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Joined: 4/1/2003 From: Springfield, VA, Status: offline
Don, I have often wondered about the twin rudder cables myself. Many planes used them but I'm not sure why? Does the Snipe have a steerable tail skid like the Camel? Just wondering.. And lastely you do need to at least make this.. the lil pulsator lol It's for observing the oil in the system..
Posts: 5153
Joined: 2/13/2004 From: Zentsuji, JAPAN Status: online
Yeah, the Snipe used two cables on the bottom to control the skid. I'll try to simulate this somehow.
Progress has been slow today. I'm still pecking away at a solution to the cables. It's getting there though. I did the linkage from the elevator servo to the bellcrank and got the servos all "zeroed out" and reading to adjust. I had to dig through a moutain of spare parts to find the throttle linkage ball attachment that I used on the elevator bellcrank. I hate this sort of stuff but it's got to get done.
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Joined: 2/13/2004 From: Zentsuji, JAPAN Status: online
Finally! Something to show for my efforts. I got the fairleads in and figured out a simple and practical way to "deflect" the cable routes. It all seems to work just fine. Still need to do the exits for the rudder. I think a simple bit of 1/64 ply reinforcement around an oblong hole ought to do it here.
< Message edited by abufletcher -- 11/3/2006 10:28:23 AM >
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Joined: 4/1/2003 From: Springfield, VA, Status: offline
Aw Don, now that's no way to be.. Soldering is FUN!. sorta. If you have the equipment and just a little practice it's not a problem. Besides you got SKILLS..!
He's obviously working on the center section struts I've found Cleanliness comes next to Godliness is especially true when it comes to soldering. The key is to keep the iron really hot (and not to start too soon) and ALWAYS clean the parts with acetone first and maybe even rub 'em down with fine sanding paper first. Holding the parts with crocodile clips (right term?) also helps, because you can then move freely and have both hands to work with. See? Just as BobH said; it's easy!!
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Posts: 5153
Joined: 2/13/2004 From: Zentsuji, JAPAN Status: online
Bob, thanks for the encouragement. And Chris, good guess but no cigar!
Well, it's been a bit of a battle but finally I've got the skid done. The plans call for a laminated skid (and the kit provides lite ply templates for the bending) but thin hardwood sheets aren't available here so I just cut one out of solid hardwood. I tested a couple to the breaking point and it takes a huge amount of force so I think I'll be alright.
The next task is to solder some rectangles of brass (with are included in the etched fillings -- but I stupidly forgot to look ) to the sides of tail post. Since I wanted to simulate the steering horn, I cut one out of the matierial left from the kit's control horn sheet. I shaped this then slipped in down against the brass pieces and CA'ed it in place. Next you drill a hole in the skid. The skid can be secured to the tail post bracket either with a bit of 1mm music wire soldered on both ends -- or as I did with a bolt. Then, mostly as scale decoration (I do fly off of a rough dirt field though) I soldered a bit of brass tube to a small brass fin that acts as a miniature plow. It's not permenantly attached to the skid yet so I'll give it a bit more thought.
Then almost magically it occurred to me that I could quite easily make the whole tail assemby steerable -- or at least hold out that option for the future. All it takes is to slip the regular tail post into another just larger tube and put in a couple of corter pins. Again this is still "alterable" in case I decide that this is a bad idea. It just seemed a shame to have figured out how to do it and then NOT do it! If I keep it I'll have to rethink the rudder hinging.
I knew I wanted to use a bungee but didn't know exactly how I could do this. A little testing showed that I would need around 15 loops of sewing shop "bungee" material to get the sort of resistence I wanted. There's no point having it, if it's going to bottom out on each landing. It's also important that it not be so tight that it holds the skid in an unnatural position during flight. First, I tried making a bungee separately. But that wasn't going to work plus I already had that eyebolt in place. So I basically did the same thing again but in place on the model with a dowel to anchor one end. I burned out more than a few brain cells trying to figure out how to attached the skid to the other end of the bungee but eventually I worked out a simple bracket held with miniature bolt.
Oh, and I also got the rudder cable guides done (which required ripping out the balsa sides and drilling holes through F10 for some bits of plastic tubing). The only thing left of the tail is the mock tail incidence tubes.
I can't believe this has taken me ALL day! I'm looking forward to getting back to "chartered waters" with the rudder, stab, and wings!
I'll think I'll practice soldering a bit before I tackle the cabane strut wires!
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Joined: 2/13/2004 From: Zentsuji, JAPAN Status: online
As I lie here trying to sleep, it's already clear that improvements to my current skid arrangement will be needed. First, putting strain on the skid reveals a lack of lateral stabilty to the current tail box. Two possible solutions are 1) include lite ply triangular supports as in the photo or 2) put in bamboo cross-bracing or I suppose both. Next, my bungee is TOO strong for this size model! I'll need to reduce the number of strands (10-12?). I can also use thin aluminum for the bungee bracket to save a bit of weight.
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Joined: 5/25/2003 From: pelham, NH, USA Status: offline
Hi Don, Its always a treat to follow one of your build thread and this one is no different. Its very generous to allow strangers to get inside your head while your ideas evolve. I would not change the general concept of the tail skid but you are correct about trying to lighten it. I don't think you can underestimate the weight problem especially on a Snipe or Camel. I would brace the tail but only using one of your options and even then I would use the lightest option. One ounce of weight back there will translate to many usless ounces up front when it comes time to balance it. TRy to have a" free flight "mindset when you do anything to the fuselage behind the cockpit.
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Joined: 9/26/2004 From: San Diego,
CA, USA Status: offline
I would be a lot more concerned about tail weight as you work out these details. Every unnecessary bolt, piece of brass or plywood is going to cost you big time down the road.
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Joined: 2/13/2004 From: Zentsuji, JAPAN Status: online
quote:
ORIGINAL: allanflowers I would be a lot more concerned about tail weight as you work out these details. Every unnecessary bolt, piece of brass or plywood is going to cost you big time down the road.
That's what started rolling through my head almost the moment I posted the photos. The bamboo cross-bracing is probably the lightest solution and I can probably figure a way to eliminate one (small) bolt from the bungee attachment. I might even be able to use a plastic strap for a bracket. And sadly, I may have to loose the double tailpost that allows from a steerable skid.
On the topic of tail weight, I was thinking that it is possible to reduce the weight of the stringer by close to half by carefully trimming them to about half of their current depth in between the formers. This is just the sort of thing that WWI designers did with longerons and such. I don't know if that's stlll and option for me though.
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Joined: 2/13/2004 From: Zentsuji, JAPAN Status: online
Here's a photo of the bamboo bracing laid in place. This adds possibly 1gram of weight (it doesn't even register on my little letter scale). Doing this would also allow me to eliminate the balsa side pieces and just run the fabric out a hole in the fabric (as per the original). I'll also remove 1/4" from the plastic guide tubes.
My apologies to Chris for getting a bit "off track" with the building of his kit. This particular detail however is current left "open to the builder" with just a dotted line on the plan connecting the skid to the corner. I'd be interesting to see how he's done this on his Pup.
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RE: CD ScaleDesigns Sopwith Snipe build - 
