1/2A RC speed - such a popular pasttime
04-12-2014, 10:26 AM
#103
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Once I picked out all the plasticine, plywood, glazing putty, and surface coat, it became magically light once again.
Here is a record of the archeological dig this morning. Buried in amongst all the debris was a pristine but slightly sticky Profi .049. I haven't seen it in two months. Being so close to Easter and all, I was scared I'd open it up and find an empty engine-shaped cave.
04-12-2014, 10:27 AM
#104
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Oh btw.. not being highly experienced making molds, today's lesson is "now you know why an opaque surface coat is so handy, dumbass.. you can see the surface irregularities".
Last edited by MJD; 04-12-2014 at 12:56 PM.
04-12-2014, 12:58 PM
#106
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Did okay - a couple of small occlusions on one side, I had an issue with laminating resin kicking off too soon. They are now filled and curing, so once I dress those up I can wax and polish this evening, if the light holds out get a coat of PVA on.
04-12-2014, 09:36 PM
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Hi CP,
Good advice on epoxy layup time. Hot water and mixing up the resin/hardener batches before mixing together works for me.
I do a test mix, while preparing for the 'real' job...
MJD,
Now, you are scaring me !
That plane was 'light as a feather', with the plasticine ! ! !
Try taking a frontal photo of it...I doubt if there is anything to see...
I offer my left handed handlaunching skills...
Need something solid around the CG to hold on to....
This is Epic ! Minimalist at the Maximum !
No kidding, I have seen this plane, and it 'will' go. Dialing it in will be the fun part...
One hour drive away, let me know MJD...
Take care,
Have fun,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team
Good advice on epoxy layup time. Hot water and mixing up the resin/hardener batches before mixing together works for me.
I do a test mix, while preparing for the 'real' job...
MJD,
Now, you are scaring me !
That plane was 'light as a feather', with the plasticine ! ! !
Try taking a frontal photo of it...I doubt if there is anything to see...
I offer my left handed handlaunching skills...
Need something solid around the CG to hold on to....
This is Epic ! Minimalist at the Maximum !
No kidding, I have seen this plane, and it 'will' go. Dialing it in will be the fun part...
One hour drive away, let me know MJD...
Take care,
Have fun,
Dave'crosscheck'Fallowfield
Maac 6437
Unabashed Combat Team
04-13-2014, 05:39 AM
#109
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Yup, thin film times are much longer than anything approaching a sphere. In this case I was down to the dregs of my laminating resin and had none to spare. In the cold basement I have to pull out the heat gun now and then to gently limber things up as I go = recipe for accelerated gelling. Otherwise I would have tossed it and mixed more. Only a small bubble, I filled it with spot putty, wet sanded and waxed it up - all good. Already PVA'ed and ready for layup.
04-13-2014, 12:19 PM
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Some years ago at the company I worked for (where me made adhesives and resins amongst other stuff) we gave a sample of neat epoxy resin and a couple of aliphatic amine curatives to a PhD researcher working on a pet project, with clear and strict instructions on batch size, temps etc.
Several days later he called in a panic as his salad bowl with a quart of epoxy and very reactive curative sailed past the 400 degree mark and was stinking/smoking out his workshop.
"Didn't listen, did you?" was our response.
I work in small batches and toss the material when it gets to the point where I should. But I was running out so I stretched it a bit too far. The only issue was not wetting out two little spots which were easily repaired.
Just back from my assigned chores for the day, got my release signed, and now down to the workshop to lay up a first cowl!
Several days later he called in a panic as his salad bowl with a quart of epoxy and very reactive curative sailed past the 400 degree mark and was stinking/smoking out his workshop.
"Didn't listen, did you?" was our response.
I work in small batches and toss the material when it gets to the point where I should. But I was running out so I stretched it a bit too far. The only issue was not wetting out two little spots which were easily repaired.
Just back from my assigned chores for the day, got my release signed, and now down to the workshop to lay up a first cowl!
04-13-2014, 02:26 PM
#112
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Ha ha! Done.
I fully expect to reject this one but who cares. It's curing by the wood stove now, I have to keep an eye on it to catch it at a nice green stage for trimming flush to the mold face.
UPDATE:
I trimmed the halves, joined them with a 1/2" wide strip of cloth, set that for a nap in front of the wood stove again, and later this evening popped out a cowl. Now, I won't post a picture - this was a quickie job, with crappy resin and needs more glass and joined with 15 minute. But it looks like the pattern and fits the airframe nicely. The sole purpose was to pop out a reasonable facsimile of a cowl and test fit it. Looks good so far. This one came out at 5.1 grams, I expect a flight ready cowl to come out more like 10 grams. I "budgeted" 15 grams earlier so no guilt in adding some material. I
I did screw in the engine, fit the cowl, fit a prop, and mount the wing. At this point missing the Rx, battery and fuel bladder, it feels more like the engine is missing it is so light.
Glad I made the mold, there is a 1cc version of this FIRE motor too. .061 vs .049 is 25% more displacement, not a small difference.
I fully expect to reject this one but who cares. It's curing by the wood stove now, I have to keep an eye on it to catch it at a nice green stage for trimming flush to the mold face.
UPDATE:
I trimmed the halves, joined them with a 1/2" wide strip of cloth, set that for a nap in front of the wood stove again, and later this evening popped out a cowl. Now, I won't post a picture - this was a quickie job, with crappy resin and needs more glass and joined with 15 minute. But it looks like the pattern and fits the airframe nicely. The sole purpose was to pop out a reasonable facsimile of a cowl and test fit it. Looks good so far. This one came out at 5.1 grams, I expect a flight ready cowl to come out more like 10 grams. I "budgeted" 15 grams earlier so no guilt in adding some material. I
I did screw in the engine, fit the cowl, fit a prop, and mount the wing. At this point missing the Rx, battery and fuel bladder, it feels more like the engine is missing it is so light.
Glad I made the mold, there is a 1cc version of this FIRE motor too. .061 vs .049 is 25% more displacement, not a small difference.
Last edited by MJD; 04-13-2014 at 08:18 PM.
05-13-2014, 07:41 PM
#113
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Finally I reconstituted a half gallon can of good laminating epoxy and returned it to the world of the living, so tonight I laid up what I hope is the real cowling. The mold is sitting in a 140 degree oven now all clamped up, I trimmed the sides and joined it about 30 minutes ago. I want to stay up to play with it, but really ought to get to bed being a work day and all.
05-14-2014, 08:11 PM
#114
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Popped the cowl out with little trouble this morning, washed off the PVA in the kitchen sink, and started hacking off all the parts that don't look like a cowling. It ain't perfect, but it is rugged, and it will work. I'll do a little filling and shaping here and there, primarily in the intake area and where the nose that is supposed to blend in nice and snug to the groove in the drive washer, seems not to have worked according to plan. Nothing a bit of putzing and sanding and mixing goo won't fix.
And it is half the weight I had estimated, 7.1g. One outer layer .75oz glass, two small strips .75 oz for the fuel line blister, one main structural layer 6oz, doubler strips 1/2" wide 6oz over the flared mating edges. Feels tough enough to me. So that's about a 1/4 ounce off the total.. yeehah.
And it is half the weight I had estimated, 7.1g. One outer layer .75oz glass, two small strips .75 oz for the fuel line blister, one main structural layer 6oz, doubler strips 1/2" wide 6oz over the flared mating edges. Feels tough enough to me. So that's about a 1/4 ounce off the total.. yeehah.
05-15-2014, 04:45 AM
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And the speed tape covering the hole something unknown punched in the wing (#$%#%) just adds a touch of class. I am pleased with the cylinder fit, will need a little baffling to get the air up to the cylinder rather than sneaking around the crankcase.
05-15-2014, 07:02 AM
#118
Looks clean. The control line speed guys usually leave the head sticking out for cooling as that is the hottest part. We used to have the tubing exposed where you have the bump on the side. Refilling the bladder was done right there. I have a pic here, It isn't mine just kind of an average better one.
05-15-2014, 06:26 PM
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Looks clean. The control line speed guys usually leave the head sticking out for cooling as that is the hottest part. We used to have the tubing exposed where you have the bump on the side. Refilling the bladder was done right there. I have a pic here, It isn't mine just kind of an average better one.
05-16-2014, 04:10 AM
#122
.21 Proto speed, I think. Usually they use a Novarossi .21 2000. No pipe allowed, just a straight stack up to 6" I think. There is also a regional North West region that has an F2D speed class. They use the combat motors on a profile plane. I have looked for results but have been unable to find any. I guess it isn't too popular.
Last edited by aspeed; 05-16-2014 at 04:13 AM.
05-16-2014, 09:03 PM
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Tonight I ground/sanded off some offending bits around the intake, wrapped the intake and prop driver in T-tape, then fit the cowl on to the index marks and taped it in place. Then mixed up some epoxy faring putty - nice light microballoon filled stuff - and buttered up the areas I want to reshape and fair in tighter to the engine. Now basking in a warm place overnight, I must keep my paws off it until fully cured..!
Gliding season has started too, reckon I'll be going for my checkout flights Sunday. That's where I'll fly this thing.
Gliding season has started too, reckon I'll be going for my checkout flights Sunday. That's where I'll fly this thing.