Boston Observer

[g_kandylakis]

movie quality is fine, as is the flight... Quite a long one 

Some nose weight or little downthrust will cure the slight stalling, but in all a good flight

George

[korale]

the video was at about 1/2 winds I did have to add a tiny bit of nose weight to get it to behave with more winds in the rubber. Could not get a video of it flying at the higher winds.

[OZPAF]

You have a nice flying Bostonian there Korale.
John

[rick121x]

You say that you "preshrunk" the tissue twice. OK, I understand that.  But the covering looks so very nice, appearing to have been applied wet or shrunk again after application.

Richard Ranney

[cd_webb]

You went from looking for a plan to that flight in about a week?! I love it!! Nice job!

[Indoorflyer]

Different thread--

Pburress was looking for a Bostonian plan in this discussion:

http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=17470.0

[cd_webb]

Well, that's embarrassing. Still a nice plane and a beautiful flight, in spite of my ignorance.

CD

[korale]

Rick,

   If you are asking about my model, I preshrunk it, printed it and then after covering the model doped a single coat of very thin (20%/80%) dope over it. The finish is ok but RolandD6's technique gives far better results, mine looks very drab next to his.

Korale

[Indoorflyer]

I used Esaki tissue pre shrunk twice to prevents warps and applied it with 50/50 white glue and water.  I doped the tissue first then put it on the tail surfaces to prevent warpage.

[korale]

That'll teach me to post at 1:00 AM , sorry .

Korale.

[TheDope]

How have my fellow Observer builders attached the landing gear? From his pictures it looks as though scigs30 went with the sandwich method but on other's photos it isn't clear. From the plan alone I am unable to figure out the designer's intention. I assume that scigs30 followed the article, since he posted a photo of it, and that the sandwich method is advocated therein but I am still interested to find out about how you've attached your gear.

[Indoorflyer]

You could do it with or without the 1/16" sheet shown on the plan.  I suspect that was something added to the plan when it was prepped for publication.  The author's model shows a well gusseted intersection where each gear leg comes out of the fuselage.  The sheet part "beefs up" the attachment and does add weight...

Builder's option.

Do you plan to fly in- or outdoors?


 

[TheDope]

Thanks Indoor Flyer. I couldn't find a copy of the article when I looked and with a picture being worth 1000 words you've easily answered the main question I had. I will fly outdoors as a kind of free flight 'park flyer' only in really calm conditions so that'll be once or twice a year judging by past experience I would be thrilled to find an indoor venue that welcomes rubber freeflight near me but I don't know of any.

[RalphS]

I liked the look of the Observer so I have been making one. 

The u/c (gear) fixing had me unsure of the correct location and having glued the little diagonals in and fixed the wire to a piece of balsa the only place I could fit it was behind the framing.  There is a pretty hard bend between the front of the cockpit and the nose and I found this quite difficult to achieve.  The other thing to look out for is the downloaded plan gives the wing an oversize chord - for UK competitions that is it is greater than 3". As a result it will not fit on the cockpit top without an overhang. I suspect mine will be a bit overweight.  A couple of pictures show mine before covering.  I have just covered the fuselage but no pics of that just yet. 

[Indoorflyer]

There is a pretty hard bend between the front of the cockpit and the nose and I found this quite difficult to achieve. 

I asked about that a couple of yrs ago, back in post 12, didn't get a response.  I'd just leave the sides parallel from the noseblock to the trailing edge, if I were building one now.  Builder's license!  A bigger cross section at the front  just makes it easier getting a blast tube in...

[RolandD6]

There is a pretty hard bend between the front of the cockpit and the nose and I found this quite difficult to achieve. 

I asked about that a couple of yrs ago, back in post 12, didn't get a response.  I'd just leave the sides parallel from the noseblock to the trailing edge, if I were building one now.  Builder's license!  A bigger cross section at the front  just makes it easier getting a blast tube in...

Or crack the sides just forward of the cockpit and angle them inwards. See photo of my model in Reply #14

Paul

[RalphS]

[quote author=IndoorFlyer link=topic=10463.msg157070#msg157070 date=1422320382

I asked about that a couple of yrs ago, back in post 12, didn't get a response.  I'd just leave the sides parallel from the noseblock to the trailing edge, if I were building one now.  Builder's license!  A bigger cross section at the front  just makes it easier getting a blast tube in...
[/quote]

Thanks for response.  I should have read the earlier posts with more care!  I have done it now but not without a bit of surgery.  My blast tube fits the hole ok.

[RalphS]

Yes, this would make it easier.  The design problem is that the junction of the cockpit front parts are ahead of the bottom stringer and the sides do not want to bend in the same place.  The designer and others are obviously more skilled than me at this size.  It is still a pretty little model.

I can't get the hang of these quotes within quotes feature and the reply looks messy.  I suppose there is an explanation somewhere - I will have to look.

[RalphS]

Covered, painted and assembled the bits today. Silver mylar covering with acrylic paint silver and red colour.

The cg, with a 2g motor (2 x 3/32") was just where it is shown on the plan.  It needed 1.3g of ballast to bring it up to 14.01g so it is taped under the fuselage at the moment. I was just a bit too early for the Bostonian cook-up but will keep an eye on that.  They look an interesting little class. 

[Pete Fardell]

I think the appeal of Bostonians is maybe that they have something for everyone; bit of duration, bit of fun, bit of scope for scale or self design if you wish, and they're relatively quick to build.

That's really nice. I do like the look you get with that silver mylar. Very classy!

[RalphS]

I think the appeal of Bostonians is maybe that they have something for everyone; bit of duration, bit of fun, bit of scope for scale or self design if you wish, and they're relatively quick to build.

That's really nice. I do like the look you get with that silver mylar. Very classy!

Haven't tried flying one yet!  There were silver (aluminium) Spitfires you know.

[glue_finger]

That does look very nice, ralph.  Your too, scigs.  I want to build one of these by and by.  Ralph, what prop is that you used?

[RalphS]

That does look very nice, ralph.  Your too, scigs.  I want to build one of these by and by.  Ralph, what prop is that you used?

Thanks.  The prop is an IGRA 150mm (nearly 6").  It is slightly heavier than the 6" Peck but has a bit more area towards the tips. 

[OZPAF]

Nicely built Ralph - i agree with Peter re the silver finish. Very eye catching. Did you mean that you painted the silver mylar - to increase the opacity?
John

[RalphS]

Nicely built Ralph - i agree with Peter re the silver finish. Very eye catching. Did you mean that you painted the silver mylar - to increase the opacity?
John

Thanks John, as usual it looks better in the photographs than in real life.  I hurried it a bit to get it ready for an indoor meeting at Manchester Velodrome.  The silver mylar is opaque off the roll.  It takes acrylic and cellulose paint ok but can be difficult to unmask without pulling bits of paint off. Silver mylar is very shiny on one side and matt on the other side.  I cover with the shiny side inside in an attempt to get better adhesion of paint on the matt surface.  The shrinking process, using an iron causes stretch marks so I lightly airbrush with silver acrylic (in this case) to cover the stretch marks. I have used other colours on a Guillows Bird Dog and a Megows Skua - pictures in this site somewhere. I prefer opaque covering - just my preference.

I have wondered if I just covered with mylar and the put the covered parts in a suitably heated domestic oven it would shrink more evenly so that the shrink marks would not occur and silver painting would become unnecessary.  I don't know if you have seen the amazing pre-printed colour schemes on Chinese RTF r/c models.  I assume these are shrunk in some sort of autoclave.  -- So that is something else to try.