Grumpy1940

Ok... we have some sirious balance point problems... very short nose, and long inline engine which is very light...
looks like with composite elevator and rudder, nose weight should be about 4kg!!!!!
so only choise with light gasser will be build up controls...

so will be back with solution... now its time to seat back for while....

d***

Grumpy1940

I was testing how the balancepoint reacts with electrics. i just put motor and spinner on place and batteries free to inside cowl.
electrics looks like to have some advantages coz all the useful weight is in nose. ony those airtires on nose and balancepoints is good.
with long and light inline gasser (2,8kg) the useful weight is too close the BP. so i will give to Tero build up tailsurfaces and, try to find other good solutions for him. 4kg is just something we dont need... so, no maiden soon...
here balancetest with 9800mah batteries.

tadaa

Jukka

tetsa

Today the project received a bit of a blow. I finally managed to bolt everything in to the airframe and checked how much ballast was needed in the nose. As Jukka stated, the weight needed to get the C of G to a range of "just about flyable" was roughly 4 kilos.

Well... First of all there simply is no room for this kind of weight up front. Secondly I feel it would be stupid to even try. The tail is simply too heavy. The main reason is the laminated control surfaces, where a weight reduction of some 400 grams is obtainable simply by using built-up surfaces. So, the next thing to do is to rip the laminated surfaces out and replacing these with ones made from balsa and plywood. Not a nice task, but has to be done. To some this 400 grams of weight might seem insignificant on a ~20 kilo plane, but when torque effect of about 1,5 meters from the balane point to the surfaces is taken in to consideration, the weight saving behind the spinner is in a region of some 1,5-2 kilos.

As Jukka said, the ZDZ inline engine is a bit too long and light for this plane. The firewall is almost level with wings leading edge, so there is not enough leverage for the engine to really help in this C of G issue. The spinner and prop, heavy as they are, don't really help much. So, lead it is...

But for now the maiden flight is pushed back by at least a week, unless I get seriously motivated to work on this thing. Now I just don't feel like it, and then I really should not try to force things to happen. Ask me how I know this... (Or better yet, don't.)

I still wanted to include a picture. Sorry 'cause it's so crappy... I took it with my cell phone from our backyard while fitting the wing to the fuse.

transatlanticflight

Grumpy /Tetsa!

Sorry to hear about the CG trouble. Could either of you rig up a digital scale under the tail to tell us what the weight forward of balance point needs to be regardless of powerplant? ie. with just the spinner, prop, wing, fuse, sierra landing gear, and molded control surfaces installed - no servos or other bits and pieces...just a dry fit. Would help a lot... my goal is to configure a gas engine, silencer, live exhaust setup, maybe even water cooled to get useful weight under the cowl. Not going to have to worry about noise where I fly. My guess is the light engine and the fuse installed silencer isn't helping things much, Tetsa.... Question is...how much weight does the airframe really need?

TFF

I understand how frustrated you are, but I wish I was in your shoes with such a beautiful plane to work with. If it does come down to adding some weight to the nose, tungsten might be a way to go and I only mention it because it is very expensive and would not be doable with a lesser model, but in the space of about two standard receivers you can have about 2-2.5 lbs. Bucking bars used for full size planes can be ordered in tungsten, but expensive!

Grumpy1940

Well now i understand why the is not mk1a 1/4 scale kits on market. that about 2 inches shorter nose makes things much harder.
specially in spitfire which is known tailheavy plane. and build up elevator is only 130g and rudder 92g. and for laminated surfaces with details this is totally impossible i will try ultra light laminate for controls next. but for sure those will be heavier than build up ones.
CG should be about 7 inch from leading edge in center of wing. in real mk1a it was 29-31% from leading edge, but in models it must be about 26-28%. everything have went well to this point, maybe too 'easy'. i have to use high vacuum laminates in tailcontrols.
its ok to me i need to work more, but feeling bad Teros efforts with heavy controls was real waste of time... hes work for me is priceless.... but for sure these kind of things is sirious delay for production..

i need to take few drinks coz of this, shake my wrists and go back on designing table....

Jukka

Grumpy1940

Ok. i got the fuse about balanced with 2700g driving batteries+500g soloprop+400g spinner+1350g motor+500g sound system+ 500g receiving batteries. this is 5950g =13lbs. if saving 300 to 400g from tail means almost 2kg weight saving total. 4,4lbs total.
so that really need to be done, fuse itself is light(2900g inc. tailplane and tailstrut), but those controls were badly over builded with sandwich construction. hope this helps....

Jukka

tetsa

Well, having slept a good nights sleep on this thing I feel more positive about life and one particular Spitfire project as well...

Using tungsten as weight is of course a good idea, how ever it is not that easy to come by and it's melting temperature of some 3500 degrees centigrade makes it practically impossible to cast. (Tin has a melting temperature of 230 degs C and lead 327 degs C) The available space up front in my case is such that it would be very hard to use material in "bar" form.

Today it's pouring down with rain, so I'll setup the plane for weight measurements when the weather clears. My wife would kill me if I tried to do this in our living room, which is the only room big enough to house the Spit in one piece.

I'm sure that after I chance the control surfaces to built-up ones, I can get the C of G to maybe 27-28% with usual ballast materials. I think this is a fair starting point for maiden flight. Any input?

transatlanticflight

Tetsa and Grumpy,

Remember, this is a British plane. And seeing that I own and restored a 1952 MG TD roadster from the ground up...I know a thing or two about British engineering. Why should YOUR Spitfire be any different than the original...what say?...Heck there are only 24 different Mk's and infinite variations trying to "sort things out," as they say. You should have expected as much.

Anyway, call it Spitfire MK1 Rev 2.2!

When you do have time I would appreciate some measurements to play with...the weight of the tail (empty as stated before) and also the length from the CG to front of the cowl (back of spinner) and length from CG to tail. Probably could calculate from scale but emperical data should be handy enough for you to produce. Many thanks

Rick

tetsa

Rick, I was so fed up with lousy weather, that I packed my down hill skis and headed some thousand kilometers north to Finnish Lappland. So the project is on hold until next thursday when I drive back home.

But no post without a photo! In the picture you can see what I encountered about 40 kilometers before I reached our cottage at Ylläs, our Lappland 'base camp'. There was a full heard of these, but this was the only one stupid enough to hop on the road... Mind you, the car is stationary at the time I took the picture, so no harm was done to the reindeer featured in the picture... (Gotta be sure I don't get sued by some animal rights activist... )

Sorry for the off-topic stuff.

BobH

My Feedback: (2)

I remember buying a pair of reindeer boots when I visited Finland.. way back in the late 60's. Since I was there during christmas I remember lots of snow!

transatlanticflight

Tetsa,

Good for you! Clear the mind and make the best of the weather...seems very British in spirit. And the picture is not so off topic either...judging from the profile and attitude of that beast in the road, I would say he, too, was the product of British engineering!! Enjoy your reSPITe (no pun intended). It will all look better when you return.

Cheers,

Rick

tetsa

LOL! Spot on!

Anyway, we've discussed the C of G situation with Jukka and came up with a cunning plan! While I rest, ski and gererally enjoy the finer moments in human life, Jukka works he's tail off to find me some suitable ballast material and laminates a set of scale exhausts to house some of the weight. I think this sounds fair enough. For me that is.

But seriously I got to tell you all: Jukka has really made an exceptional effort with this plane, and these small set backs are really nothing compared to the work and love he has poured into making this plane. So all this ballast BS is merely just minor inconvenience. Nothing more. It's about two evenings work, if that.

tahustvedt

On my 1/6 scale Spitfire XIV (long nose Griffon model) I had to add 700 g og noseweight in the front of the cowling. It flew fine at 6.6 kg.

jran

Hi Jukka,
I am sure you will get that balance point right. Just a small point on the sound.

I think at 500g it may be a little light to be really effective on a plane which will fly some distance away from you. Unless you have found a really efficient speaker, all the tests that I have done indicate that the sound output of the sound system is almost proportional to the weight carried (basically the loudspeaker weight). You seem to have the one pound sound which will give out about 100 dBa at one metre - if the speaker is not restricted. By fitting the speaker inside then you may get less than this.

The two pound sound (as fitted to the Hornet) gives out 103dBa - twice the 'one pound sound'. So if you want some more weight up front then could you possibly fit extra speakers? Although you may have tested the sound system inside and think that it is loud enough, you will be surprised how quickly the sound reduces with distance when flying.

A chap over here has fitted 'four pound sound' to his Lancaster and it sounds really good!

All the best,

John

Grumpy1940

Hi Thor and John!
indeed i havent seen any spitfires without nose ballast. i have soon 20000mah batteries. so there wont be any balance point problems. its harder with gasser.
it would be nice to get maximum sound effect, i have now 5inch speaker. going to make very good sound box for the speaker. its between exhausts and instrument panel.
will see how it works. i think there would be room for 6inch speaker too. and the speaker is so front as possible. batteries will be on bottom of cowl keeping balance point lower. it should work against noseovers too. i going to laminate lighter wing soon. just received my 30kg of epoxy... and silicon for detail molds.
and i will laminate full carbon elevator and rudder. thinnest possible. today i lost coz of cleaning my workshop.

cheers

Jukka

transatlanticflight

Where'd you go boys...don't give up! If you need weight in the nose...how bout a fat pilot? lol Is it too late to consider a drive reduction like that sold by mick reeves? Would put weight where you need it and maybe help with the solo prop...maybe even take a scale sizeprop. Good luck what ever you decide. Stiff upper lip as they say.

Rick

tetsa

Rick,

In fact I tried to order the reduction unit from Mr. Reeves, but that didn't work out...

Here's where we're at: It's bloody cold at wind is howling. The snow on the ground doesn't help either... So It seems that unless the snow melts away before it REALLY gets cold, the Spit will not fly before next spring. We basically lost the race with winter. And what really bugs me is that it was so close...

My Spit would be ready for flight in some 4-6 hours of work (One evening). All I really need is the bloody ballast.

Cheers,

Tero

Grumpy1940

Hi Rick!
still working here, bit more relaxed way now, no rush. the winter weather have been quite nasty few days.... dark, windy, cold, raining snow and water.. i have been cutting parts for my wing and shaping the exhaust plugs. so waiting for better days.
i'll be back!

Jukka

transatlanticflight

OK,

Winter just starting to make an appearance here in Massachusetts as well. Got a lot on my plate too. Finishing house construction, getting married in the Spring, refurbishing my shop to do plenty of building as the weather gets cold. Will look for your posts.

Rick

Grumpy1940

ok!
i got some batteries for my spitty. i have now:
4x5s5000mah + 4x6s4500mah batteries. so i can make test with 10,11 or with 12s lipos. and for sure have all the ballast for nose i need.
i have laminated bottom of wing. and epoxied spars and ribs in it. it will be lot lighter now. here i come f4c... some installions need to be done still, before laminating upper skin and closing the mold. here is something to finish my outfit...

cheers

Jukka

Grumpy1940

Hi!
long time since last time..
i laminated second wing. and just opened the mold. and put everything on scale. including everything with out driving battery. and the weight is 12,8kg. so i believe i have very good changes for f4c. just need to do installions very light and painting too. will see but now i have changes for under 16kg flying weight with battery.
so pics soon... need to think light all the way now...

cheers

Jukka

ohahonen

Hi Guys,

How is Tetsa's project progressing? Have you managed to solve the ballast issue?

Otto

tetsa

Otto: There's nothing really to solve: I just need to stuff about 4 kilos of lead in the nose. But seriously, the weather is so appalling that I haven't even thought about the Spit. It's basically ready to go as soon as I get some lead. (I should get a 10 kilo lump before christmas). I moght have to move LiPo batteries behind the firewall to make room for this ballast, but that's a no-brainer 1 hour job.

I've already hooked up all the servos and pneumatics, so as soon as I get the lead and set the CofG, I'll just wait for snow to melt from our field...

ohahonen

OK,

I thought you guys were up make the tail lighter. But if thats impossible, then the 4 kilos shall be the way. BTW. I just got 70-300 mm Zoom lens on my camera (equals 140-600 mm on film SLR), so now I have the tools to take some decent aerial photos. Compared to those "fly droppings" shot with 150 mm...

Otto