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Aug 10, 2019, 09:57 PM
Crash and fly again
mwood's Avatar
[QUOTE=FLOEY;42482217]I would probably tried a 3S 650mah Gaoneng or Gens Ace Tattu
https://www.aliexpress.com/item/32863153639.html

Got some Turnigy Graphene 500mah that I'm flying with in my NiceSky P-47 (680mm wingspan)
In the video I'm using a "normal" 500mah so the performance wasn't great.../QUOTE]

Thanks for the tips. The 500mah size seems to give good results.
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Aug 17, 2019, 02:34 PM
Crash and fly again
mwood's Avatar
Quote:
Originally Posted by CaseySP
...Best will be to swap the power, flight systems and mechanics into a new airframe. Like the mods I did to the Beaufighter and Corsair, now I’ve down it once the second time will be faster and neater.
CaseySP. I studied your crash photos soberly. With the eggshell thin surfaces of Doug Bader's Spitfire chopped into salad by the runaway propeller, it seems a bit silly now to ask if there was hope of repair.

Are you indeed going to order a replacement airframe? If you do, I will tell Callie I want the same Bader livery as well.

My elegant little Alpha Spitfire finally arrived after two months of travel from a post office in exotic Czechoslovakia. The bare airframe with cowl weighs a mere 160 grams.

Now that it's on the bench, I feel a perverse reluctance to begin the assembly. Damaging it would be a pity, and disheartening accidents (hopefully minor) will be inevitable. But never seeing it fly would be the greater pity, right?

To power this featherweight model I was going to use a Rimfire 400 that I had on hand, but thinking better of this I've opted to save 20 grams by using an Elite 370 equivalent. So I obtained a 40 gram Suppo A2208/17T 1100kv from Altitude Hobbies. I also have a nice selection of RaceStar BR2208's that appear to be virtually identical to the Suppo, with the same 40 gram weight, but with four different KV ratings-- 1100, 1400, 1800, and 2600kv, purchased inexpensively from Banggood for use in this or future projects.

What motor choice would be best from this selection?
Last edited by mwood; Aug 17, 2019 at 02:56 PM.
Aug 18, 2019, 07:28 AM
Registered User
CaseySP's Avatar
Quote:
Originally Posted by mwood
CaseySP. I studied your crash photos soberly. With the eggshell thin surfaces of Doug Bader's Spitfire chopped into salad by the runaway propeller, it seems a bit silly now to ask if there was hope of repair.

Are you indeed going to order a replacement airframe? If you do, I will tell Callie I want the same Bader livery as well.

My elegant little Alpha Spitfire finally arrived after two months of travel from a post office in exotic Czechoslovakia. The bare airframe with cowl weighs a mere 160 grams.

Now that it's on the bench, I feel a perverse reluctance to begin the assembly. Damaging it would be a pity, and disheartening accidents (hopefully minor) will be inevitable. But never seeing it fly would be the greater pity, right?

To power this featherweight model I was going to use a Rimfire 400 that I had on hand, but thinking better of this I've opted to save 20 grams by using an Elite 370 equivalent. So I obtained a 40 gram Suppo A2208/17T 1100kv from Altitude Hobbies. I also have a nice selection of RaceStar BR2208's that appear to be virtually identical to the Suppo, with the same 40 gram weight, but with four different KV ratings-- 1100, 1400, 1800, and 2600kv, purchased inexpensively from Banggood for use in this or future projects.

What motor choice would be best from this selection?
The scheme I used was the J. A. A. Gibson (RAAF) scheme included in the kit's decal sheet (I just like Donald Duck :-) ).

Haven't ordered a new one yet. The AUD has crashed against the CZK, but nonetheless and with Father's Day just around the corner, every time the wife walks past my workbench I pick up the damaged Spitty and sigh forlornly. Hopefully she takes the hint :-)

Not sure if I would describe the Alfa's as "eggshell thin" but I see that repeated a lot here - maybe it is an American term that I just don't get? Eggshells being incredibly strong and hard to protect the chick while it develops (as well as being porous so it can breath). But also allow the chick to break out from the inside when it is ready.

'I think that, if required on pain of death to name instantly the most perfect thing in the universe, I should risk my fate on a bird's egg'
Thomas Wentworth Higginson, 1862


I have repaired Alfa's from crash damage before - most notably my old P47 back when I had more time and a great curiosity if it could actually be done.

https://www.rcgroups.com/forums/show...-Repair-Part-1

https://www.rcgroups.com/forums/show...57777-New-foam

https://www.rcgroups.com/forums/show...7780-Finishing

But in this case a few too many pieces were missing, the wing spar was cut and I have too many other projects that I'm not getting done quickly enough.

So get out there any fly yours - they are surprising resilient but of course are built to fly and fly well.

Good rule of thumb for the Alfa fighters is 1000 - 1200kV and at least 100W on a 8" or 9" prop.

On that matter - for me personally (and I know others will disagree) I think that motor, while adequate, is a bit on the "weak" side and would not give terribly spritely performance. Looking that the Dr Kiwi test sheets, it barely draws 100W (if propped down to 6" and on 4S) and is recommended for 350g aerobatic planes. The Spitty will be about 50 - 100g more than that and would be ruined with a 6" prop.

I would go a size up as you may likely need extra weight in the nose with the smaller motor and tiny battery.

The other thing I would add that will cause some disagreement, I like my warbirds to look "planted" in the sky - so I wouldn't be pursuing to build the ultimate featherweight as if that is an ends in itself. Rather keep it around the recommended weight and able to penetrate winds and bumps without looking too floaty and toy-like.

I would fit a 1000mAh 3S battery and more capable motor for good speed, strong vertical and loops as large as you like.
Aug 18, 2019, 11:18 PM
Crash and fly again
mwood's Avatar
[quote=caseysp;42544625]... The aud has crashed against the czk...

This is interesting. Czech kroners are at present more expensive if purchased from Australia. The global reach of this forum becomes more evident from this currency perspective. I write this at 9pm on Sunday evening in Seattle, when it is 2pm Monday afternoon in Canberra. I am getting ready for bed, and you are near the end of a day's work! Globalism indeed. :-)

not sure if i would describe the alfa's as "eggshell thin" ...

Forgive the negative implication. I suppose this term does seem a criticism. I hadn't meant to imply that the alpha design was faulty. I've never seen this semi-monocoque stressed shell foam design technique used over a conventional internal spar, and the broken white shell reminded me of the fruit of the hen, whose sublime perfection i humbly acknowledge.

I have repaired alfa's from crash damage before - most notably my old p47 back when i had more time and a great curiosity if it could actually be done.

https://www.rcgroups.com/forums/show...-repair-part-1

https://www.rcgroups.com/forums/show...57777-new-foam

https://www.rcgroups.com/forums/show...7780-finishing


I look forward to studying the information from these links, thank you. Your advice is valuable and has me re-considering my options for power. Other perspectives would be most welcome as well.
Last edited by mwood; Aug 18, 2019 at 11:29 PM.
Aug 19, 2019, 06:18 AM
Registered User
CaseySP's Avatar
[QUOTE=mwood;42550641]
Quote:
Originally Posted by caseysp
... The aud has crashed against the czk...

This is interesting. Czech kroners are at present more expensive if purchased from Australia.
To be fair, the AUD has crashed against just about most of the leading currencies. Gone are the heady days of parity with the USD - now we are lucky to get 0.68 USD for 1 of ours.

I enjoy the globalisation of this forum too. Would have never heard of products (or sought them out) like UHU Por, Gorilla Glue and WBPU otherwise
Aug 19, 2019, 09:48 AM
Registered User
[QUOTE=CaseySP;42551663]
Quote:
Originally Posted by mwood
.
.
products .. Gorilla Glue ...
You may find similar (may be better) polyurethan glue
https://titebond.com.au/products/polyurethane/

Now You've no excuse to not fix Your Alfa Spit ... Just remember to pin/fix the parts (I assume You know ...)
Aug 19, 2019, 12:58 PM
2 metre rule applies!
DRAMJET's Avatar
The AUD was once remarked as “the Little Aussie Battler”.
But now better known as “the Little Aussie Sinker”!
Aug 19, 2019, 01:04 PM
Registered User
Foam carryout food containers can supply material for repairing an Alfa or Flying Styro . You can form curves by rolling it with dowel rod of various diameters and it can be heat formed with hot water once it it rubber banded or taped to a form that won't deform when very hot water is poured over the foam. The spar could be replaced with a balsa spar sistering balsa along side the intact sections you patch into.

The plane will be heavier but if you are careful on glue usage you won't add unnecessary weight from glue not adhering parts together or excess glue...

Nothing preventing you from using thicker foam sheeting and carving/sanding the sheets and blocks to shape either. Foam is very easy to repair, not to mention pretty quick to repair. Crushed areas can be cutaway and new foam spliced in, bridging the two areas together inside with a reinforcing backing piece.

David
Aug 19, 2019, 03:10 PM
Crash and fly again
mwood's Avatar
Rafster, thanks for sharing those foam repair tips. I have a feeling that I will (reluctantly) acquire experience with them, sooner or later.

Floey, I like the properties of white Gorilla Glue. For those who may not have used it yet, I'll explain. When applied it is a sticky syrup that can be managed with a cotton swab or popsicle stick. It expands into a low density foam that cures in a reasonable period of time after receiving a light misting of water. White Gorilla Glue foam works quite well to create a new surface for crushed or missing areas. Sadly, I need to use it often.
Last edited by mwood; Aug 19, 2019 at 03:25 PM.
Aug 19, 2019, 03:54 PM
Registered User
You can premix the polyurethane glues like Gorilla Glue and Titebond's with water in a cup and then apply the prefoamed glue as well. You can control the amount of glue easier and when you do not need it to expand but merely adhere pieces together it works very well.
Aug 19, 2019, 04:56 PM
Registered User
speedy01's Avatar
Quote:
Originally Posted by RAFster
You can premix the polyurethane glues like Gorilla Glue and Titebond's ... .
How does it sand?

Gene K
Aug 19, 2019, 05:06 PM
Registered User
Depron is always going to be softer than the glue but it sands well I think.
Aug 19, 2019, 06:07 PM
Crash and fly again
mwood's Avatar
Gorilla glue sands rather like 5 lb. density polyurethane foam. A dremel can be useful for getting it near level, then hand sanding.
Aug 19, 2019, 06:36 PM
Registered User
speedy01's Avatar
Quote:
Originally Posted by mwood
Gorilla glue sands rather like 5 lb. density polyurethane foam. A dremel can be useful for getting it near level, then hand sanding.
Thanks. I always found GG to be too gummy to sand well, but I never tried the white formula.

Gene K
Aug 20, 2019, 12:29 AM
Crash and fly again
mwood's Avatar
Quote:
Originally Posted by speedy01
Thanks. I always found GG to be too gummy to sand well, but I never tried the white formula.

Gene K
Gene, I can recommend 3M 'Sandblaster' sandpaper as wonderful stuff to use when sanding White Gorilla Glue. I think it's wonderful for any sanding job really. In my first career as a commercial sculptor for television and print advertising I did countless hours of hand sanding, and to my knowledge there is nothing on the market that works better. This rather ordinary looking yellow paper cuts very quickly, keeps on cutting much longer, and doesn't clog easily, making it worth the extra cost. Fill the well sanded Gorilla Glue with a thin layer of Famowood, then sand that out smooth and what was a smashed foam nose section looks right as rain. A bit of primer and paint and the result can look good as new.


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