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Discussion in 'Scratch Built' started by lakeroadster, Dec 27, 2018.
If you would put an Estes E9 or E12 in there you're a braver man than I am.
Nice book stack.
Props! Those centering rings, and bulkheads too, are TOUGH to pull off. Well done!
Agreed. But it takes very little effort to make space for a 1 inch longer motor, which gives a BAR options. Then, just throw in a 1" spacer and run D12's.
Great stuff. I want to see an image showing the arrangement of the ignition system.
I have had a bad experience with forward-engine rocket glider, where the connectors fell and 'hooded' the rear of the model.
Thanks for the comment.
That's another useful purpose of the strut rods.. or what you may call "anti-hooding" rods.
My initial thought is to build a fixture that has (3) vertical rods rising up from below the rocket to above the cluster. The ignition wires run up through the tubes. Once ignition occurs, the wires fall away from the rocket. I'll make a CAD model and post it up for comments and suggestions.
More work on the fin can. Post 1 of 3
This is kind of photo intense.. just want to make it clear how I did these steps.
The fins are 3 plys of Balsa, the center ply and the (2) outer ply's
Here the insert is held in place along with the center ply and one outer ply
I am using a Dewalt countersink bit and turning it by hand. First drilling through the center dowel hole and through the outer ply.
Here the bit is fully engaged
The dowels are 3/16" diameter
Hard to see but there is a dowel in place in the center hole. This dowel is temporary and just in place to hold the insert in place. I repeated the process for the outer dowel hole and placed another temporary dowel
More work on the fin can. Post 2 of 3
I sanded a bit of a chamfer on the dowel and then cut them using a Craftsman Accu-Cut pliers
Then sand the dowel to length and check length with dial calipers
Next step is to drill the final dowel hole, then place the other outer ply in position and use the existing hole to drill thru it.
Now insert the short dowel and push it into place. Note that no glue has been used yet. Repeat the hand drilling and dowel insertion to replace the remaining (2) dowels.
Cool stuff. Interesting drill bit, don't think I've seen one of those before (I'm not much of a woodworker).
Also relieved to see that your "Wooden Round Dowels" are "Made of Real Wood!"
More work on the fin can. Post 3 of 3
Time for some glue. Remove the outer ply from the dowels. Apply glue to the face of the outer ply and into the dowel holes. Place the outer ply into position, pressing it over the dowels. Flip the fin over, push the dowel down, place glue in the (3) dowel holes. Flip the fin over and push the dowels back down so they are flush with the face of the outer ply
Place the fins on wax paper and apply weight to keep them flat while drying.
The drill bits are for old school decking screws. Really nice for making the screws flush without splintering the wood. I've used them for a multitude of projects other than decks too!
In today's world.. between lawyers and fake everything... I'm guessing saying it twice was the marketing guys idea.
Here's the ignition arrangement... Comments / Suggestions are appreciated.
Looks good from here. The pipes keep the whip from catching on various protuberances.
Stabilizes the horse, catches motor parts in the event of a CATO, nice for putting out fires.
So I screwed up and didn't quite leave enough extension on the fin for the through wall mount.
To turn lemons into lemonade, I came up with a fix that should make the attachment even stronger. Basically balsa reinforcing pads that attach to the motor tube. I sanded the re-pads to fit the contour of the motor tube.
Excellent fix, I’ll need to remember one. Could be helpful to do that intentionally in some instances methinks.
The motor tube is only 0.013 thick. It may have been intervention by the God of Perpetual Fin Shredding.
0.013 ... a standard BT-50,then?
Coming from the world of rocket boost gliders: Is there a concern with the weight of the wires on the motor igniters?
Good point. Easy enough to put a strain relief inside the top of each of the 3 pvc tubes to support the wires.
Or simply offset the PVC tubes so part of the wire rests on the edge of the tubing.
Not really. The goal here is that once the motor lights, there is nothing hanging out of the pvc tube that can snag the fins.
Another day.. another revision to the fin can sub-assy.
I went to glue the first fin into the motor mount and wasn't happy with the fit. Everything was sloppy and alignment of the fin onto the motor mount was basically a blind fit.
So I revised the motor mount by gluing on 1/8" square balsa fin guides. These hold the fins in place and also give more glue surface area to make the joint stronger.
Now, fill the trough with glue, slide the motor mount into the body tube and place the fins into the glued guides.
It's been an adventure, but so far so good.
The lower centering is still not glued on, just shown in the photo for ref.
I love it when a plan comes together. lots of glue fillets yet to do....
And a preview of coming attractions...
Glue fillets on the fin to motor mount attachment.
Using Gorilla Wood Glue.. I like it better than Titebond Quick&Thick. The Gorilla glue, being thinner, gets into all the nooks and crannies much better. But it's a slow process.
Interesting, well engineered solution. I always just attached long pigtails to each igniter and then connected them below the rocket.
Finished all the glue fillets on the motor mount yesterday.
Today I cut the rear stiffener ring to fit around the fins and then installed the motor mount - fin subass'y into the body tube. This entailed gluing the forward fin sections and the front motor mount centering ring to the BT-60.
Anybody else here "spin" the body tube when making internal glue fillets? I've found that when gluing internal items, such as Centering Rings and Motor Thrust Rings, that spinning the body tube allows centrifugal force to push the glue outward and create more uniform internal glue fillets.
Here's a video:
Lookin’ great. What were you doing with the hole punch?
The stiffener fits over the rear of the body tube and a portion of it straddles the fins. So I cut the edges and used the hole punch to make a nice round radius at the end of the slot.
that you do
So, just a comment...
Next to diagram labeled "5" please let me know what an 'ignition wipe' is
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