buzzard bait

I started asking questions about this on Abufletcher's thread about his scratch built 1/6 Dr.1, and decided I would start a separate thread.

I've really learned a lot reading through the amazing scale WWI builds I've been seeing here. This will NOT be one of them. I just want to do a basic build of the VK kit, with an emphasis on practicality at the field. Unfortunately, that seems to be a contradiction for Dr.1 models. It's just inherent in the design that they are difficult on the ground.

Even though I'm not going in for detail, I'd like some things to be right. The wheel size is an issue because the Wms Bros wheels specified are actually a bit under-size. I could go with the Dubro 1/6 scale wheels, which are correct in size, but the tires are black, which I'm pretty sure is wrong. Wms Bros sells white tires, which is really nice and I think truer to scale. Someone said they like the Wms Bros 5 inch wheels, which are a bit over-size. I might compromise on that.

The cowl face goes down too far and lacks a lip at the bottom edge, which I will try to correct. It is also too long, but VK did that to accommodate engines, and my old Enya 45 just fits under it, so I won't change that.

I think that keeping it light is extremely important. There is a thread on RCG that goes much farther lightening the structure than I will, but I will post any mods I try out.

Also, I think the ground looping might be controlled by gluing the wheels to the axle so both have to turn at the same speed. I read somewhere that German pilots sometimes had the wheels welded to the axle for that reason. Anyone try this?

Anyway, I hope to get some discussion going about simple, modest modifications to this kit, which is still in production after almost 40 years (thanks to Proctor taking it over). Once I've made some progress, I'll post pics of anything that I've done differently from what is already on other threads.

buzzard bait

Ah-ha, someone did glue the wheels to the axle and said it worked: http://scalebuilder.org/dr1.shtml

Javier, if you're tuned in, please tell us what you did and if you encountered any problems.

Jim

abufletcher

I'm looking forward to seeing your VK DrI build. But why are we already talking about wheels? BUT, there IS a problem with the "fixed wheel" solution, namely, that if the wheels are fixed to the axle, the axle itself has to be able to spin freely. I'm not sure how to manage that if you're using scale bungees.

buzzard bait

Ha, busted! I'm sure it's a form of procrastination, to go over the whole kit checking out issues before getting started and worrying about wheels before building a plane to put them on.

I thought about that axle problem too, but from my study of the VK plans it appears that the axle is already designed to be held in 2 pieces of brass tubing at either end, which in turn gets held by the bungees. Now, will the brass pieces get out of line and cause drag on the axle? Maybe that's one problem I WON'T try to solve before I start.

No idea how those German pilots did it.

Jim

TFF

The brass tube has two washers soldered to it. Outboard for the wheel to ride against and the inboard to keep the axel from moving in. The bungee is wrapped between. The tubes are soldered to the steel axel. Mine is bungeed with #64 rubber bands, but I think I would bind and solder it solid and add the bungees for looks, if I did it again; the axel wing would have to be assembled in a different sequence, slightly.

summerwind

TFF, i'm anxious to see your DR1, or anything you build for that matter

buzzard bait

Yes, I took another look at the plans and I can see that the brass tubes extend out to the wheel and the wheels turn on them. I think I will have to use a brass tube the full span of the axle except for where the wheels go, and the axle will turn inside the tube. If it weren't full length I think the two pieces the bungee attaches to would bind.

I'd be delighted to hear from the people who have already done this.

I'll start the wings first because I have the fewest questions about them. My theory about the wings is that I will not be flying this plane inverted, so the bottom spars will always be in tension. Since balsa is quite strong in tension, I think it will be fine to substitute balsa for bass on the lower spars, keeping the basswood upper spars. It's all tied together with spar webs. Save a bit of weight.

Another place to save weight is the wing tips, which are carved block. It would be much lighter, and more scale like, to substitute sheet balsa, curved to the camber line of the airfoil as on the full scale. I'll show what I mean as soon as I get it going.

Jim

TFF

I am not sure what you are saying about the axel. The wheel turns on the brass tube; they are extensions and mounts for the wheels soldered to the steel piece.
I built my wing tips like you are talking about and pretty simple to do and looks better. If you want to save weight, the WB wheels are your enemy; they are 1/3-1/2 of a pound by themselves. I made some ply disk wheels filled out with balsa treads and spokes and covered in old style Coverite for a Fokker DVII; the WB wheels on my Dr1 were first on that plane. Adding the lighter wheels made it fly much better and I reserve the change for later on the Dr1. The whole plane is so strong, all of the plane could be built in balsa.

R/C Art

My Feedback: (38)

Food for thought.......because the ground handling is atroceous on these little beasties, the lower wingtips will take a beating, and in turn the spars will see stress other than flying stresses.
I think if it were me, I would use the basswood for all of the spars.


Cheers,
Art

buzzard bait

Good point about the WB wheels, TFF. Never tried making my own, but it makes sense. Very interesting that it flew better after the substitution. I think weight is a huge issue in how these planes fly. Landings and take-off problems must be exacerbated by weight, multi-wing inefficiencies must only get worse at higher speeds, the planes just don't look right flying fast, and lightness gives a floatier flight that is appropriate.

Yes Art, I thought about the stress on the lower wing too. It's banded on, so it is supposed to give. Also, if I keep the whole plane light enough the stresses will be less. At least that's the theory. I think I'll stick with my plan, but thanks for the thoughts.

Shop is a disaster area at the end of the flying season so I've got to clear that up first. I can't believe all the little pieces and subtly different sizes of strip wood that have to be sorted out in this kit. Not a complaint! Great kit, but I need to clear the decks.

Jim

summerwind

ZACTLY!!.......changing the lower wing spars out to balsa is like having 2 strikes against this plane.
having built the Proctor N11, the lower wing is essential to the survival of this plane.......sorta the "Archilles Heal".
when Vern designed these planes to fly he took many things into consideration to save weight. i'd leave the spars as designed.

remember, the radios we had back when these kits came out were always over a pound and you can cut that by almost half these days. careful selection on power will save you a couple more ounces too.
i built one of these in the mid 70's along with the N17. never got a chance to fly either as an out of town flyer just had to have 'em.

buzzard bait

Yes, radios were much heavier when the plane was designed. VKs kits were a marvel because they actually allowed you to build a survivable 1/6 scale model with the radios of the time. But now I think you can lighten them.

Take a look at the construction of the Aerodrome kit over on RCG...http://www.rcgroups.com/forums/showt...ght=dreidecker
You just wouldn't believe some of the wood choices, almost entirely balsa. Yet the builder got a 4 1/2 pound plane, using an electric power system that was heavier than my glow engine, full fuel tank and throttle servo. And he made successful take offs, and landed without dumping over.

From this I tend to agree with TFF's comment that the whole plane could probably be built with balsa. I won't go quite that far, though. That's the great thing about these forums...we can see how different ideas pan out and learn from each others mistakes and successes.

Jim

abufletcher

Power plant weight is not the issue. Vibration is. Electric motors don't have much. You can't expect (and should want) to build a gas-engines model as lightly as one for electric power. Oh, and I'll second those saying not to mess with the spars. That's NOT a good place to spare a few grams. BTW, you can lighten the WB wheels significantly just by selectively removing a lot of the plastic in the hub. For starters, you can drill four big lightening holes. Since they will look better with some scale "recovering" anyway, it doesn't matter how they look underneath. Try to keep the wheels balanced though.

buzzard bait

Need some advise on cutting plastic.

The cowl and center section of the VK are very heavy plastic. What do you use to cut it? I was thinking a hot knife, but when I looked up Exacto people said the blade didn't get very hot.

Abu...I assume you use a hole saw for cutting the WB wheels? If you've got this in one of your threads I'll have a look.

One of the young electric guys in our club saw my glow plane make a low slow glide in and said, "I thought nitros were heavy". I told him it just depends on how they are built. All my glow planes are pretty light. I suspect the vibration business is over stated. Yes, engines vibrate, but if you have good glue joints and the radio is protected, who cares? Even my PAW .40 diesel actually is not that bad. I think glow planes are built heavier mainly because that's how people always did it. How do you decide on your structure? Look at what the other guy did. But when people first started building electrics they couldn't do that anymore because the power/weight ratio of nicads was so poor. So they started a different culture of building that has continued even though the power/weight ratio is as good as glow now.

But consider Pat Trittle's super light designs, like his recent Tiger Moth. That plane could easily be flown on an Enya 09. You would need a little extra balsa in the nose and a thicker fire wall...add one more ounce or even two...big deal. The only problem is the prop would be ridiculously small. The advantage of the electric is they can turn a bigger, more efficient prop much slower. But I suspect it would fly great with the Enya 09, even if the fuselage drag was absorbing a lot of the power. People just don't do it.

Anyway, enough jaw boning; thanks everyone.

Jim

buzzard bait

Actually one guy DID do something just like that. He carved out most of the wood on a Goldberg Cub and flew it with an Enya 09! Then he scratch built an 84 inch Pietenpol...and flew it on an Enya 09. Of course, the prop looked tiny...but he sent me a picture of it in flight. He posted on RCU some time ago.

Jim

summerwind

the plastic can be scored with an exacto then you simply bend it till seperates.....try on a scrap area first.
the deck you are talking about was one piece i did away with and use balsa instead.

abufletcher

For all of you WWI builders out there with a wheel fetish here are the threads for YOU!

http://www.rcuniverse.com/forum/m_17...tm.htm#1775839

http://www.rcuniverse.com/forum/m_31...tm.htm#3197779

http://www.rcuniverse.com/forum/m_26...tm.htm#2693952

abufletcher

I generally agree that many models care overbuilt and that good engineering (and often SCALE engineering) can mean a lighter model. But I still wouldn't mess with the spars!

summerwind

what spars.....thought we were still hagglin over wheels

TFF

Here it is at the field today after its first flight. No wind and late in the afternoon to get the crowd to thin out. The plane could not have been more well behaved for its type. Takeoff in about 12 feet into a stable climb which gave me time to add some down elevator to trim it out. A little left trim and I was set. I have had sport planes trim out worse; no need to add rudder in the turns. All I flew were circles around the field, but this thing should loop and roll without drama. I did not even flip it on landing! Good thing I came down, my fuel tank is too small, and it would have run out of fuel if I stayed up a couple of more minuets.

buzzard bait

What a beauty...congratulations! Did you do a thread on this? I'm looking at those interplane strut attachments and thinking that I saw your metal work. So glad to hear the takeoff and landing went so well. You're going to have a lot of fun with that plane. Looks like a nice oldie in the background.

OK, now for all you people stressing about my spars. I took weights and made calculations. The balsa I would use for the spars is actually 2//3rds the weight of the basswood, which surprised me. Anyway, when you figure out the weight savings, substituting only the bottom spar, it's about 9 grams for all three wings combined. So it's not worth slicing up the balsa to make the spars. I'd guess it's also about 2/3rds the strength of the basswood and it would be just fine, but I'm not doing it.

There...everybody happy?

Thanks for the threads...I think I've found them now but I'll check them out.

Jim

abufletcher

Wow, TFF, that's fantastic! Congrats on both the model and the maiden!!! [sm=thumbs_up.gif][sm=thumbs_up.gif] I'm sure Jim wouldn't mind if you posted a couple of close-up "glamour" photos in his thread! And, yeah, Jim, I'll sleep much better tonight knowing that you'll be using basswood for your spars.

*****

(BTW, looks like I'm not the only one with fall colors.)

summerwind

what he said
nice job TFF, very well done.

Jim, glad you decided to stick with the basswood.
for the record, i am a weight nut too, and have cut, hacked, gouged and whittled til my fingers were bleeding on items i was sure to save a ton of weight on, only it ended up being less than worth the trouble and weaker to boot.
you chose wisely[8D]

buzzard bait

By all means, TFF, please post more shots here...there are only a few Dr.1 modeling nuts around and we seem to be congregating here for the time being.

It's not often I can make so many people happy so easily, so I'm happy too. But I might keep a secret or two till the end...

Cheers,

Jim

TFF

I will try to make some better shots, but it is a 10 ft plane. It does not have the pretty details like abuflecher's builds or others. It needs an engine, combing, some simple details, and a pilot. It is done up as 403/17.