rinnander

Thanks Matt,

Originally the plane would weigh 18lbs and the engines I got were bigger than recommended so I hope an extra couple of lbs wont hurt. This is a slow mover type of plane with a large wing and big flaps for short take offs and landings. Thanks for your help Matt. The only problem know is I was almost done with this model and then I see the nice fiberglass models on the site and want to be able to paint mine with a nice camo paint job. I will try and post some pics as the project gets under way next week. Any other advice you can think of will be a great help.
PaulR

rinnander

Sorry Matt,
One more question. I went to apc web page and I found 3.0 oz/sq yd satin weave witch is .0035 thick, and 2.3 oz/sq yd plain weave witch is .0029 thick and their ez-lam resin. What would you recommend?
Thanks again,
Paul

dhal22

both are too heavy. i use either .5 or .75 oz (per square yard) fiberglass cloth and over open bays/areas i use koverall (1.5 oz i think). and to keep it even lighter apply it with waterbased polycrylic. there are many threads here on how to do that.

MTK

Paul,

Look for the 0.6 oz per sq yd. That's the stuff you want. The thickness I quoted is with finish fully applied and RTF

EZ Lam works fine but you need to know some technique. you will need to squeegee as much off as you can with an old credit card. I prefer using epoxy paint such as Klass Kote to apply glass. Nitrate dope works well also and is lighter but not fuel proof.

If you read the thread earlier on you would see that the carbon cloth is applied with nitrate and after initial bedding of the carbon, I use the epoxy paint slurry (microballons and baby powder) which fills and fuel proofs. This technique works superbly with glass

BTW I use 3 os cloth for things like wheel pants, chin cowls, canopies,etc.

MattK

serious power

Hi Matt,
What do you think of this water based 'polycrylic' for glass or carbon veil ??

One advantage of epoxy is that it is hard/tough, so when sanding it is resistant to wearing through .
Is it possible to apply the glass etc with dope or that polycrylic and then fill it with epoxy ??

I suppose I'm asking what is the lightest and stiffest/strongest and or most stable combo to get a paint ready finish.

Brian

iron eagel

You can use pretty much whatever you want to use to bond it to the wood as long as it is compatible with your paint. Using carbon fiber veil you will find that there is little or no problem filling the weave. I use nitrate dope to prime the wood before I apply carbon fiber veil and use the nitrate to bond it as well. A couple more coats of nitrate and a bit of sanding gives you a nice smooth surface to paint with anything you care to use after that.

MTK

Brian,

I have used polycryllic before. It has advantages, mostly health related. No face mask required.

The issue with these water based materials is warps. No matter how I apply coverings, my balsa always warps using water. Especially the TE's...but I've also had whole panels bow from it. Not to belabor the obvious, with only two hands I can't work on both sides of a panel simultaneously. I don't use water based stuff until after the wood has been sealed with solvent based materials.....

Epoxy is much better regarding warps but will get heavy. I don't use epoxy for finishing; only for skinning. Nitrate dope is good, and is the lightest and thinnest so hanger rash is an issue. Klass Kote epoxy paint is similar to nitrate but also can get heavy if not really careful. I've found that every technique I have discussed has its strong points and they all have compromises.

The very lightest finish for wings, stabs, rudders is nitrate and lite silkspan or Japanese tisue. Lite silkspan and Jap tissue have their own tricks of application. The easiest way to work with these coverings is to hang them from a rafter or other frame and lightly spritz them with fine water spray. A mist only is needed to loosen and expand the fibers. Then the misted paper (never dripping wet...warps) is placed on the sealed surface and tacked on its perimeter only. Then the other surface is treated the same way.

The secured paper is allowed to fully dry. directly attached to each surface. Only after drying is the paper fully laid down with nitrate. See, as the paper dries, it shrinks and eliminates all creases/wrinkles. Also, there is no water left to warp my wings.

Jap tissue is superior to silkspan regarding strength and stiffness, but neither is as stiff as carbon veil. And none of these finishes is bullet proof because they are all very thin, thinner than wrinkle kotes (plastic films)....Good luck your learning curve. Technique isn't difficult (although it took some time to figure and work out lite silkspan) but is tedious.Lots of elbow grease required. But the painted finish is superior in my opinion.

saramos

I think Paul was referring to G-10, which is a fiberglass sheet product. The sheet is cut to shape and can be glued using gorilla glue directly to the framework and replaces the traditional balsa and glass finish. It gives a ready to paint surface. One source is FliteSkin. You can also find generic G-10 too. I've seen it as thin as .005", but for skinning wings, I would go with the .010". It will not conform to compound curves as a single sheet. If you did have compound curves, you would have to strip cover, or use relief cuts.

Here's a horizontal stab covered with the .010 G-10


Here's a turtledeck covered with G-10. gorilla glue on the open structure, and contact cement was used for the ply sides. If memory serves me correctly, this was the .005"


This shows the sharp trailing edges you can get. In this case, the G-10 was applied as a skin on top of a solid balsa core using contact cement.


Here's the painted result of the plane in the second and third photo. It was painted with automotive poly paints and clear coated with MinWax water base poly gloss. The wing was balsa sheeted and glassed the traditional way, but the ailerons were also covered with the .005" G-10


ACP Composites has a great selection and the best prices I've seen.
http://www.acpsales.com/Solid-Fiberglass-Sheets.html


Scott

serious power

Hi Matt,
Again thank you.
No water so as these wings are going to be thin. Though I used to skin foam cores with water thinned PVA with 0 warps - had to stay under the weights or vac for a couple of days and then dry in a cold dark room over a few days. Very light. These were lightened cores - (geodetic pattern panel removal to lighten) for 4st power and film covering - plenty strong.

Based on your response and a jot of recent reading I'm down to a choice between carbon veil and glass.
I've done lots of glassing in the past (20+ years ago) using 1/2oz and two coats of a hard lam,,, resin thinned 50/50 with methanol.
That was different though as was only 700sq'' and I had all other weight totally under control.
This is for a bipe ,full 2M, with thin wings.
So really needs to be light and also really needs to be stiff - dilemma !
I'm leaning towards the veil - your idea re both sides - this will be stiff enough - but ;
Also needs to be ding proof ,reasonably anyway, as assembling these bipes is is an exercise in dexterity especially in the wind - struts hitting off wings etc - adds to the dilemma !

Thus my question re glass !
Can I seal with nitrate, attach the glass with nitrate and then fill with resin or a resin based slurry - thinned with methanol ???
Would the fuel proof dope work for this.
I will make up test samples anyway - just need to know what supplies to buy without wasting cash.

Brian

iron eagel

Brian, the nitrate really isn't that good of a choice for adhesive for the fiberglass. It is perfect for sealing the wood to prevent the epoxy or other resin from soaking into the wood, and an excellent choice as far as applying silk, tissue or carbon fiber veil. If you looking for something a bit more durable the flight skin may be a option to pursue. As far as a ding proof finish for balsa there really isn't anything that will give you that. Carbon fiber veil applied with nitrate and finished with an epoxy paint will give you a pretty nice finish over balsa and as long as your careful as Matt cautioned very lightweight. I have done several planes with the carbon fiber veil and paint and it holds up fairly well but is by no means "bullet proof". Using the veil over sheathing makes a very stiff wing and it is very lightweight as long as you careful with the paint.

serious power

Hi ie,
Thanks.
I've decided to go with the carbon veil - probably both sides - or maybe just some strategic placing underneath as a min.
I will make up test samples , 10 cm sq, to measure weight gain with different application sequences.
It will not be for a while yet but I will try to report back with results.

Brian

MTK

Hi Brian,

Do you mean apply carbon to both sides of a single skin? Or both sides of a wing panel (outside surfaces only)?

If the former, that will not be necessary for a bipe and it will add weight (and strength which is not really required). Consider that your bipe will likely have about 700 squares per wing. Loading will be very low, lower than that of an 1100 square mono. Two wings are more work but I think weight-wise, you can actually come out a little ahead than the typical mono. No reason why a 700 square inch wing can't be built RTF at around 10-11 ounces each and be plenty strong for the application........ Let me suggest another area to shave weight. If you decide to skin with balsa, taper thickness of the skin as I do on my monos. I start the root at 0.065" and taper it down to the tips to about 0.035". That saves 25-30% of the weight of a skin or about 15 grams per 530 square skin. This has been strong and resilient enough for a DLE55 in my Delta. Same technique was used on my Temptress wings 10 years ago which had over 2000 flights before I retired her earlier this year. A lot of sanding of course but worth it to me.....I use the 3 foot T bar sander for the final pass to smoothen whatever bumps of the earlier block sanding.

If you decide to forgo balsa entirely and make sets of glass or kevlar skins, carbon veil on the inside will help stiffen things up. I would use 2.5 oz kevlar (bias cut) and add a double layer from root out to the 40% span line. The doubler can be 1.5 oz glass (ortho cut), Then the carbon veil. This will be considerably more ding resistant and you get to control weight build up. Thickness at the root would be around 0.006" and around 0.004" at the tips.......The four or eight skins may need to be built independently in a vacuum press (which yo already have). I have large 0.010" thick mylar sheets I use on top and bottom to produce a smooth shiny surface. Don't use primer tho. unless you PVA the mylar sheets first. In a pinch, I suppose you can pay the money and buy the glass panels discussed earlier, except you won't have any control over their weight and strength distribution....

There are several inexpensive epoxies....CJ Composites has a good one as does US Composites. The old stand by's, West Systems, MGS, Pro Set, heck even EZ Lam, all work fine but are more expensive.

serious power

Hi Matt,
I will be sticking with balsa skins.
If the skins are stiff enough I can lighten the foam cores more.
Then once built I will/should have stiff wings.
The issue with these thin bipe wings is not really that of load carrying.
Resistance to twist is what I'm after.

I have read your derivative thread.
I also taper skin thickness to the tip - you don't miss many tricks !
I'm hoping to pull a little chord-wise curve in the skins while applying the veil to the inside.
Based on your thread the internal applied veil will weigh approx 15g so say 20g for both wings.
The veil itself will weigh 10g.
I estimate the foam cores at 63g to 85g per panel depending on foam used - will be either 15Kg/m\3 or 20Kg/m\3.
Using the 15Kg variety the total for cores will be 250g.
Removing ; 30% = 75g - 50% = 125g
I will remove at least 30%. - but because of the mount system/ boxed lay-out of the bipe wings (ie the model in the middle and then the out-rigger struts working in both tension and compression) I should get close to 50% out.
The plane will not only be electric it will be contra driven- no vibes,torques, or asymmetric thrust issues to deal with - just flight loads as applied.

Perhaps you could check my inside applied veil weight estimates in case I got you wrong !?
I will do test samples anyway.
Thanks again.

Brian

MTK

Brian

I assume that your two wings will have an area of about 1400 squares, or roughly 10 square feet. For skinning or veiling purposes, the actual area is twice that. That's equal to about 2.3 square yards of area so veil alone (assume your veil is 0.2-0.3 ozs per sq yard) should weigh about 14-18 grams total. Add roughly 10 grams total each wing for dope to help affix the veil to each skin. The affixed veil should add about 35-40 grams total to both wings. Epoxy or gorilla will add its own weight of course which will likely be around 25- 30 grams each panel (two sheets, around 350 squares each). The balsa should weigh around 30 grams each sheet.

If my rithmetic is right, 175 grams for cores, 240 grams for sheets, 110 grams for epoxy, 40 grams for veil. Less than 570 grams for two wings with no substructure added.

The heaviest parts are the sheets. Have you considered 0.75mm thick balsa? With the veil inside, it will be strong enough especially for E-power. No need for tapering. That's what I used on the stab of my DLE55 powered Delta...just an idea unless you've purchased the wood already

serious power

Hi Matt,
I think I'm happy to go with the 1.5mm and sanding - I need the exercise. I have some/most of the sheeting already.
What I do is some of the thinning in advance of sheeting the cores and then the rest while sanding the tip 'block' , LE and TE etc.
I try to stick with 10g sheets (10cm x 100cm) ; = 200g - sanding - so maybe 160g !!
We're on the same page.
My existing wings are over 1000g with no radio - if I can get these out at 750g total ready for radio I'll be happy - if 700g I'll be delighted.
I'm tempted to glue the skins with PVA but I think I'll got with gorilla (PU) to be safe.

Brian

kenh3497

Would the lacqure avaialble at the big box stores used for wood finishing be a suitable substitue for nitrate dope? It has good handeling properties as in it sands easy, dries fast etc. It's also available is gloss, satin etc.

Ken

serious power

Hi Matt,
Ok it seems that I am going ahead with this.
I rec'd a batch of 'virgin' 15Kg foam from the only remaining manufacturer left here after the crash.
They don't normally make it virgin - the norm is up to 5% recycled material, but this always results in hard bits that delay the wire when it encounters them which distorts the cut.
My foam is actually 15.75 Kg//m\3 - damm building reg's .

A former club-mate (he went surfing 3 years ago) has a home-made cnc cutter.
We spent Friday last getting it up and running and by that evening I had a very acceptable sample to take away.
He has some fine tuning to do and when he has time he is going to cut all my cores.

My Sample weighs 70g which, considering that the foam is 15.75Kg, is right on target.
Making a coring template as we speak - 40g - 45g min,, target.

I have sourced Randolph's in the UK - so all looking good.
This will be a slow burner as there is no chance of painting until March or Apr due to the damp cool weather we get here for the next few months- sometimes seem like all the time.

Brian

UAVC

hi...
iam new user at the rcuniverse
very happy.....