D.P.R Rare Bird Sailplane

he means like this Sarah >< bit small, but you get the idea,

Klipkopwildlife wrote: Just looking at the wood and the construction I'd say this bird is going to be quite heavy, in terms of oz/sq ft.

I have no idea but reckon after a few bits fall off on its first flight it will weigh a lot less

Soft, light balsa can sometimes have a milky look to it, but the only sure way of finding out is to weigh it to get the weight and and try a bending test to get the stifness. I'll put some words and pictures in a thread I'll start on balsa characteristics, but in the meantime, for Sarah, I would suggest the following:

Try to work out the high and low stress areas of the model. For example, the wing roots will take the stress of holding the model in the air and up the launch. The tailplane ribs are at the back and need to be light to save on nose weight.

The balsa in a kit will be variable in both weight and stiffness. Lets take the strip wood as an example. Taking all the strip of a similar size, either weigh each piece or make up a rudimentary balance and weigh each piece relative to the others. You should end up with a line of strip balsa with the heaviest at one end and the lightest at the other. Mark the ends of the strip in some way to indicate their relative weight - i.e. 1 mark for the light strip, two marks for the medium and three marks for the heavy.

Then, line the strip up on the end of a table with most of it overlapping and see how far it droops. The less droop, the higher the stiffness. Mark the various grades in a similar way.

You can now choose the heaviest wood for the wing spars and main fuselage longerons, matching the stiffness on opposite sides of the model. Medium wood can be used for fuselage uprights and crosspieces and tailplane spars, and the lightest wood for tailplane and fin ribs.

Andy Sephton wrote: . I'll put some words and pictures in a thread I'll start on balsa characteristics, but in the meantime, for Sarah, I would suggest the following:

.

Brilliant idea,yes please- also can you include the reasons why other wood (such as plywood) may be used at certain points, eg my build has plywood used for the towhook

I would love to be able to say I am intelligent enough to work out what wood to use at certain stress points- but am not lol!! I followed the instructions which luckily enough stated when to test the wood and get the stronger piece of the bunch to use at certain points ( ie the harder 12.5mm x 2.25mm to use for the fuselage sides, use the harder strips for the fuselage top longerons, use the harder strips for the wing leading edges etc etc) Had it not stated to do this, admit I wouldn't have given it a thought

I tested for harder wood by very gently bending them and picking the ones with the most resistance. I was worried about warping the wood though so was ever so careful, however next time will defo use your methods, thank you

have been working on the wings, but was having one of those days yesterday when I kept getting parts wrong and having to reglue bits that kept popping out!! lol but both wings finished (pictures to follow)

I do have a question though regarding the wing ribs. The instructions did not state to glue each rib to the trailing edge, however they are kept in place here by the short spacers glued between each rib and to the trailing edge. My question is that with regards to the leading edge it only specifies to glue the first and last rib to the leading edge, thus leaving all other ribs NOT attached to the leading edge (hope this all makes sense lol)

Why is that?

Hmmm
I will also be interested in the answer to that! Seems odd to me.

Quorneng wrote: Hmmm
I will also be interested in the answer to that! See odd to me.

Have re read the instructions about 50 times lol, not once does it say to glue the rib ends to the leading edge. Unless I am reading it wrong?
Here is the exact instruction-

Pin a length of 9mm x 3mm shaped trailing edge in position, gluing to the rear of W1 and W10 (the first and last rib) Glue and pin a length of 6mm x 3mm strip upright across the front of W1 and W10 for the leading edge. Glue and pin ribs w2-w9 in position making sure these are upright and rest comfortable on the plan

Now, I read that later part to mean to glue in position to the top spar, which was introduced in the instruction prior to the above. Doesn't mention gluing to the leading edge though

Quorneng wrote: Hmmm
I will also be interested in the answer to that! Seems odd to me.

It seems odd to me too. I suspect what they want is for you to glue the LE to the root and tip ribs (W1 and W10) to set it's position, then when it says glue and pin ribs W2 - W9, it means glue them to what ever is available - i.e. to the LE, TE, spars, etc.

PS: you can also test balsa by digging a fingernail into it.....but such a thing is frowned upon by the purists.....and the model shop proprietors......so it wasn't me that told you.......

Sarah
"Glue and pin ribs w2-w9 in position making sure these are upright and rest comfortable on the plan"
Apart from the dubious grammar I would definitely take the above sentance to mean glue them in everywhere they touch any part of the structure.

Just repinned it to the board and gluing them in as we speak.

Really dreading this build finishing have so enjoyed just sitting here gluing and sanding and watching my own plane take shape plus is keeping my mind off 'things/people' ( and it is working )
Am very tempted to go get one of the cheapo Guilows kits from hobby craft just to give me something else to do, I know you said they were heavy Andy but nearest model shop is all the way over Warrington way and I think I really need to keep going

Sarah-Jane Smith wrote: Just repinned it to the board and gluing them in as we speak.

but nearest model shop is all the way over Warrington way and I think I really need to keep going

Cant agree with your logic Sarah, surly the nearest place is Alan 's house rather than going right to Warrington, or am I miles out?? He has more there than the model shop. He offered, so take him up on it

Garry

Eric wrote: Put - stockport model shops - into google!
First one I saw was - www.modelshops.org/listing-details.php?shop_id=104
Don't know if it any good, or even still there. but it's only 'round the corner' from you!

It was there.....it is long gone though Have been looking at others in the area, but none have what I am looking for- all mainly RTF and ARTF kits Just looked at SAMS models but either out price range or prolly not likely to get here for ages with the xmas post
Alan am coming to get youuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu