Building/Flying kit 902 Bird Dog

[1778ppr]

WIDDOG,
I’m hijacking your thread but staying on topic. I’m building a Guillows 902 Cessna Bird Dog box stock and intend to fly it rubber power. The only changes I plan to make are the rubber motor, prop, and necessary trim adjustments. I will try it with stock prop and rubber first and go from there. Even the instructions say to use 36 inches of 3/32” rubber for the motor.
The 902’s wing area is 50.75 square inches. Using Don Ross’s book as a guide at 0.5 grams per square inch the targeted flying weight should be no more than 25.4 grams. Max air frame weight should be no more than 16.9 grams leaving 8.5 grams for the rubber motor. I’m not sure what 36 inches of 3/32” rubber weighs yet.
Again using Don Ross’s book as a guide the rubber weight should be 25% to 30% of the flying weight and the prop should be around 6 inches. The kit comes with a Guillows D5 propeller which is 5 inches in diameter. I don’t know the pitch. I plan to try a Guillows D6 propeller which is 6 inches in diameter. Again I don’t know the pitch.
Here’s where I’m at so far. See pictures.

902Contents.JPG

902SandSheets.JPG

902PartsPunchOut.JPG

TBC, John

[1778ppr]

While waiting for the fuselage side pieces to cure I started on the wings and tail. I plan to notch formers and ribs after initial assembly to keep the spars and longerons in line. The vacuumed formed plastic cowl and “stiff paper” cut outs have been cut out. I used printer paper for the “stiff paper” (not sure if there is a better choice) by copying the instructions and cutting right on the lines of the copy. The instructions say to use tissue for the top piece but I’m going with the printer paper for now.
TBC, John

[stx44]

So Ive built two bird dogs, the second of which there is a picture of in this thread.

Both built stock, bar the second I found a 6" prop kn my bits.

Built stock, with a coat of PVA to seal and single coat of acrylic on the tissue the first ran to 29 grams, the second to 31 grams.

Both required around 4-5 grams of nose balast.

This may help as to achieve your target of 25g your going to need to modify it slightly.

[1778ppr]

STX44,
What did you use for your motor? Is that black prop the 6” kn? What is kn? Is it available somewhere? It looks like it is molded in black and lighter weight than the Guillows. I like that color scheme and that will be the way I do mine. You painted yours with acrylic paint and a coat of PVA. What is PVA? Sorry for the newb questions if this has been covered already. I plan on dope sealing the kit tissue only no paint. It will be white not grey but I think it will save a gram or 2.
Thanks for the info. Especially the weights.
John

[stx44]

PVA is white glue- I use selleys aquadhere, because its a good brand and readily available here in Oz. PVA is water soluble before it sets. Whilst it takes longer to set than the traditional model glue, I use it in construction as well as it is less toxic, so I can build in air conditioned comfort instead of the shed.

It can also be used to seal wood for sanding and for sealing the tissue instead of dope- the older (not colour) guillows pamphlets acutally suggest this. If you are going to do that, though you will need to dilute it. I use a plastic syringe (50c Au from the chemist) and an old spaghetti sauce jar- mix it 70/30% and your away- just brush it over the frames and lightly sand before covering, and you can then brush it on instead of dope to shrink/seal the tissue.

The prop- dont know what brand it was- it was in the bits box, and could be many years old. No branding on it. I chucked it on becuase I think the kit props are a bit small.

The weight was with the kit rubber in it- I am stil waiting on proper rubber as the local hobby shop is sold out.

For acrylic paint, I have been using Games Workshop, for no other reason than Im a mad keen wargamer, and have a pile of their paints in my stock. I did try at one point enamel paint, but it doesnt cover as well if you use PVA to seal the tissue (makes sense- water and oil repel).

And never be sorry for a question!

Hope this helps...

[WIDDOG]

Hi John,

Excellent build you have going on. Thanks for posting it. Great work very informative!

My Bird Dog weights in at 32g AUW ( All Up Weight) . Rubber motor and prop weights in at 8 grams.

I already have a picture of a model sent into Guillow's Modelers Photo for September. I decided to wait till next month to turn in a picture of the Bird Dog. I have a "Hat Cam" that is ok for documenting flights. However, I am starting to work on trying to get a nice still pic of the Bird Dog in flight.

[WIDDOG]

I also wanted to mention that I use Pledge Future Acrylic Floor Shine to seal/finish the tissue. IMHO it works great, does not smell and cleans up with water. Great stuff worth a try. BTW I get mine from Wal Mart.



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[stx44]

So the wind has settled, and Ive managed to get in some flying with the Bird Dog, and frankly, I'm impressed!

Stil running kit rubber (Im waiting on real rubber to be delivered), but its been flying real well now I have the trim sorted.

Only problem has been broken rubber (apparently you can't safely run over 160 turns regularly!). And isnt a broken motor a complete b*%! to get out?!

[WIDDOG]

Hi Stx44,

Looking forward to seeing some pics. Even though I am afflicted with Rapier Madness I still follow the build threads very closely. I agree with you I also am impressed with the 900 series kits.

We Who Are About To Fly Salute You.

[stx44]

So Ive been playing around with different props and rubber to see what works.

The kit seems to indicate using a double loop of rubber with the kit prop- I have so far tried single loops only.

Does the double loop work, or does it overpower the machine, particularly if its got the kit prop fitted?

[Wildpig]

I'm going to guess that the little prop usually put in those kits is not the best choice for the double loop, 36" motor. I have used that size motor with, I think it was a 7 inch prop, worked very nicely.

[WIDDOG]

I built my Guillow's Bird Dog from scratch. Actually I don't have anything bad to say about the kits. However, I do use Peck Polymer propellers, rubber motors and Contest Balsa. I would have bought the whole kit even though I don't use most of the stuff that comes with them. However, they where out of stock on this kit at the time.

[DenisCullinan]

[quote="WIDDOG"]Hi Mitch.

Sorry the picture is misleading. What I wanted to represent was the "Stringers" being bent and glued into place. Not the Landing Gear. I used Wood Glue to glue my Landing Gear in place. I like your suggestion about the Epoxy.

Here's the a motivational video for the Bird Dog http://youtu.be/BG9n0GFFCkI[/quote]

Hi Mitch,

I've used epoxy pretty often to secure wire landing gear struts (the 5-minute epoxy works fine) with excellent results. I'd bet that the former that the wire is attached to would break instead of the wire coming loose. I'm sold on epoxy for this purpose.

-----------------Denis

[David Lewis]

No problem with using epoxy. Another option is to bind the wire to the former with thread wrap. Then you are not depending solely on glue to hold the wire in place.