mh9162013
Well-Known Member
This is a little different from my last one in that this one will be flyable with a 13mm MMT. It's also got a flat finish.
Another feature about it is that it combines the MMT and baffle and they're both installed and removable as a single unit. There's a thrust ring/engine block above the baffle to keep everything from sliding up the main body tube. To keep things from sliding down during ejection, there are 3 little bits of cardboard (made from spent 18mm engine casings) that are glued to the inside of the main body tube, but not to the MMT. In other words, the MMT + baffle are free floating within the main body tube. To remove everything, you just take an Xacto knife blade and carefully cut away at the 3 little bits of cardboard. It's a bit cumbersome compared to the other removable baffle systems, but because my removable baffles are lasting so long (a dozen or more launches), it'll be several months or years before I need to remove the baffle and MMT system.
Why go through all this trouble? Well, my BT-20 removable baffle works with the regular 18mm engines with friction fit. But it's not an ideal set up as the increased backpressure from the baffle means the engine has to be set even tighter into the rocket.
Additionally, using a baffle with a larger diameter than the engine is a good thing and results in better recovery protection performance and most likely, longer life of the baffle. So in this retro Yankee, I'm using an 18mm baffle with 13mm engines. These engines are held in place with masking tape. I've also built a similar MMT + baffle system in another BT-20 rocket (a retro Wizard) which uses an engine hook instead of masking tape.
So which is better: engine hook or masking tape? Well, on the pad, the engine hook looks better (in my opinion). But on the shelf, the masking tape method looks better (in my opinion).
Hopefully, this all makes sense with the below pictures.
Another feature about it is that it combines the MMT and baffle and they're both installed and removable as a single unit. There's a thrust ring/engine block above the baffle to keep everything from sliding up the main body tube. To keep things from sliding down during ejection, there are 3 little bits of cardboard (made from spent 18mm engine casings) that are glued to the inside of the main body tube, but not to the MMT. In other words, the MMT + baffle are free floating within the main body tube. To remove everything, you just take an Xacto knife blade and carefully cut away at the 3 little bits of cardboard. It's a bit cumbersome compared to the other removable baffle systems, but because my removable baffles are lasting so long (a dozen or more launches), it'll be several months or years before I need to remove the baffle and MMT system.
Why go through all this trouble? Well, my BT-20 removable baffle works with the regular 18mm engines with friction fit. But it's not an ideal set up as the increased backpressure from the baffle means the engine has to be set even tighter into the rocket.
Additionally, using a baffle with a larger diameter than the engine is a good thing and results in better recovery protection performance and most likely, longer life of the baffle. So in this retro Yankee, I'm using an 18mm baffle with 13mm engines. These engines are held in place with masking tape. I've also built a similar MMT + baffle system in another BT-20 rocket (a retro Wizard) which uses an engine hook instead of masking tape.
So which is better: engine hook or masking tape? Well, on the pad, the engine hook looks better (in my opinion). But on the shelf, the masking tape method looks better (in my opinion).
Hopefully, this all makes sense with the below pictures.
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