rharshberger
Well-Known Member
My next project (running concurrently with several other rockets) is a scale/sport scale of the Nike Smoke sounding rocket. The airframe is BMS T300 and the motor mount is BMS T52H tubing, with custom rings and fins by myself. Nose cone is one I picked up from a member of TRF a while back and is a Estes PSII Nike Smoke nose cone, while I could turn one from wood myself (that's my planned Nike Wood Smoke project). The design will include a chute shelf/shock cord anchor point and a nosecone Altimeter bay for electronic deployment.
First up is the fins,
Left Photo: Fin cores getting prepped for skins each core averages about 16.9g without the basswood or balsa parts, just the 1/8" Baltic Birch Plywood (I buy it in 5' by 5' sheets from my local wood wholesaler). The holes lighten the fins by about a third and without much loss in strength. Strength really shouldn't be much of an issue as this rocket should be able to fly on about any commercial 29mm motor that will fit in the pipe, and its being built to handle the longest ones from both Cesaroni and AT.
Center Photo: Center balsa skins and basswood ribs installed, one fin has outer triangular skins installed as well.
Right Photo: The pressure is on the fins are stacked in pairs with wax paper between them and the books stacked on. The technical drawing book I have had for nearly 30 years as it was the very same one I studied drafting with in high school, the other drawing book is the one I used in college 27 years ago. Still struggling my way through Solidworks, and have yet to learn AutoCad though AutoCad was taught to us as an intro module in high school using a Apple IIe (iirc) and a digitizer pad with pen. In a couple of hours I will pull the books off and then tomorrow start profiling the fins.
My technique for multi faceted fins is to use harder woods like basswood for ribs then sand for example profile of the center of the fin with the taper from root to tip, the basswood being harder than the balsa but softer than the plywood allows the sanding to not cut to much into the core material. The once the root to tip taper is complete the triangular pieces tapers from fin center to leading and trailing edges along the root edge will be sanded. After the basswood is properly profiled the balsa is easy to get sanded to the correct profile. For me its a simple way to get nice even fin tapers on fins like the Nike Smoke and my Nike Hercules 2 stage.
First up is the fins,
Left Photo: Fin cores getting prepped for skins each core averages about 16.9g without the basswood or balsa parts, just the 1/8" Baltic Birch Plywood (I buy it in 5' by 5' sheets from my local wood wholesaler). The holes lighten the fins by about a third and without much loss in strength. Strength really shouldn't be much of an issue as this rocket should be able to fly on about any commercial 29mm motor that will fit in the pipe, and its being built to handle the longest ones from both Cesaroni and AT.
Center Photo: Center balsa skins and basswood ribs installed, one fin has outer triangular skins installed as well.
Right Photo: The pressure is on the fins are stacked in pairs with wax paper between them and the books stacked on. The technical drawing book I have had for nearly 30 years as it was the very same one I studied drafting with in high school, the other drawing book is the one I used in college 27 years ago. Still struggling my way through Solidworks, and have yet to learn AutoCad though AutoCad was taught to us as an intro module in high school using a Apple IIe (iirc) and a digitizer pad with pen. In a couple of hours I will pull the books off and then tomorrow start profiling the fins.
My technique for multi faceted fins is to use harder woods like basswood for ribs then sand for example profile of the center of the fin with the taper from root to tip, the basswood being harder than the balsa but softer than the plywood allows the sanding to not cut to much into the core material. The once the root to tip taper is complete the triangular pieces tapers from fin center to leading and trailing edges along the root edge will be sanded. After the basswood is properly profiled the balsa is easy to get sanded to the correct profile. For me its a simple way to get nice even fin tapers on fins like the Nike Smoke and my Nike Hercules 2 stage.