Brad330l

My Feedback: (1)

Hi Carosel43,
I would like you to calculate mine if you would.
I use 13x8 3 blades Master Airscrews @ 10300 RPM and
14 x6 two blade APC props @ 11200 RPM.

These are approximate RPM's but pretty close.

Cheers,

Brad

Carosel43

Sadly my calculator dosent alwaysgive numbers that work in the real world when using 3 blade props so take them with a pinch of salt. having said that in this case they are plausable.

Static thrust 24lbs
Max speed 78mph
Engine hp 2.3

for the 2 blade APC 14x6's you get:

Static thrust of 28lbs
max straight line speed 63.6mph
Engine hp2.2

The figures are for both engines added up. for one engine then you half the thrust, speed remains constant as it is a product of rpm and pitch.

Also you can see that using 2 blade props the 75ax's match the lasers for performance almost exactly, but i would not expect the same pull from the two strokes with the smaller props, especially at lower revs, also i bet they dont sound as good! :P

drob

Interesting figures there. Here is something else that I think all of you will find interesting.
At the end of the WIKIPEDIA entry for the Tigercat there is a link to the Pilots Handbook for the Navy version of the aircraft. It contains good detail on the cockpit amongst other points of interest, with page 27 listing the permissible maneuvers, unladen.
Loop, Immelman Turn, Aileron Roll, Wing-Over, Chandelle and Vertical Turn. It goes on to say that spins intentionally induced are not permitted.

Also the maximum level speed is stated as 460mph. When this is appropriately scaled down we get 61mph! Pretty close to Carosel43 's calculations for Brad's and my models. It makes for interesting reading. To save you searching here is the link.

http://www.scribd.com/doc/53345349/1...F-4N-Airplanes

David

Brad330l

My Feedback: (1)

Wow,, that is awesome drob. I'll have a good read of that.
Just a note, I have inspected the crashed center section of the wing of mine and it is still basically in one piece with a bit of 'peripheral' damage where things departed company. I lent it on the floor and my knee and leant firmly right in the middle and not a sound or any indication of any weakness. I might even think about rebuilding this one with the spar mods and covering it in glass cloth as a finish.

Might think about it.

Cheers,

Brad

drob

Glassing the whole center section sounds like a good idea to me, Brad. Here is something to consider with your rebuild which ever way you go. I was faced with the dilemma of trying to remove the ABS wing fairings before recovering or leaving them on and covering around them. I found that I had done too good a job installing them so left them on. Instead of covering around them however, I am extending the covering over the fillets. I have already done the outer panels as you will see.

I first feathered the ABS into the balsa sheeting and took the covering right around to the 'intake'. For the center section I am feathering and also using micro sphere filler to give, I hope, an even better look. One thing to watch is to not apply too much heat to the ABS plastic with covering iron....it tends to soften as I found. Gets over the problem of fuel seeping into the wing somewhat. I have four oil cooler fillets fitted, two are from Tigercat #1 which I did not bother to fit.

Your stress test should give some degree of comfort to others. I have done a similar test with mine which seems to be rock solid. Hardly surprising! My repairs are now completed except for the final covering which I will do tomorrow. If it is any consolation to you all, the glue used in the wing seems to be much better that that used elsewhere in the airframe. That is, where it touches! See last photo.

David

(Visit www.gmac.org.au)

drob

Make that gmac.org.au

drob

Make that
http://www.gmac.org.au/

Brad330l

My Feedback: (1)

Awesome site and good work drob. After that last picture of the sheeting of the wing not touching I am definitely pulling some sheeting to do the mods.
I have just ordered one of these http://www.sonictronics.com/xcart/pr...cat=422&page=1 so I am thinking I want to have my Tigercat for a long time.

Cheers,

Brad

Carosel43

Looking at those spar mods i seriously doubt those spars are going to move in any event, looks like a good job to me and far betterthanit was.

Also with the plastic intakes if the center sectionis to be glassed they could be gluedon and blended with filler then have glass over thetop. they would be tougher, look better and be fuel resistant.

softshell29

Maidened mine today.

This is the T model, but its no Model T. The Grumman Turbo Cat.

Fantasy Scale.

Its my concept of what the designers originally intended the T Cat to look like. They didn't design such a sleek, streamlined fuse only to stick 2 bloated radial engines on.

With the turbine version's superior streamlining, I expected the top end and energy retention to shine. Its real fast and just keeps going. The surprise today was the glide. Despite the heavy wing loading, no problem shutting both motors off indefinitely. Even thermalled for almost 30 seconds. Yes, continued to gain altitude with both motors off for 30 seconds. What?

Brad330l

My Feedback: (1)

Wow! That looks really neat. Well done softshell.
Please post some close ups of the cowl area.

And welcome.

Brad

drob

Hmmm. To each his own I guess.
Well, I have completed the covering of the complete wing and reinstalled all the gear. Am waiting for some larger tanks before I balance. As expected the weight has gone up, 10.6kg (from 9.6kg). I think I will really need those Lasers now.
David

Brad330l

My Feedback: (1)

I will always prefer ours drob

Brad

ausfester

Hey guys,

Im about to start building a asm tigercat in melb australia.
Before i ordered it i didnt realise that part of the fuz is plastic and its worrying me a little. Should i be concerned?

Second question is either a pair of DLE 20s or satio 100s.
I would prefer the dle engines as i gave up nitro awhile ago but the sound of 2 fours would be magic.
Im concerned that the additional vibrations that gassers product might cause structual issuses on what most of you seem to be already facing.

Any thoughts n feedback would be appreciated

Carosel43

in my experience single pot petrol two strokes vibrate more than almost anything, and saito's are known for vibrating alot although the 100 is not the worst. I know what enginei would use, but i am more than a little bias!

Also your repair looks great drob, you will have to send me some more photos for our website and a video if you can.

Brad330l

My Feedback: (1)

ausfester the fuselage is indeed ABS plastic and will survive quite well if the internal structure is kept intact and your landings are not too heavy. My fuselage lasted very well for 35 flights (i think 35) until I crashed it from an engine out at take off. Mine didnt even split or crack like some of the other guys. I flew mine as fast as it would go with all the aeros thrown in and it was great. That is why I bought another one and this is the very first time I have ever done that with a model I have lost.
As for the engines, if you go with the DLE's just do some strengthening and have a good maintenance/inspection regime and you will be right. AND, land it well.

Good luck and let us know how you are going. (GO CATS!!!!!!!)

Brad

Lebus1

Hi all. I had a couple of "heavy" landings and in the process enlarged the holes for the landing gear wires. I cracked one of the supports as well. The repair of the cracked wood is very straight forward but I was wondering about the best method of rebuilding or tightening up the holes for the landing gear wire. I was thinking of useing JB weld to fill the hole completley and then redrill the hole for the wire. I am concerened that the JB will be harder than the wood and the drill bit will wander off into the surrounding wood. Everything else is standing up well. I just need to figure out how to come in slower. With the surrounding crop gone I can make a lower approach hopefully that will help. DB

drob

My 'To each his own' comment was directed to mods to the classic Tigercat design. It has occurred to me that it could have been interpreted as a response to Brad's post. I simply replied to the wrong post. This has been worrying me. So, sorry Brad.

Brad330l

My Feedback: (1)

Ha,,, no worries mate, I knew what you meant.[sm=thumbs_up.gif]

Brad

ausfester

Hey guys,

Well i decided to put a pair of the new OS 95v four strokes in, i have a turbine so if i have the need for speed i that will fill the void.
Whats everyones consensis on areas that require strengthining, from what ive read the balsa braces down the fuzz and perhaps some sort of brace for the main centre wing, not sure how ill do that tho,i dont have glassing skills.

Is the latter one important, are there any other areas i should be worried about?
Thanks boys im excited about joining the tiger club

Staggerflyer

I think you'll be fine with ALL the fuselage fixes. Those seem to be the most common. I think the wing center section break was a rare one, as no one else has had the problem, yet.

I think you'll be happy with the OSs.

We got one radar speed check on my electric powered TCat. Got a reading of 86mph. Problem with getting a reading on it, is that all the radar "sees" is the props, and if the plane is not pointed directly at the gun, there is no return for the gun to read.

I need to get my Eagle Tree MPH sensor mounted, so I can get a true reading.

drob

Staggerflyer, that's an interesting result you got with the speed gun. You have previously stated that you get 9921rpm from your Rimfires with the 14x9x3 props. Carousel43 has suggested that speed is a direct relationship between propeller pitch and rpm. Using the formula ((Pitch * RPM) * minutes per hour) / inches per mile) or ((9*9921)*60)/63360) I get 84.55mph! Pretty close to your speed gun reading. I have wondered how much the efficiency of propellers should be factored into the calculated speed. Perhaps Carousel43 might give us his thoughts on this.

As for the mods to the airframe ausfester, I would join Staggerflyer in recommending that you at least do ALL the fuselage strengthening described in previous posts. If you choose to also add a dihedral brace, you will find it easier if you do it through the bottom of the wing using a bit of key-hole surgery. You would only need to remove the covering in the immediate area. Take care to not interfere with the carbon fiber tube at the back of the spar.

Adding a glass fiber bandage around the join between the two wing halves need only necessitate removal of the covering immediately affected. No need to do the whole wing as I did. I am certainly no expert where glass fibre is concerned. It's not that difficult really. For your information the main spar is 100mm or 4 inches back from the leading edge. I used a 4 inch wide bandage in an attempt to keep it inside the fuselage. Hope this helps.

Staggerflyer

drob,

yes, the figures come out pretty close. The reading was taken after a split S and still a shallow dive, trying to get a direct point at the gun. It took about 4 passes to get a reading at all. So the plane would have been going as fast as it was going to go. And who knows on the accuracy of the gun, also.

We get a good reading on my Staggerwing, max 95mph, because of the big prop, 20", and the larger frontal area. We have a member with a high speed Sig prop jet, (suddenly can't remember the name,) with a tuned pipe, and it took two flights of trying to get a reading on it. 142mph.

Brad330l

My Feedback: (1)

Lebus1 with your wire U/C legs you could try coating them with some light oil and setting them in place and mixing some fiber glass powder and filling the enlarged part of the hole. You could even drill it out a tiny bit before hand to get more of the mix in there. The U/C legs should be able to be removed as the resin wont stick to the oil.

I have found a very therapeutic way of relaxing in the shed when I am feeling lazy or cant decide what to do and that is to slowly pull my crashed Tiger apart and check the damage. Man I was kidding myself if I thought I was ever going to rebuild this thing,,,,, It has not survived well.[&o] Cracks every where, wood shattered and plastic split. All the equipment seems OK though.

Cheers guys,

Brad

Staggerflyer

[quote]ORIGINAL: Brad330l


Was beginning to wonder about that, what with all the poor wood we are finding. ABS, while pretty strong, does not take sharp, hard hits well.

I'm also beginning to wonder if the metal used in the retracts isn't softer than the wood.