Fiberglass Electronics bay in an otherwise cardboard rocket

[SeanW78]

Now that I'm L1 certified with a simple single deployment flight on a Madcow Super DX3, I'm looking forward to setting up dual deploy. I have a Formula 98 from Composite Warehouse, which has a nice coupler and bulkheads that just happen to nicely fit in the Madcow tube. Is there any reason I shouldn't use a fiberglass coupler/bay in a cardboard rocket?

 

[tim cubbedge]

No reason you can’t. I’ve done it myself. Might have to do some sanding to get it to fit in cardboard. I had to, I put a FG AV bay in 7-1/2” cardboard airframe and initial fit was way too tight.

 

[David Schwantz]

the only thing I will add is harden the areas in the card board that the shear pins and rivets go into.

 

[Scott_650]

the only thing I will add is harden the areas in the card board that the shear pins and rivets go into.

If this is an odd question no worries about the answer - I’m a HPR newbie with a thick skin

would a plastic snap in grommet be an effective way to deal with the rivet holes? On LPR/MPR rockets I use CA on rivet holes...

 

[SeanW78]

the only thing I will add is harden the areas in the card board that the shear pins and rivets go into.

That's the plan. Trying to make the nav bat a workhorse that can function in my fleet of 4' rockets. I'll either glass the cardboard tubes or epoxy the inside.

 

[David Schwantz]

CA should work fine for HPR also. Have never used a plastic grommet, so cannot say.

 

[Banzai88]

CA should work fine for HPR also. Have never used a plastic grommet, so cannot say.

Yep. Simple is good. Folks use CA and push rivets on 4" and larger L2+ rockets all the time with no issues.

 

[afadeev]

I have a Formula 98 from Composite Warehouse, which has a nice coupler and bulkheads that just happen to nicely fit in the Madcow tube. Is there any reason I shouldn't use a fiberglass coupler/bay in a cardboard rocket?

None at all, if they fit.
Many of us build a few eBay units for each diameter (2.6", 3", 4", etc), and transfer them across multiple rockets.
This is way easier, quicker, and more reliable then transferring and rewiring the electronics between different eBays and rockets.

No reason you can’t. I’ve done it myself. Might have to do some sanding to get it to fit in cardboard. I had to, I put a FG AV bay in 7-1/2” cardboard airframe and initial fit was way too tight.

That's the tricky part - cardboard, plastic, and fiberglass ID/OD sizes are non-standard. Each manufacturer sizes them as they wish. Sometimes they fit OK across tubes, other times sanding or adding layers of masking tape is required.
I don't bother with sheer pins in paper airframes. Tight fit via masking tape does the trick.

YMMV,
a

 

[Handeman]

The Push Pin rivets and shear pins work great with fiberglass to fiberglass joints. Not so much when you use cardboard, especially if you use strong or oversized ejection charges. Using CA on the cardboard might delay the inevitable tearing and ripping of the cardboard.

I would recommend friction fit for cardboard tubes. I use 3 or 4 Xs of tape on the outside of the coupler. That lets the tube slide over the tape easily until it gets to the double thick area at the center of the X. This tends to prevent the tape from bunching up when you slide the tube on the coupler and allows you to control the friction closely. Just make sure to check the joints every time you fly because temps will affect the friction.

 

[BSNW]

The Push Pin rivets and shear pins work great with fiberglass to fiberglass joints. Not so much when you use cardboard, especially if you use strong or oversized ejection charges. Using CA on the cardboard might delay the inevitable tearing and ripping of the cardboard.

I would recommend friction fit for cardboard tubes. I use 3 or 4 Xs of tape on the outside of the coupler. That lets the tube slide over the tape easily until it gets to the double thick area at the center of the X. This tends to prevent the tape from bunching up when you slide the tube on the coupler and allows you to control the friction closely. Just make sure to check the joints every time you fly because temps will affect the friction.

I have never had paper tear or "smoosh" or anything...in the hundreds of flights I have done with 2/56 or 4/40 shear pins in paper rockets (from 2.5" up to 5.5" LOC tubing). As long as the paper tubing around the hole of the shear pin has been saturated with watery/thin CA it will be fine.

I have a paper payload bay from a rocket I made in 2014 that is currently on its 4th booster and I still use 4 2/56 pins and the paper holes look like new. Just saturate them in CA (after drilling your holes) and "tap" with a metal 2/56 screw and you are good to go. I put mine 1.5" down from the top of the payload.

I also currently use 4 - 4/40 shear pins in one of my LOC-paper 5.5" payloads with no issues to the paper

Peace.
Andrew