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1/7 Harvard Conversion

PostPosted: Tue Apr 16, 2013 11:05 am
by Dale
(Is it wrong to have 2 build threads on the go?)

Anyway, let me tell you guys a story.

A few years ago, i decided it was time to move up to bigger models. (Bigger flies better right?) Life up to that point had consisted of 40-60 2 stroke glow, and a bunch of smaller electrics.
As a lot of us do, i have a soft spot for the old Harvard, having been watching them since being a lad, and so some money was exchanged for the 1/7 scale World Models Texan ARF at Top RC.
I acquired an RCV.91, and had much fun tinkering with this, and eventually flew it, and had great delight in flying it too, this model flew really well, can't complain about her flying characteristics.
However, her time came too early, with a deadstick on takeoff, the resulting forced landing pretty much destroying the nose, cowl and wing center section.
This setback made me ever more keen, being left with a feeling of "unfinished business".
IMG_3086.JPG
#1 Pre-flight
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#1 In Flight
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Sometime more recently, I won a TM auction for the same kit NIB, from a kindly gentleman in Chch. - this is a story in itself:
The auction closed like a day before the big earthquake, and naturally he had more pressing issues to deal with than send out trademe packages. However after a couple of weeks, he emailed me to say that the plane was fine, and at his first opportunity, he would get it sent up. Almost as an aside, he mentioned that his house was heavily damaged (up on the port hills i recall), wasn't allowed in it, but the garage (where the box was) was ok.
Eventually it arrived at my place, and all good there.
So, my good man (sorry i have forgotten your name), i hope you have been treated well during the rebuild and life has returned to normal for you. (If you read this, drop me a line on here).

So this second airframe went together, including the use of some parts from the original.
By this time the RCV had disappeared, and on the nose went a pumped OS .91 4st,, with onboard glow driver.
We had a couple of good flights on it, then early on the third, she went in, victim of radio failure. (Since identified and resolved).
The amazing thing is she went in vertically into one of the large drains that surround our field, so the mud and long grasses absorbed the impact forces. Other than an good soaking, there was only little damage, and nothing structural.
The engine was removed and cleaned up, and now has a home in the nose of a P-40.

This unfortunately (second time!) left me very determined to get her flying again, so her time has come. (I think i also owe it to the TM seller after all his efforts!)
DSC01258.JPG
The bits to put back together (or make a biplane from?)
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This time we're going different:
Colour scheme will be different, i think i've done my dash with the classic 078.
Every last piece of stupid iron-on plastic covering will be finding a new home in the bin, replaced with something a bit more "genuine"
It will NOT be glow powered.
Along the way, we'll be making a few improvements and adjustments, hopefully to come out the other side with a reliable, good looking, and good to fly model.

Re: 1/7 Harvard Conversion

PostPosted: Sun Apr 21, 2013 3:12 pm
by Dale
Well i have stripped the fuse, and started the repairs.
One day soon i'll meet up with a mate with a laser cutter and whack out a couple of new bits to reinforce some damaged areas in the framing in the front fuse. (Wing seat mounting, doublers, and will put a new skin on firewall)
Managed to get the factory-glued rudder and elevators off, and have pulled off all the iron-on off with some assistance from the Missus' hair dryer.
Build quality looks pretty good on this model, certainly no less than the Top Flite kit i've been working on for years. Wood of apparently suitable quality, with glue in the right places. Pretty happy, and much better than some of the rubbish ARF's i've played with over the years.
Once the wooden repairs are done, this fuse assy will be getting fibreglassed.
Weight of this assy as pictured is 666 g.
DSC01259.JPG

Interesting, note the root fairings and taiplane fairing are fibreglass, as are several other bits on the wing.

Re: 1/7 Harvard Conversion

PostPosted: Tue Apr 23, 2013 8:27 pm
by Dale
I spent a couple of hours reminding myself how to draw with cad, and came up with this:
Harvard Parts.jpg

This was followed by spending last night bugging me mate learning about laser cutting and related taskings.
The end result is we have these:
DSC01310.JPG
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New fuse doublers and firewall (The large ply circle) is the short explanation. The firewall had a few too many holes in it to be comfortable moving forward, as i am not replacing the original engine with the same. - The evidence points to this airframe had the RCV bolted to it at one point, so slightly confusing the story presented in the opening post, and adding at least 4 more holes to the "swiss cheese" that called itself a firewall.
A small fettle with the sandpaper and file, and we have this:
DSC01313.JPG
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This is one of me new doublers in approx position, prior to gluing.
It goes all the way from the rear of the firewall (you can make out the blind nuts still in the firewall to the left), past the wing "dowel" slotted former, doubling the wing seat, all the way to the back wing saddle, and note the slot for the wing bolt plate to the right. (this had broken out on both sides). (ok i lied when i said "nothing structural" was broken).
You'll note the bottom of this new doubler is not "wing shaped", this will be manually trimmed to exact shaped once glued in postion.
You may also note that the fuse is in process of getting spackled, wood repairs are completed. Will be glassing fuse once have finished adding the new wood parts.

Re: 1/7 Harvard Conversion

PostPosted: Tue Apr 23, 2013 8:30 pm
by Dale
Re laser cutting, it's only fair i give a plug:
Milestones Trophies and Engraving, details at http://www.milestonesengraving.co.nz/
Check 'em out if you need any trophies, engraving, awards etc etc.

Re: 1/7 Harvard Conversion

PostPosted: Sun Apr 28, 2013 9:20 pm
by Dale
Slight tangent:
It will NOT be glow powered.

Conveniently, this arrived in the post the other day from Mike's Chainsaws & Outdoor Power (http://www.mikeschainsawshop.co.nz)
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So my first foray into petrol (gas) begins with the GT17 from NGH. (17cc)
-Separate cylinder head and piston liner
-Genuine Walbro WT carburetor
-Remote REXEL CDI ignition system
-Max Power: 1.8 HP @ 12,000 r.p.m.
-Recom. Prop Size: 13 x 8 - 15 x 8
-Net Weight: 730 gram

Appears to be a sweet little engine, certainly looks good. Brian Winch gave it a glowing review. http://www.justengines.co.uk/acatalog/GT17reveiw.pdf (note is 15Mb). Is designed from the outset to be a replacement/alternative for the .91 4st glow motor.

I spent the day giving this about an hour of bench running as per the instructions, which took a surprising amount of getting organised for.
As i haven't had gas before, i needed a field tank, oil, pump, tubing, filters etc etc.
Also needed to organise the test stand, as well as the hardware required to get it running, like a battery for the ignition system, switch, prop etc.
Late in the afternoon i finally got it sorted, and she roared into life without issue.
Put a couple of tanks through it (about an hour and a half of runtime) at 16:1, the first hour without muffler, on a 13x8 prop. Normal fuel is 20:1 which it will go on hence forth, and probably fly on a 14x7.
All well with this, real happy with the operation. Have been doing a lot of reading on RCGroups about gas engines. Next time it runs it'll be bolted to a firewall.

Re: 1/7 Harvard Conversion

PostPosted: Wed May 01, 2013 5:37 pm
by Dale
Fuse repairs and additions are complete.
New wood items are in, the new firewall skin i had no choice but to epoxy on, as the firewall was of course already epoxy coated for fuel proofing.
The firewall backing and fuse doublers were PVA'd in.
Weight of fuse now is 861g, so added 195g with the new bits and repairs. Quite a bit i agree, but this is getting a larger and heavier motor than it was perhaps designed for, so i feel increasing the rigidity and strength is a worthwhile exercise.
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New bits in
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Have been going over it with the filler and final sanding
Next step will be to seal the wood, to prevent it soaking up too much epoxy during the glassing stage. This was something i didn't do on the Typhoon, and thus added a not inconsiderable amount of weight in terms of excess epoxy. Followed by glassing proper.
DSC01452.JPG
ready to begin the glassing process
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Re: 1/7 Harvard Conversion

PostPosted: Wed May 01, 2013 9:30 pm
by DH100
You are certainly on the right track with sealing the balsa before glassing. I'll interested in the results you get with your petrol engine.

Good stuff.

Brian

Re: 1/7 Harvard Conversion

PostPosted: Sun May 05, 2013 3:25 pm
by Dale
Cheers Brian.

Re sealing, I was recommended to look into Wattyl's Estapol Hi-Build sanding sealer, so i did.
Bought a small tin, and gave the entire fuse a coat.
Interestingly, the wet coat apparently weighed some 20 odd grams, which then when dried weighed only 14g. After a quick sand, it was down to 11g. (so my $20 trademe scales tell me - probably has all the accuracy of a wooden ruler)
Image
(Pic stolen from Wattyl's website)

So next stage is glassing, and rubbish weather this weekend has given me the incentive to get on with that.

I got some resin and cloth and some other bits and pieces from NZ Fibreglass Ltd (via trademe), and set to work.
The front fuse i've done with 48gm/m2, from the firewall back to the front of the cockpit opening at top and rear of wing seat area, to hold the repairs and bits and pieces together, including wrapping the cloth around onto the firewall and over the wing seat and onto me new doublers.
The mid and rear fuse, and the find and tailplane are all being done in 25gm/m2.
I thin the resin with around 1/3 straight methanol (cause i have plenty of this lying around), makes it go on real easy, and then the methanol evaporates out in minutes. Followed up by the tissue paper excess absorber trick.
Hoping to do a bit a day as the previous part dries off.

Once it's all done i'll mix up another batch, with some microballoons mixed in, to fill the weave and strengthen it up a bit more.
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Glassing in progress in what was once the spare room in the house. Now resembles a modelling shed!
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Re: 1/7 Harvard Conversion

PostPosted: Sun May 12, 2013 11:26 am
by Dale
Glassing of the fuse continues, which pretty much means spend 10 min getting organised, 10 min putting the piece of glass on, 10 min cleaning up, and then 23 hours and 30 min waiting for it it dry to do the next bit.

In the mean time, i thought i'd start playing with the next bit, which is the wing centre section.
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Wing centre top

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Wing centre underside

This has had a repair previously but this time is pretty much good to go, after stripping the covering and a tickle up, will be glassing.
The wheel bay area (painted yellow) is factory fibreglass.

The only major mod i have planned here is to hinge the flaps in a different manner than factory, to enable scale flap deployment of flaps at something like 60°, rather than the typical arf value of way-not-enough.

Re: 1/7 Harvard Conversion

PostPosted: Tue May 14, 2013 8:30 pm
by Dale
Colour Scheme:
Last time i was in Chch, i dropped around the Air Force Museum, as was pleasantly surprised to see the Havard on the the pole had been repainted and looked real shiny, and i quite liked the scheme, and knew straight away that this was the scheme my bird would go in when she got back on the building bench.
DSC08054.JPG

Inside said museum, i picked up a great paper model of her, which gives me more detail - in short, if it is printed on here, it will be represented on mine. means i get the main detail, without going "overboard", i can't bring myself to put on rivets and stitching etc...
Havard1.jpg

Havard2.jpg


In short, painted silver, with the bits of orange (dayglo) around the place, with markings etc will likely be vinyl cut.

Re: 1/7 Harvard Conversion

PostPosted: Sun May 19, 2013 8:49 pm
by Dale
Fuse = done.
Completed the glassing, (including the second fill coat of filler epoxy).
Gave it a rubdown, then hit it with a good coat of automotive highbuild primer.
Touchups where required with a second coat and/or a single pot filler compound. (I'm not a fan of automotive "bog" fillers, just too hard they are a pain) and sand all over and we are ready to paint.
Painting will wait though until all the various bits are done, then will hit it all at once.
If my math is correct, the sealing, glassing, filling, priming etc came to something in the region of 50-60g. Perhaps a little more practise would result in lesser numbers, but thats not a lot of weight over a model this size.
DSC01472.JPG
Fuse in process of final sand

Re: 1/7 Harvard Conversion

PostPosted: Sun May 19, 2013 8:56 pm
by Dale
So the next bit I'm tackling is the wing centre section.
Pics uploaded previously, if you look carefully you'll note one of the alu tubes was bent, this has been straightened.
Am in process of filling and fairing this, but i think i better put some thought into the u/c, in case i need to do some wood mods to fit.
Will be using some form of electronic servoless retracts.
Also got the flaps challenge too.
Will glass this centre section, both top and bottom, in 48gm/m2 glass. It's sheeted pretty thin, have already broken it twice though rough handling, and this area will get a lot of knocks during transport etc.

Re: 1/7 Harvard Conversion

PostPosted: Mon May 27, 2013 8:50 pm
by Dale
Flaps.
I want to hinge the flaps a bit better than factory, being standard centre hinged, with bevelled leading edge, giving a big ugly gap, and, only about 30° of travel. This means i needed bottom hinged.
I spent ages pondering this, checking out different hinge types, but kept getting stumped with the dual challenges of split flaps, and them flap sections only being about 9mm thick. This prevented me putting robart hingepoints in, which i am using on other control surfaces. Eventually decided to go for external hinges. (Which are not scale, but will look cool).
DSC01488.JPG
Hinge

Made up new flaps, about 6 lams of 1.5mm and recessed the tabs of the hinges into the flap and trailing edge.
Epoxied them in place, then will glass right over the mounting tabs to extra security.
Pics prior to glassing. Have since pulled the pins from the hinges to seperate them for glassing and painting.
End result looks pretty good, and looks and works better than factory = success!
DSC01489.JPG
Closed flap

DSC01492.JPG
Flaps down! (a few degress excess, but something like this)

Also working on the remainder of the centre section, giving it a tidyup, and will glass soon.
Have identified the Eflite 60-120 retracts will "bolt in" without mod, so have ordered a pair, these are in the post now, once they come, will confirm the fit then finish up and glass the centre section.

Re: 1/7 Harvard Conversion

PostPosted: Mon May 27, 2013 9:03 pm
by Dale
Was also tinkering around with the fuse, starting to think about all the other bits that have to happen prior to painting.
The Havard has a couple of intake scoops immediately aft of the cowl, one underneath, and one on port side.
These are pretty rough fibreglass moldings, i'm just gonna give them a quick sand then put them back on. Originally just stuck on, but now at least i can blend them in with some filler. (are a bit overscale i think, but i can't be bothered making uber scale bits like this! "Cartoon Scale" is my motto :D
So it goes like this:
Mount against cowl aft edge.
This meant i need to know exactly where the cowl is to mount. (The original mounting location disappeared in the fuse/firewall repairs)
This meant i need to know exactly where the engine must be to mount the cowl
This meant i need to assemble the engine on the mount.
This meant i found out the engine mount i is actually incompatible with the engine at the mounting distance required.
This also identified the fact that the muffler won't fit in the classic position, as the rear of the muffler will hit the firewall. Thankfully, i can reverse the muffler, (have it pointing "forward" alongside the carb, and it will fit sweet.

So to glue these on, i need to find an engine mount!
DSC01494.JPG
Port scoop in approx position, with original cowl. (That's a whole nother job to fix and fit!)

Re: 1/7 Harvard Conversion

PostPosted: Mon May 27, 2013 10:01 pm
by spitfirekid
Looking very nice Dale, im impressed!
and the perfect paint scheme you have chosen as well
Cant wait to see it at the field :D

Re: 1/7 Harvard Conversion

PostPosted: Tue May 28, 2013 7:43 pm
by Dale
Thanks for the reply, it's a bit of a ghost town around here, so good to see some life, and know people are reading!
Yeah, definitely looking forward to having this one on the field, hoping to have it flying early Aug. (Hoping to take it to Forsyth, so need it bedded in prior).
My next build thread will "suit" you a bit too.

Re: 1/7 Harvard Conversion

PostPosted: Tue May 28, 2013 9:16 pm
by spitfirekid
sounds interesting,, thinking out loud here ,,,,,Spitfire,,,,,,,,
im still building the mk2b spitfire that i showed you and are now also building same scale size Hurricane, its a mk2 but will be removing canons and fitting in the 8 browning machine guns and turning it into a mk1 so it keeps in with my Battle of Britain era planes. and of course in the colours of one of our boys machines,

Re: 1/7 Harvard Conversion

PostPosted: Mon Jun 03, 2013 8:45 pm
by Dale
Progress this week hasn't amounted to a lot
2013-06-03 20.28.40.jpg

Fuse, (inverted).
Note the new flap in grey primer, and the scoops now fitted and being faired in.
The cowl is from a Top Flite 60 sized Corsair, which is a very close fit.

Regarding cowl, i have decided not to refit the original, (or replace it with like), as it is a pretty crappy product, and the wrong shape and size.
Therefore, will be making my own, a job to get to in the next couple of weeks.

Raided the spares box, found a engine mount that with a slight tweak, am using, which puts the rearmost part of the engine only a few mm clear of the firewall, so i can go somewhere towards making the front end slightly more scale. (Out of the box, the ARF nose is pretty long, with a really long cowl. The real Harvard has quite a short cowl.)

Spending a lot of time going between a couple of great references websites: (both NZ too) http://rnzaf.proboards.com/thread/17601 and http://www.kiwiaircraftimages.com/harvard.html check 'em out if you wanna see some excellent pics.

Re: 1/7 Harvard Conversion

PostPosted: Tue Jun 04, 2013 8:20 pm
by DH100
I agree with the comment about the colours ...great choice. Looking good Dale.

Re: 1/7 Harvard Conversion

PostPosted: Sat Jun 08, 2013 11:24 pm
by Dale
Retracts arrived. Pictured is one of them, with the original beside. I've simply pulled the leg out of the original, and fitted to the new. Pretty simple in theory. (Needs a sleeve, but them's details).
IMG_20130608_094616 (Medium).jpg

Only needed a couple of minor adjustments to the sheeting around the mount, and a quick buzz inside the slot to clear the retract motor, and they fit right in. They even work too!
IMG_20130608_111959 (Medium).jpg

Doors will come later on.
Now that this part is sorted, i can glass and fill etc this centre section and move onwards.