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Author Topic: Another "JETSTREAM" build  (Read 1123 times)
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gman
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« Reply #25 on: April 15, 2021, 09:01:38 AM »

It needs 45 grams in the snout in its present state to balance at the point indicated on the plan. Legal weight for flying in the "classic" events is 220.

Hi Pit, if your Jet stream is intended for Stu Darmon's postal "Classic Glider" event then there is no minimum weight. His intention was to allow any 1950-'60 glider of less than 18dmsq to compete and he reasoned that any sort of weight limitation would hobble the small ones. Anyway, in the day the A1 minimum was much less than 220g though I can't remember what it was, mind you in the UK it was to a 3 minute max!
Lovely build BTW,
Gavin
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Pit
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« Reply #26 on: April 15, 2021, 10:55:31 AM »

Thanks for the links Urs!  I've been out of the loop for the past 2 years, so a lot of stuff has passed me by.
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flydean1
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« Reply #27 on: April 15, 2021, 08:16:51 PM »

Weight of "old" A1 was 5.08 oz.   Whatever that was in grams.
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Pit
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« Reply #28 on: April 16, 2021, 09:27:16 AM »

5.08oz = 144 grams.  Thanks for that bit of info.  The 220 gram min. weight is for the current F1h class and has the same wing area limit as the old A1 and flown from a 50 meter tow line - also allows circle tow and bunt.

I am very pleased by the effort here in Germany to encourage this class for newcomers with 3 different sub-classes (thanks again USch):

DHP 25:- Straight tow off a 25meter line (60 second MAX)
DHP S:-  Straight tow off a 50meter line (120 second MAX)
DHP K:-  Circle tow off 50meter line with or without bunt (120 second MAX)

NO hybrid or LDA wings allowed and no minimum weight!  Really perfect for those flyers just getting into the sport and those "older" people, or those simply wanting to have some fun "competing" on a national level and minimum financial outlay.

Just about ANY glider that meets the <18 dmĀ² wing area can enter.

My JETSTREAM will probably finish out at the "correct" A1 weight of 144 grams.
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cvasecuk
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« Reply #29 on: April 16, 2021, 11:04:13 AM »

From 144g to 220g is a big jump. Does anyone know when it came about?
Ron
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flydean1
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« Reply #30 on: April 17, 2021, 10:22:28 PM »

Spent all spare time the last 6 weeks removing all the hunting/shooting stuff and generally cleaning the garage and workshop.  At last today, the workbench is clear and I at opened my BMJR Jetstream kit.  The kit is really well engineered; the laser cutting very precise.  However, most of the sheet parts are from fairly heavy wood.  The rib stock however is right on spec and the fuselage parts are generally usable.  I'll be cutting my own stab and wingtip ribs and fin as well as some of the balsa tips.  I have a huge store of wood so not a big issue.

So tomorrow I'll copy the plans so I can cut them up and set to work.  Looking forward to the build.
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Pit
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« Reply #31 on: April 21, 2021, 08:43:25 AM »

Yeah, Laser cutting is nice.  I carved and mounted the wingtips last night and gave the airframe a coat of thinned sanding sealer.  I hope to start covering tomorrow.

Flydean, are the wingtips in the BMJR kit triangle stock or square?  Square was what is/was in the Midwest (my) kit and was quite wasteful (and fairly HARD/heavy material Undecided).
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flydean1
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« Reply #32 on: April 21, 2021, 11:14:38 PM »

Square solid balsa.

Been fighting with getting some straight fuselage parts.  Should have just gone with plans and patterns.
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Pit
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« Reply #33 on: May 02, 2021, 10:18:18 AM »

I had to clean up the contact areas of the fuse sides to get a nearly invisible joint, and I also discovered that my plan was age distorted.  Not by much, but enough to foil a straight build.  I ended up using a metal meterstick (or yardstick, depending in what part of the World you're in), plus a few lines drawn on the building board.

The bottom of the fuselage is straight, as are all of the lifting surfaces.  About the only thing I used the plan for was the former locations and rib spacing measurements.

I covered the stab the other day with JAPICO tissue.  No wet strength but similar grain as ESAKI, slightly heavier and the colors are more intensive (except for blue).  I have used this stuff in the distant Roll Eyes past and liked it, as it toughens up nicely when doped.  It also does not have the aggressive shrink-rate of ESAKI.  The color separations will be trimmed with a contrasting 1/8th strip.
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flydean1
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« Reply #34 on: May 02, 2021, 03:04:39 PM »

How are you mounting the tow hook.  I really didn't like the "pool of epoxy" shown on my plan.  Really need some form of adjustment.

I'll post build photos as soon as I figure how to post photos.  Mine never seem to come through.

Fuselage and stab ready to cover.  Wings about half done.
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Pit
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« Reply #35 on: May 03, 2021, 06:18:08 AM »

A buddy, who had built and flown one of these, had told me to definitely make provision for some sort of tow hook adjustment and to reinforce the mount.  He had gone with the plans "glob of glue" with the hook in the plan location was OK for light wind (<5 mph).  Anything stronger, the model climbed at too steep an angle and started to weave (became nearly uncontrollable, even when he slowed down), and, the hook usually departed.  He modified the mount after three hook depatures (this was back in 1968)...

I added a strip of 1mm ply on the inside, atop the hook mount strips and a 0.4mm strip of ply on the outside.  Drilled a series of holes that are the same diameter of the wire used, marking the hole where the "standard" hook location would be.  The hook itself is per plan.  I'll be using two small screws to clamp the wire to the mount.
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flydean1
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« Reply #36 on: May 03, 2021, 09:16:25 AM »

that looks like what I was considering.  I have an old adjustable hook mount from FAI, but it is too large for an A-1.
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Pit
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« Reply #37 on: May 05, 2021, 08:28:43 AM »

At first, I was thinking of using an adjustable hook that I've had for ages.  Very nicely made an compact, BUT, the hook itself is much too short - intended for elastic hi-start (small to 2 meter rc sailplanes of the "gas bag" type).

Taking a break from covering (I hate covering undercamber 'foils...) to cut holes in the beautiful fuselage wood for the DT electronics/servo Sad.  I prefer to have the stuff inside the fuse when possible (aerodynamic reasoning), but still accessible.  Everything except the micro-switch is mounted on a bit of 1mm ply and screwed into place.
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flydean1
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« Reply #38 on: May 05, 2021, 06:03:14 PM »

I'm having to slum it with a clockwork timer I got from Mike Woodhouse.  I too hate to chop holes in that smooth nose.  

Finished the wing framing.  Now to much sanding and whittling.
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« Reply #39 on: May 06, 2021, 10:17:54 AM »

Cutting the holes neatly was the hard part using only a scalpel and some sanding sticks/dowels.  My usual tools are still inaccessible for the most part.  Once the covers are finished - they'll get a balsa "veneer" to better blend in - and the timer attached to the rear cover, I'll cover the fuselage.
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