 rails buttons on.
If you are not going for maximum altitude then putting both lug & buttons on is good idea as it gives flexibility of available launch pads (as messedupryan said).

 

[duodenumnums]

When I built my 1.6" Weasel I had similar questions. I went with BOTH! That way I figure I can launch it from whatever is available. I put a launch lug tube on one side and rail buttons on another.

To attach the rail buttons, I pre-drilled a hole, and slathered the small bolts with JBWeld and screwed them in. This ensured I got epoxy on/in/behind the hole a bit. At my club launches 1010 rails are the most readily available option, so that is what I used so far. I have not had any issues with them.

Got any pictures of your BBX? I am currently building the 2.6" and would love to see what you are doing

Thanks for the reply! If I read that correctly, you drilled holes, applied epoxy to the screws, and screwed the buttons in, relying on the epoxy to secure them?


Here’s what I’ve done so far. I attached a motor retainer and I’ve replaced the included kevlar/nylon system with a lengthy kevlar cord.
By the way, nice scarf collection! I think I saw a Portland Thorns scarf hiding in there. We’ve been season ticket holders since day 1 back in 2013.

 

[dr wogz]

check with your club (or other clubs you want to fly at..) Buttons are becoming "required" for any rocket with a G motor or higher.

Look up 'button attachment'. Generally, we use either blind nuts, or screw them into the CRs of the rocket.

What size lug did it come with?

 

[JackC]

Thanks for the reply! If I read that correctly, you drilled holes, applied epoxy to the screws, and screwed the buttons in, relying on the epoxy to secure them?

View attachment 511368
Here’s what I’ve done so far. I attached a motor retainer and I’ve replaced the included kevlar/nylon system with a lengthy kevlar cord.
By the way, nice scarf collection! I think I saw a Portland Thorns scarf hiding in there. We’ve been season ticket holders since day 1 back in 2013.

I agree about using blind nuts or screwing into the centering rings. You could also put a little JB Weld on the face of a regular nut and screw the rail button into the nut.

As for whether you should have one or the other, you can do both. Buttons on one side; lugs on the other. That way you’re ready for any launch situation.

 

[duodenumnums]

AFAIK my club allows lugs for G motors and has both rods and rails in their mid-power range. The included lug is 6" long and 3/8" in diameter.

 

[duodenumnums]

Thank you for the responses everyone, sounds like both a lug and buttons is the way to go. Next question--how far up should the forward button be? The rocket splits pretty much in the middle when the chute deploys, so should the forward button go in the payload section?

 

[JackC]

AFAIK my club allows lugs for G motors and has both rods and rails in their mid-power range. The included lug is 6" long and 3/8" in diameter.

Since I know which club you are in, you are right about the lugs. However, if you want to use the rocket for your L1, I recommend installing rail buttons on one side and your lugs on another side. I would also cut the lug into three two inch sections. Discard one section and use two, one about an inch from the aft end of the rocket, the other about a sixteen inches above the first. You can use the tracks of a garage door or the space between the drawer and the face of a Chester drawer to draw your buttons/lugs guidelines. You should also use similar distances between your buttons, too.

 

[mikec]

FWIW, I like conformal rail guides for this size. https://giantleaprocketry.com/collections/launch-systems/products/acme-rail-guide-3-00in

 

[bjphoenix]

This size rocket will work fine with a launch lug. Adding buttons will give you more options depending on the equipment at the launch field. For instance at a recent launch we had a lot of pads set up with rails but only a couple with rods.

 

[danisman]

Tim at Apogee recommends putting the aft button as far back as possible (while avoiding CRs) and the forward one forward of the CG (while avoiding NC shoulders and couplers). He has a nice newsletter that goes over details: https://www.apogeerockets.com/Peak-of-Flight/Newsletter489

 

[dpower]

Best of both worlds - use mini rail buttons! They have less drag than 1/4" lug or 1010 buttons, mini-rail is far stiffer than 1/4" rod, and they're less visually intrusive. I did this on my LOC Park Flyer Hawk.

 

[DragonRocketry]

I drill and tap into the centering ring. I harden the threads with CA and thread the screw in. The rocket below has 30+ flights with zero issues

 

[duodenumnums]

Best of both worlds - use mini rail buttons! They have less drag than 1/4" lug or 1010 buttons, mini-rail is far stiffer than 1/4" rod, and they're less visually intrusive. I did this on my LOC Park Flyer Hawk.

Do mini rail buttons fit a standard rail?

 

[cerving]

My general rule of thumb is that if it weighs over 12 oz it's getting buttons. Anything heavier, and you risk rod whip or bending the rod. If you're flying with a club, no issues... they'll have rails. If you're flying Class 1 on your own, you would do well to invest in some kind of rail launcher... search for "rockwell jaw stand launcher", you'll find lots of posts how to make one fairly cheaply and easily.

 

[prfesser]

Best of both worlds - use mini rail buttons! They have less drag than 1/4" lug or 1010 buttons, mini-rail is far stiffer than 1/4" rod, and they're less visually intrusive. I did this on my LOC Park Flyer Hawk.

One caveat which I found out about too late. Mini-rails---20x20mm---that are not genuine 80/20 brand often have slots that are about 0.25" wide. I've had rockets with mini buttons actually slip off the off-brand rail before launch. I think the genuine rails have slots about 0.20" wide. Got to think about a fix for the buttons already attached.

Still...rail buttons forever!

 

[dpower]

Do mini rail buttons fit a standard rail?

They fit a mini rail: 80/20 (Mini Rail) 20mm

Buttons: Mini Rail Buttons

LOC Park Flyer Hawk with mini rail buttons:

 

[JackC]

I would recommend sticking with the regular buttons unless you will bring your own mini-rail to the launch site. I was in charge of procuring launch rails for our fairly large club and had only one member request the club to buy a mini-rail. That simply wasn’t efficient but we were okay with him bringing his own rail if he so chose.

 

[krislhull]

I have two of the LOC parkflyer kits, and both have 1010 rail buttons. My personal rule is that if it is capable of taking a H or larger motor, it gets buttons. I have flown my parkflyer Black Brant on a H115 for example.

 

[prfesser]

FWIW the mini rail has a hole in each end that is the right size to tap 1/4-20. Tap the hole, screw in a stainless steel bolt (not all-threaded), saw off the bolt head and file the edges smooth. This works nicely for low/mid-power pads that use a chuck to hold the launch rod.

Terry

 

[duodenumnums]

I have two of the LOC parkflyer kits, and both have 1010 rail buttons. My personal rule is that if it is capable of taking a H or larger motor, it gets buttons. I have flown my parkflyer Black Brant on a H115 for example.

Where did you put each button on your BB?

 

[Back_at_it]

On my Park fliers I've used only the 1/4" lugs included with the kit and have flown on F and G motors without any issues. I typically don't move to rail buttons until I'm over 3" body tube or the rockets is over 20oz. Just my personal preference.

 

[krislhull]

Where did you put each button on your BB?

I drilled a hole through the airframe where the centering rings are, reinforced them with thin CA, then screwed the rail buttons in. This method has withstood three flights on my BBX so far (2 G76 flights, and one on a H115), and I used the same method on my Sandhawk, but it has not flown yet.

I also have a few rockets, such as my Estes PSII Nike Smoke and Ventris, as well as my Madcow mini Tomach, where I simply epoxied the rail buttons directly to the airframe, and they are still holding strong. My PSII Nike Smoke has seen 8 flights with G motors, and 1 on a H115. the mini tomach has seen a couple G flights and a H115 as well. I have yet to have one of those rail buttons break off.

 

[prfesser]

I drill the hole, dip the tip of the screw in epoxy, screw it in place. Then I use a straw, long piece of plastic tubing, or similar, and apply a rounded blob of epoxy, say 3/4" diameter, to cover the tip of the screw. The blob anchors the screw nicely and it prevents shroud lines from catching on the threads.

 

[DaHabes]

One caveat which I found out about too late. Mini-rails---20x20mm---that are not genuine 80/20 brand often have slots that are about 0.25" wide. I've had rockets with mini buttons actually slip off the off-brand rail before launch. I think the genuine rails have slots about 0.20" wide. Got to think about a fix for the buttons already attached.

Still...rail buttons forever!

The fix is to buy genuine rails and scrap the fakes...

 

[DaHabes]

I put rail buttons on 38mm and up. Ever had a launch lug rip off when putting it on the rod? Rail buttons don't do that...

 

[duodenumnums]

Ended up putting the forward rail too far forward but hopefully we’ll have a rail long enough that it won’t matter. She’s skyworthy now, I just need to make her look pretty.

 

[Tractionengines]

Wow, that is very far forward... I would "CAREFULLY" add a 3rd button in line with those 2. Making sure its inline. About 1/4 to 1/3 up from bottom button to top button.

Remember as soon as there is only 1 button in the rail you are not getting guidance. (If it is windy it can really push you off course.)

 

[duodenumnums]

Thanks for the reply. I had someone in another group advise that it’s likely safe on an 8’ rail and probably ok on a 6’. I’m not sure what length my club (Oregon Rocketry) has.
I’m hoping to fly it this weekend and if I need to just use the launch lug, then so be it; I can see about adding a 3rd button in time for the next launch.