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Old Nov 27, 2012, 07:35 AM
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J Morgan's Avatar
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Just an awesome balsa build. Really respect the patience required on a build like this. Great work, keep it up!

J
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Old Nov 27, 2012, 10:03 AM
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Doug Bartley's Avatar
Canada, ON, Owen Sound
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Hi eye4wings, J Morgan: I do build in the house, so no shoveling snow to get to the garage! I end up running out to the garage (heated-hehe) to do machining and welding, drilling bigger holes etc.
Right now, I seem a little stuck, we made our own cowls, much shorter than the available one from BT, that leaves a lot of real estate behind the cowl not covered where it blends into the wing. I am currently fitting up a cowl, motor assly to get the actual opening. Another big mod that up front seemed so simple and straight forward. Not so simple. Getting a 7" long cowl to sit still to match a 4 1/16th" spinner backplate is a test of patience!!
J, thank for the kind words, all three of us are looking forward to getting these Mossy's out in the spring. Detailing such you have done makes or breaks the build, time and patience is rewarded with outstanding planes. I've been watching every day on the 119, awesome workmanship. Doug B
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Old Nov 28, 2012, 07:53 AM
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eye4wings's Avatar
Ware, herts. U.K.
Joined Sep 2008
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Cowls can be so much of a pain Doug! So much that I have almost given up on them! I have gone back to building up from balsa - it's another way of using up all the offcuts that lie around for just such a job.

Just last week I built up the cowl for the Fox Moth. Installed engine, wrapped tube round engine to act as spacer, added a couple of thicknesses of soft 1.5mm balsa - that's the front done and in line - bent another bit of soft balsa around to join the nacelle sides (in 1.5mm ply) then all the infilling and shaping from scrap.
It's a bit of trouble but no more than engendered by forming a blank to mould from, forming the cowl, cutting and fitting, then trying to paint it the same colour as everything else.
And in the event of a nose-over it's just as easy to fix.

How about extending a balsa skin from the cowl and fitting part formers in afterwards? Just getting the sides pegged onto it would at least give you a start and hold the cowl in place while filling in top and bottom.
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Old Nov 28, 2012, 10:25 AM
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Doug Bartley's Avatar
Canada, ON, Owen Sound
Joined Oct 2008
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Hi eye4wings: The last three twins I built all had built up balsa cowls. I hate working with fiberglass, so used methods very similar to yours to make them.
They all worked out fine, with a little effort.
I must have been having a bad day Mon, I simply couldn't get the cowl to sit still. Yesterday I came back to it, attached some scrap balsa to pin to, and finished the hard points in 20 minutes or so. So with the process semi perfected, the second one will go much easier!
maybe I just need a little more sleep. hehe. I'll post a pic later, still trying to inhale the first morning coffee. Doug B
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Old Nov 28, 2012, 11:19 AM
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Ware, herts. U.K.
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Great stuff!

Coffee or no, another problem solved is an encouraging component of a day.

Rock on!
Robin
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Old Nov 28, 2012, 09:11 PM
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Doug Bartley's Avatar
Canada, ON, Owen Sound
Joined Oct 2008
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Because both Ken and Paul have their fuselages all but complete , I decided today was a good day to make antenna masts. I recieved the aluminum latches from HK yesterday. So it was out to the shop to lathe out the parts!
Pics show the first cowl mounted, clearance on backplate is a little over 1/32", fiberglass spinner should be flush to cowl od.
The original cowl went right back over the wing, ours leaves a 4" opening to be filled in, balsa stick show the approx shape at centre. This will be fun!!Doug B
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Old Nov 29, 2012, 01:17 AM
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Liverpool, England
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Nice Doug, love the idea of hiding the latch with an antenna mast, is it to release the cockpit hatch?
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Old Nov 29, 2012, 08:20 AM
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Paulofthenorth's Avatar
Owen Sound, Ontario
Joined Jan 2006
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great progress

Hey Doug,

Looking good. I've just finished putting the top skin on wing #1. Your advance work and advice from Ken continues to make it easy for me.

Paul
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Old Nov 29, 2012, 10:58 AM
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Canada, ON, Owen Sound
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Quote:
Originally Posted by heli_madken View Post
Nice Doug, love the idea of hiding the latch with an antenna mast, is it to release the cockpit hatch?
Hi Ken: Yes, the antenna mast, aka latch is placed at the rear hatch area, effectively doing two jobs. The antenna itself will be made from some stretchable cord to allow latch movement. Doug B
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Old Dec 05, 2012, 08:21 PM
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Canada, ON, Owen Sound
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There doesn't appear to be a lot of progress here, but I've worked on these d...med wings every day!! Filling in the spaces behind the fiberglass cowl has been quite a project. Installed wing tubes, servos for the LG doors, sheeted in the wing bottoms.
Tonite I decided to take a little break from balsa, so carved out the nacelle intakes from blue foam. They'll be attached to the glass cowl after epoxy coating. Need to pick some spackle tomorrow, mine went hard in the tube.
Ken and Paul are both working on their Mossy's as time permits, its a busy season for both guys. Here's some pics. Doug B
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Old Dec 06, 2012, 02:09 AM
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eye4wings's Avatar
Ware, herts. U.K.
Joined Sep 2008
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Nice tidy intakes there! - Looks like you enjoyed making them. Clingy blue dust everywhere now though....

Which prompts me to wonder about cooling air for the motors (not the dust - the intakes!). It's a problem getting any with Merlin-engined fighters so I'm guessing the motors will be well oversized so as not to get more than warm.
Outlets are even more of a problem since there are only the exhaust stacks on the full-size.

I do wonder about those props though.
They cost the earth and come with those prissy little trendy tip extensions that seem to be in fashion at the moment when no WW2 aircraft had them. I suppose the manufacturers think we can always sand them off... when I say 'we' I mean modellers in general - not me personally, having spent an hour and a half yesterday extending the hub of a stock Zinger 15" x 10" wood prop and rounding the tips to get to a scale-looking prop for a DH Fox Moth - it seems to matter to my eye not to have some feature that immediately grabs the eye as being 'off'... how sad am I ?!

Sorry about that mini-rant! Hope you don't mind my occasionally jaundiced interjections.

Your three Mossies are going to be quite the show-stopper and I am sorry that I'm an ocean away and won't see them fly except by video.
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Old Dec 06, 2012, 03:24 PM
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Doug Bartley's Avatar
Canada, ON, Owen Sound
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Hi eye4wings: While the motors are slightly oversized, we have devised a plan to get air in to the motor. Our exhaust will have the shrouds typical of some models of Mosquito's to hide the exhaust fires. The front end of this shroud will be blocked off at approx 50% and holes cut thru the cowl to let air in. Air outlet will be adequate we think thru the nacelles around the LG/ doors.
It may be possible to have an air exit on the inboard nacelle.
The propeller mounted in the last pics is a 16/8/3 blade EMP. The cost of each EMP was $11 delivered Ebay seller. They come far better balanced than MAS props. Several have balanced perfect as sent. I really wish they made more sizes. I have not run any tests with these yet.
Original plan is to run Master 16/10/ 3 bladers. If the EMP look suitable, I'll round out the tips. A while ago I modified one this way, it made no difference I could see to flight behaviour. Time will tell. Doug B
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Old Dec 06, 2012, 08:19 PM
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Paulofthenorth's Avatar
Owen Sound, Ontario
Joined Jan 2006
68 Posts
progress report

Nice progress on the cowls Doug.

I have my second wing built and both are fitted to the fuse with the wing tube installed with the wing attachment bolt and alignment pin installed. Top and bottom views are included in the photos, along with hatch on and off.

Works as planned!

Paul
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Old Dec 07, 2012, 02:33 AM
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eye4wings's Avatar
Ware, herts. U.K.
Joined Sep 2008
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Quote:
Originally Posted by Doug Bartley View Post
Hi eye4wings: While the motors are slightly oversized, we have devised a plan to get air in to the motor. Our exhaust will have the shrouds typical of some models of Mosquito's to hide the exhaust fires. The front end of this shroud will be blocked off at approx 50% and holes cut thru the cowl to let air in. Air outlet will be adequate we think thru the nacelles around the LG/ doors.
It may be possible to have an air exit on the inboard nacelle.D
I have a similar situation on my (still unfinished) Pe-2 - but worse because the exhausts are unshrouded. What I have had to do is use the mainly hidden from view inner side of the nacelles to make them into rather inefficient venturi tubes with an intake slot just aft of the spinner and an outlet bulge formed by splaying the side sheeting out at the point you have it still open at about half wing chord to positively drag the air out of the nacelle. I didn't think the gaps around the gear doors (even with my poor building accuracy) would do the job as they are not at a point where there is sufficient difference in air pressure inside to out in my estimation.
I will be interested to see how your strategies work out as it may well affect my own build (eventually!)

Quote:
Originally Posted by Doug Bartley View Post
The propeller mounted in the last pics is a 16/8/3 blade EMP. The cost of each EMP was $11 delivered Ebay seller. They come far better balanced than MAS props. Several have balanced perfect as sent. I really wish they made more sizes. I have not run any tests with these yet.
Original plan is to run Master 16/10/ 3 bladers. If the EMP look suitable, I'll round out the tips. A while ago I modified one this way, it made no difference I could see to flight behaviour. Time will tell. Doug B
That's a surprisingly good price Doug! Not that I use many non-wood props since I took up making my own multi-bladers - if they get broken they're waste, whereas a wooden prop can be repaired. The MAS three-blade props are serious money. The cost of three 2-blade ones is more to my liking as source material for the pair of 3-bladers.

Robin
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Old Dec 07, 2012, 09:33 AM
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Doug Bartley's Avatar
Canada, ON, Owen Sound
Joined Oct 2008
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Quote:
Originally Posted by eye4wings View Post
I have a similar situation on my (still unfinished) Pe-2 - but worse because the exhausts are unshrouded. What I have had to do is use the mainly hidden from view inner side of the nacelles to make them into rather inefficient venturi tubes with an intake slot just aft of the spinner and an outlet bulge formed by splaying the side sheeting out at the point you have it still open at about half wing chord to positively drag the air out of the nacelle. I didn't think the gaps around the gear doors (even with my poor building accuracy) would do the job as they are not at a point where there is sufficient difference in air pressure inside to out in my estimation.
I will be interested to see how your strategies work out as it may well affect my own build (eventually!)



That's a surprisingly good price Doug! Not that I use many non-wood props since I took up making my own multi-bladers - if they get broken they're waste, whereas a wooden prop can be repaired. The MAS three-blade props are serious money. The cost of three 2-blade ones is more to my liking as source material for the pair of 3-bladers.

Robin
Hey Robin, my original idea for air to the motor involved using the front half of the carb intake with some 1/32ply ducting bringing the air forward and up to the motor. That was squelched when the idea of exhaust shrouds being used. The nacelle is 27" long overall, so its inside volume should look after the cooling area. Thats the theory here.
I used to buy the props from Hobby King, their price was $5.50, but shipping put them at the $10 mark! They no longer sell them, thats OK, the Ebay seller is faster. Doug B
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