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Old Sep 01, 2008, 01:41 AM
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Build Log
Dumas 30" Bonanza V35 Conversion

hi all,
last week i got the dumas bonanza kit. as i couldnt find a thread about this kit i thought i'd start a build log, dont know how fast i can build it, but i will finish

the kit looks very nice, standard dumas-quality with light wood and nice laser cutting. i plan to use a 16gram brushless ourunner from hobbycity, not sure about the battery, depends on how the weight comes out - i think 200grams (~7oz) should be possible. the construction doesnt seem to be too complicated so no extra lightening is needed.
gear will be removable (static only) to save weight. the only thing i want to change is the airfoil. i will make some new ribs, the standard airfoil seems to be good for free-flight, it looks a bit like the dumas bearcat airfoil. i plan on using a clarky (the herr corsair-airfoil semms to be one, and it is a great flyer) or a s3021 or a semi-symmetrical if there is a suited one. maybe you can help me a bit with choosing the right one. flat bottomed would be easier to build than semi-sym....

if someone has experience with this kit let me know, icant be the first one to try a conversion on this one.
thanks m.r.
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Old Sep 01, 2008, 02:46 AM
56S
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I think you are headed in the right direction and the 7oz weight is about right for this size. I have one of these on the drawing board right now. After having built and flown both the Herr Corsair and the Dumas Bearcat, the Corsair is a better flier: But only slightly. I plan to keep the airfoil stock mainy because the extra work involved in making all new ribs for a tapered wing. The UH Sweet-16 if rewound 19T 26ga performs well with the GWS 6030 & 7035. On 2s with the 7035 I found 172gr thrust @ 3.3A. To mount a prop and spinner I use the GWSDS001 prop adaptor that gives the ability to have a 3mm threaded prop shaft and enough left over for a GWS rubber spinner. For only a few more grams I decided to use the 2204-12 that will require changing the shaft to a GWS 3mm threaded shaft. One reason for the change is that I have a habit of bending the 2mm shafts and I can spin the 7035 in 3s if I get bored with slow flight.
Keep us posted on your progress!
Dan
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Old Sep 01, 2008, 06:23 AM
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thats funny, i thought exactly the same about the gws shaft and spinner, but its not so easy to get them (shipped to Austria). where do you get them from? and can you tell me which gws spinner is about 30 or 32mm and will fit the 3mm shaft?
the 16gram outrunner should come with a prop adapter, do you know the prop shaft diameter of the stock adapter?

and another thing i found: there is no down- or rightthrust drawn in the plan. i assume it will be better to add ~2 down and rightthrust?
thanks
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Old Sep 01, 2008, 07:15 AM
56S
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I believe you are correct in adding right and down thrust to models but not too much. Some say 2 deg. is about right but I have never found a reliable way to measure that so I just eye-ball it and hope for the best. Usually two thin flat washers under the top/left mount, none opposite than and one on the remaining two lugs if four lugs are used. I've also used 1/64th ply for flat washers. As for the GWS parts, I'm lucky enough that my LHS carrys a good rack of GWS parts left over from yester-year. I don't know their part numbering system to know the 3mm from the 4mm spinners so his spinner bags have little holes poked in them where somebody has test fit 3mm shafts into spinners. I will say this, the LPS drives have 3mm shafts and spinners and the IPS uses 2mm. The LHS had a good supply of GWS 6050 props that included a 2mm threaded shaft for the IPS drives. I cleaned him out of these and use the shafts on the Sweet-16 and the UH 1811 10gr. (Don't worry, the 6050 props do not go to waste; I use them to pack the wire around the teeth during a re-wind.) In doing the shaft change you need to find a spacer for the 3mm prop. Heatshrink tubing works well enough. The 16gr does require a .035" hex key to change shafts and pressing in new shafts results in bent shafts on occasion.
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Old Sep 01, 2008, 07:58 AM
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Dan ,

The IPS shafts are the same as the GWS 300-350 drives ( 3mm ) The LPS are a bit smaller ( 1.5mm or 2mm ) and the 400C drives ( 4mm )shafts .

-John
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Old Sep 01, 2008, 08:12 AM
56S
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Hello John,
Have you figured out the part numbering system for the spinners? I just noticed that I got the Indoor Power System and the Lightweight Power System all messed up. Yes, the IPS are 3mm and the LPS, the lighter system uses the 2mm shaft. Thanks for steering that rudderless ship back on course!
Dan
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Old Sep 01, 2008, 08:36 AM
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i found and ordered the 2mm gws adapter and spinner, should fit nicely.

maybe someone knows more about airfoils than me: i've read something about the naca2415 airfoil, it should be a good high-lift semi-symmetrical airfoil, which would look nicer (more scale) on the wing/fuselage bottom. do you know if its useable for this wing or is it only good when building with flaps for slower stall speeds?
i really want to build a new wing, just to learn how to do it for my planned future scratch-built projects...
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Old Sep 01, 2008, 08:38 AM
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about the spinners: i think that there are different sizes of spinners (best look at tower hobbies for diameters) and the letter A in the product # stands for 3mm shaft drill and B for 4 or 5mm.
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Old Sep 01, 2008, 09:07 AM
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Dan ,

I wasn't sure of the LPS shaft . I have one new in the package but haven't used one as of yet ( got it with a little LPS size Feiggo 12mm ) Got some plans for a nice little J3 Kitten ( 24" span ) to try it in .

As far as the GWs spinners that one I do not know

-John
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Old Sep 01, 2008, 09:15 AM
56S
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I'm not sure I'd adjust the airfoil. The Dumas kits seem to fly nice as they are. I think my preference to the Corsair has to do with frontal area and the overall stubbyness of the Bearcat. I will say the Bearcat is less tolerant of an aft CG. Both are about the same weight and both fly about the same speed. Miki, what about the dihedral? I'd go scale instead of the ultra-stable FF designed. Another question, what about the scale tail feathers? I'm hoping to see my lipo near the CG so I can go 3s if desired.
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Old Sep 01, 2008, 09:29 AM
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N2856S
dihedral:
as i will build flaps, scale dihedral should be good

tailfeathers:
i'll go with the standard kit size, as i think that a bit more area at the tail helps a lot with slowflying and stall characteristics

i'm thinking about the wing - i know that it would fly on stock airfoil, but i really want try to build it with new ribs. I allready sarted the planing (not at all dificult with the nice software available), and if it gets too complicated i stop, maybe...
i've built the bearcat too, and i found that it flew slowly very well, but when going faster it cant compare to the corsair. the corsair is the allrounder, and i believe its because of the airfoil.
but as i said: i want to do it simply to prove myself i can
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Old Sep 01, 2008, 10:23 AM
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Everett Wa.
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MR,
At this size and with this construction technique published airfoil data is not valid. I'd look at the general shape not the exact curve. Unless I'm making an aerobatic ship I like a rather aft high point (40% of cord) and a camber somewhere around 4% of cord. I do insist on a philips entry (bottom front quarter of the airfoil come up to meet the leading edge). A true Clark Y is good but I'd make it thinner and move the high point of the camber aft. I also like the Helmut Quaback airfoils.

I think the original Piper has a 5 digit NACA airfoil. I do like the NACA 2415 for my 1.5 kg plus sport ships . I have never flapped any NACA24xx section not even the NACA2406 that I love.

Konrad
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Old Sep 01, 2008, 08:10 PM
Balsa Flies Better!
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Depends on what you're looking for in terms of airfoils. I think Konrad and I would probably come up with a similar airfoil- a bit thinner than the one shown there- but if I built that airplane for rubber- I'd leave it alone. I'd probably go to heavier spars than 1/16" though- while structurally they're fine- in terms of handling- they break too easy and the aft spar on top is just along for the ride.

A thinner airfoil on a rubber ship would fly on less power- the fatter airfoil will be more forgiving at the higher loading of an RC version. But IIRC- the Bonanza is actually kind of fat in the fuse. My rule of thumb is for a slick airplane- you can use a thin airfoil- for a draggy airplane- you want a fat airfoil to slow things down and increase load carrying. You can also look at the thread on the Acme 35" Bonanza- an airplane which if you found a kit- would be a heck of a lot less work- and probably fly better.

Note- I'm just a seat of the pants guy when it comes to airfoil selection and design- but I have won a couple of FF FAC mass launch events.

Sam
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Old Sep 02, 2008, 12:26 AM
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hi megowcoupe,
i know about the acme kit. before i could order one, the site went down. but i'v read somewhere else that he might be back in business soon...?

anyway, i've drawn a set of ribs with the clarky and i hope it flyes well, if not i've learned something and make it better on the next one . its my 4th plane so its time to start experimenting, and i think its better getting some experience with modifying kits before starting a scratch build (what i plan to do somewhere in the future).

need to cut the ribs now, but i dont know when i can start, its a busy week for me...
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Old Sep 02, 2008, 04:08 AM
56S
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Ailerons or rudder. Or both? Since it is going to be hand launch I'd consider forgetting the rudder. I made the mistake of building a low wing with rudder only and now it hangs on the wall awaiting ailerons.
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