Reply
 
Thread Tools Search this Thread
 
Old 18 April 2012, 13:43   #1
Member
 
demondesmond's Avatar
 
Country: UK - England
Town: Blackpool
Boat name: Indigo
Make: Humber
Length: 5m +
Engine: Etec 60 Hp
Join Date: Jun 2011
Posts: 57
Transom Weight Limits

Hopefully some of you experienced boaters (or even boat designers) can help me........I have a 5mtr Humber Destroyer which is rated at max of 90HP or 135kg outboard weight. According to the Humber website Rigid Inflatable Boats - a vast range of quality ribs for both leisure crafts and sports craft from Humber Inflatables the 5.3 is also rated at 90 HP but a max weight of 165kg. My question is why does the short increase in length (30cm) make such a big difference to outboard weight limit? To my untrained eye the other outboard weight figures and baggage weight limits accross the Desroyer range (at least between 5 and 6 mtrs) seem to be somewhat eratic. Can anyone explain to me how these limits are worked out?

Thanks
__________________

__________________
demondesmond is offline   Reply With Quote
Old 20 April 2012, 07:57   #2
Member
 
demondesmond's Avatar
 
Country: UK - England
Town: Blackpool
Boat name: Indigo
Make: Humber
Length: 5m +
Engine: Etec 60 Hp
Join Date: Jun 2011
Posts: 57
Is it really such a dark art or am I being extremly thick? Can nobody offer an explaination?
__________________

__________________
Blue is the new Orange!
demondesmond is offline   Reply With Quote
Old 20 April 2012, 08:27   #3
Member
 
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,611
This isn't going to be a very teccy answer, but it basically boils down to the structure and balance (both at rest & when on the plane) of the boat. For example mine is a mid 80s version of what is now the O-Pro. the transom is 50mm thick (including the fibreglass) and has no solid bracing. Rated 60Hp / 110Kg. The current 5m O-Pro takes 75 gee gees & 140 odd KG (I forget the exact number).

As the boats get longer they will also get heavier. To beef up the transom on the 5m to take a heavier (bigger) engine will likely mean 3 things - 1) it will be so tail heavy it will handle like a pregnant whale. 2) when you stop, you get flooded. 3) you end up being able to hang waaaay too much Hp on the back for a 5m hull.

Your extra 0.3m may be "out the back" - i.e the cones protude further, thus giving more bouyancy so more weight can be added as there's extra toob to keep them afloat?

I'll have to had you over the he Humber experts for the fine details of that hull range tho'.
__________________
9D280 is offline   Reply With Quote
Old 20 April 2012, 09:04   #4
Member
 
Country: UK - England
Town: Truro-Cornwall & Brazil
Boat name: Bananas in Blue
Make: Humber Destroyer 5.5
Length: 5m +
Engine: E-Tec 115
Join Date: Jun 2007
Posts: 385
I remember being equally confused when I bought mine.

I was looking at a 5.3 but decided on a 5.5 as an extra 20cm meant I could have 25 more HP on the back.

Looking at the figures, despite being allowed a 115 on the 5.5 instead of a 90 on the 5.3 you are only allowed 5kg more on the transom actually making me 3kgs over with the E-tec 115.

I'm not sure you can even get a new 115 under 170kg, especially with the XL Transom I have.
__________________
Markyboyo is offline   Reply With Quote
Old 20 April 2012, 09:09   #5
Member
 
demondesmond's Avatar
 
Country: UK - England
Town: Blackpool
Boat name: Indigo
Make: Humber
Length: 5m +
Engine: Etec 60 Hp
Join Date: Jun 2011
Posts: 57
Now then. There are a few things there that I hadn't thought about. I had assumed that the construction of the transom / hull would be exactly the same for all Destroyers just slightly longer. Also, the length of the sponsons from transom backwards is interesting.
My problem is that I'd like to put a small amount more HP on the back but finding a new donk to replace my 60HP ETEC within the weight limit is a nightmare. Yam F70 is an option but there is an additional weight penalty with this and I'm not sure I get he extra 5 / 6 Knots top end I'm after. I've been trying to find someone with 5m Destroyer + Yam F70 (another thread) but no luck yet. I can't understand how the boat can be rated at 90HP when there are no current 90HP engines less that 135Kgs. I have spoken to Humber about this but their answer was "it is rated at what it is rated at". I should have gone for 5.3 or above but storage was the issue.

Thanks 9D280
__________________
Blue is the new Orange!
demondesmond is offline   Reply With Quote
Old 20 April 2012, 09:15   #6
Member
 
demondesmond's Avatar
 
Country: UK - England
Town: Blackpool
Boat name: Indigo
Make: Humber
Length: 5m +
Engine: Etec 60 Hp
Join Date: Jun 2011
Posts: 57
Thanks Markyboyo
Sounds like you'll have some grunt there. If you are slightly tail heavy whats the handling like on your boat? Does it washover when you drop off he plane and stop? Can you trim the engne in far enough to keep the nose down on take off?

Des
__________________
Blue is the new Orange!
demondesmond is offline   Reply With Quote
Old 20 April 2012, 09:44   #7
Member
 
Country: UK - England
Town: Truro-Cornwall & Brazil
Boat name: Bananas in Blue
Make: Humber Destroyer 5.5
Length: 5m +
Engine: E-Tec 115
Join Date: Jun 2007
Posts: 385
I think it is a little stern heavy but once you are up and running the bow comes down nicely and it handles fine. It does come up if not trimmed right in but it gets onto the plane fast enough for this not to be a problem even if 6 up.

If I could go back I would probably have had a 5.3 with a 90 E-tec as I could maybe have sneaked that onto an un-braked trailer.

I don't have any issues with wash coming over the transom when stopping but then I did specify an XL transom when I bought the boat which raises it by 5". I'd used several ribs before that were prone to this hence my choice.

I'd be tempted to throw caution to the wind and stick a 90 TLDI or E-tec on yours as soon as the warranty is up!
__________________
Markyboyo is offline   Reply With Quote
Old 20 April 2012, 10:19   #8
Member
 
demondesmond's Avatar
 
Country: UK - England
Town: Blackpool
Boat name: Indigo
Make: Humber
Length: 5m +
Engine: Etec 60 Hp
Join Date: Jun 2011
Posts: 57
Markyboyo... look at you with your caution to the wind! 90 Etec is an option that I have been thinking about for some time (albeit more power than I think I need but I'm sure the boat will handle it) and I think that is the most likley outcome. I have the long shaft transom but as you can see from the attached pic she sits pretty high at rest next to my mates One Design with 115Etec. He does get wash over the back if not careful dropping off the plane. I might have to lose the A frame though.
With the Yam F70 I was trying to see if I could solve the problem by sticking to Humbers weight limt.

Thanks for your comments

Des
Attached Thumbnails
Click image for larger version

Name:	SAM_0007.jpg
Views:	299
Size:	118.3 KB
ID:	67334  
__________________
Blue is the new Orange!
demondesmond is offline   Reply With Quote
Old 20 April 2012, 11:08   #9
Member
 
Country: UK - England
Town: Truro-Cornwall & Brazil
Boat name: Bananas in Blue
Make: Humber Destroyer 5.5
Length: 5m +
Engine: E-Tec 115
Join Date: Jun 2007
Posts: 385
I see where you are coming from with respect to staying within Humber's weight limit but for what it would cost to upgrade from your 60 it would be expensive for an extra 10 horses.

That One design does look very low in the water, I wonder how different your destroyer would look if you chopped off the raised splash plates down to the same level as the centre of the transom like the one design? I also reckon that the tubes on the one design hull are mounted slightly lower on the hull relative to the centre of the transom?

My Aframe is a double one and I was very surprised at how light it was when I fitted it. It bolts to the inside of the transom and also to the floor a foot or so forward so I hope it provides more strength to the transom than its weight takes away.

I'd love to see how yours handles with that little weight on the transom, I bet you can really throw it around. Let me know if ever you decide to do some ribbing in Cornwall!
__________________
Markyboyo is offline   Reply With Quote
Old 20 April 2012, 11:14   #10
Member
 
Country: UK - England
Town: Dorset & Hants
Boat name: Streaker/Orange
Make: Avon/Ribcraft
Length: 4m +
Engine: 50Yam/25 Mariner
Join Date: Apr 2007
Posts: 5,551
Quote:
Originally Posted by demondesmond View Post
He does get wash over the back if not careful dropping off the plane.
Des
That'll be why he has water coming out the bilge pump in that pic on flat calm day ?
__________________

__________________
PeterM is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 05:28.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.