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Old Apr 13, 2005, 09:31 PM
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White Glue Fillets or Just Use Thick CA? Glue / Construction Question.

I just got in a Guillow 26.5" wingspan B-25 that I'm planning on convernting to RC.
B25withFW190 B25_BoxSide.jpg

As you can see on right the box photo, it's a pretty scale looking kit just as stock. I'm going to really enjoy working on this one. I'll be using .061 Norvels for power, which kind of leads me to my question...


I just built a 16" wingspan Guillow FW190, which I had originally planned on converting to RC and mounting with a TD .010, but I ended up using the uncovered model as a display model over my attic workshop (pic 1, pic2) because I just simply didn't think of having to fit in the controls, and RC equipment when I was glueing it all together lol. It was my first venture into mini RC.

FW190_GlueFillet3 FW190_GlueFillet2 FW190_GlueFillet0

Now, as you can see in the pics, I took the time to make Elmers white glue fillets at all the joints to strengthen the model, which I thought would be of paramount importance for RC use with such a light model.

Should I take the comparatively large amount of time and effort to use white glue and make fillets for the B25 model? How much stronger (or is it stronger?) than just using thick high-quality CA glue? Perhaps it is stronger, but heavier than CA -- to heavy to be of benefit?

Thanks!

DrCR

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Edit: Clickable thumbnails should be seen. I know I got the syntax right. Are image tags not allowed here? Edit2: Just made them links.
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Old Apr 13, 2005, 09:38 PM
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TWO Norvels??? Wow, that much power would pull a model twice the size of the one you describe (26.5"span). I ran a pair of 049 reedies (1/2 the power, if that) on a 42" P38 and it was nearly uncontrollable, very happy when the 2nd engine quit.

As far as glue fillets are concerned, I have the ugly habit of testing glue joints (!), and my experience is that glue fillets make very sure that the only failures are in the wood, not the joints. No experience with thick CA for the same job.
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Old Apr 13, 2005, 09:55 PM
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Quote:
Originally Posted by TLyttle
No experience with thick CA for the same job.
Hopefully someone with experience with both will comment then.

As for the engines, the kit recommends 2 x .02-.049. Norvel dosen't make their .049 RC anymore, and since their .061 RCs are basically the same, just bored out more, that's what I figured it would use. I plan to make them diesels in an attempt for more scale sound and lower RPM power.

Do you know of anyone making .020 RC engines? I don't.

Thanks for the advise/caution!
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Old Apr 14, 2005, 11:38 AM
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The "Stock" Guillows B-25...

Was designed as a control line plane only. They gave you no options of rubber power f/f or R/C It was heavilly-loaded on the "strings" as we used to say, and was fast. BUT... the minute the engines quit it had the glide path of a full beer can. If You are truely set on building the standard size kit, I'd go electric, or two Cox 020's... and there's barely enough wing there to fly 020's
The Guillows kit is VERY scale,.. it's just a shame they made it so small. If it were a 38-40" span, and made of light wood, it would be a FANTASTIC R/C twin!
Now.... ALL the parts are on the Guillows plan. If You take the plan sheets to a CAD/Blueprint shop, and enlarge the span to the above dimensions, You can replicate every part easilly on the plan. If you take your newly enlarged plans to Office-Max You can run the parts through the copier off the plans...
Then all you need do to get the parts to nice, light graded wood, is to follow the directions here...
http://www.rcgroups.com/forums/showthread.php?t=77687
Now.. Your saying... "but what about the plastic parts?" I have no Vacuforming equipment or skills"... Well You can make about all the parts You need.. Cowls, turrets, nose blister, nacelles. from 2 & 3 litre soda bottles, 1 litre Wally-world water bottles, or even Dixie cups. and a basic how-to is here: http://www.rcgroups.com/forums/showt...0&page=2&pp=15
You THINK it's a lot of work... but it's not,.. and I THINK you'd be a LOT happier with a Larger of the Guillows B-25... unless you are a sponsored , professional expert on the transmitter sticks (I know that a Guillows B-25 stock with 2 X PAW 033's would be the most intense 28 seconds of My life, before picking up the pieces & going home)
Now.. 2X 033's in a Liberator, or a B-17... I'd stand a chance of getting back to the house with a 1-piece plane, and the chance of cardiac-arrest is greatly diminished! Bob
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Old Apr 14, 2005, 12:09 PM
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Fw-190......

The Electric Boys are flying the HECK out of those small Guillows kits! You should go up to the Micro-R/C forum and do a search for Guillows cfonversions. I used to be a "Hard-Core" I.C. Dinosaur( that's Internal Combustion) But,.. I like to fly electric as well. I can pick up the plane Tranmitter & battery packs & go out the door. I have old "Jumbo scale rubber kist from the 30's 40's 50's etc. etc. That I can build electric, and have full-house R/C.. including flaps, retracts, or even a bomb or torpedo drop!
I'll probably get in trouble posting this in fuel, or tarred & feathered,.. But you need to see this.. building one on the table now between postings.
http://home.comcast.net/~echassin/Yuk54.wmv
If You don't like the plane,.. You may enjoy the AC/DC soundtrack!
Oh.. I still LOVE My engines.. sometimes I'll just start them to hear them run off a prime in the house (Mrs. doesn't appreicate the beauty, though ) Bob
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Old Apr 14, 2005, 01:43 PM
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Quote:
Originally Posted by Demon-Leather
(I know that a Guillows B-25 stock with 2 X PAW 033's would be the most intense 28 seconds of My life, before picking up the pieces & going home)
:lol: that line gave me a laugh.

How much should I enlarge the plan to accomadate a pair of PAW .033s? How large for a pair of PAW .049s? If the .049s are only a small percent more expensive, maybe I should just make a larger model out of this. That said, I'ld probably go the .033 route.

Maybe 150% enlargement for .003 and 200% or .049 PAWs?

FYI, since this is turing into a larger airplane, I'm really tempted to sheet the whole plane. I am after all looking for a scale look. I'm not sure if you will advice me against it, but if not, then I just wanted you to be aware of the extra weight as I'm thinking it may induce a larger enlargement percentage.

Yeah, it would probably be a good choice to go the electric route for the FW-190. But... electrics just sound all wrong! Your Yuk54 looks like a keeper! But it's not scale, so the electric aspect doesn't distract. In fact, its attractive because of the convience and no exhaust aspects. But a FW190 represents something. A affect of a FW190 zooming by at ground level is just going to be totally distroyed if the model sounds like a hand drill or a whinny motorcycle. Boom, there goes the immersion factor. If only those $1 a day oriental sweet shops would start turning out multi-cylinder 4stroke micro RC engines... I've never heard the TD .010, but I think the PET (RC) TD .010 would be my best choice.

Edit: Oh, Bob, any comment on white glue fillets or just use CA? Thanks!

DrCR

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Old Apr 14, 2005, 06:52 PM
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Answers & Examples....

Ok.. first, lay off the white glue, use thin CA to glue initially then medium CA for fillets, and ONLY in "High-stress" areas. A LIGHTER plane flys better and lands slower.especially a light warbird! I recommend sheeting 1/2A models, even My electric warbirds get sheeting. What I do is sheet with 1/16" sheet soaked in hot water for about 10 minutes... It's like spaggetti and can do compund curves in a snap. Just towl off the excess water, and thin CA will glue it in place damp. After it dries, sand it to about 1/20th or so.. You get a light & VERY strong fuselage. On Guillows kits, if You are sheeting, skip every other rib, unless it's key to something like landing gear.
Here is a photo of a 27 3/4" Guillows Zero, enlarged to 40"... I used an internationally recognized product 12oz product for "scale reference" This plane, built in the above described manor would fly pretty scale-like with an 049. But, for aerobatics and that "extra" cushion, I'd use a 070-09 in it.
A 40" B-25 would fly with the two 033's because when they are together, they will more equal the power of a .10. Save weight and sheet only the front part of the BOTTOM wing, and capstrip the ribs. The sun won't shine through the wing flying.
For cowls, you can't beat a heat shrunk water or pop-bottle. If you looked at My PA-25 Pawnee Cropduster build thread, You will see what a great job they do. I'd NEVER been able to vacuform a cowl that deep! And they also make GREAT canopies! ( the Zero will eventually get a canopy & cowl made of these)
Also, while you are there looking at cowls, go to the end of part 2 and see the weight of that 6' chord wing panel on the postal scale... I believe it's .08 of an oz, with aileron, and built-up wing tip, and the span of that one is the same as the Zero's (I like 40" span ships! can you tell? ) The whole airframe will weigh around 4.5- 5 oz total.. but you could slap a 1/8 ply firewall on it & add an 049 and have verticle with it! The plan was a Walt Mooney, but the building characteristics & style is Ken Willard ( see, old guys ARE good for something! )
So... to boil it down,.. enlarge to about 40"... Build & Sheet, use your PAW's and have a GREAT time with a LIGHTLY-Loaded twin!
Oh..when You enlarge, DON't enlarge the size (thickness) of the formers or ribs.. with sheeting, 1/16th is fine. To make the sheeting easier to apply You can make your stringers 1/8" wide, but only 1/16" thick ( kind of like a 1 x 2" board) When all glued together it makes a VERY light & STRONG structure. get you some .015" X 1/2" x 6 or 10 ft carbon fiber laminate and do your leading edges like the PA-25 build thread wings... stonger than ANY hardwood or ply reinforcement (approaches the tensil strength of steel!) Bob
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Old Apr 14, 2005, 08:04 PM
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DrCR,
My rule of thumb is :
Any glue you can see around a joint is too much. Just adds weight & very little strength.
Bob G
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Old Apr 14, 2005, 10:20 PM
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The wood is the structural material. Glue is just for joining the pieces together. The less used the better. As boberos says "any glue you can see around a joint is too much".
If doubt this I suggest you make a few joints with scrap material. Now break them. I bet the balsa broke in every case. Glue is stronger than balsa. (The reason we don't build out of glue is that it's also considerably heavier. If you are going to build out of glue you do it by impregnating a fibre such as kevlar, glass or carbon.) It doesn't matter how much glue you use the balsa will still break. It may break in a different place but it will break. Now going by your picture you added a huge amount of weight with all that glue. The balsa between the fillets didn't get any stronger and now it has to deal with extra loads due to the added weight.
If you want more strength do it by adding wood. Alternatively use some carbon fibre or fibre glass. Whichever way you go you're better off regarding glue as the material you want least of.

Aidan
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Old Apr 14, 2005, 11:10 PM
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PA-25 Pawnee Cropduster

Nice work! I like the catstip wingtips. Never thought of doing them like that.

This is going to be a really cool challenge. First time with diesels, plan enlargement, and forming my own plastic parts, and all for the same project!

Do you think only catstrips (except the bottom leading quater) would be sufficient looks wise? I haven't use catstrips too extensively, so I'm not sure how close it looks to a fully sheeted model. Also, if I was planning on building a boom-and-zoom fighter like a F4U Guillow, would you recommend full sheeting for strength? (The B25 will obviously not be succumbed to the same Gs I would put an F4U thorough).

Wouldnít thin CA be too brittle? Couldnít it be dangerous to use in heavy load applications? Again, not really an issue with this scale bomber project. Just wondering for in general.

Points well taken on that more glue is just excess weight. Besides, itís really not that strong in an of itself. Iím sure a laid up glass and epoxy fillet would be a ton stronger than an epoxy mixed with microballoons or something. Glass plus epoxy vs. basically just epoxy, Iím sure the glass combo would win every time. Glass is probably lighter. Kevlar sure would be. ...of course, it would be hard to lay up a composite fillet on such a tiny scale anyway lol.

I donít know if I would use carbon fiber for the leading edge. Iíve only used hardwood for leading edges in the past (all on larger models) though, and my experience with carbon fiber is rather small. At least, Iím sure, compared to you. But graphite has horrible impact resistance. Iím going to try to get my hands on some Kevlar fabric. It has the best impact resistance of any composite I know of, trumping S and E type glass, ceramic, and graphite. In fact, the only area it is inferior to graphite is stiffness. 40% stronger, 25% lighter, but half the stiffness as graphite (still trumps both glassesí stiffness though). The trick will be finding a fabric suitable for RC size aircraft use.

Bob, would you email me that Zero plans pic? It got really shrunk when attached. Probably a forum imposed size limit. Thanks!

Thanks for the input guys!

DrCR

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Old Apr 15, 2005, 12:32 AM
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A "Capstrip" makes an "I" beam out of your rib. great strength is achieve by doing this with minimal weight.Sheeting just the front of the wing on the bottom just to the first spar makes a "D" shape with some vertical webbing between the top & bottom.The combination of the two, with a bit of carbon fiber make a VERY strong wing! My wings survive cartwheels all the time... they usually break away from the fuselage (hey,.. they don't call me "experienced-crasher for nothing! You see the pile of broke planes in the avitar. )
Thin CA is fine for 1/2 A applications.. I seldom use any medium or thick CA on small planes, unless there is a gap, or a "stress" area. Always use epoxy for ply to balsa, or ply to ply bonding.. and you don't have to pile it on.. just a bit will do.. a wet film..on both pieces. You can even use micro ballon filler in it to make it go further and a lot lighter.. it just has to remain a "wet" mix, and not dry-looking. "Light flys right!" Bob
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Old Apr 15, 2005, 12:57 AM
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Some lightweight sheeting in key areas is definitely the simplest and most effective way to increase airframe strength and stiffness.
As Demon-Leather said thick CA is for gaps. If you make a good joint thin CA is better.
If you use ply remember to sand it before gluing. The surface is usually contaminated with release agent from the laminating process. You'll get the best joint by preparing the surfaces well and then using the minimum amount of adhesive to wet the surfaces.

Aidan
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Old Apr 15, 2005, 10:02 AM
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Aidan, I never thought of residue on ply before. Thanks for mentioining it. I usually prep even the nicest kit parts anyway though.

Quote:
Thin CA is fine for 1/2 A applications.. I seldom use any medium or thick CA on small planes, unless there is a gap, or a "stress" area.
Ah, OK. It's because the size and weight we are working with are so relatively small.

I was asking in general because I'm getting in a RWDRCTempest MkII which I will be pairing with a Saito 30, perhaps an OS40 4stroke. Thin CA is great because it wicks so well and cures so fast, but, and apparently you confirmed this, isn't approperiate for larger models like this. I assume medium or thick CA would be OK for this Tempest though? Forgive me for asking a non 1/2A scale question.

FYI, the Hawker Tempest page: www.hawkertempest.se and the webmaster's Ron Daniel's (RWDRC) Tempest MkV kit worklog and movie: http://www.hawkertempest.se/ronstempest.htm

DrCR

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Old Apr 15, 2005, 10:49 AM
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Thin CA is equally appropriate for any size model.
Thicker CA is not stronger.
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Old Apr 15, 2005, 11:41 AM
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Quote:
Originally Posted by Aio_1
Thin CA is equally appropriate for any size model.
Thicker CA is not stronger.
I thought thin CA is more brittle than thick and could 'pop' under high stress. Guess I learned wrong. That's what I've though for years. Then again, I believe the same source also touted aliphatic resin (i.e. high-grade white glue) as the glue of choice for wood apps. Maybe that's wrong too? Perhaps is was an older source when CA was skill in developement and the stuff on the market wasn't as good as what is avaiable now?


For sheeting, I've heard of a technique where you apply a thin layer of aliphatic resin to the parts being joined (ribs and sheeting) and let it dry completely. Then "iron" on the sheeting. You guys tried this?

Thanks for answering all my quasi noob questions!

DrCR

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