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Thread: How do I make this part?
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23rd April 2009, 10:21 PM #16
malb - thanks for the post - yes it's a very good engine! I have been out to Rotec and had a look at their manufacturing setup. Very nice CNC work and they have used some very clever modern techniques to produce a fantastic engine. Unfortunately even at 110hp (advertised) it doesn't produce the thrust I need. Even their 150hp model is too light weight I'd need around 180-220hp at 2400rpm to get the thrust needed. Although Rotec claim (from memory) it will swing a 92" prop I have heard that around 84" is the limit for good performance. This engine is very popular for the light weight replicas made of modern materials and slightly smaller (7/8th scale). They look great and handle better than the original. BUT I'm Like one of those people who think a E-type Jag is a great car to own - mongrel to work on and no modern conveniences but that's what fires my rockets!
The gyrosopic procession is a real problem with the Rotaries. Although I think the full-loss oil system is worth a mention. Essentially you fill the oil tank with castor oil and as it lubricates, the engine's rotation flicks it out into the air stream with no scavanging back into the oil tank. Often this was straight into the pilot's face (another reason for the scarf - to wipe oil off your goggles). I guess some of the old-timers here know what happens when you ingest too much castor oil? Combine that with high-g maneouvres...it's no way to fight a war...
I have access to the original engine drawings but that's really a last resort. Although they have a very distinctive sound I do hope someone like Rotec make a bigger engine for replicas like mine.
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23rd April 2009, 10:25 PM #17
Close - the main reason is that you can vary the prop's pitch depending on whether you want to climb or cruise. Before their invention you had to optimize the fixed pitch prop for one or the other or somewhere in between (meaning you didn't climb OR cruise well!).
It would be a complication that I'd try to avoid - this is a fairly light airframe and variable pitch props add a bit of weight.
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23rd April 2009, 10:43 PM #18
Thanks! It will be a slow project though - budget and time constraints mean it will be trickle fed over many years. However, I will try to post as much as I can. The main forum I post in for this sort of thing is at http://www.theaerodrome.com. On the replica aircraft forum you will see some amazing projects much more advanced than mine (try this one from Melbourne: http://www.theaerodrome.com/forum/re...e-project.html)
Once I have a few pics I'll set up my own web page.
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24th April 2009, 11:01 PM #19Novice
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Omg!!
Hi brinesharks, Great project! I'll be following this with much interest. I have a Homebuilt project in its absolute infancy..( planning stages) so your links were made to order, thanks.
I take it aircraft grade spruce is a pretty rare commodity these days, can you give any tips about its availability?.
most excellent... I'm clad I found this forum
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25th April 2009, 12:30 AM #20Senior Member
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If there are lots of custom parts, a CNC mill might be nice!
I was fascinated by the parts one can make on a CNC mini mill - see for example at the small extreme:
http://www.minitech.com/Last edited by blouis79; 25th April 2009 at 12:32 AM. Reason: typo
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25th April 2009, 08:29 PM #21
Hi BrettG - what project are you looking to start? Aircraft grade spruce is still available out of the US and some parts of Europe. But if you are registering experimental you just need to use materials that are suitable. The term 'aircraft grade' doesn't really apply to timber though. Find a good reference you trust (try 'Wood in Aircraft Construction, 1936) which will give you the guidelines for choosing aircraft timber. Good ply is hard to find but really good quality marine grade can be used. Alternativley you can buy all your material from an aircraft supply place in the US and get it shipped out. I'm told you should count on a nearly 25% rate of timber that's unusuable in it's original role (eg. 25% of spar material will be unsuitable but you could cut it up into capstrips). In the end you must be happy with the material - so educating yourself is a good invetment in your own longevity!
Search for any forums that have posts by 'Spadmaker' - he has some invaluable advice on wood selection. If you can't find anything, let me know.
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25th April 2009, 08:44 PM #22
I get someone else to cut my parts but as he is an 'amateur' wooden boat builder he takes the time to understand what I want and to produce usable parts. I found some commercial firms just want to cut the part and take your money - no real interest in what you are doing. Try telling then it's for a flying aeroplane - many refuse to talk to you!
The CNC routing/milling of wood is a great way of cutting repetitious parts like the wing ribs. I have seen laser cutting used but I don't believe the glue joint is suitable - the laser burnishes the edge of the wood slightly making gluing a little dicey. This isn't a breadboard - it has to hold together under g-load at 200km/h...
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27th April 2009, 01:37 AM #23Novice
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brinesharks ~ my project is ( will be) a WAR P40E I'm determined to build the thing, although I have a few concerns. I've been unable to contact the designer of the P40 (Aussie) bit of a worry! At any rate I have LOT of skill building to do before I can start, and as you mentioned every little bit of info I can gather will be gold. Thanks for the clarification and info. I'll take every bit I can get ~ so I don't end up as a local headline.
Good luck with your project, I'll enjoy following its progress ( I suspect I'll be working in an even slower time frame .)
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29th April 2009, 12:12 AM #24
Was sent this link tonight to reproduction aircraft by a friend in the US .
I remembered your post so I though it was timely to post it here .
These guys are building brand new WW1 aircraft from original drawings by hand and actually flying them when completed .
Big task but great work.
http://thevintageaviator.co.nz/proje...ying-masterton
Kev."Outside of a dog a book is man's best friend ,inside a dog it's too dark to read"
Groucho Marx
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29th April 2009, 06:59 PM #25
Thanks Kev - these guys are really punching above their weight! It really shows you how tough it would have been to fight in these craft. I'm hoping mine will be comparable to these guys but I don't have the commercial backing! Apparently a lot of the NZ work is paid for by Peter Jackson of Lord of The Rings fame. He is a real military history enthusiast and a little bird tells me he has a whole bunch of WW1 uniforms and equipment too - I hope his next movie is a WW1 ANZAC epic!
Having a team of CAD designers to draw up modern plans must really speed things up. You know beforehand if the part will fit or not.
Wish I had an original engine. Just have to keep saving my pennies...
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29th April 2009, 07:10 PM #26
Materials?
Can anyone suggest a place for timber. Some timbers I need are:
Ash (true European Ash): 20mm x 28mm and about 2m long x4
Ash: Lots of strips 30mm x 5mm x 1.2 (approx)
Maple: 8mm thick and large enough to make the fuselage formers on the turtledeck
Walnut: strips 9mmx13mm x 1.2m
Poplar: Need Poplar ply but I think I'll substitute Birch ply
Spruce: Lots and lots!
I was under the impression that Walnut is hard to come by these days in anything except veneer. If it's too difficult to source I could use a good quality Birch ply.
Any leads/suggestions are welcome. I can re-saw timber but not sure how to finish the thinner strips - ie. how does thin material go through a thicknesser?
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29th April 2009, 08:38 PM #27
BrettG - the WAR designs were what first fired my interest in homebuilding. I love WWII fighters but knew I'd never afford one.The WAR designs are like big model aeroplanes - timber structure with foam shaped and glassed to make it look like the full-sized ones. I have an article from 1974 on the first FW190 prototype they made. I'll try to scan it and send it through. One thing though - the WAR replicas are pretty small. If you are above about 5'10" I don't think you'll fit. I sat in the P47 and couldn't close the canopy. If you are willing to go bigger (and more complex) try:
http://www.marcel-jurca.com/index.ph...tpage&Itemid=1
All wood - Marcel Jurca's designs come in 3/4 scale and full scale!!!! Feel free to build a Spitfire or ME109 if you like! A 1200hp V12 Allison would drink a bit of juice though...
I'd love to build the 3/4 Fw190 (maybe after my Nieuport!) and the 'Sperocco' looks great too.
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29th April 2009, 11:26 PM #28Novice
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Thanks for the link brinesharks, I'll certainly scope those designs out = A P40!! music to my ears my friend. [Sigh].. yeeesss.. the size of the WAR aircraft is definitely a concern = 5'10'' + Kg ++.. curse my parent's lofty stature and healthy appetite. I'd like to investigate rescaling them ( the WAR design, not my parents) I believe there's a 75% design in development based on the WAR construction. Plenty of research to do as yet.
Btw. Re your request for timbers. In the FEB 09 issue of Recreational Aviation Australia, Steve Bell ( technical editor ~ Wood and fabric man) offered a trailer load of Spruce to anyone that could get to Canberra and collect it. (If I was able to, I'd be on the road right now!!) Probably to late, although it may pay to contact him. ( sorry I don't have the mag handy right now ~ contact details?.. google the mag title..?)
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30th April 2009, 01:45 AM #29
Briney
what tools do you currently own?
If you saw the strips from larger stock with a table saw there'll be heaps of waste, so I suggest you use a band saw and plan on beaking down larger stock
I also suggest you use a drum sander to finish thickness the strips – I'm guessing that consistent thickness is critical for you, but because the strips are thin, you can accomodate a certain amount of twist – hence you may not need a jointer.
ian
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30th April 2009, 06:40 PM #30
I have a table saw but also have access to a large (enormous!) bandsaw that can re-saw old Jarrah posts! Also a jointer and thicknesser. I don't have a drum sander though.
I plan to pick up some Ash tomorrow and try cutting some cap strips. I think I might substitute Birch ply for the Maple formers (can't fathom why Maple was used in the first place). I could even face the ply with Maple veneer.
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