TBK

Here is the float deck plug with a finish coat prior to sanding and priming. You can also see the float hull bottom templates laid on the building board ready for planking, as soon as I can get some more 1/8" balsa.

Idealist

Dear TBK,
what great progess! -
Keep up the outstanding building quality, I really love it!

Two questions, if I may:

- Did you use the original keelrocker from the original Mk.VII plans for the floats,
or the flatter modified keelrocker from the (later) provided coordinate set? -

- Did you reduce the 3mm balsaplanks from the diameters of all cross sections -
or leave them as they where in the plans?

TBK

Ernst

Some answers to your questions as follows:

No, I didn't modify the keel rocker from the original MKVII plans, just moved the mast/fin back slightly. It still balances out very well right on this new point.

I used the plans as is without a reduction to account for the balsa planking to make up the plugs. Therefore as such the actual moulds are slightly larger by about 3mm or 5%. Other than making them slightly heavier there should not be any appreciable difference in performance. When I made the bulkheads to insert into the new moulds I simply took the original plans and photocopied them at 105% and that was sufficient to account for the 3mm thickness. It's also important to note that there is an apprecialbe amount of sanding and fairing that goes on once the hull is initially planked and that usually results in about a 50% reduction in the overall thickness of the balsa plug, so in fact it really isn't that much different from the actual plan size.

Things are continuing to progress. I only get a chance to work on the boats a little at night. I've ordered all my rigging materials and they should be arriving soon. I plan to make two complete boats - one all glass and one all carbon fiber. On the CF boat I am going to work to optimize to as minimal a weight as possible with significant reductions in the internal structures and the use of CF reinforced components instead of glass reinforced. It will be interesting to see how much weight I can shave off the glass boat and how much of an impact it will make on the water. As always there will be a trade-off in overall strength/stiffness vs overall weight. High stress points will still need to be adequately addressed to ensure that they won't fail under load.

TBK

Idealist

Dear TBK,
thanks for this fast and detailed answers!

As said earlier - I believe you know what you do and why you do it the way you are doing it!

So don`t worry - my questions aren´t ment as any kind of criticism -
it´s more like putting some specific designaspects and possible buildingproblems to the attention of other potential builders with less experience than you have.

The original linedrawings where planned for plugs of solid foam, sanded and covered with glass.
Then resanded and shells taken from them. 2-2.5 mm difference overall won´t make such a huge difference in the performance. Basically just the bows radiusses will be a bit blunter.

I´m looking forward to see your boat(s) sailing - and especially the final weight of your carbonversion!

TBK

Idealist

No problem I completely understand. I'm probably going to finish the float plugs and make up the new moulds for the crossbeams before I begin the finishing on the carbon boat. I'll keep making routine updates as I continue to make progress. My target is to get both boats finished and ready to sail before the ice thaws on my local pond. That means about another month or so of work.

TBK

TBK

The float deck hull plug was primed, sanded and faired. Then three coats of mould release wax was added , followed by two light coats of PVA release agent. Attached pictures show the first float deck hulls being moulded on the plug using two layers of 4 oz cloth and epoxy resin.

TBK

I've now made the two float hull decks in glass and will be moving to make the carbon fiber versions shortly. As you can see from the photos below I also begun the planking of the float hull bottom plug. Next to it is the float hull deck plug. I finally got all my rigging parts so once I complete the float hull plugs and moulds I can move back to completing the main hull and bonding the top and bottom sections together.

TBK

I finished the float hull bottom planking and it was then sanded, faired and glasssed. Also shown in the photos below is the first carbon float hull deck being moulded.

Idealist

WOW!!!
Even if I repeat myself - I can´t wait to see your trimarans sailing!

TBK

Thanks. Things are moving along although not as fast as would have liked due to the limited amount of spare time I can devote to the build. I now have all the hull plugs finished and most of the parts moulded. Next, I will be laying out the float hull internals and making templates for the bulkheads. Once all that is finished I will move on to the crossbeam fabrication.

TBK

NY_Rocking_Chairs

I love the work and detail. My question is about the rigging of the sail servo. I last built a sailboat about 8 years ago and it served me well. The sail control servo setup with the loop of string is new to me and I cannot quite grasp the concept of how it works. My other boat uses a servo with a long arm on it and that would pull or release string to allow the masts to swing further or stay close-in to the keel.

Can you provide a brief description of how this style rigging system works? Thanks.
-Rich

TBK

NY Rocking Chairs

No problem. The photos showing the the lines to the sail winch are incomplete and are just there to determine the position of the turning block and the sheet guides. Before I close up the two hull sections I will be installing the complete sheet system including the sheet lines for the main and jib. It is really very simple. I install an eyelet between the winch and turning block on one side of the line. As the winch winds and unwinds the eyelet either moves forward to the turning block or back. The jib sheet and main sheet are then both attached at one end to this eyelet, effectively pulling in or letting out the sheets as the eyelet moves forward or back. The ends of the two sheets are routed upward at each point through pulleys and then guided to the boom attachments via small carbon fiber posts mounted to the deck. When I get the sheets all laid out I will take some photos so you can see what it all looks like before I bond the two hull halves together.


TBK

NY_Rocking_Chairs

So does the winch servo provide constant rotation? The 2-channel systems I know about only provide point-to-point rotation so was wondering if there is a special setup to get the winch to run longer, ie for multiple revolutions.

Thanks.
-Rich

eltoro

NY Rocking Chairs,

I believe TBK is using the Hi-Tec 785 sail winch. It has 3 1/2 rotations max, which should be more than enough for this boat. Any end point adjustments are usually done via the transmitter.

TBK, excellent work, I think you are making quick progress. I am currently building the same boat, except I choose the round bottom version. I am almost finished the main hulls, so I am way behind you in your build. I am not sure if I will do molds like you have done, I am kind of leaning to a one-off. I have experience in doing mono-hull scratch builds, I have a six foot AC boot that will be getting its hull wet for the first time this coming sail season for example but this Trimaran will be my first multi-hull build. You have become my building guide mentor. Keep those photos and descriptions coming!

Tory

TBK

Tory is right. I am using the Hitec Sail winch which does about 3 1/2 revolutions from start to finish giving an overall shert travel of about 14" which is more than enough for this boat. I have used the same winch in my previous tri. The only drawback with the Hitec winch is its slower speed about 1.4 sec/rev. You can use the Futaba winch which will provide a much quicker response but it costs about 2-3 times as much as the Hitec and requires a direct connection to the battery vs through the Rx. Since I am building two boats simultaneously (one glass and one carbon fiber) I might try out the Futaba winch in the CF boat. They are not the same overall size so that they cannot be readily interchanged without some mounting adjustments. I didn't really find the slower speed to be an issue as the tri's are more stable in response to wind puff's and only require small trim adjustments vs the much quicker responses that I need on my USOM. A sail arm servo can be used but without doubling up on the internal purchase you'll be limited to only about 8-9" of sheet length since you can only fit about a 3-4" arm inside the narrow width on the hull.

Idealist

Eric G., the owner of the carbon/epoxy prototype of the "Nightmare Mk.VII"
used the described doubled system for his HITECH armwinch.

But he installed it horizontal, instead of vertical.
As the mainhull at it´s lowest point is deeper than the boat is wide,
he therefore could use a longer arm for the winch.

But be careful - at the sailinglimit of the A-rigg this armwinch is quite weak.
A stronger, faster, better, more expensive drum winch may be worth the investment.

Pics of the building - including the arm winch before installation:
http://www.rc-network.de/forum/showthread.php?t=94097

If you need some translations from me just ask -
but the pics basically show everything you need to know.

TBK

Idealist

That is a good idea as well. I never thought to install it that way. There ceratinly would be more space to allow for a larger arm, thence additional sheeting length. There is a very powerful sail arm servo ( and not too expensive) made by Hitec that puts out 230 oz of torque at 6v and is comparable to the high end winches available. It is directly connected to the battery not through the Rx. It is more than adequate for the A-rigg. I used this on my USOM (overkill really) and it is brutally strong and fast and could be a good choice to use in the orientation described. However if I recall Hitec didn't recommend that it be installed that way.

TBK

Idealist

Haha - you´re right TBK, but HITECH doesn´t build or sell trimarans either!
The solutions we find for technical problems will be picked up by the modelbuildingindustries later.

TBK

Idealist

You are right about that. The innovative ideas almost always come from the minds of the builders. Just the other day as I was studying the overall shape and profile on the main hull I thought about using a modified version of it (same bottom profile but altered deck) to make a keelboat. Since I have already made the plugs this is something I might try after I've finished both tri's. It looks very similar to many of the current ocean racing machines, although somewhat slimmer. (Just a thought - err maybe I've been sniffing too many acetone fumes.........)

TBK

Idealist

Haha - just take care not to use a lighter at the same time - you might blow up!

Idealist

@TBK
No updates on the buildlog?
Did you complete all shells?
How about the weight of the carbonshells of the floats?

Or did you even use the lighter accidently? *ggg*

TBK

Yes , I have made more progress and will be posting more pictures tonight. I have made all the shells except for one last carbon fiber float bottom still to be made. Check back tomorrow to see the updates. I'll weigh everything and include that on the update as well.

TBK

TBK

Here are some more pics of the build. Below you can see a set of glass float hulls deck & bottom. You can also see the first set of carbon float hulls top & bottom. The glass pieces are made with two layers of 4oz cloth and epoxy resin. The carbon hulls are made with one layer of 6oz carbon twill and one layer of 2oz glass and epoxy resin. Both hulls virtually weigh the same (within 10g) at 5.05 oz/145g for the decks and 5.9oz/168g for the bottoms. The main difference is that the carbon hull is much more rigid and stronger, as would be expected. Also you can see that I'm starting to put in the internal bulkheads on the float hull to reinforce the attachments for the crossbeams. The only other internal pieces will be for the shroud stay attachments.

TBK

TBK

Here are some photos showing the main sheet and jib sheet arrangements and the cutouts on the main deck for access to the servo and for the radio pot. Once the two hull halves are bonded together, the sheets will be routed through some short carbon fiber posts epoxied to the deck.

NY_Rocking_Chairs

Very cool. I understand the rigging better now thanks. Just wondering if anyone can point me to a supplier for all those tiny little block and tackle parts, preferably in the US so shipping is kept to a minimum.

Thanks.
-Rich